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Song YK, Kim HW, Chung CM. Repeatable Self-Healing of a Protective Coating Based on Vegetable-Oil-Loaded Microcapsules. Polymers (Basel) 2022; 14:polym14102013. [PMID: 35631895 PMCID: PMC9146027 DOI: 10.3390/polym14102013] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Revised: 05/11/2022] [Accepted: 05/13/2022] [Indexed: 02/01/2023] Open
Abstract
Generally, microcapsule-based self-healing materials have the limitation of single local self-healing. A few studies have reported repeatable self-healing in these microcapsular materials, but there is a challenge to develop multi-cycle self-healing materials that have the advantages of easier preparation and a more efficient operation. In this work, a mixture of two vegetable oils, soybean and olive oil, was used as a healing agent. The atmospheric oxygen-induced reaction behavior (in the presence of a catalyst) was investigated for various compositions of the vegetable oil mixtures; infrared spectroscopy, recovery testing, and viscoelasticity measurement were performed to find an optimum composition of the healing agent. Microcapsules loaded with soybean oil and catalyst-containing olive oil were separately prepared and used to prepare a dual-capsule self-healing coating. It was demonstrated through optical and scanning electron microscopy that, upon scribing the self-healing coating, the vegetable oils flowed out from microcapsules to self-heal the damaged area. When the healed area of the self-healing coating was re-scribed, self-healing was repeated, which was confirmed by scanning electron microscopy (SEM) and anticorrosion and electrochemical testing. Our new repeatable self-healing coating provides the merits of easy preparation, no need for external intervention such as light irradiation, and an environmentally-friendly nature.
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Choi YJ, Ko JH, Jin SW, An HS, Kim DB, Yoon KH, Kim HW, Chung CM. Transparent Self-Cleaning Coatings Based on Colorless Polyimide/Silica Sol Nanocomposite. Polymers (Basel) 2021; 13:polym13234100. [PMID: 34883605 PMCID: PMC8659165 DOI: 10.3390/polym13234100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 11/18/2021] [Accepted: 11/22/2021] [Indexed: 11/16/2022] Open
Abstract
We herein report transparent self-cleaning coatings based on polyimide-fluorinated silica sol (PIFSS) nanocomposite. Polyamic acid-silica sol (PASS) suspensions were synthesized by adding four different amounts of a silica sol suspension to each end-capped polyamic acid solution. The PASS suspensions were spin-coated on glass slides, thermally imidized and treated with triethoxy-1H,1H,2H,2H-perfluorodecylsilane (TEFDS) to prepare PIFSS coatings. The PIFSS coatings showed high resistance to separation from glass substrates and thermal stability. Furthermore, the PIFSS coatings on the glass substrate could be cleanly removed using polar aprotic solvents and repeated coating was possible. As the amount of silica sol particles in the PIFSS coating was increased, the hydrophobic contact angle increased. Among them, PIFSS-10 and PIFSS-15 coatings showed nearly superhydrophobic contact angles (144° and 148°, respectively) and good self-cleaning property. It was confirmed by SEM and AFM studies that their hydrophobic and self-cleaning properties are due to uniform particle distribution and relatively high surface roughness. PIFSS-10 coating showed a high transmittance value (88%) at 550 nm and good self-cleaning property, therefore suitable as a transparent self-cleaning coating. The advantages of the coating are that the fabrication process is simple, and the substrate is reusable. The PIFSS coating is expected to be applied in solar cell panels, windows, lenses and safety goggles.
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Jang J, Choi JY, Jeon J, Lee J, Im J, Lee J, Jin SW, Park HJ, Lee SH, Kim DB, Chung CM, Cho S. Flexible Transparent Electrode Characteristics of Graphene Oxide/Cysteamine/AgNP/AgNW Structure. Nanomaterials (Basel) 2020; 10:nano10122352. [PMID: 33260819 PMCID: PMC7760301 DOI: 10.3390/nano10122352] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 10/26/2020] [Accepted: 11/24/2020] [Indexed: 11/16/2022]
Abstract
Graphene oxide (GO)-cysteamine-Ag nanoparticles (GCA)-silver nanowire (AgNW) fabricated by depositing GCA over sprayed AgNWs on PET films were proposed for transparent and flexible electrodes, and their optical, electrical, and mechanical properties were analyzed by energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, atomic force microscopy, scanning electron microscopy, transmission electron microscopy, current-voltage measurements, and bending test. GCA-AgNW electrodes show optical transmittance of >80% at 550 nm and exhibit a high figure-of-merit value of up to 116.13 in the samples with sheet resistances of 20-40 Ω/◻. It was observed that the detrimental oxidation of bare AgNWs over time was considerably decreased, and the mechanical robustness was improved. To apply the layer as an actual electrode in working devices, a Pt/GO/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate/GCA-AgNW/polyethylene terephthalate structure was fabricated, and resistive switching memory was demonstrated. On the basis of these results, we confirm that the proposed GCA-AgNW layer can be used as transparent and flexible electrode.
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Affiliation(s)
- Junhwan Jang
- Department of Physics, Yonsei University, Wonju, Gangwon-do 26493, Korea; (J.J.); (J.J.); (J.L.); (J.I.); (J.L.)
| | - Ju-Young Choi
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea; (J.-Y.C.); (S.-W.J.); (H.-J.P.); (S.-H.L.); (D.-B.K.)
| | - Jihyun Jeon
- Department of Physics, Yonsei University, Wonju, Gangwon-do 26493, Korea; (J.J.); (J.J.); (J.L.); (J.I.); (J.L.)
| | - Jeongjun Lee
- Department of Physics, Yonsei University, Wonju, Gangwon-do 26493, Korea; (J.J.); (J.J.); (J.L.); (J.I.); (J.L.)
| | - Jaehyuk Im
- Department of Physics, Yonsei University, Wonju, Gangwon-do 26493, Korea; (J.J.); (J.J.); (J.L.); (J.I.); (J.L.)
| | - Jaegun Lee
- Department of Physics, Yonsei University, Wonju, Gangwon-do 26493, Korea; (J.J.); (J.J.); (J.L.); (J.I.); (J.L.)
| | - Seung-Won Jin
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea; (J.-Y.C.); (S.-W.J.); (H.-J.P.); (S.-H.L.); (D.-B.K.)
| | - Hyeong-Joo Park
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea; (J.-Y.C.); (S.-W.J.); (H.-J.P.); (S.-H.L.); (D.-B.K.)
| | - Seung-Hyun Lee
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea; (J.-Y.C.); (S.-W.J.); (H.-J.P.); (S.-H.L.); (D.-B.K.)
| | - Dam-Bi Kim
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea; (J.-Y.C.); (S.-W.J.); (H.-J.P.); (S.-H.L.); (D.-B.K.)
| | - Chan-Moon Chung
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea; (J.-Y.C.); (S.-W.J.); (H.-J.P.); (S.-H.L.); (D.-B.K.)
- Correspondence: (C.-M.C.); (S.C.); Tel.: +82-033-760-2266 (C.-M.C.); +82-033-760-2868 (S.C.)
| | - Soohaeng Cho
- Department of Physics, Yonsei University, Wonju, Gangwon-do 26493, Korea; (J.J.); (J.J.); (J.L.); (J.I.); (J.L.)
- Correspondence: (C.-M.C.); (S.C.); Tel.: +82-033-760-2266 (C.-M.C.); +82-033-760-2868 (S.C.)
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Choi JY, Lee J, Jeon J, Im J, Jang J, Jin SW, Joung H, Yu HC, Nam KN, Park HJ, Kim DM, Song IH, Yang J, Cho S, Chung CM. High-performance non-volatile resistive switching memory based on a polyimide/graphene oxide nanocomposite. Polym Chem 2020. [DOI: 10.1039/d0py01281e] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Chemical structure of PI-GO, schematic structure of the ITO/PI-GO/Al device and its memory characteristics.
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Song IH, Kim DM, Choi JY, Jin SW, Nam KN, Park HJ, Chung CM. Polyimide-Based PolyHIPEs Prepared via Pickering High Internal Phase Emulsions. Polymers (Basel) 2019; 11:polym11091499. [PMID: 31540300 PMCID: PMC6780585 DOI: 10.3390/polym11091499] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Revised: 09/10/2019] [Accepted: 09/11/2019] [Indexed: 11/16/2022] Open
Abstract
Pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline (ODA) oligoimide particles and PMDA-ODA poly(amic acid) salt (PAAS) were synthesized and used as stabilizers to prepare oil-in-water Pickering high internal phase emulsions (HIPEs). The stability of the Pickering HIPEs was investigated by dispersion stability analysis. Polyimide-based polyHIPEs could be prepared through freeze-drying and subsequent thermal imidization of the Pickering HIPEs. The characteristics of the polyHIPEs, including their morphology, porosity, thermal decomposition temperature, and compression modulus, were investigated. The thermal decomposition temperature (T10) of the polyHIPEs was very high (>530 °C), and their porosity was as high as 92%. The polyimide-based polyHIPEs have the potential to be used in high-temperature environments.
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Affiliation(s)
- In-Ho Song
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - Dong-Min Kim
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - Ju-Young Choi
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - Seung-Won Jin
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - Kyeong-Nam Nam
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - Hyeong-Joo Park
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - Chan-Moon Chung
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea.
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Lee WK, Lo A, Chong G, Chang SYS, Lu V, Yip PLI, Liu CMK, Leung M, Chung CM, Wong KY, Yeung YYE, Chan SMA, Ngai YS, Wong PS, Lo TL. New Service Model for Common Mental Disorders in Hong Kong: a Retrospective Outcome Study. East Asian Arch Psychiatry 2019; 29:75-80. [PMID: 31566182 DOI: 10.12809/eaap1822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
OBJECTIVE To review the first 8-month outcome of the Common Mental Disorder Clinic model in Hong Kong in terms of patient exit status and improvement in depressive and anxiety symptoms. METHODS During the first appointment, patients were interviewed by a multidisciplinary team comprising a psychiatrist, a psychiatric nurse, and an occupational therapist. A multidisciplinary case conference was conducted to discuss clinical observations, diagnosis, issues of concern, and the optimal individualised treatment plan. Low-intensity interventions by nurses and/or occupational therapists were provided, as were optional, time-limited, protocol-based interventions by clinical psychologists for those with mild to moderate depressive and anxiety symptoms. Pharmacological intervention may be used when indicated. Upon completion of the treatment plan, patients were reassessed by the treating psychiatrist. Discharge options included discharge without psychiatric follow-up, step-up to psychiatric outpatient clinics, and step-down services. The self-administered Patient Health Questionnaire-9 (PHQ-9) and Generalised Anxiety Disorder 7-item scale (GAD-7) were used to assess the past 2 weeks' depressive and anxiety symptoms, respectively, at baseline and at each session. RESULTS From July 2015 to February 2016, 1325 Chinese patients received the new service. Of them, 170 men and 363 women (mean age, 52.6 years) completed the treatment plan. After treatment, their mean PHQ-9 score decreased from 11.06 to 7.55 (p < 0.001), and the mean GAD-7 score decreased from 9.94 to 6.54 (p < 0.001). After treatment, 42.4% and 48.2% of the patients were within the normal range of PHQ-9 and GAD-7 scores, respectively, compared with 16.9% and 20.8% before treatment. The mean time to implementation of the individualised treatment plan was 82.33 days. Of the patients, 54.4% were discharged without any need for medical or psychiatric follow-up; 28% were stepped up to psychiatric outpatient clinics; and 17.3% were stepped down. The predictors of exit status were whether psychiatric medication was prescribed during initial intake (p = 0.011), whether psychiatric medication was prescribed at last follow-up (p < 0.001), the service period (p = 0.010), and the GAD-7 final score (p = 0.005). CONCLUSIONS The first 8-month outcome of the new service model was encouraging, with shortened waiting time, reduced severity of symptoms, and better exit status (high recovery and step-down rates).
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Affiliation(s)
- W K Lee
- Kwai Chung Hospital, Hong Kong SAR, China
| | - A Lo
- Kwai Chung Hospital, Hong Kong SAR, China
| | - G Chong
- Kwai Chung Hospital, Hong Kong SAR, China
| | | | - V Lu
- Kwai Chung Hospital, Hong Kong SAR, China
| | - P L I Yip
- Kwai Chung Hospital, Hong Kong SAR, China
| | - C M K Liu
- Kwai Chung Hospital, Hong Kong SAR, China
| | - M Leung
- Kwai Chung Hospital, Hong Kong SAR, China
| | - C M Chung
- Kwai Chung Hospital, Hong Kong SAR, China
| | - K Y Wong
- Kwai Chung Hospital, Hong Kong SAR, China
| | | | - S M A Chan
- Kwai Chung Hospital, Hong Kong SAR, China
| | - Y S Ngai
- Kwai Chung Hospital, Hong Kong SAR, China
| | - P S Wong
- Kwai Chung Hospital, Hong Kong SAR, China
| | - T L Lo
- Kwai Chung Hospital, Hong Kong SAR, China
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Choi JY, Jin SW, Kim DM, Song IH, Nam KN, Park HJ, Chung CM. Enhancement of the Mechanical Properties of Polyimide Film by Microwave Irradiation. Polymers (Basel) 2019; 11:polym11030477. [PMID: 30960461 PMCID: PMC6473371 DOI: 10.3390/polym11030477] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 03/05/2019] [Accepted: 03/07/2019] [Indexed: 11/17/2022] Open
Abstract
Polyimide films have conventionally been prepared by thermal imidization of poly(amic acid)s (PAAs). Here we report that the improvement of tensile strength while increasing (or maintaining) film flexibility of polyimide films was accomplished by simple microwave (MW) irradiation of the PAAs. This improvement in mechanical properties can be attributed to the increase in molecular weight of the polyimides by MW irradiation. Our results show that the mechanical properties of polyimide films can be improved by MW irradiation, which is a green approach that requires relatively low MW power, very short irradiation time, and no incorporation of any additional inorganic substance.
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Affiliation(s)
- Ju-Young Choi
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - Seung-Won Jin
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - Dong-Min Kim
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - In-Ho Song
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - Kyeong-Nam Nam
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - Hyeong-Joo Park
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - Chan-Moon Chung
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea.
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8
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Cho YJ, Kim DM, Song IH, Choi JY, Jin SW, Kim BJ, Jeong JW, Jang CE, Chu K, Chung CM. An Oligoimide Particle as a Pickering Emulsion Stabilizer. Polymers (Basel) 2018; 10:E1071. [PMID: 30960996 PMCID: PMC6403722 DOI: 10.3390/polym10101071] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 09/17/2018] [Accepted: 09/25/2018] [Indexed: 12/05/2022] Open
Abstract
A pyromellitic dianhydride (PMDA) and 4,4'-oxydianiline (ODA)-based oligoimide (PMDA-ODA) was synthesized by a one-step procedure using water as a solvent. The PMDA-ODA particles showed excellent partial wetting properties and were stably dispersed in both water and oil phases. A stable dispersion was not obtained with comparison PMDA-ODA particles that were synthesized by a conventional two-step method using an organic solvent. Both oil-in-water and water-in-oil Pickering emulsions were prepared using the oligoimide particles synthesized in water, and the size of the emulsion droplet was controlled based on the oligoimide particle concentration. The oligoimide particles were tested to prepare Pickering emulsions using various kinds of oils. The oil-in-water Pickering emulsions were successfully applied to prepare microcapsules of the emulsion droplets. Our new Pickering emulsion stabilizer has the advantages of easy synthesis, no need for surface modification, and the capability of stabilizing both oil-in-water and water-in-oil emulsions.
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Affiliation(s)
- Yu-Jin Cho
- Department of Chemistry, Yonsei University, Wonju 26493, Korea.
| | - Dong-Min Kim
- Department of Chemistry, Yonsei University, Wonju 26493, Korea.
| | - In-Ho Song
- Department of Chemistry, Yonsei University, Wonju 26493, Korea.
| | - Ju-Young Choi
- Department of Chemistry, Yonsei University, Wonju 26493, Korea.
| | - Seung-Won Jin
- Department of Chemistry, Yonsei University, Wonju 26493, Korea.
| | - Beom-Jun Kim
- Department of Chemistry, Yonsei University, Wonju 26493, Korea.
| | - Jin-Won Jeong
- Department of Chemistry, Yonsei University, Wonju 26493, Korea.
| | - Chae-Eun Jang
- Department of Chemistry, Yonsei University, Wonju 26493, Korea.
| | - Kunmo Chu
- Samsung Advanced Institute of Technology, Suwon 16678, Korea.
| | - Chan-Moon Chung
- Department of Chemistry, Yonsei University, Wonju 26493, Korea.
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Choi JY, Yu HC, Lee J, Jeon J, Im J, Jang J, Jin SW, Kim KK, Cho S, Chung CM. Preparation of Polyimide/Graphene Oxide Nanocomposite and Its Application to Nonvolatile Resistive Memory Device. Polymers (Basel) 2018; 10:E901. [PMID: 30960826 PMCID: PMC6403621 DOI: 10.3390/polym10080901] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Revised: 08/04/2018] [Accepted: 08/09/2018] [Indexed: 11/28/2022] Open
Abstract
2,6-Diaminoanthracene (AnDA)-functionalized graphene oxide (GO) (AnDA-GO) was prepared and used to synthesize a graphene oxide-based polyimide (PI-GO) by the in-situ polymerization method. A PI-GO nanocomposite thin film was prepared and characterized by infrared (IR) spectroscopy, thermogravimetric analysis (TGA) and UV-visible spectroscopy. The PI-GO film was used as a memory layer in the fabrication of a resistive random access memory (RRAM) device with aluminum (Al) top and indium tin oxide (ITO) bottom electrodes. The device showed write-once-read-many-times (WORM) characteristics with a high ON/OFF current ratio (Ion/Ioff = 3.41 × 10⁸). This excellent current ratio was attributed to the high charge trapping ability of GO. In addition, the device had good endurance until the 100th cycle. These results suggest that PI-GO is an attractive candidate for applications in next generation nonvolatile memory.
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Affiliation(s)
- Ju-Young Choi
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - Hwan-Chul Yu
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - Jeongjun Lee
- Department of Physics, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - Jihyun Jeon
- Department of Physics, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - Jaehyuk Im
- Department of Physics, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - Junhwan Jang
- Department of Physics, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - Seung-Won Jin
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - Kyoung-Kook Kim
- Department of Nano-Optical Engineering, Korea Polytechnic University, Siheung 15073, Korea.
| | - Soohaeng Cho
- Department of Physics, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - Chan-Moon Chung
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea.
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Kim DM, Cho YJ, Choi JY, Kim BJ, Jin SW, Chung CM. Low-Temperature Self-Healing of a Microcapsule-Type Protective Coating. Materials (Basel) 2017; 10:ma10091079. [PMID: 28906465 PMCID: PMC5615733 DOI: 10.3390/ma10091079] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Revised: 09/09/2017] [Accepted: 09/12/2017] [Indexed: 11/17/2022]
Abstract
Low-temperature self-healing capabilities are essential for self-healing materials exposed to cold environments. Although low-temperature self-healing concepts have been proposed, there has been no report of a microcapsule-type low-temperature self-healing system wherein the healing ability was demonstrated at low temperature. In this work, low-temperature self-healing of a microcapsule-type protective coating was demonstrated. This system employed silanol-terminated polydimethylsiloxane (STP) as a healing agent and dibutyltin dilaurate (DD) as a catalyst. STP underwent a condensation reaction at −20 °C in the presence of DD to give a viscoelastic product. The reaction behavior of STP and the viscoelasticity of the reaction product were investigated. STP and DD were separately microencapsulated by in situ polymerization and interfacial polymerization methods, respectively. The STP- and DD-loaded microcapsules were mixed into a commercial enamel paint, and the resulting formulation was applied to glass slides, steel panels, and mortars to prepare self-healing coatings. When the self-healing coatings were damaged at a low temperature (−20 °C), STP and DD were released from broken microcapsules and filled the damaged area. This process was effectively visualized using a fluorescent dye. The self-healing coatings were scratched and subjected to corrosion tests, electrochemical tests, and saline solution permeability tests. The temperature of the self-healing coatings was maintained at −20 °C before and after scratching and during the tests. We successfully demonstrated that the STP/DD-based coating system has good low-temperature self-healing capability.
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Affiliation(s)
- Dong-Min Kim
- Department of Chemistry, Yonsei University, Wonju 26493, Gangwon-do, Korea.
| | - Yu-Jin Cho
- Department of Chemistry, Yonsei University, Wonju 26493, Gangwon-do, Korea.
| | - Ju-Young Choi
- Department of Chemistry, Yonsei University, Wonju 26493, Gangwon-do, Korea.
| | - Beom-Jun Kim
- Department of Chemistry, Yonsei University, Wonju 26493, Gangwon-do, Korea.
| | - Seung-Won Jin
- Department of Chemistry, Yonsei University, Wonju 26493, Gangwon-do, Korea.
| | - Chan-Moon Chung
- Department of Chemistry, Yonsei University, Wonju 26493, Gangwon-do, Korea.
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Chung CM, van Zijl M, Keelan JA, Mol BW. Progesterone to prevent preterm birth: the studies are getting better, but there is still room for improvement. BJOG 2017; 124:1016. [PMID: 28319314 DOI: 10.1111/1471-0528.14648] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- C M Chung
- Women's and Children's Division, Northern Adelaide Local Health Network, South Australian Health, Adelaide, SA, Australia
| | - M van Zijl
- Department of Obstetrics & Gynecology, Academic Medical Center, Amsterdam, the Netherlands
| | - J A Keelan
- Discipline of Obstetrics & Gynaecology, King Edward Memorial Hospital, University of Western Australia, Perth, WA, Australia
| | - B W Mol
- The Robinson Research Institute - School of Medicine, The South Australian Health and Medical Research Institute, University of Adelaide, Adelaide, SA, Australia
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Ju H, Kim T, Chung CM, Park J, Nikawa T, Park K, Choi I. Metabolic Suppression by 3-Iodothyronamine Induced Muscle Cell Atrophy via Activation of FoxO-Proteasome Signaling and Downregulation of Akt1-S6K Signaling. Biol Pharm Bull 2017; 40:576-582. [PMID: 28163294 DOI: 10.1248/bpb.b16-00653] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The homeostasis of muscle properties depends on both physical and metabolic stresses. Whereas physical stress entails metabolic response for muscle homeostasis, the latter does not necessarily involve the former and may thus solely affect the homeostasis. We here report that metabolic suppression by the hypometabolic agent 3-iodothyronamine (T1AM) induced muscle cell atrophy without physical stress. We observed that the oxygen consumption rate of C2C12 myotubes decreased 40% upon treatment with 75 µM T1AM for 6 h versus 10% in the vehicle (dimethyl sulfoxide) control. The T1AM treatment reduced cell diameter of myotubes by 15% compared to the control (p<0.05). The cell diameter was reversed completely by 9 h after T1AM was removed. The T1AM treatment also significantly suppressed the expression levels of heat shock protein 72 and αB-crystallin as well as the phosphorylation levels of Akt1, mammalian target of rapamycin (mTOR), S6K, forkhead box O1 (FoxO1) and FoxO3. In contrast, the levels of ubiquitin E3 ligase MuRF1 and chymotrypsin-like activity of proteasome were significantly elevated by T1AM treatment. These results suggest that T1AM-mediated metabolic suppression induced muscle cell atrophy via activation of catabolic signaling and inhibition of anabolic signaling.
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Affiliation(s)
- Hyunwoo Ju
- Division of Biological Science and Technology, College of Science and Technology, Yonsei University
| | - Taewan Kim
- Division of Biological Science and Technology, College of Science and Technology, Yonsei University
| | - Chan-Moon Chung
- Department of Chemistry and Medical Chemistry, College of Science and Technology, Yonsei University
| | - Junsoo Park
- Division of Biological Science and Technology, College of Science and Technology, Yonsei University
| | - Takeshi Nikawa
- Department of Nutritional Physiology, Institute of Health Biosciences, University of Tokushima Graduate School
| | | | - Inho Choi
- Division of Biological Science and Technology, College of Science and Technology, Yonsei University
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Kim DM, Yu HC, Yang HI, Cho YJ, Lee KM, Chung CM. Microcapsule-Type Self-Healing Protective Coating for Cementitious Composites with Secondary Crack Preventing Ability. Materials (Basel) 2017; 10:ma10020114. [PMID: 28772475 PMCID: PMC5459122 DOI: 10.3390/ma10020114] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Accepted: 01/24/2017] [Indexed: 11/25/2022]
Abstract
A microcapsule-type self-healing protective coating with secondary crack preventing capability has been developed using a silanol-terminated polydimethylsiloxane (STP)/dibutyltin dilaurate (DD) healing agent. STP undergoes condensation reaction in the presence of DD to give a viscoelastic substance. STP- and DD-containing microcapsules were prepared by in-situ polymerization and interfacial polymerization methods, respectively. The microcapsules were characterized by Fourier-transform infrared (FT-IR) spectroscopy, optical microscopy, and scanning electron microscopy (SEM). The microcapsules were integrated into commercial enamel paint or epoxy coating formulations, which were applied on silicon wafers, steel panels, and mortar specimens to make dual-capsule self-healing protective coatings. When the STP/DD-based coating was scratched, self-healing of the damaged region occurred, which was demonstrated by SEM, electrochemical test, and water permeability test. It was also confirmed that secondary crack did not occur in the healed region upon application of vigorous vibration to the self-healing coating.
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Affiliation(s)
- Dong-Min Kim
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - Hwan-Chul Yu
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - Hye-In Yang
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - Yu-Jin Cho
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea.
| | - Kwang-Myong Lee
- Department of Civil and Environmental Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do 16419, Korea.
| | - Chan-Moon Chung
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 26493, Korea.
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Yu HC, Jung JW, Choi JY, Oh SY, Chung CM. Structure-property relationship study of partially aliphatic copolyimides for preparation of flexible and transparent polyimide films. Journal of Macromolecular Science, Part A 2017. [DOI: 10.1080/10601325.2016.1261622] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Hwan-Chul Yu
- Department of Chemistry, Yonsei University, Wonju, Republic of Korea
| | - Jae-Woo Jung
- Department of Chemistry, Yonsei University, Wonju, Republic of Korea
| | - Ju-Young Choi
- Department of Chemistry, Yonsei University, Wonju, Republic of Korea
| | - Se Young Oh
- Department of Chemical and Biomolecular Engineering, Sogang University, Seoul, Republic of Korea
| | - Chan-Moon Chung
- Department of Chemistry, Yonsei University, Wonju, Republic of Korea
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Abstract
Ectothermic animals rely on behavioral thermoregulation due to low capacity of heat
production and storage. Previously, lizards were shown to achieve ‘fever’ during microbial
infection by increasing their preferred body temperature (PBT) behaviorally, thereby
attaining a relatively high survival rate. The purpose of this study was to investigate
whether domesticated lizards pursued ‘behavioral hypothermia’ induced by a hypometabolic
agent 3-iodothyronamine (T1AM). We found that treatment with 8.0 mg/kg T1AM caused a
lizard species, the leopard gecko (Eublepharis macularius), to decrease
its ventilation and oxygen consumption rates 0.64- and 0.76-fold, respectively, compared
to those of the control (P<0.05). The lizards, habituated at an
ambient temperature of 30 ± 0.5°C, also showed a significant decrease in the PBT range
over a freely accessible thermal gradient between 5°C and 45°C. The upper limit of the PBT
in the treated lizards lowered from 31.9°C to 30.6°C, and the lower limit from 29.5°C to
26.3°C (P<0.001). These findings demonstrate that the treated lizards
pursued behavioral hypothermia in conjunction with hypoventilation and hypometabolism.
Because prior studies reported a similar hypometabolic response in T1AM-injected
laboratory mice, the domesticated lizards, as a part of the vertebrate phylogeny, may be a
useful laboratory model for biological and pharmacological researches such as drug potency
test.
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Affiliation(s)
- Kyoungbong Ha
- Division of Biological Science and Technology, College of Science and Technology, Yonsei University, Wonju, Gangwon-do, 26493, Republic of Korea
| | - Haksup Shin
- Division of Biological Science and Technology, College of Science and Technology, Yonsei University, Wonju, Gangwon-do, 26493, Republic of Korea
| | - Hyunwoo Ju
- Division of Biological Science and Technology, College of Science and Technology, Yonsei University, Wonju, Gangwon-do, 26493, Republic of Korea
| | - Chan-Moon Chung
- Department of Chemistry and Medical Chemistry, College of Science and Technology, Yonsei University, Wonju, Gangwon-do, 26493 Republic of Korea
| | - Inho Choi
- Division of Biological Science and Technology, College of Science and Technology, Yonsei University, Wonju, Gangwon-do, 26493, Republic of Korea
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Yang HI, Kim DM, Yu HC, Chung CM. Microcapsule-Type Organogel-Based Self-Healing System Having Secondary Damage Preventing Capability. ACS Appl Mater Interfaces 2016; 8:11070-11075. [PMID: 27070306 DOI: 10.1021/acsami.6b02118] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We have developed a novel microcapsule-type organogel-based self-healing system in which secondary damage does not occur in the healed region. A mixture of an organogelator, poor and good solvents for the gelator is used as the healing agent; when the good solvent evaporates from this agent, a viscoelastic organogel forms. The healing agent is microencapsulated with urea-formaldehyde polymer, and the resultant microcapsules are integrated into a polymer coating to prepare self-healing coatings. When the coatings are scratched, they self-heal, as demonstrated by means of corrosion testing, electrochemical testing, optical microscopy, and scanning electron microscopy (SEM). After the healed coatings are subjected to vigorous vibration, it is demonstrated that no secondary damage occurs in the healed region. The secondary damage preventing capability of the self-healing coating is attributable to the viscoelasticity of the organogel. The result can give insight into the development of a "permanent" self-healing system.
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Affiliation(s)
- Hye-In Yang
- Department of Chemistry, Yonsei University , Wonju, Gangwon-do 220-710, Republic of Korea
| | - Dong-Min Kim
- Department of Chemistry, Yonsei University , Wonju, Gangwon-do 220-710, Republic of Korea
| | - Hwan-Chul Yu
- Department of Chemistry, Yonsei University , Wonju, Gangwon-do 220-710, Republic of Korea
| | - Chan-Moon Chung
- Department of Chemistry, Yonsei University , Wonju, Gangwon-do 220-710, Republic of Korea
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Yu HC, Jung JW, Choi JY, Chung CM. Kinetic study of low-temperature imidization of poly(amic acid)s and preparation of colorless, transparent polyimide films. ACTA ACUST UNITED AC 2015. [DOI: 10.1002/pola.28013] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Hwan-Chul Yu
- Department of Chemistry; Yonsei University; Wonju Gangwon-Do 220-710 Republic of Korea
| | - Jae-Woo Jung
- Department of Chemistry; Yonsei University; Wonju Gangwon-Do 220-710 Republic of Korea
| | - Ju-Young Choi
- Department of Chemistry; Yonsei University; Wonju Gangwon-Do 220-710 Republic of Korea
| | - Chan-Moon Chung
- Department of Chemistry; Yonsei University; Wonju Gangwon-Do 220-710 Republic of Korea
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Uma Maheswara Rao K, Namkoong S, Yu HC, Park J, Chung CM, Oh SY. Green synthesis and biological evaluation of new di-α-aminophosphonate derivatives as cytotoxic agents. Arch Pharm (Weinheim) 2013; 346:851-9. [PMID: 24214666 DOI: 10.1002/ardp.201300249] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 08/19/2013] [Accepted: 08/29/2013] [Indexed: 11/10/2022]
Abstract
A series of novel di-α-aminophosphonate derivatives were synthesized by a one-pot method in the presence of PEG-H2 O under ultrasonic irradiation and were characterized by IR, (1) H NMR, (13) C NMR, mass spectrometry, and elemental analysis. The newly synthesized compounds were evaluated for their cytotoxic activities against the human lung cancer cell line H1299 and the human breast cancer cell line MCF7 in vitro by the MTT method. All compounds showed moderate cytotoxic activity on both cell lines, and compounds 4b and 4c showed marked activity.
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Affiliation(s)
| | - Guda Dinneswara Reddy
- a Department of Chemistry , Yonsei University , Wonju , Gangwon-do , 220-710 , South Korea
| | - Chan-Moon Chung
- a Department of Chemistry , Yonsei University , Wonju , Gangwon-do , 220-710 , South Korea
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Song YK, Jo YH, Lim YJ, Cho SY, Yu HC, Ryu BC, Lee SI, Chung CM. Sunlight-induced self-healing of a microcapsule-type protective coating. ACS Appl Mater Interfaces 2013; 5:1378-1384. [PMID: 23373694 DOI: 10.1021/am302728m] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Photopolymerization behavior of a methacryloxypropyl-terminated polydimethylsiloxane (MAT-PDMS) healing agent was investigated in the presence of benzoin isobutyl ether (BIE) photoinitiator by Fourier transform infrared (FT-IR) spectroscopy. MAT-PDMS and BIE were microencapsulated with urea-formaldehyde polymer. The surface and shell morphology of the microcapsules was investigated by scanning electron microscopy (SEM). Mean diameter and size distribution of the microcapsules could be controlled by agitation rate. A coating matrix formulation was prepared by sol-gel reaction of tetraethyl orthosilicate (TEOS) in the presence of a polysiloxane and by subsequent addition of an adhesion promoter. The formulation and microcapsules were mixed to give a self-healing coating formulation, which was then sprayed to surface of cellulose-fiber-reinforced-cement (CRC) board or mortar. Contact angle measurements showed that both the polymerized MAT-PDMS and the prepared coating matrix are hydrophobic, and the coating matrix has good wettability with MAT-PDMS. It was confirmed by optical microscopy and SEM that, when the self-healing coating is damaged, the healing agent is released from ruptured microcapsules and fills the damaged region. The self-healing coating was evaluated as protective coating for mortar, and it was demonstrated by water permeability and chloride ion penetration tests that our system has sunlight-induced self-healing capability. Our self-healing coating is the first example of capsule-type photoinduced self-healing system, and offers the advantages of catalyst-free, environmentally friendly, inexpensive, practical healing.
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Affiliation(s)
- Young-Kyu Song
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do 220-710, Korea
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Yu HC, Kumar SV, Choi J, Kudo K, Jang YH, Chung CM. Effect of unsymmetrical spiro dianhydride structure on properties of fully aliphatic polyimides. HIGH PERFORM POLYM 2012. [DOI: 10.1177/0954008312441641] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Structure-property relationship was studied for fully aliphatic polyimides containing alicyclic dianhydride and diamine units. Rel-(1′R,3S,5′S)-spiro[furan-3(2H),6′-[3]oxabicyclo[3.2.1]octane]-2,2′,4′,5(4H)-tetrone (DAn) was used as an unsymmetrical spiro dianhydride, and 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA) and bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BOCA) were used as symmetrical non-spiro dianhydrides. 4,4′-Methylenebis(2-methylcyclohexylamine) (MMCA) and 5-amino-1,3,3-trimethylcyclohexanemethylamine (AMCH) were N-silylated, and reacted with the dianhydrides to prepare the fully alicyclic polyimides. The formation of the polyimides was confirmed by Fourier transform infrared spectroscopy. DAn-based polyimides showed higher solubility than the polyimides derived from CPDA or BOCA. This was explained based on the results of wide-angle X-ray diffraction (WAXD) analysis of the polyimides. The WAXD study showed that DAn-based polyimides have greater full width at half maximum (FWHM) and d-spacing values than the other polyimides. This indicates that DAn-containing polyimides have lower intermolecular order, decreased intermolecular interaction, and less close chain packing compared to the other polyimides. It is considered that the morphology of DAn polyimides is attributable to the unsymmetrical spiro structure of DAn that leads to bulkiness, irregularity, and non-linearity of the polyimide chains. Decomposition temperatures of the polyimides were investigated by thermogravimetric analysis (TGA) and UV-visible spectroscopy was performed to evaluate the optical transparency of the polyimides.
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Affiliation(s)
- Hwan-Chul Yu
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do, Korea
| | - S. Vijay Kumar
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do, Korea
| | - Jiyoung Choi
- Institute of Industrial Science, The University of Tokyo, Tokyo, Japan
| | - Kazuaki Kudo
- Institute of Industrial Science, The University of Tokyo, Tokyo, Japan
| | - Yong-Hoon Jang
- School of Mechanical Engineering, Yonsei University, Seoul, Korea
| | - Chan-Moon Chung
- Department of Chemistry, Yonsei University, Wonju, Gangwon-do, Korea
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Song YK, Lee KH, Hong WS, Cho SY, Yu HC, Chung CM. Fluorescence sensing of microcracks based on cycloreversion of a dimeric anthracene moiety. ACTA ACUST UNITED AC 2012. [DOI: 10.1039/c1jm13709c] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Kim JG, Song YK, Jeon SY, Lim YJ, Ju H, Choi I, Chung CM. A New Efficient Synthetic Method for 3-Iodothyronamine and Its Potent Hypothermic Efficacy. CHINESE J CHEM 2011. [DOI: 10.1002/cjoc.201180382] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Yu HC, Kumar SV, Cho SY, Kudo K, Takayama T, Oh JM, Jung H, Kim JG, Chung CM. Preparation and characterization of nanoporous thin films from fully aliphatic polyimides. J Nanosci Nanotechnol 2011; 11:6141-6147. [PMID: 22121674 DOI: 10.1166/jnn.2011.4342] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Fully aliphatic polyimides (APIs) were prepared from rel-(1'R,3S5'S)-spiro[furan-3(2H),6'-[3]oxabicyclo[3.2.1]octane]-2,2',4',5(4H)-tetrone (DAn) as unsymmetrical spiro dianhydride, and either cis-trans-1,4-diaminocyclohexane (mix-DACH) or trans-1,4-diaminocyclohexane (trans-DACH) as diamine. Structure of all prepared monomers and polymers was confirmed via 1H-NMR and FT-IR. The solubility, optical transparency, and thermal properties of the full APIs were investigated. The solubility and decomposition temperature of the full APIs were found to be correlated with their intermolecular regularity confirmed via wide-angle X-ray diffraction (WAXD). Triblock copolyimides were synthesized through the incorporation of a thermally labile polymer, poly(propylene glycol) (PPG), into the full APIs, and their thermal properties were studied via thermogravimetric analysis (TGA). Nanoporous thin films of the full APIs were prepared via thermolysis of the labile block in the copolyimide films. Phase separation and nanopore formation in the copolymer films were confirmed via atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. Nanoporous pores were successfully prepared inside the films.
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Affiliation(s)
- Hwan-Chul Yu
- Department of Chemistry, Yonsei University, Wonju, Kangwon-do 220-710, Republic of Korea
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Kim JG, Song YK, Jo YH, Yu MR, Ju HW, Choi IH, Chung CM. A New Efficient Synthetic Method for 3-Iodothyronamine Involving Sonication and its Potent Hypothermic Efficacy. B KOREAN CHEM SOC 2011. [DOI: 10.5012/bkcs.2011.32.4.1131] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Ju H, So H, Ha K, Park K, Lee JW, Chung CM, Choi I. Sustained torpidity following multi-dose administration of 3-iodothyronamine in mice. J Cell Physiol 2011; 226:853-8. [DOI: 10.1002/jcp.22573] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Kumar SV, Yu HC, Choi J, Kudo K, Jang YH, Chung CM. Structure–property relationships for partially aliphatic polyimides. J Polym Res 2010. [DOI: 10.1007/s10965-010-9513-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Abstract
Four kinds of cinnamate-type monomers were synthesized as healing agents. Photoirradiation of the monomers gave cyclobutane-containing crosslinked polymers via [2+2] cycloaddition. Cyclobutane cleavage upon cracking of the crosslinked polymers and re-cycloaddition of the cracked polymers were investigated by FT-IR spectroscopy. Photochemical crack healing was demonstrated by measurement of flexural strength of crosslinked, cracked, and healed polymers. It was observed that microcracks with width of 200 nm to 2 microm were healed by photoirradiation.
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Affiliation(s)
- Sung-Youl Cho
- Department of Chemistry, Yonsei University, Wonju, Kangwon-do 220-710, Korea
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33
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Chung CM, Cho KW, Hong SW, Kim YJ, Chung TH. Feasibility of electroflotation to separate solids and liquid in an activated sludge process. Environ Technol 2009; 30:1565-1573. [PMID: 20184001 DOI: 10.1080/09593330903313802] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
In this study, electroflotation (EF) has been applied as a secondary clarification in the activated sludge process to improve the efficiency of the solids-liquid separation, which is essential in maintaining effluent quality. The effects of sludge settleability were examined through a series of batch and semi-continuous experiments. The results of the batch experiments revealed that thickening efficiencies using EF were 2.6 to 9.2 times higher than those with gravity settling (GS). In addition, clarification efficiencies were not significantly influenced by sludge settling properties, as compared with GS as a control. In the semi-continuous EF experiments, the concentrations of solids in the float layer were maintained above 10 g L(-1) during flotation, regardless of variations in sludge settleability. Furthermore, the volumetric gas proportion in the float layer increased as the gas to solids (G/S) ratio rose. This allowed the float layer to be more stably suspended against gravity at the top of the reactor. Based on the results obtained from these batch and semi-continuous experiments, an anoxic/oxic (AO) reactor combined with EF clarifier remained in successful continuous operation for four months. In comparison with conventional AO processes using a GS clarifier, enhanced clarification and thickening efficiencies were achieved through the EF-AO system. In addition, higher mixed liquor suspended solids concentrations (averaging 5300 mg L(-1)) in the bioreactor (EF-AO) were maintained via the return of highly concentrated sludge (averaging 16,400 mg L(-1)) from the EF clarifier. These findings suggest that EF could be a promising and effective alternative for the solids-liquid separation of poorly settling sludge.
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Affiliation(s)
- C M Chung
- Department of Civil and Environmental Engineering, Seoul National University, Seoul, Korea
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35
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Cho SY, Song YK, Kim JG, Oh SY, Chung CM. Photoconversion of o-hydroxycinnamates to coumarins and its application to fluorescence imaging. Tetrahedron Lett 2009. [DOI: 10.1016/j.tetlet.2009.06.031] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Chung CM, Man C, Jin Y, Jin C, Guan XY, Wang Q, Wan TSK, Cheung ALM, Tsao SW. Amplification and overexpression of aurora kinase A (AURKA) in immortalized human ovarian epithelial (HOSE) cells. Mol Carcinog 2005; 43:165-74. [PMID: 15880741 DOI: 10.1002/mc.20098] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Immortalization is an early and essential step of human carcinogenesis. Amplification of chromosome 20q has been shown to be a common event in immortalized cells and cancers. We have previously reported that gain and amplification of chromosome 20q is a non-random and common event in immortalized human ovarian surface epithelial (HOSE) cells. The chromosome 20q harbors genes including TGIF2 (20q11.2-q12), AIB1 (20q12), PTPN1 (20q13.1), ZNF217 (20q13.2), and AURKA (20q13.2-q13.3), which were previously reported to be amplified and overexpressed in ovarian cancers. Some of these genes may be involved in immortalization of HOSE cells and represent crucial premalignant changes in ovarian surface epithelium. Investigation of the involvement of these genes was examined in four pairs of pre-crisis (preimmortalized) and post-crisis (immortalized) HOSE cells. Overexpression of AURKA (Aurora kinase A), also known as BTAK and STK15, by both real time-quantitative polymerase chain reaction (RT-QPCR) and Western blotting was detected in all the four immortalized HOSE cells examined while overexpression of AIB1 and ZNF217 was observed in two of four immortalized HOSE cells examined. Overexpression of TGIF2 and PTPN1 was not significant in our immortalized HOSE cell systems. The degree of overexpression of AURKA was shown to be closely associated with the amplification of chromosome 20q in immortalized HOSE cells. Fluorescence in situ hybridization (FISH) with labeled P1 artificial clone (PAC) confirmed the amplification of the chromosomal region (20q13.2-13.3) where AURKA resides. DNA amplification of AURKA was also confirmed using semi-quantitative PCR. Our study showed that amplification and overexpression of AURKA is a common and significant event during immortalization of HOSE cells and may represent an important premalignant change in ovarian carcinogenesis.
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Affiliation(s)
- C M Chung
- Cancer Biology Laboratory, Department of Anatomy, Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong SAR, China
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Kim JG, Chung CM. Elution from light-cured dental composites: Comparison of trimethacrylate and dimethacrylate as base monomers. J Biomed Mater Res B Appl Biomater 2005; 72:328-33. [PMID: 15529333 DOI: 10.1002/jbm.b.30158] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The effect of the number of functional units on a monomer on the elution property of dental composites was first studied. Elution from a composite of a trifunctional methacrylate, 1,1,1-tris[4-(2'-hydroxy-3'-methacryloyloxypropoxy)phenyl]ethane (THMPE), was compared to that of bis-GMA, a typical difunctional base monomer in current dental composites. The degrees of cure and the water solubilities of composites prepared from the two kinds of methacrylates were measured. The concentration of unreacted methacrylates (base monomer and diluent) present in the photo-cured composites as well as the quantity of the methacrylates eluted into water (or 75%, volume fraction, of ethanol in water) from the composites were determined by high-performance liquid chromatography (HPLC). THMPE-based composites showed lesser amounts of residual and eluted methacrylates when compared with bis-GMA composites. This is attributed to the higher degree of functionality and larger molecular size of THMPE compared with those of bis-GMA.
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Affiliation(s)
- Joong-Gon Kim
- Biotechnology Division, Hanwha Chemical R&D Center, Taejon 305-345, Korea
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Chung CM, Kim MS, Kim JG, Jang DO. Synthesis and photopolymerization of trifunctional methacrylates and their application as dental monomers. J Biomed Mater Res 2002; 62:622-7. [PMID: 12221711 DOI: 10.1002/jbm.10359] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
1,1,1-Tris[4-(2'-hydroxy-3'-methacryloyloxypropoxy)phenyl]ethane (THMPE) and tris[4-(2'-hydroxy-3'-methacryloyloxypropoxy)phenyl]methane (THMPM) were synthesized and evaluated as base monomers in a dental composite system. The photopolymerization reactivity of the trifunctional methacrylates was similar to that of conventional 2,2-bis[4-(2'-hydroxy-3'-methacryloyloxy-propoxy)phenyl]propane (bis-GMA). Of the three monomers (THMPE, THMPM, and bis-GMA), THMPE has the greatest molecular volume, and its composite showed the lowest photopolymerization shrinkage of the composites derived from the three monomers. The water-solubility values for the light-activated composite resins formulated with THMPE and THMPM were much lower than that for a control bis-GMA composite. The trimethacrylates were not leached out into water from their corresponding photo-cured composites whereas the difunctional bis-GMA was eluted from its composite. The water sorption and flexural strength of the composite resins based on THMPE and THMPM were comparable to those of the bis-GMA composite. THMPE is promising for application as a photocurable dental monomer because of its good polymerization reactivity along with relatively low curing shrinkage and water-solubility of its photo-cured composite.
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Affiliation(s)
- Chan-Moon Chung
- Department of Chemistry, Yonsei University, Wonju, Kangwon-do 220-710, Korea.
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Abstract
Transthyretin (TTR) is a plasma protein that transports thyroid hormone and retinol binding protein-vitamin A complex. Eighty-four variants of TTR have been identified and seventy-four are associated with familial amyloidotic polyneuropathy. Normal TTR is the major protein found in the fibrillar deposits in the heart at time of autopsy of individuals with senile systemic amyloidosis. The mechanism by which normally soluble TTR deposits as organ-damaging, insoluble, pathological fibrils late in life is unknown. Understanding the mechanism of fibrillogenesis of normal TTR is critical to the design of clinical treatments aimed at retardation, prevention, or reversal of fibril deposition. We have employed a biophysical approach to explore the hypothesis that an instability in a particular secondary or tertiary structure plays a role in the ability of normal TTR to form fibrils at physiological pH. Using far UV circular dichroic (CD) spectroscopy as a function of temperature we have identified simultaneous, cooperative, reversible structural changes in the beta-sheet and alpha-helical regions. The flexible short, surface-located loops undergo an irreversible conformational change at a lower temperature. Spectra before and after heating are different, particularly in the wavelength region associated with these loops, strongly suggesting that the major portion of TTR returns to its initial conformation while the loops do not. Near UV CD reveals partially reversible and irreversible changes in tertiary structure. Using calorimetry to directly measure the enthalpy associated with these changes, two peaks are observed, with further analysis suggesting conformational intermediates. Precipitates from heated samples reveal pre-fibrillar morphology by negative stain electron microscopy. These biophysical studies suggest that heat-induced conformational rearrangements enable normal TTR to assemble into pre-fibrils at physiological pH.
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Affiliation(s)
- C M Chung
- Department of Biophysics, Boston University School of Medicine, and Boston Medical Center, 715 Albany Street, Boston, MA 02118, USA
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Moon SY, Chung CM. THREE-COMPONENT PHOTORESISTS CONTAINING VINYL ETHER CROSSLINKING AGENTS. Journal of Macromolecular Science, Part A 2001. [DOI: 10.1081/ma-100103346] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Chung CM, Kim JG, Choi JH. Photopolymerization Behavior of a Carboxylic Acid Dimetharylate and Its Application as a Dental Monomer. J PHOTOPOLYM SCI TEC 1999. [DOI: 10.2494/photopolymer.12.401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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