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Zhang S, Fu N, Cui W, Peng S, Srivatsan N, Chen Z. Probing the Saltwater Immersion Effect on Buried Interfacial Structures between a Sealant and Adhesion Promoter at the Molecular Level. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024. [PMID: 39150881 DOI: 10.1021/acs.langmuir.4c01449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/18/2024]
Abstract
In this research, we used sum frequency generation vibrational spectroscopy to investigate the buried interface of a thiol-epoxy model aerospace sealant in contact with a silane-based adhesion promoter (6111) following exposures to 3% saltwater at elevated temperatures and elevated temperatures alone. The results suggest that the saltwater caused a change at the interface between the adhesion promoter and sealant, while an elevated temperature of 60 °C itself did not affect the interfacial structure noticeably. Model hydrolyzed and nonhydrolyzed silanes were also used in the study to compare with the adhesion promoter 6111 to understand the interfacial behavior of main silane components in 6111 as well as their potential role in adhesion. The amino silane in 6111 likely segregates more at the sealant/adhesion promoter interface and interacts with the sealant compared to the vinyl silane. The results imply that the saltwater immersion process led to the disordering of the adhesion promoter/sealant interface (caused by interfacial structural randomization), which could potentially have implications for adhesion.
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Affiliation(s)
- Shuqing Zhang
- Department of Macromolecular Science and Engineering, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States
| | - Na Fu
- PPG Aerospace, 2890 W. Empire Ave, Burbank, California 91504, United States
| | - Weibin Cui
- PPG Aerospace, 2890 W. Empire Ave, Burbank, California 91504, United States
| | - Shane Peng
- PPG Aerospace, 2890 W. Empire Ave, Burbank, California 91504, United States
| | | | - Zhan Chen
- Department of Macromolecular Science and Engineering, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States
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Wang C, Ma YH, Han X, Lu X. Re-Examining Interaction between Antimicrobial Peptide Aurein 1.2 and Model Cell Membranes via SFG. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:690-699. [PMID: 36576332 DOI: 10.1021/acs.langmuir.2c03068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Aurein 1.2 (Aur), a highly efficient 13-residue antimicrobial peptide (AMP) with a broad-spectrum antibiotic activity originally derived from the Australian frog skin secretions, can nonspecifically disrupt bacterial membranes. To deeply understand the molecular-level detail of the antimicrobial mechanism, here, we artificially established comparative experimental models to investigate the interfacial interaction process between Aur and negatively charged model cell membranes via sum frequency generation vibrational spectroscopy. Sequencing the vibrational signals of phenyl, C-H, and amide groups from Aur has characteristically helped us differentiate between the initial adsorption and subsequent insertion steps upon mutual interaction between Aur and the charged lipids. The phenyl group at the terminal phenylalanine residue can act as an anchor in the adsorption process. The time-dependent signal intensity of α-helices showed a sharp rise once the Aur molecules came into contact with the negatively charged lipids, indicating that the adsorption process was ongoing. Insertion of Aur into the charged lipids then offered the detectable interfacial C-H signals from Aur. The achiral and chiral amide I signals suggest that Aur had formed β-folding-like aggregates after interacting with the charged lipids, along with the subsequent descending α-helical amide I signals. The above-mentioned experimental results provide the molecular-level detail on how the Aur molecules interact with the cell membranes, and such a mechanism study can offer the necessary support for the AMP design and later application.
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Affiliation(s)
- Chu Wang
- State Key Laboratory of Bioelectronics, School of Biomedical Engineering, Southeast University, Nanjing 210096, China
| | - Yong-Hao Ma
- State Key Laboratory of Bioelectronics, School of Biomedical Engineering, Southeast University, Nanjing 210096, China
| | - Xiaofeng Han
- State Key Laboratory of Bioelectronics, School of Biomedical Engineering, Southeast University, Nanjing 210096, China
| | - Xiaolin Lu
- State Key Laboratory of Bioelectronics, School of Biomedical Engineering, Southeast University, Nanjing 210096, China
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Du R, Li X, Ma YH, Luo Y, Wang C, Ma Q, Lu X. Exploring Interfacial Hydrolysis of Artificial Neutral Lipid Monolayer and Bilayer Catalyzed by Phospholipase C. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:8104-8113. [PMID: 35749224 DOI: 10.1021/acs.langmuir.2c00995] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Phospholipase C (PLC) represents an important type of enzymes with the feature of hydrolyzing phospholipids at the position of the glycerophosphate bond, among which PLC extracted from Bacillus cereus (BC-PLC) has been extensively studied owing to its similarity to hitherto poorly characterized mammalian analogues. This study focuses on investigating the interfacial hydrolysis mechanism of phosphatidylcholine (PC) monolayer and bilayer membranes catalyzed by BC-PLC using sum frequency generation vibrational spectroscopy (SFG-VS) and laser scanning confocal microscopy (LSCM). We found that, upon interfacial hydrolysis, BC-PLC was adsorbed onto the lipid interface and catalyzed the lipolysis with no net orientation, as evidenced by the silent amide I band, indicating that ordered PLC alignment was not a prerequisite for the enzyme activity, which is very different from what we have reported for phospholipase A1 (PLA1) and phospholipase A2 (PLA2) [Kai, S. Phys. Chem. Chem. Phys. 2018, 20(1), 63-67; Wang, F. Langmuir 2019, 35(39), 12831-12838; Zhang, F. Langmuir 2020, 36(11), 2946-2953]. For the PC monolayer, one of the two hydrolysates, phosphocholine, desorbed from the interface into the aqueous phase, while the other one, diacylglycerol (DG), stayed well packed with high order at the interface. For the PC bilayer, phosphocholine dispersed into the aqueous phase too, similar to the monolayer case; however, DG, presumably formed clusters with the unreacted lipid substrates and desorbed from the interface. With respect to both the monolayer and bilayer cases, mechanistic schematics were presented to illustrate the different interfacial hydrolysis processes. Therefore, this model experimental study in vitro provides significant molecular-level insights and contributes necessary knowledge to reveal the lipolysis kinetics with respect to PLC and lipid membranes with monolayer and bilayer structures.
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Affiliation(s)
- Rongrong Du
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, P. R. China
| | - Xu Li
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, P. R. China
| | - Yong-Hao Ma
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, P. R. China
| | - Yongsheng Luo
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, P. R. China
| | - Chu Wang
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, P. R. China
| | - Qian Ma
- Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing 210029, P. R. China
- Department of General Dentistry, Affiliated Hospital of Stomatology, Nanjing Medical University, Nanjing 210029, P. R. China
| | - Xiaolin Lu
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, P. R. China
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Lin T, Wu Y, Santos E, Chen X, Kelleher-Ferguson J, Tucker C, Ahn D, Mohler C, Chen Z. Probing Covalent Interactions at a Silicone Adhesive/Nylon Interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:2590-2600. [PMID: 35166546 DOI: 10.1021/acs.langmuir.1c03218] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Covalent bonding is one of the most robust forms of intramolecular interaction between adhesives and substrates. In contrast to most noncovalent interactions, covalent bonds can significantly enhance both the interfacial strength and durability. To utilize the advantages of covalent bonding, specific chemical reactions are designed to occur at interfaces. However, interfacial reactions are difficult to probe in situ, particularly at the buried interfaces found in well-bonded adhesive joints. In this work, sum frequency generational (SFG) vibrational spectroscopy was used to directly examine and analyze the interfacial chemical reactions and related molecular changes at buried nylon/silicone elastomer interfaces. For self-priming elastomeric silicone adhesives, silane coupling agents have been extensively used as adhesion promoters. Here with SFG, the interfacial chemical reactions between nylon and two alkoxysilane adhesion promoters with varied functionalities (maleic anhydride (MAH) and epoxy) formulated into the silicone were observed and investigated. Evidence of reactions between the organofunctional group of each silane and reactive groups on the polyamide was found at the buried interface between the cured silicone elastomer and nylon. The adhesion strength at the nylon/cured silicone interfaces was substantially enhanced with both silane additives. SFG results elucidated the mechanisms of organo-silane adhesion promotion for silicone at the molecular level. The ability to probe and analyze detailed interfacial reactions at buried nylon/silicone interfaces demonstrated that SFG is a powerful analytical technique to aid the design and optimization of materials with desired interfacial properties.
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Affiliation(s)
| | | | - Elizabeth Santos
- Dow Performance Silicones, Auburn, Michigan 48611, United States
| | - Xiaoyun Chen
- Core R&D, The Dow Chemical Company, Midland, Michigan 48674, United States
| | | | - Chris Tucker
- Core R&D, The Dow Chemical Company, Midland, Michigan 48674, United States
| | - Dongchan Ahn
- Dow Performance Silicones, Auburn, Michigan 48611, United States
| | - Carol Mohler
- Core R&D, The Dow Chemical Company, Midland, Michigan 48674, United States
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Shi L, McMillan JR, Yu D, Chen X, Tucker CJ, Wasserman E, Mohler C, Chen Z. Effect of Surfactant Concentration and Hydrophobicity on the Ordering of Water at a Silica Surface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:10806-10817. [PMID: 34455791 DOI: 10.1021/acs.langmuir.1c01731] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The performance of nonionic surfactants is mediated by the interfacial interactions at the solid-liquid interface. Here we applied sum frequency generation (SFG) vibrational spectroscopy to probe the molecular structure of the silica-nonionic surfactant solution interface in situ, supplemented by quartz crystal microbalance with dissipation monitoring (QCM-D) and molecular dynamics (MD) simulations. The combined studies elucidated the effects of nonionic surfactant solution concentration, surfactant composition, and rinsing on the silica-surfactant solution interfacial structure. The nonionic surfactants studied include ethylene-oxide (EO) and butylene oxide (BO) components with different ratios. It was found that the CH groups of the surfactants at the silica-surfactant solution interfaces are disordered, but the interfacial water molecules are ordered, generating strong SFG OH signals. Solutions with higher concentrations of surfactant lead to a slightly higher amount of adsorbed surfactant at the silica interface, resulting in more water molecules being ordered at the interface, or a higher ordering of water molecules at the interface, or both. MD simulation results indicated that the nonionic surface molecules preferentially adsorb onto silanol sites on silica. A surfactant with a higher EO/BO ratio leads to more water molecules being ordered and a higher degree of ordering of water molecules at the silica-surfactant solution interface, exhibiting stronger SFG OH signal, although less material is adsorbed according to the QCM-D data. A thin layer of surfactants remained on the silica surface after multiple water rinses. To the best of our knowledge, this is the first time the combined approaches of SFG, QCM-D and MD simulation techniques have been applied to study nonionic surfactants at the silica-solution interface, which enhances our understanding on the interfacial interactions between nonionic surfactants, water and silica. The knowledge obtained from this study can be helpful to design the optimal surfactant concentration and composition for future applications.
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Affiliation(s)
- Lirong Shi
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Janet R McMillan
- Core R&D, The Dow Chemical Company, Midland, Michigan 48674, United States
| | - Decai Yu
- Core R&D, The Dow Chemical Company, Midland, Michigan 48674, United States
| | - Xiaoyun Chen
- Core R&D, The Dow Chemical Company, Midland, Michigan 48674, United States
| | | | - Eric Wasserman
- Dow Home & Personal Care, The Dow Chemical Company, Collegeville, Pennsylvania 19426, United States
| | - Carol Mohler
- Core R&D, The Dow Chemical Company, Midland, Michigan 48674, United States
| | - Zhan Chen
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
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Zhang C, Gao J, Hankett J, Varanasi P, Kerobo CO, Zhao S, Chen Z. Interfacial Structure and Interfacial Tension in Model Carbon Fiber-Reinforced Polymers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:5311-5320. [PMID: 33880927 DOI: 10.1021/acs.langmuir.1c00403] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Carbon fiber-reinforced plastics (CFRPs) are widely used materials with outstanding mechanical properties. The wettability between the polymer matrix and carbon fiber in the interphase region significantly influences the strength of the composite. Sizing agents consisting of multiple components are therefore frequently applied to improve wetting and interfacial adhesion between polymers and carbon fiber in CFRPs. However, the complex compositions of sizing solutions make detailed interpretations of their impacts on interfacial wetting difficult. In this work, surface-sensitive sum frequency generation (SFG) spectroscopy was utilized to characterize the sizing/polymer and sizing/carbon fiber interfacial structures to gain molecular-level understandings of the wetting improvements afforded by sizing. A mixture sizing solution containing polyethylenimine (PEI, adhesion promoter) and Lutensol (surfactant) was investigated when contacting nylon (model plastics), polypropylene (model plastics), and graphite (model carbon fiber). Our results demonstrated that although the addition of the surfactant led to an interfacial tension decrease (in comparison to pure PEI solution) on nylon and polypropylene, the interfacial tension was surprisingly increased on graphite, contrasting with the commonly accepted function of surfactants. SFG characterizations revealed the multilayer molecular structures at these buried interfaces. The peculiar interfacial tension increase at the graphite/sizing interface was then correlated to the strong amine-π interactions between PEI and graphite. PEI was therefore demonstrated to be an effective adhesion promoter for carbon fiber. This article reports the first investigation of (polymer + surfactant) complex structures at solid-liquid interfaces. The valuable structural insights obtained by SFG analysis enable more accurate understandings of the composition-wettability (structure-function) relationship. These detailed understandings of interactions between sizing and the substrates promote more informed and optimized selections of sizing formulae.
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Affiliation(s)
- Chengcheng Zhang
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States
| | - Jinpeng Gao
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States
| | - Jeanne Hankett
- BASF Corporation, 1609 Biddle Avenue, Wyandotte, Michigan 48192, United States
| | - Prabodh Varanasi
- BASF Corporation, 1609 Biddle Avenue, Wyandotte, Michigan 48192, United States
| | - Charles O Kerobo
- BASF Corporation, 1609 Biddle Avenue, Wyandotte, Michigan 48192, United States
| | - Shouxun Zhao
- BASF Corporation, 1609 Biddle Avenue, Wyandotte, Michigan 48192, United States
| | - Zhan Chen
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States
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Comparing vibrational sum frequency generation responses at fused silica and fluorite/liquid ethanol interfaces. Chem Phys 2020. [DOI: 10.1016/j.chemphys.2020.110814] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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