A Review of the Properties and Applications of Poly (Methyl Methacrylate) (PMMA)

Characterization of polymethylmethacrylate microspheres loaded with silver and doxycycline for dental materials applications

OBJECTIVES

The manufacturing of polymethylmethacrylate(PMMA) microspheres loaded with doxycycline(DOX) and/or silver sulfate(Ag₂SO₄) to be incorporated into glass ionomer cement(GIC).

METHODS

PMMA microspheres were manufactured with Ag₂SO₄(1-5%) and/or DOX(5-15%). Particle size, encapsulation efficiency and drug release were measured by light microscope, ICP, and HPLC. Microspheres were added to a dental GIC(20%w/w). Drug release and DTS were investigated. Minimum inhibitory concentration and antibacterial effects of PMMA microspheres into GIC materials were tested.

RESULTS

The median diameter of 50 µm was obtained for microspheres. DOX was encapsulated at an efficiency of 8.3% using a theoretical loading of 15%DOX + 5%Ag₂SO₄. The Ag₂SO₄ encapsulation efficiency was 0.63% using a theoretical loading of 5%AgSO₄. All groups showed burst release within the first day and continued released up to 15 days, with 60-83% of DOX and approximately 30% of silver. For GIC, approximately 15% of DOX and 0.18% of silver were released in a 7-day period. Microbiological results showed an antimicrobial effect against S. mutans when the lead formulation of microspheres was added. The DTS was reduced by the inclusion of microspheres.

SIGNIFICANCE

PMMA microspheres containing DOX and Ag₂SO₄ offer a sustained antimicrobial activity for dental applications and promising potential for the biomedical field.

Energy Storage Application of All-Organic Polymer Dielectrics: A Review

With the wide application of energy storage equipment in modern electronic and electrical systems, developing polymer-based dielectric capacitors with high-power density and rapid charge and discharge capabilities has become important. However, there are significant challenges in synergistic optimization of conventional polymer-based composites, specifically in terms of their breakdown and dielectric properties. As the basis of dielectrics, all-organic polymers have become a research hotspot in recent years, showing broad development prospects in the fields of dielectric and energy storage. This paper reviews the research progress of all-organic polymer dielectrics from the perspective of material preparation methods, with emphasis on strategies that enhance both dielectric and energy storage performance. By dividing all-organic polymer dielectrics into linear polymer dielectrics and nonlinear polymer dielectrics, the paper describes the effects of three structures (blending, filling, and multilayer) on the dielectric and energy storage properties of all-organic polymer dielectrics. Based on the above research progress, the energy storage applications of all-organic dielectrics are summarized and their prospects discussed.

Influence of Geometric Parameters of Conical Acrylic Portholes on Their Stress–Strain Behaviour

Translucent elements in the form of truncated cones, which are made of organic glass, are widely used in the structures of portholes, submersible vessels, space vehicles, pressure chambers, teleboxes and other types of technical equipment. The decisive factor in designing portholes is to ensure the strength of their translucent elements. In order to reduce the weight of portholes and, accordingly, to increase the payload, it is necessary to optimise the geometric parameters of the translucent elements, which include the tapering angle and the ratio of thickness to radius of the smaller base. The paper deals with development of the applied (engineering) method for determining the stress–strain behaviour of the conical translucent elements of portholes made of organic glass under the action of a uniform hydrostatic pressure. Finite-element modelling of the translucent element of the conical porthole is performed, with the calculation of its stress–strain behaviour. External hydrostatic pressure of 10 MPa, absence of loads from the inside and continuous sliding of the translucent element with friction along the conical supporting surface of the porthole metal body are the boundary conditions for the computational model. Full-scale tests of translucent elements of portholes made of organic glass were performed under the action of uniform hydrostatic pressure. Analysis of the influence of geometric characteristics of the portholes on stress–strain behaviour showed that the increase in the tapering angle at the constant relative thickness of the translucent element reduced its axial displacement in all cases. Equivalent stresses acquire minimum values when the tapering angle is in the range from 75° to 105° (when the relative thickness increases, the optimal tapering angle becomes smaller). It is shown that the developed method for determination of the stress–strain behaviour of the conical translucent elements of portholes made of organic glass reflects the real picture of deformation and agrees with the results of full-scale tests. Results of the work allow us to choose the rational parameters of the translucent element for increasing the reliability of portholes through the creation of an effective distribution of stresses and strains in the translucent element, and improving its optical characteristics due to a relatively small deflection in operation.

Disinfection efficacy and fracture strength of PMMA denture-based polymer with chlorhexidine, PDT utilizing Rose Bengal and hematoporphyrin, and Er, Cr: YSGG laser

OBJECTIVE

The study aimed to assess and compare disinfection efficacy and fracture strength of PMMA based DBPs using chlorhexidine (CHX), PDT utilizing Rose Bengal (RB) and hematoporphyrin HPD, and Er,Cr:YSGG laser (ECL) induced antimicrobial action against in-vitro biofilms colonized with C.albicans, S.aureus, S. mutans, and E. coli.

MATERIAL AND METHODS

American Type Culture Collection (ATCC) of C.albicans, S.aureus, S. mutans and E. coli were cultured. Forty-eight PMMA-based denture base plates (DBPs) were prepared by heat-cure acrylic resin and contaminated by in-vitro biofilm under-stimulated in-vitro conditions. DBPs were treated with group1; ECL group 2; RB 5µm, group 3; HPD 500 mg/L and group 4; 0.12% CHX (controls) respectively, for the disinfection of biofilms. All photosensitizers (PS) were activated by LED at a different wavelength. Each contaminated DBP was sprayed on all its surfaces with the aforementioned photosensitizers and CHX. One-way analysis of variance (ANOVA) was used to test the efficacy of disinfection and fracture load testing. Tukey multiple comparison tests were performed to compare means of CFU/mL (log10) for exposed E. coli, C. albicans, S aureus, and S. mutans.

RESULTS

Specimens in group 1 disinfected with erbium laser, group 3 disinfected with HPD, and group 4 sterilized with chemical disinfection were effective in decreasing bacterial load CFU/mL (log10) against C.albicans, S. aureus, S.mutans, and E. Coli (p>0.05). Intergroup comparison demonstrated ECL, CHX and HPD demonstrated a comparable reduction against C.albicans and S.aureus (p>0.05). Similarly, S.mutans and E.coli were sensitive against all experimental groups (p>0.05). no significant difference in fractural load analysis among the different investigated groups was noted (p>0.05).

CONCLUSION

ECL and HPD photosensitizer revealed a significant reduction in CFU/ml of exposed viable colonies of C.albicans, S.aureus, S. mutans, and E. coli comparable to 0.12% CHX mediated disinfection of PMMA-based DBPs. Irrespective of the type of disinfection no influence of disinfection was noted on the fracture load of PMMA DBPs.

Microelectromechanical Systems Based on Magnetic Polymer Films

Microelectromechanical systems (MEMS) have been increasingly used worldwide in a wide range of applications, including high tech, energy, medicine or environmental applications. Magnetic polymer composite films have been used extensively in the development of the micropumps and valves, which are critical components of the microelectromechanical systems. Based on the literature survey, several polymers and magnetic micro and nanopowders can be identified and, depending on their nature, ratio, processing route and the design of the device, their performances can be tuned from simple valves and pumps to biomimetic devices, such as, for instance, hearth ventricles. In many such devices, polymer magnetic films are used, the disposal of the magnetic component being either embedded into the polymer or coated on the polymer. One or more actuation zones can be used and the flow rate can be mono-directional or bi-directional depending on the design. In this paper, we review the main advances in the development of these magnetic polymer films and derived MEMS: microvalve, micropump, micromixer, microsensor, drug delivery micro-systems, magnetic labeling and separation microsystems, etc. It is important to mention that these MEMS are continuously improving from the point of view of performances, energy consumption and actuation mechanism and a clear tendency in developing personalized treatment. Due to the improved energy efficiency of special materials, wearable devices are developed and be suitable for medical applications.

Fracture Behavior of Polyrotaxane-Toughened Poly(Methyl Methacrylate)

The fracture behavior of polyrotaxane (PR)-modified poly(methyl methacrylate) (PMMA) was investigated. PR is a supramolecule with rings threaded onto a linear backbone chain, which is capped by bulky end groups to prevent the rings from de-threading. The ring structure is α-cyclodextrin (CD), and it can be functionalized to enhance its affinity with the hosting polymer matrix. Adding only 1 wt % of PR containing methacrylate functional groups (mPR) at the terminal of some of the polycaprolactone-grafted chains on CD promotes massive crazing, resulting in a significant improvement in fracture toughness while maintaining the modulus and transparency of the PMMA matrix. Dynamic mechanical analysis and atomic force microscopy studies reveal that mPR strongly interact with PMMA, leading to higher molecular mobility and enhanced molecular cooperativity during deformation. This molecular cooperativity may be responsible for the formation of massive crazing in a PMMA matrix, which leads to greatly improved fracture toughness.

Reinforcing Poly(methyl methacrylate) with Bacterial Cellulose Nanofibers Chemically Modified with Methacryolyl Groups

Nanofibrillated bacterial cellulose (NFBC), a type of cellulose nanofiber biosynthesized by Gluconacetobacter sp., has extremely long (i.e., high-aspect-ratio) fibers that are expected to be useful as nanofillers for fiber-reinforced composite resins. In this study, we investigated a composite of NFBC and poly(methyl methacrylate) (PMMA), a highly transparent resin, with the aim of improving the mechanical properties of the latter. The abundant hydroxyl groups on the NFBC surface were silylated using 3-(methacryloyloxy)propyltrimethoxysilane (MPTMS), a silane coupling agent bearing a methacryloyl group as the organic functional group. The surface-modified NFBC was homogeneously dispersed in chloroform, mixed with neat PMMA, and converted into PMMA composites using a simple solvent-casting method. The tensile strength and Young’s modulus of the composite increased by factors of 1.6 and 1.8, respectively, when only 0.10 wt% of the surface-modified NFBC was added, without sacrificing the maximum elongation rate. In addition, the composite maintained the high transparency of PMMA, highlighting that the addition of MPTMS-modified NFBC easily reinforce PMMA. Furthermore, interactions involving the organic functional groups of MPTMS were found to be very important for reinforcing PMMA.

Polymethylmethacrylate nanoplastics can cause developmental malformations in early life stages of Xenopus laevis

Polymethylmethacrylate (PMMA) production has increased almost 20% over the last years. With its release into the aquatic environment, its breakdown or degradation to nano dimensions (nanoplastics-NPLs) due to biological and physical/mechanical action is, theoretically, anticipated. The occurrence of PMMA-NPLs in aquatic ecosystems may thus cause adverse effects particularly to early life stages of amphibians, which may be in contact with PMMA-NPLs suspended in the water column or deposited in upper layers of the sediments. Accordingly, this work aimed at assessing the effects of PMMA-NPLs to aquatic early life stages of the model anuran species Xenopus laevis. To attain this objective, two types of toxicity assays were carried out by exposing embryos [Nieuwkoop and Faber (NF) stage 8-11] or tadpoles (NF 45) to three concentrations of PMMA-NPLs (1, 100 and 1000 μg/L): i) 96-h embryo teratogenicity assay, where survival, malformation, and total body length (BL) of embryos were assessed; and ii) 48-h feeding rate assay, where survival, feeding (FR), malformations and growth rates (body weight-BW and BL) of tadpoles were evaluated. PMMA-NPLs exposure had no significant effects on mortality, malformations of X. laevis embryos but BL was lower at 1000 μg PMMA-NPLs/L. In tadpoles, no effects on survival or FR were observed after exposure to PMMA-NPLs, but significant changes occured in BW and BL. Moreover, anatomical changes in the abdominal region (externalization of the gut) were observed in 62.5% of the tadpoles exposed to 1000 μg PMMA-NPLs/L. Despite the lack of knowledge regarding the environmental levels of NPLs, it is expected that sediments constitute a sink for these contaminants, where they can become available for organisms that, like tadpoles, feed on the organic matter at the surface of sediments. Considering the continuous release and subsequent accumulation of PMMA, the malformations obtained in the feeding assays suggest that, in the future, these nano-polymers may constitute a risk for aquatic life stages of amphibians.

Considerations for Polymers Used in Ocular Drug Delivery

PURPOSE

Age-related eye diseases are becoming more prevalent. A notable increase has been seen in the most common causes including glaucoma, age-related macular degeneration (AMD), and cataract. Current clinical treatments vary from tissue replacement with polymers to topical eye drops and intravitreal injections. Research and development efforts have increased using polymers for sustained release to the eye to overcome treatment challenges, showing promise in improving drug release and delivery, patient experience, and treatment compliance. Polymers provide unique properties that allow for specific engineered devices to provide improved treatment options. Recent work has shown the utilization of synthetic and biopolymer derived biomaterials in various forms, with this review containing a focus on polymers Food and Drug Administration (FDA) approved for ocular use.

METHODS

This provides an overview of some prevalent synthetic polymers and biopolymers used in ocular delivery and their benefits, brief discussion of the various types and synthesis methods used, and administration techniques. Polymers approved by the FDA for different applications in the eye are listed and compared to new polymers being explored in the literature. This article summarizes research findings using polymers for ocular drug delivery from various stages: laboratory, preclinical studies, clinical trials, and currently approved. This review also focuses on some of the challenges to bringing these new innovations to the clinic, including limited selection of approved polymers.

RESULTS

Polymers help improve drug delivery by increasing solubility, controlling pharmacokinetics, and extending release. Several polymer classes including synthetic, biopolymer, and combinations were discussed along with the benefits and challenges of each class. The ways both polymer synthesis and processing techniques can influence drug release in the eye were discussed.

CONCLUSION

The use of biomaterials, specifically polymers, is a well-studied field for drug delivery, and polymers have been used as implants in the eye for over 75 years. Promising new ocular drug delivery systems are emerging using polymers an innovative option for treating ocular diseases because of their tunable properties. This review touches on important considerations and challenges of using polymers for sustained ocular drug delivery with the goal translating research to the clinic.

The Biological Effects of 3D Resins Used in Orthodontics: A Systematic Review

Three-dimensional (3D) resin medical-dental devices have been increasingly used in recent years after the emergence of digital technologies. In Orthodontics, therapies with aligners have gained popularity, mainly due to the aggressive promotion policies developed by the industry. However, their systemic effects are largely unknown, with few studies evaluating the systemic toxicity of these materials. The release of bisphenol A and other residual monomers have cytotoxic, genotoxic, and estrogenic effects. This systematic review aims to analyze the release of toxic substances from 3D resins used in Orthodontics and their toxic systemic effects systematically. The PICO question asked was, "Does the use of 3D resins in orthodontic devices induce cytotoxic effects or changes in estrogen levels?". The search was carried out in several databases and according to PRISMA guidelines. In vitro, in vivo, and clinical studies were included. The in vitro studies' risk of bias was assessed using the guidelines for the reporting of pre-clinical studies on dental materials by Faggion Jr. For the in vivo studies, the SYRCLE risk of bias tool was used, and for the clinical studies, the Cochrane tool. A total of 400 articles retrieved from the databases were initially scrutinized. Fourteen articles were included for qualitative analysis. The risk of bias was considered medium to high. Cytotoxic effects or estrogen levels cannot be confirmed based on the limited preliminary evidence given by in vitro studies. Evidence of the release of bisphenol A and other monomers from 3D resin devices, either in vitro or clinical studies, remains ambiguous. The few robust results in the current literature demonstrate the absolute need for further studies, especially given the possible implications for the young patient's fertility, which constitutes one of the largest groups of patients using these orthodontic devices.

Radical reaction extrusion copolymerization mechanism of MMA and N-phenylmaleimide and properties of products

Using the method of bulk reactive extrusion radical copolymerization, N-phenyl maleimide (N-PMI) and styrene (St) and methyl methacrylate (MMA) were copolymerized. Through multi-detection gel permeation chromatography, bulk copolymerization kinetic analysis, UV-Vis spectroscopy, elemental analysis, and ¹H NMR and ¹³C NMR analysis, it was found that, contrary to the classical free radical copolymerization theory, N-PMI and MMA could not only achieve copolymerization, but could even reach the level of azeotropic copolymerization. The factor that caused this change turned out to be the viscosity of the system. Secondly, through DSC, TG and GC-MS analysis, it was found that N-PMI units were randomly inserted into the molecular chain of PMMA, which greatly improved the stiffness of its molecular segments and the T_g of the copolymer; at the same time, the insertion of N-PMI units also very effectively blocked the zipper-style de-end group degradation that often occurs in PMMA. When the mass content of the N-PMI copolymer reached 10%, the T_g, initial degradation temperature and semi-degradation temperature of the copolymer increased by 19 °C, 58 °C and 47 °C, respectively. In addition, St, N-PMI can also significantly improve the processing fluidity of the PMMA copolymer, and after St participates were introduced in the copolymerization, the melt flow rate can be increased by 3.5 times. Furthermore, the copolymer not only had good mechanical properties and transparency, but also had excellent antibacterial properties against E. coli and S. aureus with only the effect of trace residual N-PMI in the copolymer. This provides an excellent reference for the preparation of antibacterial PMMA with high heat resistance, good mechanical properties and high transparency.

Using the method of bulk reactive extrusion radical copolymerization, N-phenyl maleimide (N-PMI) and styrene (St) and methyl methacrylate (MMA) were copolymerized.

Acrylate and Methacrylate Polymers' Applications: Second Life with Inexpensive and Sustainable Recycling Approaches

Polymers are widely employed in several fields thanks to their wide versatility and the easy derivatization routes. However, a wide range of commercial polymers suffer from limited use on a large scale due to their inert nature. Nowadays, acrylate and methacrylate polymers, which are respectively derivatives of acrylic or methacrylic acid, are among the most proposed materials for their useful characteristics like good biocompatibility, capping ability toward metal clusters, low price, potentially recyclability and reusability. Here, we discuss the advantages and challenges of this class of smart polymers focusing our attention on their current technological applications in medical, electronic, food packaging and environmental remediation fields. Furthermore, we deal with the main issue of their recyclability, considering that the current commercial bioplastics are not yet able to meet the global needs as much as to totally replace fossil-fuel-based products. Finally, the most accredited strategies to reach recyclable composites based on acrylic polymers are described.

Process Analysis of PMMA-Based Dental Resins Residues Depolymerization: Optimization of Reaction Time and Temperature

This work aims to optimize the recovery of methyl methacrylate (MMA) by depolymerization of polymethyl methacrylate (PMMA) dental resins fragments/residues. In order to pilot the experiments at technical scale, the PMMA dental resins scraps were submitted by thermogravimetric analysis (TG/DTG/DTA). The experiments were conducted at 345, 405, and 420 °C, atmospheric pressure, using a pilot scale reactor of 143 L. The liquid phase products obtained at 420 °C, atmospheric pressure, were subjected to fractional distillation using a pilot scale column at 105 °C. The physicochemical properties (density, kinematic viscosity, and refractive index) of reaction liquid products, obtained at 345 °C, atmospheric pressure, were determined experimentally. The compositional analysis of reaction liquid products at 345 °C, 30, 40, 50, 60, 70, 80, and 110 min, at 405 °C, 50, 70, and 130 min, and at 420 °C, 40, 50, 80, 100, 110, and 130 min were determined by GC-MS. The morphology of PMMA dental resins fragments before and after depolymerization was performed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDX). The experiments show that liquid phase yields were 55.50%, 48.73%, and 48.20% (wt.), at 345, 405, and 420 °C, respectively, showing a first order exponential decay behavior, decreasing with increasing temperature, while that of gas phase were 31.69%, 36.60%, and 40.13% (wt.), respectively, showing a first order exponential growth, increasing with temperature. By comparing the density, kinematic viscosity, and refractive index of pure MMA at 20 °C with those of liquid reaction products after distillation, one may compute percent errors of 1.41, 2.83, and 0.14%, respectively. SEM analysis showed that all the polymeric material was carbonized. Oxygenated compounds including esters of carboxylic acids, alcohols, ketones, and aromatics were detected by gas chromatography/mass spectrometry (GC-MS) in the liquid products at 345, 405, and 420 °C, atmosphere pressure. By the depolymerization of PMMA dental resins scraps, concentrations of methyl methacrylate between 83.454 and 98.975% (area.) were achieved. For all the depolymerization experiments, liquid phases with MMA purities above 98% (area.) were obtained between the time interval of 30 and 80 min. However, after 100 min, a sharp decline in the concentrations of methyl methacrylate in the liquid phase was observed. The optimum operating conditions to achieve high MMA concentrations, as well as elevated yields of liquid reaction products were 345 °C and 80 min.

Nanosecond-resolution photothermal dynamic imaging via MHZ digitization and match filtering

Photothermal microscopy has enabled highly sensitive label-free imaging of absorbers, from metallic nanoparticles to chemical bonds. Photothermal signals are conventionally detected via modulation of excitation beam and demodulation of probe beam using lock-in amplifier. While convenient, the wealth of thermal dynamics is not revealed. Here, we present a lock-in free, mid-infrared photothermal dynamic imaging (PDI) system by MHz digitization and match filtering at harmonics of modulation frequency. Thermal-dynamic information is acquired at nanosecond resolution within single pulse excitation. Our method not only increases the imaging speed by two orders of magnitude but also obtains four-fold enhancement of signal-to-noise ratio over lock-in counterpart, enabling high-throughput metabolism analysis at single-cell level. Moreover, by harnessing the thermal decay difference between water and biomolecules, water background is effectively separated in mid-infrared PDI of living cells. This ability to nondestructively probe chemically specific photothermal dynamics offers a valuable tool to characterize biological and material specimens.

Photothermal microscopy is limited for imaging of thermal dynamics. Here, the authors introduce a lock-in free, mid-infrared photothermal dynamic imaging system, which significantly increases SNR and imaging speed, and demonstrate metabolism analysis at single-cell level and background removal.

Implementation of Synthetic Pathways to Foster Microbe-Based Production of Non-Naturally Occurring Carboxylic Acids and Derivatives

Microbially produced carboxylic acids (CAs) are considered key players in the implementation of more sustainable industrial processes due to their potential to replace a set of oil-derived commodity chemicals. Most CAs are intermediates of microbial central carbon metabolism, and therefore, a biochemical production pathway is described and can be transferred to a host of choice to enable/improve production at an industrial scale. However, for some CAs, the implementation of this approach is difficult, either because they do not occur naturally (as is the case for levulinic acid) or because the described production pathway cannot be easily ported (as it is the case for adipic, muconic or glucaric acids). Synthetic biology has been reshaping the range of molecules that can be produced by microbial cells by setting new-to-nature pathways that leverage on enzyme arrangements not observed in vivo, often in association with the use of substrates that are not enzymes’ natural ones. In this review, we provide an overview of how the establishment of synthetic pathways, assisted by computational tools for metabolic retrobiosynthesis, has been applied to the field of CA production. The translation of these efforts in bridging the gap between the synthesis of CAs and of their more interesting derivatives, often themselves non-naturally occurring molecules, is also reviewed using as case studies the production of methacrylic, methylmethacrylic and poly-lactic acids.

The Effect of AlI3 Nanoadditive on the Thermal Behavior of PMMA Subjected to Thermoanalytical Py-GC-MS Technique

Thermal degradation of polymethylmethacrylate (PMMA) was studied by using inorganic salt of aluminum triiodide (AlI3). The composites of PMMA were prepared with AlI3 by changing the concentration of the AlI3 additive from 2% to 10% (w/w). The PMMA composites with AlI3 were characterized by TGA, DTG, SEM, FTIR, HBT, and Py-GC-MS techniques. The FTIR peaks of PMMA composite at 1316, 786, and 693 cm-1 justify the chemical association between PMMA and AlI3. TGA study shows that the stability of PMMA is enhanced by the addition of the AlI3 additive. SEM analysis represented that there is a relationship between polymer and additive when they are mixed at the molecular level. The horizontal burning test (HBT) also confirmed that the AlI3 additive produced the flame retarding properties in PMMA polymer. The burning rate of composite with 10% of AlI3 additive decreases five times as much as compared to pure PMMA polymer. Py-GC-MS analysis deduced that PMMA composite produced less toxic and environment-friendly substances (CO2) by the influence of AlI3 additive as compared to neat PMMA.

Thermal and optical properties of PMMA films reinforced with Nb2O5 nanoparticles

The article presents the thermal and physical properties of PMMA composite films with the addition of Nb2O5 nanoparticles. The addition of nanoparticles to PMMA mainly influenced the optical transmission and glass transition temperature of composite films compared to pure PMMA. It is clearly visible in the results of the conducted ellipsometric and differential scanning calorimetry tests. X-ray studies showed that the heat treatment of the samples resulted in the ordering of the polymer structure (flattening of the polymer chains). Examining the surface of the samples with scanning electron microscopy, it can be seen that Nb2O5 nanoparticles formed unusual, branched formations resembling "snowflakes".

Combining Chromatographic, Rheological, and Mechanical Analysis to Study the Manufacturing Potential of Acrylic Blends into Polyacrylic Casts

Polyacrylics have been considered for a broad range of material applications, including coatings, dental applications, and adhesives. In this experimental study, the casting potential of a group of (co)monomers belonging to the acrylic family has been explored to enable a more sustainable use of these polymer materials in the medical and veterinary science field. The individual contributions of each comonomer have been analyzed, the reaction conversion has been studied via gas chromatography (GC), the rheological behavior has been characterized via stress-controlled measurements, and the final mechanical properties have been obtained from tensile, flexure, and impact tests. The GC results allow assessing the pot life and thus the working window of the casting process. For the rheological measurements, which start from low-viscous mixtures, a novel protocol has been introduced to obtain accurate absolute data. The rheological data reflect the time dependencies of the GC data but facilitate a more direct link with the macroscopic material data. Specifically, the steep increase in the viscosity with increasing reaction time for the methyl methacrylate (MMA)/ethylene glycol dimethyl methacrylate (EGDMA) case (2% crosslinker) allows maximizing several mechanical properties: the tensile/flexure modulus, the tensile/flexure stress at break, and the impact strength. This opens the pathway to more dedicated chemistry design for corrosion casting and polyacrylic material design in general.

Electrospun Poly(methyl methacrylate)/TiO2 Composites for Photocatalytic Water Treatment

Electrospinning was successfully used for the one-step fabrication of poly(methyl methacrylate) (PMMA) fibers loaded with an inorganic photocatalyst—titanium oxide (TiO₂). By tuning the PMMA/TiO₂ ratio and the electrospinning conditions (applied voltage, needle tip-to-collector distance, and flow rates), PMMA/TiO₂ composites with selected organic/inorganic ratios, tailored designs, and targeted properties were obtained. The morphology of the electrospun composites was affected by the amount of TiO₂ incorporated into the PMMA fibers. In addition, the inorganic photocatalyst had an impact on the wettability, thermal stability, and optical properties of the electrospun composites. In particular, the surface wettability of the composites was strongly influenced by UV light irradiation and from hydrophobic became superhydrophilic. Moreover, PMMA/TiO₂ composites had enhanced tensile strength in comparison with those of bare PMMA mats. The electrospun PMMA/TiO₂ composites showed excellent photocatalytic efficiency against the model organic pollutant—methylene blue—which is very promising for the future development of membranes that are highly efficacious for photocatalytic water treatment.

Optical spectroscopy study of the interaction between curcumin and acrylic polymers

This paper presents the results of a study conducted on the interaction between curcumin, a compound with several biomedical applications in traditional and modern medicine, and the acrylic polymers poly(methyl methacrylate), poly(ethyl methacrylate), and poly(n-butyl methacrylate), through photophysical experiments in curcumin/acrylic polymers casting films. Optical absorption intensity at ~340 nm increases relatively to its maximum at ~417 nm when the amount of curcumin in the polymeric film decreases, due to a significant change in the concentration of the isomers cis- or trans-form of curcumin, regardless of the acrylic polymer. Fluorescence (FL) spectra of the films depend on the curcumin concentration in the matrix with well-resolved line shape. They show two distinct bands, one at ~525 nm, for higher curcumin concentration (5.00 mmol.L^-1), related to the aggregated curcumin species, and another at ~465 nm, for lower concentration of curcumin (0.10 mmol.L^-1), related to the effects of the solvent on the conformational structure of the curcumin molecule and the presence of the trans-form of curcumin. The parameter K_agg, related to the contribution of the aggregated curcumin, shows the influence of the polymeric lateral chain length of the matrix in the de-aggregation of the curcumin. The Huang-Rhys factor indicates that curcumin aggregated species are conformationally more stable, and that the isolate species depends on the chemical environment and the matrix/curcumin interaction, decreasing its conformational degrees of freedom. Arrhenius plots, obtained via FL experiment in function of the sample temperature, show that, for higher curcumin concentration, the value for the relaxation energy process is not well defined, due the decrease in the interaction between the matrix and the curcumin molecules. With these results, it is possible to infer that the interaction matrix/curcumin must occur via lateral chemical alkyl groups.

Evaluation of microplastics ingested by sea cucumber Stichopus horrens in Pulau Pangkor, Perak, Malaysia

The widespread presence of microplastics has caused significant concerns on their potential effects on marine ecosystems. Microplastics are classified as plastic products of less than 5 mm in size and are known to be one of the most dangerous aquatic debris to marine species. Sea cucumbers are deposit feeders living in sediment regions and benthic zone that may collect microplastics in low-energy environments. This research aims to evaluate the types of microplastic isolated from the intestine of Stichopus horrens in Malaysia. This species is selected because it is mainly found in this island. Pulau Pangkor is one of the leading tourism destinations on the small islands is facing increasing numbers of tourists and development and it is useful for sustainable study. A total of 20 S. horrens samples collected from Pulau Pangkor, Malaysia were dissected, and their intestines were collected for digestion. Microplastics were extracted using NaOH and filtered using filter paper. Microplastic identification was conducted on the based of the physical characteristics (colour, shape, size) and chemical characterisation was evaluated using FTIR for polymer functional groups. A total of 1446 unit of microplastics were found in S. horrens. Among various types and colours, fibre (90%) and black (59%) were dominant amongst the various particles identified. The majority of microplastics sizes were 0.51 μm and 1-2 μm. Two polymer materials were identified, namely polyethylene and poly(methyl methacrylate). As a conclusion, the findings of the study will serve as primary data for pollution indicators in respective islands. The microplastics could impact the immune system and upset gut's balance of human.

Production of photoluminescent transparent poly(methyl methacrylate) for smart windows

Photochromic and long-lasting photoluminescent transparent, rigid, ultraviolet (UV) protective and superhydrophobic poly(methyl methacrylate) (PMMA) plastic able to switch colour beneath UV irradiation was developed. Photoluminescent transparent PMMA plastic was prepared by the simple polymerization process of methyl methacrylate immobilized with alkaline earth aluminate (AEA) nanoparticles. These colourless PMMA plastic substrates showed a colour switch to greenish underneath UV light as proved using CIELAB screening. The morphology of AEA was evaluated using transmission electron microscopy. Conversely, transparent PMMA samples were evaluated using energy-dispersive X-ray spectra, scanning electron microscope, X-ray fluorescence spectroscopy and for hardness properties. Additionally, the photoluminescence properties were explored by studying excitation and emission spectra. The produced luminescence colourless PMMA plastic substrates displayed excitation band at 370 nm, and three emission peaks at 433, 494 and 513 nm. Photoluminescent PMMA with lower contents of AEA showed fast and reversible photochromism under UV light, while PMMA samples with higher contents of AEA showed long-lasting luminescence such as a flashlight with the ability to replace electric power. The findings showed that the produced photoluminescence colourless PMMA plastic substrates exhibited enhanced UV shielding and superhydrophobicity.

MechaTag: A Mechanical Fiducial Marker and the Detection Algorithm

Fiducial markers are fundamental components of many computer vision systems that help, through their unique features (e.g., shape, color), a fast localization of spatial objects in unstructured scenarios. They find applications in many scientific and industrial fields, such as augmented reality, human-robot interaction, and robot navigation. In order to overcome the limitations of traditional paper-printed fiducial markers (i.e. deformability of the paper surface, incompatibility with industrial and harsh environments, complexity of the shape to reproduce directly on the piece), we aim at exploiting existing, or additionally fabricated, structural features on rigid bodies (e.g., holes), developing a fiducial mechanical marker system called MechaTag. Our system, endowed with a dedicated algorithm, is able to minimize recognition errors and to improve repeatability also in case of ill boundary conditions (e.g., partial illumination). We assess MechaTag in a pilot study, achieving a robustness of fiducial marker recognition above 95% in different environment conditions and position configurations. The pilot study was conducted by guiding a robotic platform in different poses in order to experiment with a wide range of working conditions. Our results make MechaTag a reliable fiducial marker system for a wide range of robotic applications in harsh industrial environments without losing accuracy of recognition due to the shape and material.

Cytocompatibility of Polymethyl Methacrylate Honeycomb-like Pattern on Perfluorinated Polymer

In this study, we present a simple approach for developing a biocompatible polymer scaffold with a honeycomb-like micropattern. We aimed to combine a plasma treatment of fluorinated ethylene propylene (FEP) substrate with an improved phase separation technique. The plasma exposure served for modification of the polymer surface properties, such as roughness, surface chemistry, and wettability. The treated FEP substrate was applied for the growth of a honeycomb-like pattern from a solution of polymethyl methacrylate (PMMA). The properties of the pattern were strongly dependent on the conditions of plasma exposure of the FEP substrate. The physico-chemical properties of the prepared pattern, such as changes in wettability, aging, morphology, and surface chemistry, were determined. Further, we have examined the cellular response of human osteoblasts (U-2 OS) on the modified substrates. The micropattern prepared with a selected combination of surface activation and amount of PMMA for honeycomb construction showed a positive effect on U-2 OS cell adhesion and proliferation. Samples with higher PMMA content (3 and 4 g) formed more periodic hexagonal structures on the surface compared to its lower amount (1 and 2 g), which led to a significant increase in the pattern cytocompatibility compared to pristine or plasma-treated FEP.

Overview on immobilization of enzymes on synthetic polymeric nanofibers fabricated by electrospinning

The arrangement and type of support has a significant impact on the efficiency of immobilized enzymes. 1-dimensional fibrous materials can be one of the most desirable supports for enzyme immobilization. This is due to their high surface area to volume ratio, internal porosity, ease of handling, and high mechanical stability, all of which allow a higher enzyme loading, release and finally lead to better catalytic efficiency. Fortunately, the enzymes can reside inside individual nanofibers to remain encapsulated and retain their three-dimensional structure. These properties can protect the enzyme's tolerance against harsh conditions such as pH variations and high temperature, and this can probably enhance the enzyme's stability. This review article will discuss the immobilization of enzymes on synthetic polymers, which are fabricated into nanofibers by electrospinning. This technique is rapidly gaining popularity as one of the most practical ways to fibricate polymer, metal oxide, and composite micro or nanofibers. As a result, there is interest in using nanofibers to immobilize enzymes. Furthermore, present research on electrospun nanofibers for enzyme immobilization is primarily limited to the lab scale and industrial scale is still challanging. The primary future research objectives of this paper is to investigate the use of electrospun nanofibers for enzyme immobilization, which includes increasing yield to transfer biological products into commercial applications.

A Review of Capillary Pressure Control Valves in Microfluidics

Microfluidics offer microenvironments for reagent delivery, handling, mixing, reaction, and detection, but often demand the affiliated equipment for liquid control for these functions. As a helpful tool, the capillary pressure control valve (CPCV) has become popular to avoid using affiliated equipment. Liquid can be handled in a controlled manner by using the bubble pressure effects. In this paper, we analyze and categorize the CPCVs via three determining parameters: surface tension, contact angle, and microchannel shape. Finally, a few application scenarios and impacts of CPCV are listed, which includes how CPVC simplify automation of microfluidic networks, work with other driving modes; make extensive use of microfluidics by open channel, and sampling and delivery with controlled manners. The authors hope this review will help the development and use of the CPCV in microfluidic fields in both research and industry.

Simple and facile carbon dots based electrochemical biosensor for TNF-α targeting in cancer patient's sample

Tumour Necrosis Factor (TNF-α) is a pro-inflammatory cytokine having key roles in cell death, differentiation, survival, proliferation, migration and is a modulator of immune system. Therefore, TNF-α is an ideal biomarker for several disease diagnosis including cancer. However, out of all the biomarkers of cancer, TNF-α) is less explored for cancer detection. Only a few reports are available of developing biosensors for TNF-α targeting in human serum samples. Also, Carbon Dots (CDs) remains less explored in biosensor application. In this regard, for the first time, a sensitive and low-cost electrochemical biosensor based on CDs has developed. CDs were synthesized by simple yet facile microwave pyrolysis. Poly methyl methacrylate (PMMA) was selected as the matrix to hold CDs to fabricate the biosensing platform. This novel CD-PMMA nanocomposite featuring excellent biocompatibility, exceptional electrocatalytic conductivity, and large surface area. CD-PMMA was applied as transducing material to efficiently conjugate antibodies specific towards TNF-α and fabricate electrochemical immunosensor for specific detection of TNF-α. The fabricated immunosensor was used for the detection of TNF-α within a wide dynamic range of 0.05-160 pg mL^-1 with a lower detection limit of 0.05 pg mL^-1 and sensitivity of 5.56 pg mL^-1 cm^-2. Furthermore, this CDs based immunosensor retains high sensitivity, selectivity, and stability. This immunosensor demonstrated a high correlation with the conventional technique, Enzyme-Linked Immunosorbent Assay for early screening of cancer patient serum samples.

Fixation of Transparent Bone Pins with Photocuring Biocomposites

Bone fractures are in need of rapid fixation methods, but the current strategies are limited to metal pins and screws, which necessitate secondary surgeries upon removal. New techniques are sought to avoid surgical revisions, while maintaining or improving the fixation speed. Herein, a method of bone fixation is proposed with transparent biopolymers anchored in place via light-activated biocomposites based on expanding CaproGlu bioadhesives. The transparent biopolymers serve as a UV light guide for the activation of CaproGlu biocomposites, which results in evolution of molecular nitrogen (from diazirine photolysis), simultaneously expanding the covalently cross-linked matrix. Osseointegration additives of hydroxyapatite or Bioglass 45S5 yield a biocomposite matrix with increased stiffness and pullout strength. The structure-property relationships of UV joules dose, pin diameter, and biocomposite additives are assessed with respect to the apparent viscosity, shear modulus, spatiotemporal pin curing, and lap-shear adhesion. Finally, a model system is proposed based on ex vivo investigation with bone tissue for the exploration and optimization of UV-active transparent biopolymer fixation.

Interconvertible Living Radical and Cationic Polymerization using a Dual Photoelectrochemical Catalyst

The necessity of well-tuned reactivity for successful controlled polymer synthesis often comes with the price of limited monomer substrate scope. We demonstrate here the on-demand interconversion between living radical and cationic polymerization using two orthogonal stimuli and a dual responsive single catalyst. The dual photo- and electrochemical reactivity of 10-phenylphenothiazine catalyst provides control of the polymer's molar mass and composition by orthogonally activating the common dormant species toward two distinct chemical routes. This enables the synthesis of copolymer chains that consist of radically and cationically polymerized segments where the length of each block is controlled by the duration of the stimulus exposure. By alternating the application of photochemical and electrochemical stimuli, the on-demand incorporation of acrylates and vinyl ethers is achieved without compromising the end-group fidelity or dispersity of the formed polymer. The results provide a proof-of-concept for the ability to substantially extend substrate scope for block copolymer synthesis under mild, metal-free conditions through the use of a single, dual reactive catalyst.

Plastics in biosolids from 1950 to 2016: A function of global plastic production and consumption

Plastics are ubiquitous contaminants that leak into the environment from multiple pathways including the use of treated sewage sludge (biosolids). Seven common plastics (polymers) were quantified in the solid fraction of archived biosolids samples from Australia and the United Kingdom from between 1950 and 2016. Six plastics were detected, with increasing concentrations observed over time for each plastic. Biosolids plastic concentrations correlated with plastic production estimates, implying a potential link between plastics production, consumption and leakage into the environment. Prior to the 1990s, the leakage of plastics into biosolids was limited except for polystyrene. Increased leakage was observed from the 1990s onwards; potentially driven by increased consumption of polyethylene, polyethylene terephthalate and polyvinyl chloride. We show that looking back in time along specific plastic pollution pathways may help unravel the potential sources of plastics leakage into the environment and provide quantitative evidence to support the development of source control interventions or regulations.

FECO fringes for investigating the effect of grafting process on the dispersion properties of polyamaide-6 fibers

Polyamide-6 fiber was modified by grafting it with poly(methyl methacrylate) PMMA polymer. The grafting process is widely used in industry to introduce new properties and overcome some obstacles, for instance, in storing energy applications. Multiple-beam interference techniques are very precise techniques to characterize the different properties of polymeric fibers. Fringes of equal chromatic order FECO technique was used to study the effect of grafting process on the dispersion properties of polyamides fibers. A mechanical drawing device was attached to the FECO system to evaluate the mechanical deformation impact on the samples and on their dispersion properties. The dispersion properties were evaluated by measuring their refractive indices, Cauchy's constants, average excitation energy, dispersion energy, lattice energy, interband oscillator wavelength, static dielectric constant, and Abbe's dispersion number. The results show that grafting polyamide-6 with PMMA produced a new material with a different structure and different dispersion properties. Microinterferograms, graphs and tables were given for illustrations.

An Energy Efficient Thermally Regulated Optical Spectroscopy Cell for Lab-on-Chip Devices: Applied to Nitrate Detection

Reagent-based colorimetric analyzers often heat the fluid under analysis for improved reaction kinetics, whilst also aiming to minimize energy use per measurement. Here, a novel method of conserving heat energy on such microfluidic systems is presented. Our design reduces heat transfer to the environment by surrounding the heated optical cell on four sides with integral air pockets, thereby realizing an insulated and suspended bridge structure. Our design was simulated in COMSOL Multiphysics and verified in a polymethyl methacrylate (PMMA) device. We evaluate the effectiveness of the insulated design by comparing it to a non-insulated cell. For temperatures up to 55 °C, the average power consumption was reduced by 49.3% in the simulation and 40.2% in the experiment. The designs were then characterized with the vanadium and Griess reagent assay for nitrate at 35 °C. Nitrate concentrations from 0.25 µM to 50 µM were tested and yielded the expected linear relationship with a limit of detection of 20 nM. We show a reduction in energy consumption from 195 J to 119 J per 10 min measurement using only 4 µL of fluid. Efficient heating on-chip will have broad applicability to numerous colorimetric assays.

Additive Effects of Lithium Salts with Various Anionic Species in Poly (Methyl Methacrylate)

We report that lithium salts in lithium-ion batteries effectively modify the physical properties of poly (methyl methacrylate) (PMMA). The glass transition temperature (T_g) is an indicator of the heat resistance of amorphous polymers. The anionic species of the salts strongly affected the glass transition behavior of PMMA. We focused on the additive effects of various lithium salts, such as LiCF₃SO₃, LiCOOCF₃, LiClO₄, and LiBr, on the T_g of PMMA. The large anions of the former three salts caused them to form macroscopic aggregates that acted as fillers in the PMMA matrix and to combine the PMMA domains, increasing T_g. On the other hand, LiBr salts dispersed microscopically in the PMMA matrix at the molecular scale, leading to the linking of the PMMA chains. Thus, the addition of LiBr to PMMA increased T_g as well as the relaxation time in the range of glass to rubber transition.

Synthesis and Study of the Optical Properties of PMMA Microspheres and Opals

Polymethylmethacrylate (PMMA) microspheres were synthesized by surfactant-free emulsion polymerization. These microspheres were used to obtain opals by the self-assembly method. Monomer and initiator quantities were varied systematically to monitor the size of PMMA microspheres. From SEM and DLS measurements, a trend was observed showing as the monomer and initiator amounts increased the average diameter of PMMA microspheres increased except when a minimum monomer amount was reached, for which the size of the microspheres remained practically constant. Diffuse reflectance spectra were processed by the Kubelka–Munk treatment to estimate the energy band gap (E_g) of the PMMA microspheres. It was found that PMMA microspheres present an indirect transition. From SEM micrographs, it is seen that PMMA opals photonic crystals are formed by microspheres in a uniform periodic face-centered cubic (fcc) array. Variable-angle specular reflectance spectra show that the opals possess a pseudo photonic band gap (PBG) in the visible and near-IR regions. Furthermore, it was found that PBGs shift towards larger wavelengths as the average diameter of the PMMA microspheres increases.

Biological Treatments for Temporomandibular Joint Disc Disorders: Strategies in Tissue Engineering

The temporomandibular joint (TMJ) is an important structure for the masticatory system and the pathologies associated with it affect a large part of the population and impair people's lifestyle. It comprises an articular disc, that presents low regeneration capacities and the existing clinical options for repairing it are not effective. This way, it is imperative to achieve a permanent solution to guarantee a good quality of life for people who suffer from these pathologies. Complete knowledge of the unique characteristics of the disc will make it easier to achieve a successful tissue engineering (TE) construct. Thus, the search for an effective, safe and lasting solution has already started, including materials that replace the disc, is currently growing. The search for a solution based on TE approaches, which involve regenerating the disc. The present work revises the TMJ disc characteristics and its associated diseases. The different materials used for a total disc replacement are presented, highlighting the TE area. A special focus on future trends in the field and part of the solution for the TMJ problems described in this review will involve the development of a promising engineered disc approach through the use of decellularized extracellular matrices.

Toward Development of a Label-Free Detection Technique for Microfluidic Fluorometric Peptide-Based Biosensor Systems

The problems of chronic or noncommunicable diseases (NCD) that now kill around 40 million people each year require multiparametric combinatorial diagnostics for the selection of effective treatment tactics. This could be implemented using the biosensor principle based on peptide aptamers for spatial recognition of corresponding protein markers of diseases in biological fluids. In this paper, a low-cost label-free principle of biomarker detection using a biosensor system based on fluorometric registration of the target proteins bound to peptide aptamers was investigated. The main detection principle considered includes the re-emission of the natural fluorescence of selectively bound protein markers into a longer-wavelength radiation easily detectable by common charge-coupled devices (CCD) using a specific luminophore. Implementation of this type of detection system demands the reduction of all types of stray light and background fluorescence of construction materials and aptamers. The latter was achieved by careful selection of materials and design of peptide aptamers with substituted aromatic amino acid residues and considering troponin T, troponin I, and bovine serum albumin as an example. The peptide aptamers for troponin T were designed in silico using the «Protein 3D» (SPB ETU, St. Petersburg, Russia) software. The luminophore was selected from the line of ZnS-based solid-state compounds. The test microfluidic system was arranged as a flow through a massive of four working chambers for immobilization of peptide aptamers, coupled with the optical detection system, based on thick film technology. The planar optical setup of the biosensor registration system was arranged as an excitation-emission cascade including 280 nm ultraviolet (UV) light-emitting diode (LED), polypropylene (PP) UV transparent film, proteins layer, glass filter, luminophore layer, and CCD sensor. A laboratory sample has been created.

Synthesis and Conductivity Studies of Poly(Methyl Methacrylate) (PMMA) by Co-Polymerization and Blending with Polyaniline (PANi)

Poly(methyl methacrylate) (PMMA) is a lightweight insulating polymer that possesses good mechanical stability. On the other hand, polyaniline (PANi) is one of the most favorable conducting materials to be used, as it is easily synthesized, cost-effective, and has good conductivity. However, most organic solvents have restricted potential applications due to poor mechanical properties and dispersibility. Compared to PANi, PMMA has more outstanding physical and chemical properties, such as good dimensional stability and better molecular interactions between the monomers. To date, many research studies have focused on incorporating PANi into PMMA. In this review, the properties and suitability of PANi as a conducting material are briefly reviewed. The major parts of this paper reviewed different approaches to incorporating PANi into PMMA, as well as evaluating the modifications to improve its conductivity. Finally, the polymerization condition to prepare PMMA/PANi copolymer to improve its conductivity is also discussed.

On Concept of Hybrid in Colloid Sciences

The concepts hybrid and hybridization are common in many scientific fields, as in the taxonomic parts of botany and zoology, in modern genetic, and in the quantum–mechanical theory of atomic–molecular orbitals, which are of foremost relevance in most aspects of modern chemistry. Years later, scientists applied the concept hybrid to colloids, if the particles’ domains are endowed with functionalities differing each from the other in nature and/or composition. For such denomination to be fully valid, the domains belonging to a given hybrid must be recognizable each from another in terms of some intrinsic features. Thus, the concept applies to particles where a given domain has its own physical state, functionality, or composition. Literature examples in this regard are many. Different domains that are present in hybrid colloids self-organize, self-sustain, and self-help, according to the constraints dictated by kinetic and/or thermodynamic stability rules. Covalent, or non-covalent, bonds ensure the formation of such entities, retaining the properties of a given family, in addition to those of the other, and, sometimes, new ones. The real meaning of this behavior is the same as in zoology; mules are pertinent examples, since they retain some features of their own parents (i.e., horses and donkeys) but also exhibit completely new ones, such as the loss of fertility. In colloid sciences, the concept hybrid refers to composites with cores of a given chemical type and surfaces covered by moieties differing in nature, or physical state. This is the result of a mimicry resembling the ones met in a lot of biological systems and foods, too. Many combinations may occur. Silica nanoparticles on which polymers/biopolymers are surface-bound (irrespective of whether binding is covalent or not) are pertinent examples. Here, efforts are made to render clear the concept, which is at the basis of many applications in the biomedical field, and not only. After a historical background and on some features of the species taking part to the formation of hybrids, we report on selected cases met in modern formulations of mixed, and sometimes multifunctional, colloid entities.