Polymer International最新文献

Melanins are macromolecular pigments widely spread in many living organisms, with unique physical and chemical properties. Specifically, their conductive properties have drawn attention for applications in different devices; however, the electrochemical response is equally necessary for designing technologies in sustainable bioelectronics. In this sense, we report a comparative study of the redox electrochemical properties of non-functionalized and sulfonated melanins in different pH environments. The electrochemical response was investigated using cyclic voltammetry, electrochemical impedance spectroscopy, dielectric permittivity and AC/DC conductivity at pH 3, 5 and 7. The voltammetric currents were higher at low pH, in agreement with the known proton transport properties of melanins. The effect of pH on electrochemical properties was slightly more significant in non-functionalized pigments. Melanins with a higher 5,6-dihydroxyindole carboxylic acid/5,6-dihydroxyindole ratio showed high DC current and low impedance. No significant difference was observed in the dielectric relaxation process between the different samples. © 2024 Society of Chemical Industry.

Stretchable electrodes are essential parts for flexible electronics which are widely applied in human health monitoring, wearable electronics, robotics etc. Conductive elastomer composites are good candidates for stretchable electrodes; however, it is a challenge to maintain the resistance of conductive elastomer composites during elongation due to the departure of filler networks. In this work, highly stretchable and conductive polydimethylsiloxane (PDMS)/nickel-coated graphite (NCG) composites were fabricated based on the filler sedimentation method, in which NCG was modified by the coupling agent of the end alkyl group (dodecyltriethoxysilane, DTES) and end vinyl group (vinyltriethoxysilane, VTEO), considering the force between the filler networks and filler–matrix interface. The DTES modified NCG mainly improved the filler–matrix interface, which made the resistance of the composites clearly increase with strain, while the VTEO mainly heightened the NCG networks and made the resistance of the composites insensitive to a strain of 114% when the NCG content was 23.1 wt%. These quite interesting results are closely related to the force between the filler networks and filler–matrix interface during strain and they were proved in detail through the mechanical and electrical hysteresis performance. This work presents a facile method from the concept of stability of filler networks during strain to prepare highly stretchable and conductive composites. © 2024 Society of Chemical Industry.

Current ionic polymer–metal composite (IPMC) actuators have severe actuation drawbacks (i.e. low force output and poor stability), hampering their applications. To address these issues, poly(ethylene glycol)-grafted graphene oxide (PEG-GO) is synthesized and incorporated into a Nafion matrix, thus producing a PEG-GO hybrid Nafion film with better physiochemical properties for fabricating a high-performance, low-cost IPMC actuator. The modification of PEG to GO not only prevents GO agglomeration and sedimentation, but also avoids loss of PEG in water. Driven by a 0.2 Hz, 2.5 V electric field, the hybrid IPMC actuator exhibits superior electromechanical behaviors, i.e. a swing angle of 110.3°, a blocking force of 6.89 mN and a stable working time of 485 s, respectively increasing by 92%, 209% and 294% when compared to a pure Nafion actuator. © 2024 Society of Chemical Industry.

Modern society relies heavily on producing commercial and industrial plastics to improve the quality and quantity of our lives. However, increased fire risks threaten commercial operations and the potential impact of high-performance electronic and transportation technologies that utilize polymeric materials. Despite significant monitoring and reduction of commonly used halogenated flame retardants, their worldwide usage still poses environmental hazards. Many non-halogenated flame-retardant compounds are viable additives for synthetic polymers; however, their incorporation often results in reduced composite homogeneity and mechanical strength. This review focuses on reactive flame retardants and the effect of polymer structure on inherent flame retardance in recent studies. The synthesis and characterization of polymeric systems (e.g. polyurethanes, polyamides, polyimides, polyesters and epoxy resins) are discussed in terms of structure–flame-retardant performance using a complement of analytical tools, including thermogravimetric analysis, cone calorimetry, limiting oxygen index and UL 94 testing. These commercially important polymeric systems represent a broad compositional space for future adaptation and the discovery of increasingly modular polymeric materials with, while also contributing to the fundamental understanding of unique combinations of gas- and condensed-phase mechanisms of flame retardance. © 2024 Society of Chemical Industry.

Polyurea (PU) elastomers have attracted considerable attention in the field of protective polymeric coatings. In this work, a dithiol-terminated boronic ester was synthesized and used to incorporate dynamic boron–oxygen (B–O) bonds in the PU main chain based on thiol isocyanate while amino-terminated polydimethylsiloxane (PDMS) was introduced to retain good chain flexibility. The modified PU elastomer was found to have a microphase-separated structure in which the hard blocks served as physical crosslinks. The glass transition temperature (T_g) slightly increases when dynamic B–O bonds exist while further introduction of PDMS soft segment can lower T_g to −55.63 °C. The introduction of dynamic B–O bonds and diminished hydrogen bonding led to a decrease in mechanical strength and elongation at break. Interestingly, the simultaneous incorporation of PDMS and dynamic B–O bonds is favorable for strain rate dependence and suppressing stress relaxation. The potential for bond-exchange interactions between the dynamic B–O bonds and hydroxyl groups on metal surfaces substantially improved the adhesion of the PU elastomer to metal substrates. Therefore, our work can offer valuable insights for the structural design of functional PU coatings tailored for anti-impact applications. © 2024 Society of Chemical Industry.

The development of biobased and functionalized monomers along with eco-friendly photopolymerization processes represent promising methods for the development of renewable and more environmentally friendly thermosets. Thiol–ene ‘click’ photopolymerization is particularly advantageous in this regard; however, the materials derived from this method often exhibit low glass transition temperatures (T_g) and unsuitable thermomechanical properties for applications at room temperature. Herein, we report the synthesis of biobased allyl derivatives from quercetin, a renewable flavonoid compound widely available in fruits, vegetables and plants. We demonstrated the isolation of tetra- and penta-allylated quercetin (Q1 and Q2, respectively) and their subsequent photoactivated thiol–ene polymerization. By introducing a biobased thiol curing agent (PTTMP) derived from glycerol and mercaptopropionic acid, we produced fully biobased crosslinked thermosets with high content of aromatic moieties provided by the framework of the monomers. Real-time infrared spectroscopy showed the effective thiol–ene photopolymerization of Q1 and Q2 and PTTMP with conversions of 60% and 75%, respectively, after 15 min of UV irradiation. Due to the modulated crosslinking degree from the allyl group functionalization in the monomers, the biobased crosslinked networks showed storage moduli from 420 to 739 MPa, thermal stability from 220 to 257 °C and T_g values ranging from 75 to 90 °C. This work outlines straightforward strategies for creating biobased thermosets that overcome the limited thermomechanical properties of thiol–ene networks and offer potential antimicrobial and antioxidant properties. © 2024 Society of Chemical Industry.

Myocardial infarction is one of the main causes of death worldwide. After myocardial infarction, the damaged area is typically occupied with non-contractile scar tissue owing to the limited ability of cardiac cells to proliferate. Cardiac patches can potentially restore heart function by providing sufficient electrochemical properties to the damaged area and supporting the differentiation into and proliferation of cardiac cells. In this study, we developed for the first time a poly(mannitol sebacate) (PMS) based scaffold combined with 1% (w/w)multi-walled carbon nanotubes (MWCNTs) to produce a biocompatible cardiac patch by the solvent casting method. We characterized the resultant PMS-MWCNT scaffold in terms of chemical, physical, mechanical and electrical properties. The PMS/MWCNT patch revealed appropriate hydrophilicity, elasticity close to that of the target tissue, and electrical conductivity suited for a cardiac patch. The cytocompatibility of the composite was confirmed by the successful attachment and proliferation of human umbilical cord mesenchymal stem cells (HUC-MSCs). The PMS/MWCNTs further contributed to the differentiation of HUC-MSCs by significant overexpression of cardiac-specific proteins, i.e. troponin T and connexin 43, in the presence of 5-azacytidine. The findings of this study could be of assistance in the use and development of PMS-based composites as cardiac patches for myocardial tissue engineering applications. © 2024 Society of Chemical Industry.

Uniform octahedral Ag₂O nanoparticles were in situ synthesized within natural bacterial cellulose (BC) films without any inorganic alkali. The morphological transformation of Ag₂O from nanoparticles and small nanoplates to an octahedral structure was well controlled by varying the UV exposure time. To reduce and anchor Ag₂O nanoparticles, abundant hydroxyl groups on the surface of natural BC fibers ensured an ideal environment for the mild redox reaction between Ag⁺ and –OH groups. The structural features and structure–activity relationship of Ag₂O/BC films were confirmed through TEM, energy dispersive spectroscopy assisted SEM analysis, Fourier transform IR, X-ray photoelectron spectroscopy, TGA and XRD. The structure–antibacterial activity relationship of the Ag₂O/BC films was proved against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. They also showed excellent performance in the photocatalytic degradation of organic dyes. Ag₂O/BC films have potential bactericidal applications in the field of pharmacy, specifically for wound dressing and flexible wearable materials. © 2024 Society of Chemical Industry.

Crosslinked polymers are considered to be promising materials for supporting catalysts that are effectively applied in different reactions. However, the application of polymer-supported catalysts in high-temperature processes is limited by their temperature stability. Besides thermal degradation, temperature changes can cause the restructuring of the polymer network because of changes in the valence angles and bond lengths. Thus, the study of the influence of temperature on the structure of crosslinked styrene–divinylbenzene (StDVB) copolymers is an important task. In this work, for the first time, the temperature effect limitations on StDVB copolymers are studied and justified. The changes in the polymer structure tension as well as in the specific surface area are studied using molecular dynamics simulation in the temperature range 77–723 K. Near-cryogenic temperatures are not found to affect significantly the specific surface area. The heating of the polymer up to the temperature used for the reduction of catalysts (573 K) is shown to decrease the specific surface area by 11% because of an increase in the bond tension and valence angle deformation. Further increase in temperature leads to polymer decomposition. The results obtained can be considered for taking into account when applying polymer-supported catalysts. © 2024 Society of Chemical Industry.

This study focuses on developing a sustainable and biocompatible polycaprolactone (PCL)-based scaffold for bone tissue engineering through electrospinning, utilizing calcium carbonate (CaCO₃) from Pomacea canaliculata shells and keratin from human hair, known for stimulating bone regeneration. The isolated CaCO₃ has been identified to demonstrate two polymorphs, vaterite and calcite, as determined by X-ray diffraction. The isolation of keratin from human hair was confirmed through sodium dodecyl sulfate polyacrylamide gel electrophoresis and Fourier transform infrared spectroscopy analysis, revealing the presence of α-keratin structures around 45–50 kDa and β-keratin structures around 55–60 kDa. According to scanning electron microscope observations, the addition of keratin to PCL fibers reduced their diameter from 457 ± 345 to 371 ± 103 nm. Further addition of calcium carbonate led to a mean diameter of 258 ± 76 nm. The melting temperature of PCL fibers containing keratin and CaCO₃ was determined to be 76.17 °C via differential scanning calorimetry, while thermogravimetric analysis, conducted at temperatures up to 600 °C, revealed a remaining ash content of 9.59%. Calcium phosphate accumulation was observed to initiate on PCL fibers containing keratin and CaCO₃ following a 7-day exposure to simulated body fluid. The fibers exhibit cytocompatibility, showing no toxicity while supporting the growth and proliferation of Saos-2 osteosarcoma cells. The results suggest that the innovative incorporation of keratin and CaCO₃ into PCL nanofibers could serve as a bioactive matrix compared to pure PCL matrices, thereby offering enhanced potential for bone tissue engineering applications. © 2024 The Author(s). Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.