Journal of Polymer Science最新文献

We report herein the photoinduced electron/energy transfer–reversible addition-fragmentation chain transfer (PET-RAFT) polymerization of styrene-maleic anhydride (SMAnh) using the photocatalyst, zinc tetraphenylporphirine, under a white cool LED light. PET-RAFT is an easy and convenient polymerization method that does not require deoxygenation unlike other radical polymerizations. Various parameters, for example, the amount of styrene in the feed or the solvent, and their influence on the polymerization were studied. After hydrolysis of the anhydride moieties, the resulting styrene-maleic acid (SMA) copolymers obtained by PET-RAFT copolymerization were evaluated for their solubilization efficiency of three different membrane proteins, BmrA and AcrB, overexpressed in Escherichia coli, and A_2AR, expressed in insect cells (Sf9). The different copolymers provided similar solubilization rates to the commercially available SMA; however, a highly improved migration behavior on sodium dodecyl-sulfate polyacrylamide gel electrophoresis was observed which could, facilitate downstream analyses. Overall, we demonstrated that PET-RAFT is a versatile oxygen tolerant polymerization technique to yield SMA, a suitable polymer for biochemical applications.

Meso isomers of indenyl-based group IV hafnocene complexes produce atactic polypropylene (aPP) and thus, have to be tediously separated from their racemic analogs for the production of isotactic polypropylene (iPP). Herein, we report a facile activation protocol to selectively convert only the racemic precatalysts into catalytically active species when isomeric precatalyst mixtures are employed. At the same time, the meso isomers are deactivated, thus yielding no polypropylene at all. The macromolecular characteristics of iPP, that is, melting transition, molecular weight, and tacticity, obtained by this protocol were analog to the characteristics of iPP produced by the corresponding pure racemic isomers, as proven for different complexes, isomeric ratios, and polymerization conditions. Nuclear magnetic resonance experiments revealed that the employed precatalyst activation protocol – that is, alkylation with triisobutylaluminum and subsequent generation of a free coordination site with [Ph₃C][B(C₆F₅)₄] – led to catalytically active, binuclear hydride-bridged racemic species but inactive meso resting states. The separation of both precatalyst isomers, which was believed to be crucial to obtaining pure iPP since the 1980s, rendered hafnocene syntheses unnecessarily laborious and can be circumvented by the activation protocol established in this work.

Despite their better mechanical qualities, plant fibers are now appreciated enough to be employed as an additional component in composite manufacture rather than synthetic materials. Industries are making efforts to preserve nature's ecological equilibrium in order to avoid catastrophic natural disasters. This study investigated thermal, mechanical, morphological, and moisture-capture capabilities of Licuala grandis leaf stalk fibers (LGLSFs) reinforced in an unsaturated polyester resin (UPR) matrix biocomposite. Biocomposites were fabricated by compression molding technology, with different weight ratios and sizes. The biocomposite containing 30 wt.% and 5 mm length LGLSF had best mechanical properties, with equal impact (5.4 J/cm²), hardness (70.4 HRRW), flexural (58 MPa), and tensile (64.9 MPa) values. Furthermore, prolonging LGLSF reinforcement to 15 mm increased the bio-composite specimen's tensile, flexural, hardness, and impact characteristics by 9.09%, 9.65%, 14.8%, and 6.25%, respectively. The Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD) spectra were analyzed to determine the bio-composite's feasibility for commercial use. The bio-composite specimen is ideal for usage in vehicle and aviation upholstery due to its sufficient hydrophobicity, lowered density, and heat resistance up to 236 °C, which are accomplished through a sufficient weight ratio of LGLSF and UPR, as well as LGLSF dimensions.

Interventional embolotherapy is widely used in clinical treatment of conservative liver cancer. This method has many advantages, such as good targeting, mild trauma, and low complications. The operation of transcatheter arterial embolization is to inject embolic microspheres into the arterial blood vessels of diseased organs, so as to occlude them and interrupt the blood supply, thus achieving the therapeutic purpose. However, there are still some deficiencies in clinical materials, for example catheter obstruction or vascular regeneration. In this study, pentaerythritol triallyl ether (APE) and its esterified product APEAA were used to prepare new polymeric amorphous embolic granules (PAPE and PAPEAA). The purpose is to overcome the excessive swelling problems of traditional polyvinyl alcohol granules (PVA). We verified that PAPE and PAPEAA were quickly and efficiently polymerized by photo-driven radical-mediated [3 + 2] cyclopolymerization mechanism (PRMC). RT-FTIR was used to explore the best route of photopolymerization initiated by four photoinitiators. Four physical properties experiments all prove that the particle has good physical properties. In vivo animal experiments, it is confirmed that the particles can achieve the expected effect and have good biological safety. The results show that the amorphous granules can meet the requirements of clinical injection and can be used as a new embolic material.

Artworks, particularly easel paintings, are multi-component materials intended to last indefinitely. The protective coatings applied to these artworks often consist of amorphous glass-like polymers, which undergo slow physical aging and structural recovery below their glass transition temperature. This process alters key physical properties such as mechanical strength, optical clarity, and thermal stability over extended periods. This study investigates the time-dependent evolution of these properties in Laropal A81, a widely used synthetic resin for cultural heritage conservation, particularly as a replacement for ancient varnishes. The investigation involves characterization of enthalpy recovery via differential scanning calorimetry, refractive index evolution via refractometry, and creep compliance evolution via rheological measurements. The aging behavior of Laropal A81 is further analyzed using the Kohlrausch–Williams–Watts function and the Tool–Narayanaswamy–Moynihan model, enabling the quantification of critical dynamic parameters such as activation energy, nonlinearity, partition coefficients, and non-exponentiality. The gained insights into the long-term behavior of this coating's properties can be valuable for improving preservation and restoration strategies for cultural heritage.

Segregated conductive polymer composites (CPCs) show high conductivity at low loading of filler. However, the weak interactions between fillers and polymer matrix may destroy the mechanical property of the segregated CPCs. Moreover, even with the introduction of dynamic bonds in thermoset polymers, the preparation of thermosetting CPCs remains a big challenge, as most crosslinked polymers should be ground into granules or crushed into powder with liquid nitrogen before mixing with fillers. Herein, the dynamic crosslinked polythiourethane microspheres (PTUM) are designed and synthesized. Then, a special mixing method (the mixing temperature is higher than melting temperature of soft segments of PTUM) is used to make the carbon nanotubes (CNTs) adhering closely to the surface of the crosslinked PTUM, promoting the formation of compacted conductive network. The CNT-3%/PTUM shows the electrical conductivity of 21.9 S/m and an elongation at break of 472%. Additionally, the CNT/PTUM composites exhibit good self-healing property, reprocessability, and close-loop recycling property. The construction of dynamic crosslinked microspheres and compacted segregated conductive network in this work supplies a new approach to prepare thermoset CPCs with simultaneous high electrical conductivity and mechanical property, which is expected to be applied to wearable strain sensors.

This article reports recent advances in thermally induced phase separation technology in fabricating microporous scaffold polymeric membranes as devices suitable for the controlled release of insect repellent. The key aspects, such as the crystallization behavior and morphological study of the polymeric membrane-based repellent, were reported and discussed. Studies demonstrated that trapping of such repellents into microporous polymeric materials can be achieved by spinodal decomposition of the polymer/liquid repellent system. Usually, solubility is enhanced at elevated temperatures. Rapid cooling of such solution below the UCST leads to the formation of cocontinuous phase structures by decomposition. The polymer then forms an open-cell structure with the repellent trapped inside. Approaches to forming such an open-cell polymer structure containing mosquito repellent were successfully performed and confirmed with the SEM and POM techniques. It showed the structure of a polymer and liquid repellent prepared by spinodal decomposition, providing proof that thermally induced spinodal decomposition is a route to trap liquid mosquito repellent into a microporous polymer matrix. Additionally, the effects of polymer type, repellent nature, cooling conditions, and fillers on the morphology and performance of TIPS membranes are also discussed. Finally, challenges in developing microporous polymeric membrane-based repellent using TIPS technology are addressed.

The anionic polyaddition of methyl-substituted 1,1-diphenylethylene derivatives, catalyzed by lithium diisopropylamide, was examined. Polymerization of the monomer was conducted at 50°C in THF with the addition of diisopropylamine. NMR and MALDI-TOF-MS analyses of the obtained polymer indicate that polymerization proceeded via a polyaddition reaction, in other words, repetition of the lithium amide-induced metalation reaction of the monomer at the methyl group and the subsequent nucleophilic addition reaction of the corresponding benzyllithium with the vinyl group in the monomer. On the other hand, the unsubstituted diphenylethylene monomer could not be polymerized by the same reaction condition. Consequently, the resulting polymer was indeed obtained by an anionic polyaddition mechanism. In conclusion, a novel hydrocarbon polymer containing a phenyl group in the main chain of the repeating unit was successfully obtained from a methyl-substituted 1,1-diphenylethylene monomer.

Cellulose nanocrystals (CNCs) have received an abundance of attention because of their distinctive chiral nematic structure and exceptional optical characteristics. However, the use of free-standing films is constrained by the inherent stiffness and brittleness. In this work, CNC films with robust mechanical properties are prepared by simply coating them with polymeric spherulites. Maleic anhydride-grafted polypropylene (PP-g-MA) is used to coat CNC films. The optical properties of coated films were also analyzed using polarized optical microscope. It is observed that the circular extinction patterns for the coated CNC film were created by the radial symmetry of banded spherulites, which were responsible for the perception of the optical transmission bands of the CNC film. Interfacial anchoring plays a crucial role in enhancing the overall performance and properties of the composite system. The future development of numerous portable functional components needing improved optical, mechanical, and thermal qualities of CNC films is made possible by this protective coating approach.

Polyolefin elastomer (POE) has very weak crystalline ability, consequently, applying the conventional preparative temperature-rising elution fractionation (P-TREF) to separate is challenging. Here, a unique, home-built P-TREF apparatus with an extensive range of temperatures from −80°C to 150°C is applied to first fractionate POE depending on its crystallizability. The main fractions are eluted at 0°C, 8°C, 15°C, 20°C, 25°C, 30°C, and 35°C. The corresponding weight percentages of fractions are 8.31, 13.38, 15.59, 12.05, 13.39, 17.30, and 10.53 wt%, respectively. The chain structures of fractions are further analyzed by high-temperature gel permeation chromatography (HT-GPC), ¹³C-nuclear magnetic resonance spectroscopy (¹³C-NMR), differential scanning calorimetry (DSC), and successive self-nucleation and annealing (SSA). The crystallinity of the fraction grows continually as the elution temperature rises. The 1-octene comonomer concentrations within the fractions decreases from 13.8 to 7.9 mol% when the elution temperature rises from −10°C to 40°C. These findings enable for the detailed recognition of the chain microstructure of POE resin and the extension of the TREF approach to POE resins. This lays the groundwork for fundamental studies and practical uses in industry.