Journal of Polymer Science Part A: Polymer Chemistry最新文献

A simple chain-extension reaction using diisocyanate as a chain extender was adopted to increase the molecular weight of low-molecular-weight (LMW) poly(lactic acid) (PLA) synthesized via direct polycondensation and to recover the molecular weight of commercial PLA after service life. The slow reaction between diisocyanate and the carboxylic acid terminus of PLA was successfully accelerated using a Mg(II) catalyst, affording a linear chain-extended PLA (cePLA) connected through amide bonds. To increase the number of amide bonds, which exhibit higher thermal stability than the urethane bonds that are formed in the more common chain-extension reactions between isocyanates and the hydroxy terminus of PLA, a telechelic LMW-PLA having carboxylic acid groups at both termini was prepared. Subsequent reaction of this LMW-PLA with diisocyanate in the presence of a Mg(II) catalyst afforded a cePLA with high molecular weight (M_w > 180 × 10³ g/mol) and enhanced stability against thermal degradation, while showing identical mechanical properties and biodegradability as commercial PLA.

Currently, there is limited literature on the introduction of naphthalene ring into phthalonitrile. In this study, we have successfully synthesized a novel phthalonitrile monomer (CPND) by incorporating a symmetrical rigid naphthalene ring structure, long flexible chains, and high-density cyano groups into the resin. The monomer is being cured with two different agents and procedures to investigate the impact of curing agent structure and ramp-up procedure on polymer properties. The structure of the monomer is being verified using nuclear magnetic resonance (NMR), infrared spectroscopy (FTIR), and wide-angle X-ray diffraction (WAXD). Differential scanning calorimetry (DSC) results reveal that the monomer has a low melting point of 111°C, making it easily processable. After mixing with the curing agent in the appropriate proportion, it has a calculated processing window of 129–135°C. Thermogravimetric analysis (TGA) reveals that the polymers exhibit remarkable thermal stability, with all T_5% above 470°C under a nitrogen atmosphere. Additionally, the results obtained from dynamic mechanical analysis (DMA) indicate that the polymer, which is cured using APPH as a curing agent, displays favorable thermo-mechanical properties. The storage modulus of the polymers at room temperature is all higher than 3330 MPa, respectively. Moreover, the glass transition temperature is found to be higher than 400°C, signifying the excellent thermo-mechanical properties of the polymer.

The cover image was created by Tianmin Cao and Xun Wang. The blue background with radio waves indicates the high frequency telecommunication era. Important functional groups including the pyridine ring, imide ring, tert-butyl, and amide bond are displayed in the upper left corner with concentric circles, indicating the cooperative synergistic effects of these functional groups. The backbone of polyimide films is highlighted with hydrogen bonding, and the films' potential application in chips and flexible circuits are illustrated in image bottom. (DOI: 10.1002/pol.20230217)

Growth factors can steer the biological response to a biomaterial post implantation. Heparin is a growth factor binding molecule that can coordinate growth factor presentation to cells and therefore is able to regulate many biological processes. One way to functionalize biomaterials with heparin and growth factors is via a supramolecular approach. Here, we show a proof-of-concept study in which a supramolecular approach based on ureido-pyrimidinone (UPy) was used, which allows for modular functionalization. PCLdiUPy was functionalized with a UPy-modified heparin binding peptide (UPy-HBP) to facilitates binding of heparin, which in turn can bind vascular endothelial growth factor (VEGF) via its heparin binding domain. The adsorption of both heparin and VEGF were studied in two different functionalization approaches (pre-complex and two-step) and at different molecular ratios. Quartz crystal microbalance with dissipation energy adsorption data showed that VEGF and pre-complexed heparin:VEGF adsorbed non-specifically, with no distinguish between non-specific adsorption and heparin guided-adsorption. On the biological side, heparin guided-adsorption of Heparin:VEGF enhanced HUVECs surface coverage as compared to non-specific adsorption. These results provide a detailed insight on the molecular sandwich which is useful for new design strategies of supramolecular biomaterials with well-controlled immobilization of different growth factors.

Scanning mirrors can deflect, reflect, and pattern the laser beam. Traditional laser galvanometers rely on deflection motors and mirrors, which are bulky and costly. Micro-electro-mechanical systems (MEMS) micromirrors have small size and high integration, but they require long preparation cycles and sophisticated equipment and expensive materials. Polymer scanners prepared by 3D printing technology have the advantages of low cost and rapid preparation, but their reliability needs further study. In this study, a single-axis electromagnetic scanner was proposed and tested for reliability. The mechanical structure of the scanning mirror is prepared by fused deposition modeling (FDM) using acrylonitrile butadiene styrene (ABS) as material, the radial magnetic field is provided by neodymium magnet set, and laser patterned copper foil serves as the drive coil. The prepared scanner achieved an optical scan angle of 45.2° at a resonant state of 276 Hz. The effect of temperature and humidity on the device reliability is investigated experimentally. Temperature has a significant influence on the resonance frequency and scanning angle of ABS-based scanner. In addition, the change of relative humidity has less effect on the scanner. The five scanners tested were still working properly after 240 h (more than 2 × 10⁸ cycles) of testing without failures and less than 1.5% frequency drift has been observed.

In this work, different test methods were used to investigate the flame retardancy and smoke emission of polyvinyl chloride (PVC) toughened with polycarbonate-polydimethylsiloxane block copolymer (PC-b-PDMS) and two other commercial toughening agents. The oxygen index result and heat release curves in the cone calorimetry test showed that toughened PVC has reduced flame retardancy compared to unmodified PVC. However, the vertical combustion test showed that all samples have achieved the highest flame retardant rating, indicating that the flame resistance of these toughened PVC is still adequate for use. In terms of smoke emission, the results of the cone calorimetry test and the smoke density test showed a significant difference. In the smoke density test, it was found that PVC toughened with PC-b-PDMS has less smoke generation in the early stage of combustion. In the cone calorimetry test, the total smoke production was lower for PVC and significantly higher for toughened PVC. This difference was mainly due to the different test conditions of these two tests.

With the rise of particle-based material systems in life and materials sciences over the past years, high-throughput microfluidics has gained tremendous interest as a simple fabrication method for large quantities of tailored emulsions and microparticles. Here, we present the fabrication of microfluidic systems that combine parallelized droplet formation with sequential droplet splitting by 3D printing via projection-microstereolithography for large-scale production of water-in-oil emulsions and polymer microparticles. The process of droplet splitting is investigated in a 3D-printed single-channel, flow-focusing device and then integrated into a microfluidic system with N = 3 × 20 parallelized channels with individual channel cross-sections of 60 μm. The arrangement of the integrated functional microfluidic elements is evaluated for different orientations to the 3D printing direction. Furthermore, emulsion droplet size adjustment for flow-focused and parallelized microfluidic systems is studied. For a proof-of-concept, the 3D-printed microfluidic system is used to fabricate water-in-oil emulsions and fluorescently labeled, thermally crosslinked poly(acrylamide) microparticles. With that, our platform provides a straightforward and time-efficient path toward microgel production in the size range of 140–170 μm on a milliliter-per-hour scale combining droplet formation parallelization and three integrated droplet splitting stages.

An intramolecular phosphonium bisborane Lewis pair (PBB-Br) was used for the copolymerization of o-phthalaldehyde (OPA) with epoxides under mild conditions. In particular, poly(o-phthalaldehyde-alt-propylene oxide) termed as (poly(OPA-alt-PO)), having high molecular weight (M_n = 42.5 kg/mol) with Đ = 1.12 was generated at 25 °C using PBB-Br as a highly efficient catalyst. The purity of OPA, temperature and monomer/comonomer feeding ratio effects on the copolymerization were investigated. Subsequently, the degradability and thermal stability of generated polyacetals were studied. Using alcohol as chain transfer agent, random or block polyacetal-polyethers with different structures can be obtained in one-pot synthesis. The cooperation of the two boron centers plays a pivotal role in boosting the activity of copolymerization of OPA and PO.