Journal of Polymer Science最新文献

By using broadband dielectric spectroscopy over a wide frequency and temperature range, the effect of the chain extender and cross-linkers on molecular dynamics of polyurethanes based on piperazine as a heterocyclic compound was assessed. Three relaxations attributed to local motions of polar side groups and small segments of the polyurethane chain (β, γ-mode) and glass transition (α-mode) were detected with the increase in temperature from −120 to 100 °C, along with the conductivity process at high temperatures and low frequencies. Experimental data were examined using the impedance and electric modulus for the conductivity study. Due to the presence of dipole polarization of functional groups in the hard segments, cross-linked polyurethanes are characterized by higher dielectric constant value (≈11 at 1 kHz and 25 °C) compared to the linear ones (≈6–7 at 1 kHz and 25 °C). High conductivity was achieved for the Tween 20-cross-linked polyurethanes. The activation energy for the secondary γ relaxation was in the range of 34–37 kJ mol⁻¹ for all polyurethanes, regardless of the chain extender or cross-linker used. Piperazine-based polyurethanes had lower activation energies for α relaxation and high conductivity compared to cyclohexane-based polyurethanes. This indicates that α relaxation is more vulnerable to structural alterations.

A PPC-dodecyl glucoside (PPC-APG) polymer was synthesized by the terpolymerization of carbon dioxide (CO₂), propylene oxide (PO), and the bio-based monomer APG for the first time. The thermal stability and mechanical properties of PPC-APG were significantly improved compared with those of conventional polypropylene carbonate (PPC), and its glass transition temperature (T_g) was increased by 14°C compared with that of PPC. The 5% heat loss temperature (T_d,−5%) and total heat loss temperature (T_d,max) of PPC-APG were increased by 89.1 and 92.1°C, respectively, compared with those of PPC. The tensile strength of PPC-APG was increased to 25.6 MPa, its elongation at break was decreased to 125.1%, and its thermal elongation and permanent deformation were reduced to 97.2% and 62.9%, respectively, which improved the processability of the material. In addition, the introduction of bio-based monomers also rendered PPC-APG functional, and its surface tension reached a maximum of 61.3 mN/m at a concentration of 0.05 g/mL, with a good degradability. The higher surface tension and enhanced degradability of PPC-APG indicate its potential for application as a plastic printing substrate.

Suitably modified sesbania gum as a biodegradable functional biomaterials was very attractive in many applications. Therefore, a combination of cross-linking, carboxymethylation, and oxidation was chosen to modify sesbania gum (SG) to expand its use. The experimental results indicated that cross-linking could be completed not only on SG particles, but also between different SG particles. The cross-linking decreased the number of surface hydroxyl groups on SG. The sedimentation volume decreased with the increase of phosphorus content of cross-linked sesbania gum (CLSG). The structure of SG particles was severely disrupted by carboxymethylation and oxidation, while the structure was less affected by cross-linking. The viscosities of SG and modified SG paste in acidic medium were less than those in neutral medium, while their viscosities in alkaline medium were more than those in neutral medium. Cross-linking, carboxymethylation, and oxidation could ameliorate the retrogradation of SG, but decrease its swelling power, freeze–thaw stability, acid, and alkaline resistance. The aldehyde groups had good antibacterial activity against Trichoderma harzianum, whereas the carboxymethyl groups and phosphate ester groups showed poor antimicrobial activity against T. harzianum.

Poly (lactic acid) (PLA) bead foam has a promising application because of its renewable and naturally degradable nature. However, its processing is greatly limited by inherent shortcomings such as the complex polycrystals-inducing strategy. Herein, we developed a strategy of bulk polymerization reaction of polyvinyl acetate (PVAc) to sinter PLA beads to prepare EPLA foams accompanied by supercritical CO₂ foaming technology. In order to enhance the sintering behavior and flame-retardancy of EPLA foams, two-dimensional nanolayered double hydroxides (LDHs) were introduced and dispersed in the continuous phase of the sintering layers. The formation of unique dispersion of LDHs and sintering structure of PVAc generated substantial increase in the crystallinity, melt elasticity, and sintering strength of EPLA foams, which facilitated the growth and stabilization of cells. Thus, the cell-density and expansion ratio could be increased to 8.62 × 10⁶ cell/cm³ to 9.31-fold, respectively. Moreover, the mechanical properties of the EPLA foams were improved. The tensile strength and the compression strength increased to 2.96 and 62.5 MPa. Additionally, with adding 7 wt.% LDH, the EPLA foam reached UL-94 V-0 rating with high limiting oxygen index value of 29.1% and char residue of 20.4%. This study provides a novel strategy for the preparation of flame-retardant EPLA foams with low density, three dimensional complex shapes, as well as excellent mechanical properties.

The cover image is based on the Research Article Human collagen decorating microneedle patches for transdermal therapy by Kaikai Zheng et al., https://doi.org/10.1002/pol.20230597 The first author, Zheng Kaikai, created the cover image. Microneedles are loaded with collagen with a triple helix structure and can deliver it into the skin.

In order to overcome the harmful effects of radiation exposure on lung tissue in radiation therapy, a complete comparative analysis was performed between the injectable pure hydrogel and a novel composite hydrogel, taking into account the addition of cellulose nanoparticles in varying ratios. Initially, both chitosan and tragacanth hydrogels were chemically were modified, and then characterized by FTIR spectroscopy and rheology measurement. For in vivo studies, 42 rats were divided into seven groups. Rats in group 1, were not exposed to radiation, and no injection was done. Rats in group 2 were exposed to a radiation dose of 15 Gy without any injection. Rats in groups 3, 4, and 5 got injectable chitosan/ tragacanth hydrogel containing nanocellulose 25, 50, and 75 mg/kg BW, respectively, along with a radiation dose of 15 Gy. Rats in group 6 got a radiation dose of 15 Gy and an IP injection optimal dose of cellulose nanoparticle and PBS. Rat in group 7 got a radiation dose of 15 Gy and an IP injection of hydrogel containing only chitosan–tragacanth. The pathological results demonstrated that the 25 mg/kg BW dose of nanocellulose-contained hydrogel possessed less inflammation, mucus secretion, bleeding in lung tissue, and air sac wall thickening than other groups. In addition, a biochemistry assessment was conducted by examining the activity of three enzymes of malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxide (GPx), which findings confirmed the hydrogel incorporated with 25 mg/kg BW dose of nanocellulose decreased cell death in a lung tissue damaged by radiation which was 52 IU/mL, 37 IU/mL, and 10 μM in comparison with 63 IU/mL, 40 IU/mL, and 1 μM for the control sample.

The polymerization of N-acryloyl glycineamide (NAGA) in water results in the creation of robust supramolecular hydrogels, exhibiting a network structure through inter-chain crosslinking formed by hydrogen bonds between NAGA units. The stability of these hydrogen bonds in water is based on the aggregation of NAGA units into microdomains or clusters, thereby effectively shielding the hydrogen bonds from the surrounding aqueous medium. Beyond the inherent water absorption characteristics of these hydrogels, the unique ability for the dissociation and re-association of their physical crosslinks imparts features such as reversible swelling and shrinking as well as self-healing and remolding capabilities. In this study, we synthesize a series of supramolecular hydrogels through copolymerization of NAGA and ionic sodium acrylate comonomers for a dual purpose: first, to regulate water absorption levels, and second, to introduce a salt partitioning effect into the hydrogels during their swelling in salt solution. Our findings indicate that the properties of these hydrogels are intricately influenced by the volume fraction of the solid network, the concentration of ionic units, and temperature. Notably, supramolecular samples with ionic units exhibit a 16% salt rejection in a single cycle of salt partitioning during their swelling in a 1 g·L⁻¹ sodium chloride solution.

The fabrication of nanostructured block copolymer (BCP) films endowed with lithium ion-conducting gyroid (GYR) nanochannels is an appealing solution to build solid polymer electrolytes (SPEs) that combines high ionic conductivity (IC) with suitable mechanical properties. However, the formation of a well-developed GYR structure remains challenging to achieve from the self-assembly of polyelectrolyte BCP chains. To overcome this issue, large ion conducting gyroid grains were produced within freestanding polystyrene-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) (PS-b-P2VP-b-PEO) films by combining a solvent vapor annealing (SVA) treatment with an infiltration process. Here, the SVA treatment enabled the manufacture of SPEs entirely composed of a GYR structure while the infiltration process allowed for the incorporation of an appropriate Li salt (i.e., lithium iodoacetate, LiIAc) within the 3D-interconected nanochannels via a Menshutkin reaction. By using this SVA-Infiltration strategy, it has been demonstrated that the creation of ion conducting GYR nanochannels enhances the ion transportation capacity of pyridine-containing SPEs since substantially lower ICs were measured from analog PS-b-P2VP-b-PEO/LiIAc films having a nominally disordered as-cast state. Remarkably, zwitterionic pyridinium-based moieties formed inside the interpenetrated nanochannels enable an efficient migration of Li⁺ and I₃⁻ species, leading to an IC as high as 10⁻⁴ S cm⁻¹ at 70°C.

A modified tape peel test method to determine the integrity and interlayer adhesion within a soft multi-layer polymeric film is proposed. The new methodology will greatly improve two inconsistent and highly operator dependent ASTM D3359 and ISO 2409 tests for evaluating coating layer adhesion. The proposed test method uses an instrumented machine to make a crosshatch pattern with controlled penetration depth for consistency in the sample preparation. To ensure consistency, the processes of attaching, rubbing, and peeling a tape are automated using the same instrumented machine to allow for repeatable and operator independent test. Finally, the visual assessment to rank adhesion strength of the multi-layer films, as instructed in the above standards, are now quantified using a mathematical reduction of the interfacial adhesion in the multilayer films based on the energy conservation principle. With the quantified interfacial adhesion obtained, meaningful structure–property relationships of soft multilayer films can be established. The proposed test is expected to be also applicable for other interfacial adhesion studies on different types of polymeric laminates.

In this work, blends of monomer-cast polyamide 6 (MCPA6) and polyurethane (TPU) were prepared by in situ anionic ring-opening polymerization using caprolactam as the monomer and sodium hydroxide (NaOH) as the initiator. TPU degraded under weakly alkaline conditions to form an isocyanate group, which acted as a macromolecule activator to initiate the growth of the MCPA6 chain, and the formation of TPU-co-MCPA6 copolymer in this system, which improves the compatibility between MCPA6 and TPU. The MCPA6/TPU blends were tested for conversion, viscosity, and mechanical properties, and their structures and thermal properties were analyzed and evaluated by characterization techniques such as Fourier transform infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy.