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

Meldrum's acid mediated ketene chemistry (MAMKC) is applied to synthesis of poly(ester amide)s in this work. An MA-functionalized phenolic amide compound (MA_PhOH-Am) is synthesized from the reaction between a MA-functionalized amine and 3,4-dihydrocoumarine (DHC, a biomass-based chemical) through amine-lactone addition reaction. Polymerization of MA_PhOH-Am results in the corresponding poly(ester amide) (P(Es-Am)), through MA thermolysis reaction (generating the corresponding ketene groups) and ketene-phenol addition reaction. Both MA_PhOH-Am and P(Es-Am) have been characterized with spectral methods and thermal analysis. P(Es-Am) has an inherent viscosity of 0.49 dL g⁻¹, a molecular weight of 76,500 Da, a glass transition temperature of 145°C (tanδ peak in dynamic mechanical analysis), a thermal stability of about 320°C, and a storage modulus at 50°C of 1.0 GPa. In the stress–strain measurement, P(Es-Am) exhibits a Young's modulus, a tensile strength, and an elongation at break of 10.6 ± 0.7 GPa, 165 ± 40 MPa, and 1.83 ± 0.41%, respectively. An effective approach for the synthesis of high-performance poly(ester amide)s has been demonstrated.

A high-performance hyperbranched polybenzoxazine with low dielectric constant was prepared. A hyperbranched benzoxazine (HTTr-d) was synthesized from 1,1,1-tris(4-hydroxyphenyl) ethane, 1,12-dodecanediamine and paraformaldehyde through an A₂ + B₃ approach with p-tertbutyl phenol as an end-capping reagent. After thermal curing, hyperbranched polybenzoxazine (PHTTr-d) was obtained. For comparison, trifunctional polybenzoxazine (PTr-s) with long alkyl groups was also synthesized. The introduction of long alkyl chains can effectively reduce the dielectric constants of polybenzoxazines. Due to the presence of tertiary butyl groups and the forming of hyperbranched structure, the dielectric constant of PHTTr-d was 2.59 at 1 MHz, which was lower than 2.68 of PTr-s. Compared with PTr-s, PHTTr-d exhibited higher thermal stability with the glass transition temperature (T_g) of 197 °C. These results indicated that the hyperbranched polybenzoxazine has potential application as a low dielectric constant material in the field of electronic information.

This article explores a new mode of chromatographic separation named BIST™ (Bridge Ion Separation Technique) that is designed specifically for the retention and separation of charged molecules. The proposed mechanism is supported by multiple examples. The separation technique is especially useful for analysis of low molecular weight charged polymers, the class of molecules where ion-exchange, ion-exclusion and size exclusion modes of separation do not work effectively. Among low molecular weight polymers, many compounds are of high importance for biological, medicinal, agricultural, and consumer applications. Some examples include heparin, poly amino acids, insulin, polyethyleneimine, as well as other peptides. The wide variety of applications of many charged polymers necessitates a high-quality analytical technique for testing and research of these compounds.

Reduction of plastic wastes in the environment and solving the energy demands from renewable sources are two important challenging tasks of this century. Modern day lives are highly entangled with polymers, however handling the huge wastes from plastics is also a serious concern. Translating the plastic wastes to useful products such as graphene can be an alternative for nonbiodegradable polymer wastes. Efficient energy storage devices, for instance, batteries are required for storing the renewable energies. With the aim of regulating these issues, we report, for the first time, the preparation of high energy cathode materials from the nanocomposites (NCs) having polyaniline (PANI), waste-derived graphene (WDG) derived from plastic waste and sulfur (S) for Li–S battery applications. We compare the electrochemical properties of cathodes derived from WDG/S and WDG/PANI/S in Li–S batteries. The specific discharge capacity of WDG/PANI/S at 0.1 C was obtained to be 880 mAhg⁻¹ normalized to sulfur mass at 1st cycle, 472 mAhg⁻¹ at 100th cycle, and 400 mAhg⁻¹ at 160th cycle. The rate capability is also found to be good at C-rates less than 0.5 C. We found that WDG/PANI/S showed decent electrochemical properties when compared with the reference sample, WDG/S at similar sulfur loading without PANI modification.

A versatile approach for the synthesis of polystyrene based hyperbranched polymers (hyp-PS) with tunable branching densities by combination of self-condensing vinyl polymerization and iniferter processes is reported. The technique is based on the utilization of a dual functional monomer, 2,2,2-(triphenylethyl)styrene (TPES), that contains both polymerizable and iniferter units. Branching densities of the polymers are regulated depending on the TPES concentration and polymerization time. Moreover, obtained polymers are used as macroiniferter for the copolymerization of a hydrophilic monomer (poly(ethylene glycol) acrylate) to give amphiphilic branched-core star polymers.

Recent work on non-conjugated pendant electroactive polymers (NCPEPs) has demonstrated significant impacts of structural parameters such as backbone stereoregularity and the spacer connecting the pendant to the backbone on properties, most notably on charge carrier mobilities. Tuning of the pendant group however has not been reported for stereoregular NCPEPs. Here we present a family of novel isotactic poly((carbazolyl-alkyl-triazolyl)methyl methacrylates) (PCzATMMAs) for which the effects of increasing the pendant group from carbazole to 3,6-bis(4-(2-ethylhexyl)thiophen-2-yl)-carbazole were investigated. Based on unsuccessful post-polymerization functionalization with this extended group via previously reported transesterification and thiol-ene methodologies, we report functionalization via copper-catalyzed azide-alkyne cycloaddition which was demonstrated to be highly effective. The effect of spacer length was also investigated for comparison with previously established effects with alkyl spacers. Within the family of PCzATMMAs, hole mobilities were found to increase with longer spacer length and with thermal annealing. The incorporation of an extended pendant with alkyl solubilizing chains was found to result in a lower hole mobility than the equivalent polymer with an unfunctionalized pendant group. Importantly, the copper catalyzed azide-alkyne cycloaddition proved to be an effective method of post-polymerization functionalization for stereoregular NCPEPs when extending beyond a simple carbazole pendant.

The cover image by Niels Vonk shows a polarization optical microscopy image of a 3D-printed CE-UPy-PEG3k fiber in the fully hydrated state, obtained using a Zeiss Axio Imager. D1. Polarization optical microscopy revealed a strong reduction in crystallinity of 3D-printed CE-UPy-PEG fibers between the dry and hydrated state, which is driven by the PEG chains transforming from an ordered crystalline packing to an amorphous state. Consequently, the transient swelling behavior of the fiber is strongly affected by this phase transformation. In the fully hydrated state, surface swelling instabilities become present which show up as the local buckles. (DOI: 10.1002/pol.20220648)

The behavior of gelatin hydrogels is influenced by the charges located on the amino acid side chains throughout the gelatin molecules. The presence and distribution of ionisable side chains influences the surface activity of gelatin and ultimately determines the material properties. Herein, we report the influence of pH on mechanical properties as studied by texture analysis supported by data from polarimetry, zeta potential, pH titrations and NMR experiments. When adjusted to more extreme pH values (pH 2 and 12), softer gelatin blocks were observed. However, at pH values close to the isoelectric point (pH 5–10), the material is firmer. This behavior is related to the helical content. At pH 2 and pH 12 the surface of the gelatin carries a net charge, positive and negative, respectively, that inhibits the formation of tight helices and lowers the physical crosslink network density. Chemical shift perturbations were observed for the acidic amino acids glutamic and aspartic acid, under acidic pH, where their peaks shifted to higher ppm. Intense amide signals were observed at acidic pH but diminished with increasing pH. This was due to an increase in the rate of chemical exchange between the solvent and peptide amide protons as the pH increases.

A combined analytical and molecular dynamics model for the electrocaloric effect in ferroelectric poly(vinylidene difluoride-co-trifluoroethylene) copolymer (poly(VDF-co-TrFE)) is developed. The model calculates the polymer polarization, $��P�$, and temperature change under adiabatic electric field variation, $��\Delta �T�$, as functions of temperature. An analytical component of the model is based on the Landau phenomenological theory adapted for modeling of the first order phase transitions in a polymer crystal from a ferroelectric β phase to a paraelectric conformationally disordered (condis) phase. Parameters of the free energy functional are calibrated through molecular dynamics simulations of poly(VDF-co-TrFE) perfect crystal. Random orientation and the scatter of the phase transition temperature for various crystallites in a real amorphous-crystalline polymer are incorporated into the model. Comparison of the model prediction with experimental data shows good agreement for $��P�\left(T\right)�$ while the model overestimates the value of $��\Delta �T�$ by approximately 2.5 times. We attribute this discrepancy to the presence of structural defects in real polymer crystallites, which reduces the entropy change under the phase transition compared to the perfect crystal simulated in our molecular dynamics approach. The theoretical limit of $��\Delta �T�$ calculated by the model indicates that $��\Delta �T�$ can be increased up to 3 times compared to the currently observed experimental value of $��\Delta �T�$.