Macromolecular Chemistry and Physics最新文献

In this study, polylactic acid (PLA) is compounded with cottonseed protein concentrate (CPC) by melt blending under the compatibilization of maleic anhydride (MA), and then hot-pressed to prepare PLA/CPC composite bioplastics. The attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy showed that high temperature and compatibilizer induced the protein secondary structure to transition. CPC can be used as a heterogeneous PLA nucleating agent, effectively accelerating PLA crystallization, which is characterized by polarization optical microscopy (POM), synchrotron radiation wide-angle X-ray scattering (WAXS) and differential scanning calorimetry (DSC). The highest crystallinity of the PLA/CPC10 composite is 8.9% higher than that of neat PLA. The unfolding of the protein secondary structure is likely to promote an orderly arrangement of PLA crystals, showing strong binding forces between them. Moreover, the CPC/PLA interfacial compatibility is improved by the addition of a small amount of maleic anhydride. The increased crystallinity and interfacial compatibility contribute to the improved mechanical properties, water resistance, and thermal stability of the bioplastics. Environmentally friendly plastic handicrafts (e.g., commemorative emblems, flower pots, ornaments, etc.) can be fabricated using these biocomposites for future value-added applications.

Monodomain liquid crystal elastomers (LCEs) are prepared using liquid crystal block copolymers (LCBCPs) comprised of a nematic liquid crystal (NLC) main-chain polyester linked to cross-linkable polymethacrylate (PMA) at both ends. LCBCPs at a PMA weight fraction of ≈30% are doped with a tetra-thiol compound, stretched in one direction, and then illuminated by UV light, yielding LCBCPs that formed microlamellae consisting of alternate stacking crosslinked PMA blocks and NLC polyester blocks. The LC director lay along the stretching direction (SD). Raising the temperature to the NLC isotropization temperature, the crosslinked LCBCP strips fixed at one end contracted reversibly by a factor of 1.2–1.4 along the SD, deforming the microlamellae. The strips fixed at both ends increased the tensile stress to ≈200 kPa while maintaining the microlamellae undeformed. Regardless of strip fixation at one or both ends, the NLC decreased the orientational order. The contraction amounts and the tensile stress of strips are well associated with decreased NLC orientational order.

Front Cover: The free volume within materials is crucial for gas adsorption and diffusion. Size and distribution of internal fractional free volume significantly impact barrier performance. This study innovatively combines experiments and theoretical calculations to corroborate that methylene group growth in aliphatic units leads to decreased crystallinity, elevated free volume fraction, enhanced segment mobility, ultimately diminishing barrier properties. More details can be found in article 2400051 by Zhiyong Wei and co-workers.

Chemically cross-linked hydrogels are synthesized from a set of protected L-lysine and L-glutamic acid containing homo and copolypetides. Cross-linking of the linear copolypeptides is achieved through the incorporation of L-tryptophan and its reaction with hexamethylene bis(triazolinodione). Upon deprotection, hydrogels with oppositely charged polypeptides of different L-lysine and L-glutamic acid composition form pH-dependent polyion complexes through electrostatic interaction. The obtained networks show distinct pH-dependent differences in their water swelling and rheological properties. Hydrogels at pH 4 display higher strengths compared to pH 8 and their rheological properties scale with L-lysine/L-glutamic acid ratio. At pH 8 results suggests that ionic interactions and presumably secondary structure effects have a significant impact on the hydrogel properties. This is further evident from the influence of the copolypetide structures, random versus block copolypeptides, used in the cross-linked hydrogel. None of the hydrogel shows any significant cytotoxicity against skin cell lines.

Composite xerogel films with structural orientation, controlled swelling degree, and drug-release ability are prepared using biocompatible megamolecular liquid crystalline polysaccharide (sacran) secreted by a cyanobacterium Aphanothece sacrum. The sacran xerogel films (Sac-XFs) are formed by drying sacran aqueous solution including vitamin C (L-ascorbic acid, AA) and trehalose under various conditions. In X-ray diffraction and differential scanning calorimetry of Sac-XFs, diffractions or melting points of either AA or trehalose are not detected, indicating no crystal formation. Additionally, the stability of entrapped AA in Sac-XFs is evaluated through changes in film color and percentage loss, to indicate that AA stability is enhanced by entrapment in Sac-XFs in the presence of trehalose. Scanning electron microscopy of Sac-XFs reveals the morphological orientation, and number of striped lines along the longitudinal axis of film edges on side views while no visible textures in top views. When Sac-XFs are immersed in water, anisotropic swelling is observed, and anisotropy decreases with an increase in the drying temperature of the films. AA is released preferentially from the hydrogel sheet edges, indicating the direction-controlled release. Thus, the trehalose/sacran composite xerogels offer an alternative platform for preserving and controlled-releasing sensitive substances for fields of foods, pharmaceutics, and cosmetics.

In this investigation, the fluorescent poly(N-hydroxyethyl morpholine acrylate) (PHEMA) and poly(N-hydroxypropyl morpholine acrylate) (PHPMA) are prepared and applied as fluorescent probes for the specific detection of Cu²⁺ ions. Far different from the non-fluorescent monomer, PHEMA and PHPMA emit a strong fluorescence at 410 nm due to the intramolecular aggregation of morpholine structures along macromolecular chains in the polymerization, indicating polymerization-induced emission (PIE). The fluorescent emission of PHPMA shows the dependence on external factors including solution concentration, excitation wavelength, solvent, and pH value. PHPMA specifically detects Cu²⁺ ions even in the presence of 16 common metal ions and 6 anions, with an LOD of 0.077 µM. In the fluorescent quenching, the O atom from ─C═O and N atom from morpholine moiety on the PHPMA chain participate in the complexation with Cu²⁺ ions with the ratio of the structural unit and Cu²⁺ ion of 2:1, leading to the dynamic quenching of PHPMA solution. As for the application, PIE-active PHPMA is easily made into a portable semi-quantitative filter paper with recyclability. In brief, the PIE-active PHPMA synthesized in this study can be used as a promising material for the specific detection of Cu²⁺ ions in industry, agriculture, and medicine fields.