Macromolecular Chemistry and Physics最新文献

Conjugated polymers are typically synthesized through transition metal-mediated coupling reactions, which are often costly and have significant environmental impacts. Aldol condensation represents a more cost-effective and sustainable synthetic technique for developing next-generation organic functional materials. However, controlling the molecular weight and distribution of the resulting polymers remains challenging due to the uncontrollable step-growth polymerization mechanism of aldol polycondensations. To this end, by selectively anchoring sulfonic acids inside the mesochannels of SBA-15, the aldol polycondensation is exclusively confined within the pores. Experimental results demonstrate that this nanoreactor, by providing a spatially confined reaction environment, aids in controlling the progression of the polymerization and the growth of polymer chains, thereby achieving good control over polymer molecular weight and distribution, giving linear conjugated polymers and soluble conjugated polymeric nanoparticles with polymer dispersity down to 1.31.

Anisotropic bilayer hydrogel actuators are high-performance materials engineered to exhibit unique and programmable mechanical properties, including varying stiffness and directional bending capabilities, by integrating two hydrogel layers with distinct responses to stimuli. However, programming and constructing these bilayer hydrogels remains challenging due to their lack of mechanical robustness, rapid responsiveness, and dual-actuation capabilities, which hinder their practical applications and further development. Hence, developing a double-actuating bilayer hydrogel with a temperature-responsive and auxiliary layer could address these challenges. Herein, an anisotropic hydrogel actuator is developed using a simple and economical casting method, in which a unique multiasymmetric bilayer structure locked by an interfacial is fabricated. The as-prepared hydrogels demonstrate exceptional temperature-responsive bending abilities, achieving a 360 °C angle in just 8 s, and exhibit adaptive, complex shape transformation capabilities tailored to specific needs (e.g., two dimensional (2D) letters, leaves, flower, and butterfly hydrogel). Furthermore, the hydrogels possess excellent shape memory, mechanical strength, and conductivity. Additionally, gripper and humidity alarm prototypes made from the hydrogel are also successfully developed, illustrating that this approach opens new avenues for designing and producing smart hydrogels with practical applications in sensors, smart humidity alarms, and on-demand smart grippers and actuators.

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.