Chinese Journal of Polymer Science最新文献

High catalytic efficiencies in ring opening polymerization (ROP) of a large ring-sized macrolactone, ω-pentadecalactone (PDL), by using transition metal Fe(II)-based catalysts were achieved for the first time in this study. Benefited from the bulky nature of the ligated α-diimine ligands, as evidenced from single-crystal structures, as well as the weakly oxophilic nature of the metal centers, chain transesterification reactions could be partially suppressed, allowing the polymerization proceed in a living-like and semi-controllable manner, i.e. good linear dependence of propagation rates on catalyst concentration and PDL concentration as observed in the detailed kinetics studies. The whole polymerization proceeds via a “coordination-insertion” mechanism, and with the aid of density functional theory (DFT) calculation studies, a “slow insertion → fast elimination” manner was demonstrated for the monomer propagation step, suggesting the insertion of Fe-OR into the carbonyl group C=O as the rate-determining step. The present catalytic system also showed fast chain transfer reactions to alcohol compounds, affording quasi-immortal characteristics. DFT calculations showed that such a transfer reaction only required an energy barrier of 6.4 kcal/mol, performing a good consistency with the fast chain transfer rates.

Diphenylalanine and its analogs cause many concerns owing to their perfect self-assembly properties in the fields of biology, medicine, and nanotechnology. Experimental research has shown that diphenylalanine-based analogs with ethylenediamine linkers (PA, P = phenylalanine, and A = analog) can self-assemble into spherical assemblies, which can serve as novel anticancer drug carriers. In this work, to understand the assembly pathways, drug loading behavior, and formation mechanism of PA aggregates at the molecular level, we carried out dissipative particle dynamics (DPD) simulations of PA molecule systems. Our simulation results demonstrate that PA molecules spontaneously assemble into nanospheres and can self-assemble into drug-loaded nanospheres upon addition of the cancer chemotherapeutic agent doxorubicin (DOX). We also found that the hydrophobic side chain beads of PA molecules exhibited a unique onion-like distribution inside the nanospheres, which was not observed in the experiment. The onion-like nanospheres were verified by calculating the radial distribution function (RDF) of the DPD beads. Furthermore, based on the analysis of the percentages of different interaction components in the total nonbonded energies, main chain-side chain interactions between PA molecules may be important in the formation of onion-like nanospheres, and the synergistic effects of main chain-side chain, main chain-drug, side chain-drug, and main chain-solvent interactions are significant in the formation of drug-loaded nanospheres. These findings provide new insights into the structure and self-assembly pathway of PA assemblies, which may be helpful for the design of efficient and effective drug delivery systems.

Flexible phase change materials (PCMs) have become increasingly critical to address the demand for thermal management in electronic technologies and energy conversion. However, their application remains challenging because of their rigidity, liquid leakage, and insufficient thermal conductivity. Herein, flexible glutamic acid@natural rubber/paraffin wax (PW)/carbon nanotubes-graphene nanoplatelets (GNR/PW/CGNP) phase change composites with high thermal conductivity, excellent shape stability, and recyclability were reported. Zn²⁺-based dynamic crosslinking was constructed through the reaction of zinc acetate and carboxyl groups on glutamic acid@natural rubber (GNR), which was used as a flexible matrix to physically blend with paraffin wax/carbon nanotubes/graphene nanoplatelets (PW/CGNP) to achieve uniform dispersion of PW/CGNP, continuous thermal conductivity networks, and good encapsulation of PW. The GNR/PW/CGNP composites showed excellent mechanical strength, flexibility, and recycling ability, and effective encapsulation prevented the outflow of melted PW during the phase transition. Also, the phase change enthalpy could attain 111.1 J/g with a higher thermal conductivity of 1.055 W/mK, 428% higher than that of pure PW owing to the formation of efficient thermal conductive pathways, which exhibited outstanding thermal management performance and superior temperature control behavior in electronic devices. The developed flexible composite PCMs may open new possibilities for next-generation flexible thermal management electronics.

Autonomous, adaptable, and multimodal locomotion capabilities, which are crucial for the advanced intelligence of biological systems. A prominent focus of investigations in the domain of bionic soft robotics pertains to the emulation of autonomous motion, as observed in natural organisms. This research endeavor faces the challenge of enabling spontaneous and sustained motion in soft robots without relying on external stimuli. Considerable progress has been made in the development of autonomous bionic soft robots that utilize smart polymer materials, particularly in the realms of material design, microfabrication technology, and operational mechanisms. Nonetheless, there remains a conspicuous deficiency in the literature concerning a thorough review of this subject matter. This study aims to provide a comprehensive review of autonomous soft robots that have been developed based on self-regulation strategies that encompass self-propulsion, self-oscillation, multi-stimulus response, and topological constraint structures. Furthermore, this review engages in an in-depth discussion regarding their tunable self-sustaining motion and recovery capabilities, while also contemplating the future development of autonomous soft robotic systems and their potential applications in fields such as biomechanics.

With the rise in environmental awareness, the development of smart polymer materials is gradually becoming environmentally friendly and sustainable. Fluorescent liquid crystal elastomers (LCE) can change their shape or optical properties in response to external stimuli, showing great potential for applications in sensing, information storage, and encryption. However, their life cycle is often unsustainable and not in line with the circular economy model. Based on the principle of green chemistry, a fluorescent LCE was developed through the co-polymerization of multiple monomers with 1,2-dithiolane end groups, which exhibited excellent self-healing, reprocessing, and closed-loop recyclability. In addition, by tailoring the phase transition temperature of the LCE, the transparency and fluorescence intensity of the resulting material can change at a low temperature of 8.0 °C. By further integrating light or acid/base-triggered fluorescence information, a proof-of-concept for temperature monitoring during short-time vaccine transportation using the reusable fluorescent LCE film is demonstrated. This study establishes a new environmentally friendly manufacturing strategy for multifunctional LCE materials.

Liquid crystal elastomers (LCEs) exhibit exceptional reversible deformation and unique physical properties owing to their order-disorder phase transition under external stimuli. Among these deformations, helical structures have attracted attention owing to their distinctive configurations and promising applications in biomimetics and microelectronics. However, the helical deformation behavior of fiber actuators is critically influenced by their morphologies and alignments; yet, the underlying mechanisms are not fully understood. Through a two-step aza-Michael addition reaction and direct ink writing (DIW) 4D printing technology, fiber-based LCE actuators with a core-sheath alignment structure were fabricated and exhibited reversible helical deformation upon heating. By adjusting the printing parameters, the filament number, width, thickness, and core-sheath structure of the fiber actuators can be precisely controlled, resulting in deformation behaviors, such as contraction, bending, and helical twisting. Finite element simulations were performed to investigate the deformation behaviors of the fiber actuators, providing insights into the variations in stress and strain during the shape-changing process, which can be used to explain the shape-morphing mechanism. These findings demonstrate that the precise tuning of printing parameters enables the controllable construction of LCE actuator morphology and customization of their functional properties, paving the way for advanced applications in smart fabrics, biomedical engineering, and flexible electronics.

The strain-induced crystallization behaviors of ultrasonic micro-injection molded poly(L-lactic acid)/poly(D-lactic acid) (PLLA/PDLA) samples from an amorphous state were investigated by stress-strain relations and in situ wide angle X-ray diffraction (WAXD) measurements. The formation of direct strain-induced stereocomplex (SC) was evident. In samples molded at 50 and 80 °C, this phenomenon can be attributed to the acceleration of the ordered structures due to the existence of a large number of SC nuclei. The SC nuclei are assumed to serve as the transient physical cross-links to initiate the strain-induced crystallization. The onset of strain-induced crystallization is analogous to the heating induced structural reorganization. Consequently, the observed strain-induced SC process can be considered a pseudo process, which is actually thermally induced. Upon further stretching, the actual strain-induced crystallization occurs with the exclusive formation of the homocrystallite (HC), while the preceding formed SC crystals undergo slight fragmentation during subsequent tensile deformation. At 120 °C, due to the reduced number of SC nuclei within the sample, the occurrence of cold crystallization during stretching plays a more significant role than SC nuclei with respect to the strain-induced SC process, as demonstrated by in situ WAXD measurements upon annealing in both the static and stretched states.

Thermosets are indispensable to our daily life, but their crosslinked structures make them unable to be processed by the melt processing like thermoplastics, which greatly limits their shape designs and applications. Herein, we address this challenge via an in situ self-growing strategy, i.e. utilizing the dynamic imidazole-urea moiety to suck up and integrate epoxy into the materials and making the thermoplastics grow in situ into thermosets. With this strategy, thermosets can be readily processed via hot-melt extrusion molding, including melt spinning and fused deposition modeling 3D printing. More importantly, this strategy simultaneously integrates the flexibility of polyurethane and the robustness of epoxy resin into the resulting thermosets, yielding a mechanical-reinforcing effect to make the material not only strong but also tough (toughness: 99.3 MJ·m⁻³, tensile strength: 38.8 MPa). Moreover, the crosslinking density and modulus of the as-prepared thermosets (from 34.1 MPa to 613.7 MPa) can be readily tuned on demand by changing the growth index. Furthermore, these thermosets exhibited excellent thermal stability and chemical resistance.

The strategic dispersion of carbon nanotubes (CNTs) within triblock copolymer matrix is key to fabricating nanocomposites with the desired electrical properties. This study investigated the self-assembly and electrical behavior of a polystyrene-polybutadiene-polystyrene (SBS) matrix with CNTs of different aspect ratios using hybrid particle-field molecular dynamics simulations. Structural factor analysis of the nanocomposites indicated that CNTs with higher aspect ratios promoted the transition of the SBS matrix from a bicontinuous to a lamellar phase. The resistor network algorithm method showed that the electrical conductivity of SBS and CNTs nanocomposites was influenced by the interplay between the CNTs aspect ratios, concentrations, and domain sizes of the triblock copolymer SBS. Our research sheds light on the relationship between CNTs dispersion and the electrical behavior of SBS/CNTs nanocomposites, guiding the engineering of materials to achieve desired electrical properties through the modulation of CNTs aspect ratios and tailored sizing of triblock copolymer domains.