Chinese Journal of Polymer Science最新文献

Sodium alginate (SA) is generally considered highly hydrophilic due to two hydroxyl groups and a carboxylate group on each pyranose ring. However, SA will form a gel after dissolving in water for a certain period. The two properties of SA, hydrophilicity and gelation, seem to be paradoxical. In this study, to explore the mechanism behind these paradoxical properties, the single-chain behaviors of SA in various liquid environments have been investigated by using single-molecule force spectroscopy (SMFS). In nonpolar solvents such as nonane, SA exhibits its single-chain inherent elasticity consistent with the theoretical elasticity derived from quantum mechanical (QM) calculations. Notably, the experimental curve of SA obtained in water shows a long plateau in the low force region. Further research reveals that this phenomenon is driven by the hydrophobic effect. Additionally, SA shows greater rigidity than its inherent elasticity in the middle and high force regions due to electrostatic repulsion between carboxylate groups on adjacent sugar rings. Comparative single-molecule studies suggest that SA exhibits considerable hydrophobicity, offering new insights into the gelation process in water.

Poly(lactic acid) (PLA) is a biodegradable and eco-friendly polymer that is increasingly being incorporated into various applications in contemporary society. However, the limited stability of PLA-based products remains a significant challenge for their broader use in various applications. In this study, poly(L-lactic acid)(PLLA)/poly(D-lactic acid) (PDLA) melt-blown nonwovens were prepared by melt spinning. The structure, thermal properties, thermal stability, biodegradability and crystalline morphology of the melt-blown nonwovens were investigated. DSC and WAXD confirmed the formation of stereocomplex (SC) crystallites in the PLLA matrix. The storage modulus (G′), loss modulus (G″), and complex viscosity (∣η*∣) of the PLLA/PDLA blend increased with an increase in SC crystallite content. The thermal degradation temperatures of PLLA/PDLA melt-blown nonwovens increased with the incorporation of SC crystallites, and the maximum rate of decomposition increased to 385.5 °C, thus enhancing the thermal stability. Compared with neat PLLA melt-blown nonwovens, the hydrophobicity of PLLA/PDLA melt-blown nonwovens was improved, and WCA increased to 139.7°. The SC crystallites were more resistant to degradation by proteinase K compared to neat PLLA. However, the degradation rate of PLLA/PDLA melt-blown nonwovens remained at a high level. This work provides an effective strategy to obtain high-performance PLLA melt-blown nonwovens.

Control crosslink network and chain connectivity are essential to develop shape memory polymers (SMPs) with high shape memory capabilities, adjustable response temperature, and satisfying mechanistical properties. In this study, novel poly(ε-caprolactone) (PCL)-poly(2-vinyl)ethylene glycol (PVEG) copolymers bearing multi-pendant vinyl groups is synthesized by branched-selective allylic etherification polymerization of vinylethylene carbonate (VEC) with linear and tetra-arm PCLs under a synergistic catalysis of palladium complex and boron reagent. Facile thiol-ene photo-click reaction of PCL-PVEG copolymers with multifunctional thiols can rapidly access a serious crosslinked SMPs with high shape memory performance. The thermal properties, mechanical properties and response temperature of the obtained SMPs are tunable by the variation of PCL prepolymers, vinyl contents and functionality of thiols. Moreover, high elastic modulus in the rubbery plateau region can be maintained effectively owing to high-density topological networks of the PCL materials. In addition, the utility of the present SMPs is further demonstrated by the post-functionalization via thiol-ene photo-click chemistry.

The early stages of crystallization and occurrence of surface wrinkling were investigated using poly(butadiene)-block-poly(ε-caprolactone) with an ordered lamellar structure. Direct evidence has demonstrated that surface wrinkling precedes nucleation and crystal growth. This study examined the relationship between surface wrinkling, nucleation, and the formation of crystalline supramolecular structures using atomic force microscopy (AFM) and X-ray scattering measurements. Surface wrinkling is attributed to curving induced by accumulated stresses, including residual stress from the sample preparation and thermal stress during cooling. These stresses cause large-scale material flow and corresponding changes in the molecular conformations, potentially reducing the nucleation barrier. This hypothesis is supported by the rapid crystal growth observed following the spread of surface wrinkles. Additionally, the surface curving of the polymer thin film creates local minima of the free energy, facilitating nucleation. The nuclei subsequently grow into crystalline supramolecular structures by incorporating polymer molecules from the melt. This mechanism highlights the role of localized structural inhomogeneity in the early stages of crystallization and provides new insights into structure formation processes.

Intrinsic stretchability is a promising attribute of polymer organic solar cells (OSCs). However, rigid molecular blocks typically exhibit poor tensile properties, rendering polymers vulnerable to mechanical stress. In this study, we introduce a different approach utilizing all-small-molecule donors and acceptors to fabricate stretchable OSCs. An elastomer, styrene-b-ethylene-butylene-styrene (SEBS), was embedded to modulate film crystallization and stretchability. SEBS effectively confines the growth process of donors and acceptors, leading to enhancement of the crystallization quality, thus contributing to enhanced device efficiencies. Meanwhile, SEBS can absorb and release mechanical stress during stretching, thereby preventing mechanical degradation of donors and acceptors. The mechanical properties of the OSCs were significantly improved by the incorporation of SEBS. Notably, the crack-onset strain increased from 1.03% to 5.99% with SEBS embedding. These findings present a straightforward strategy for achieving stretchable OSCs using all small molecules, offering a different perspective for realizing stretchable devices.

Functional hyperbranched polymers, as an important class of materials, are widely applied in diverse areas. Therefore, the development of simple and efficient reactions to prepare hyperbranched polymers is of great significance. In this work, trialdehydes, diamines, and trimethylsilyl cyanide could easily undergo multicomponent polymerization under mild conditions, producing hyperbranched poly(α-aminonitrile)s with high molecular weights (M_w up to 4.87×10⁴) in good yields (up to 85%). The hyperbranched poly(α-aminonitrile)s have good solubility in commonly used organic solvents, high thermal stability as well as morphological stability. Furthermore, due to the numerous aldehyde groups in their branched chains, these hb-poly(α-aminonitrile)s can undergo one-pot, two-step, four-component post-polymerization with high efficiency. This work not only confirms the efficiency of our established catalyst-free multicomponent polymerization of aldehydes, amines and trimethylsilyl cyanide, but also provides a versatile and powerful platform for the preparation of functional hyperbranched polymeric materials.

The fatigue resistance of casting polyurethane (CPU) is crucial in various sectors, such as construction, healthcare, and the automotive industry. Despite its importance, no studies have reported on the fatigue threshold of CPU. This study employed an advanced Intrinsic Strength Analyzer (ISA) to evaluate the fatigue threshold of CPUs, systematically exploring the effects of three types of isocyanates (PPDI, NDI, TDI) that contribute to hard segment structures based on the cutting method. Employing multiple advanced characterization techniques (XRD, TEM, DSC, AFM), the results indicate that PPDI-based polyurethane exhibits the highest fatigue threshold (182.89 J/m²) due to a highest phase separation and a densely packed spherulitic structure, although the hydrogen bonding degree is the lowest (48.3%). Conversely, NDI-based polyurethane, despite having the high hydrogen bonding degree (53.6%), exhibits moderate fatigue performance (122.52 J/m²), likely due to a more scattered microstructure. TDI-based polyurethane, with the highest hydrogen bonding degree (59.1%) but absence of spherulitic structure, shows the lowest fatigue threshold (46.43 J/m²). Compared to common rubbers (NR, NBR, EPDM, BR), the superior fatigue performance of CPU is attributed to its well-organized microstructure, polyurethane possesses a higher fatigue threshold due to its high phase separation degree and orderly and dense spherulitic structure which enhances energy dissipation and reduces crack propagation.

Cutting-edge research has primarily focused on flow synthesis of linear block copolymers, lacking the ability for manipulating chain architectures for more extensive applications. Herein, we develop a flow chemistry platform for the continuous microflow synthesis of bottlebrush block copolymers (BBCPs) using a grafting-through method. This involves performing ring-opening metathesis polymerization (ROMP) of two different macromonomers within two microfluidic reactors connected in series. The microflow environment allows for complete monomer conversion within a few tens of seconds, benefiting from the superior mixing efficiency achieved in Z-shaped channels as indicated by both theoretical simulations and experimental results. Consequently, a library of well-defined BBCPs of up to 528 distinct samples can be produced within one day through automation of the continuous procedure, while keeping precise control on degree of polymerization (DP<4) and polydispersity indices (PDI<1.2). The synthetic method is generally applicable to different macromonomers with different compositions and contour lengths, yielding libraries of branched block copolymers with great diversity in physiochemical properties and chain architectures. This work presents a powerful platform for high-throughput production of branched copolymers, significantly lowering the costs of the materials for real applications.

As a highly promising conductive polymer material, the synthesis method, structure regulation, and performance improvement of polyaniline (PANI) are hot research topics. In this work, the radiation-induced polymerization of aniline in HNO₃ solution was successfully achieved at room temperature without the use of chemical oxidants. Through the analysis of the radiation chemical reactions of inorganic acids and nitrate salt solutions, the characterization of the intermediate free radicals in the irradiated systems, and the influence of the pH of the solutions on the polymerization activity and product morphologies, the radiation-induced polymerization mechanism of aniline is discussed in detail and proposed. Only at a condition of [HNO₃]>[aniline], i.e., pH<2.5, PANI can be successfully obtained under γ-ray radiation. The polymerization begins with the oxidation of aniline cations to aniline cation radicals by ·NO₃ generated by radiolysis reactions, and undergoes repeated three steps of monomer free radical recombination, deprotonation, and oxidation reaction of ·NO₃, thus forming a PANI macromolecule. In addition to the polymerization reaction, the aniline units are protonated and oxidized because of the strongly acidity and oxidation of the reaction system under γ-ray irradiation, which means that the molecular chain structure of the radiation-synthesized PANI can be regulated by pH, nitrate concentration, and irradiation conditions. Radiation-synthesized PANI has a moderate protonation and oxidation state, which can be used for the preparation of PANI supercapacitors with better electrochemical properties than those prepared by chemical oxidation under the same conditions. This work presents a new radiation-synthesis method and polymerization mechanism of PANI, which not only expands the application of radiation technique in the field of polymer synthesis, but also provides a new idea for the structural regulation and electrochemical property optimization of PANI.

Hair coloring has emerged as an integral part of the cosmetic industry, particularly in response to the increasing global aging phenomenon. The natural melanin analog, polydopamine (PDA), has garnered considerable attention as an eco-friendly hair dye, and several kinds of polymerization ways of dopamine (DA) have been proposed including alkali catalysis, metal ion catalysis, strong oxidants, and enzyme-mediated oxidation reactions and polymerizations. Yet the controllability of polymerization and potential toxicity of involved metal ions are still in question. Inspired by the photoprotective mechanism in human skin, we have developed the melanin-inspired hair dyeing strategy that allowed for the in situ oxidative polymerization of DA under ultraviolet (UV) light. This polymerization was triggered by photobase generators (PBGs), a class of compounds that produced organic bases upon UV and sunlight irradiation. The resulting hair showed an adjustable color from light brown to black by tuning the ratio of DA and PBG (DA@PBG), the concentration of DA, and light exposure time. The dyed hairs showed excellent washing resistance and superior anti-static properties. Furthermore, Hair Color Spray DA@PBG also demonstrated a desirable hair dyeing effect and excellent biosecurity by simply spraying it on the hair under sunlight. This novel sunlight-induced method provided a new direction towards the preparation of natural hair dyes and could promote the development of green and safe hair dyes in colorful and brilliant artistic-grade hair coloring.