Chinese Journal of Polymer Science最新文献

Multi-component polymer systems exhibit exceptional versatility and structural diversity, making them indispensable in the polymer industry as well as in advanced and high performance applications. However, constructing accurate phase diagrams for these systems remains challenging due to inhomogeneous structures arising from the introduction of block copolymer components. Here, we present a unified and model-agnostic framework for computing phase equilibria in multi-component polymeric systems based on the concept of “effective chemical potential”. This approach directly connects key thermodynamic variables in the canonical ensemble to other ensembles, unifying phase coexistence determination without requiring the reformulation of self-consistent field theory (SCFT) calculations across different ensembles. By decoupling phase equilibrium determination from specific ensemble formulations, our approach enables the reuse of existing SCFT solvers. Moreover, it provides a useful framework to develop highly efficient phase equilibrium solvers for multi-component polymer systems.

The current work addresses the challenge of elucidating the performance of fluoroelastomers within the HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) based polymer-bonded explosives (PBXs). To simulate the confined interface in PBXs, bilayer films of F2314/HMX and F2311/HMX were designed. Neutron reflectivity (NR), nanoindentation, and X-ray reflectivity (XRR) were employed to examine the layer thickness, interface characteristics, diffusion behavior, and surface morphology of the bilayers. NR measurements revealed interface thicknesses of 45 Å and 98 Å for F2314/HMX and F2311/HMX, respectively, indicating deeper penetration of F2311 into the HMX matrix. NR also suggested a denser polymer network with a higher scattering length density (SLD) near the HMX interface for both fluoroelastomers, while the bound layer of F2311 was notably thicker. Nanoindentation cross-checks and confirms the presence of a bound layer, highlighting the differences in stiffness and diffusion ability between the two polymers. The consistency between the NR and nanoindentation results suggests that F2311 demonstrates better flexibility and elasticity, whereas F2314 is stiffer and more plastic. Accordingly, the structures and performances of different fluoroelastomers at the HMX interface are discussed, which can provide valuable insights into the selection of binders for PBX formulations tailored to specific applications.

In high-frequency electrical energy systems, polyimide (PI) composite insulation materials need to possess a low dielectric constant, sufficient thermal conductivity, and robust interfacial adhesion to ensure reliable performance under elevated temperatures and pressures. These aspects are crucial for preventing local overheating and electrical breakdown, thereby ensuring reliable equipment operation. Traditional PI insulation materials often exhibit high dielectric constants and pronounced dielectric losses, compromising their insulation efficiency. In this study, molecular dynamics simulations were employed to incorporate polyhedral oligomeric silsesquioxanes (POSS) into PI through physical blending and chemical bonding to enhance dielectric properties. Key parameters of the PI/POSS composite system, including dielectric constant, thermal conductivity, glass transition temperature, Young’s modulus, Poisson’s ratio, and interfacial adhesion energy, were systematically evaluated for both doping methods. The degradation behavior of the PI composites under high-temperature and electric field conditions was also simulated to elucidate degradation pathways and product distributions, providing insights for designing low-dielectric insulation materials. Doping with POSS significantly reduces the dielectric constant of PI, thereby improving insulation performance, thermal stability, mechanical strength, and interfacial adhesion. At an optimal POSS doping ratio, the thermal conductivity of PI is enhanced. Compared with the physical blending system, the chemical bonding system yields more substantial improvements across all evaluated properties. Under high-temperature and strong electric field conditions, POSS doping enhances interfacial adhesion and thermal stability, effectively suppressing the cleavage of key chemical bonds, reducing CO emissions, and increasing the formation of oxygen-containing intermediates and water molecules, which contributes to improved environmental sustainability.

The synthesis of functionalized rubber copolymers is a topic of great research interest. In this study, we present a novel approach for the direct construction of α-functionalized 3,4-polyisoprene through polymerization of polar monomers and isoprene monomer. The α-functionalized 3,4-polyisoprene was successfully synthesized via in situ sequential polymerization using the iron-based catalytic system (Fe(acac)₃/IITP/AlⁱBu₃), exhibiting high activity and resistance to polar monomers without requiring protection of polar groups. The structure of α-functionalized 3,4-polyisoprene was confirmed by proton nuclear magnetic resonance spectroscopy (¹H-NMR) and two-dimensional diffusion-ordered spectroscopy (2D DOSY) spectra analysis. The introduction of polar groups, particularly hydroxyl groups, enhanced the hydrophilicity of the copolymer. This was evidenced by a decrease in the water contact angle from 106.9° to 96.4° with increasing hydroxyl content in the copolymer.

The slow phase transition from form II to form I has always been an important factor that restricts the processing and application of polybutene-1 (PB-1). After extensive efforts, a set of effective methods for promoting the phase transition rate in PB-1 was established by adjusting the crystallization, nucleation, and growth temperatures. Nevertheless, low-molecular-weight PB-1 (LMWPB-1) faces challenges because this method requires a low crystallization temperature, which is difficult to achieve during extrusion processing. In this study, we attempted to increase the phase transition rate in PB-1 by changing the annealing temperature after processing rather than the crystallization temperature in the classical scheme. The results indicated that regardless of low- or high-molecular-weight PB-1, repeated annealing between 0 and 90 oC could also promote form II to form I phase transition. The initial content of form I increased with the heating and cooling cycles. The half-time of the phase transition (t_1/2) was also shortened after heating/cooling. After 100 heating/cooling cycles, t_1/2 was reduced to one-quarter of that without annealing, which had almost the same effect as the crystallization temperature at 25 °C in promoting the phase transition. This study indicates that annealing after processing is also an important factor affecting the phase transition of PB-1, and should receive sufficient attention.

Spatial confinement of block copolymers can induce frustrations, which can further be utilized to regulate self-assembled structures, thus providing an efficient route for fabricating novel structures. We studied the self-assembly of AB di-block copolymers (di-BCPs) confined in Janus spherical nanocavities using simulations, and explained the structure formation mechanisms. In the case of a strongly selective cavity wall, all the lamella-forming, gyroid-forming, and cylinder-forming di-BCPs can form interfacial frustration-induced Janus concentric perforated lamellar nanoparticles, whose outermost is a Janus spherical shell and the internal is a sphere with concentric perforated lamellar structure. In particular, Janus concentric perforated lamellar nanoparticles with holes distributed only near the equatorial plane were obtained in both lamella-forming and gyroid-forming di-BCPs, directly reflecting the effect of interfacial frustration. The minority-block domain of the cylider-forming di-BCPs may form hemispherical perforated lamellar structures with holes distributed in parallel layers with a specific orientation. For symmetric di-BCPs, both the A and B domains in each nanoparticle are continuous, interchangeable, and have rotational symmetry. While for gyroid-forming and cylinder-forming di-BCPs, only the majority-block domains are continuous in each nanoparticle, and holes in the minority-block domains usually have rotational symmetry. In the case of a weakly selective cavity wall, the inhomogeneity of the cavity wall results in structures having a specific orientation (such as flower-like and branched structures in gyroid-forming and cylinder-forming di-BCPs) and a perforated wetting layer with uniformly distributed holes. The novel nanoparticles obtained may have potential applications in nanotechnology as functional nanostructures or nanoparticles.

Sizing treatment is a suitable technique to modify the fiber-matrix interfaces without damage of inherent performance of fibers. In this work, sizing agents based on Janus particles (JPs) were utilized to enhance the interface of basalt fiber (BF)/poly(vinyl chloride) (PVC) composites. polystyrene/poly(butyl acrylate) (PS/PBA)@silica JPs were synthesized by seed emulsion polymerization and three different sizing agents were prepared for BF sizing treatment. JPs with organic soft sphere and inorganic hard hemisphere enhanced the interfaces through their amphiphilicity, chemical bonding and mechanical interlock. The mechanical properties of composite with JPs sizing treated BFs performed better when there was one JPs layer modified on the interface. According to the intermitting bonding and gradient modulus theory, JPs patterned interfaces are ideal transition layers between high modulus BF and low modulus PVC.

To enhance the properties of bio-based polyesters, enabling them to more closely mimic the characteristics of terephthalate-based materials, a series of aliphatic-aromatic copolyesters (P₁–P₄) were synthesized via melt polycondensation. Diester monomers M and N were synthesized via the Williamson reaction, using lignin-derived 2-methoxyhydroquinone, methyl 4-chloromethylbenzoate, and methyl chloroacetate as starting materials. Hydroquinone bis(2-hydroxyethyl)ether (HQEE) and 1,4-cyclohexanedimethanol (CHDM) were employed as cyclic segments, while 1,4-butanediol (BDO) and 1,6-hexanediol (HDO) served as alkyl segments within the copolymer structures. The novel copolyesters exhibited molecular weights (M_w) in the range of 5.25×10⁴–5.87×10⁴ g/mol, with polydispersity indices spanning from 2.50–2.66. Evaluation of the structural and thermomechanical properties indicated that the inclusion of alkyl segments induced a reduction in both crystallinity and molecular weight, while significantly improving the flexibility, whereas cyclic segments enhanced the processability of the copolyesters. Copolyesters P₁ and P₂, due to the presence of rigid segments (HQEE and CHDM), displayed relatively high glass transition temperatures (T_g>80 °C) and melting temperatures (T_m>170 °C). Notably, P₂, incorporating CHDM, exhibited superior elongation properties (272%), attributed to the enhanced chain mobility resulting from its trans-conformation, while P₁ was found to be likely brittle owing to excessive chain stiffness. Biodegradability assessment using earthworms as bioindicators revealed that the copolyesters demonstrated moderate degradation profiles, with P₂ exhibiting a degradation rate of 4.82%, followed by P₄ at 4.07%, P₃ at 3.65%, and P₁ at 3.17%. The higher degradation rate of P₂ was attributed to its relatively larger d-spacing and lower toxicity, which facilitated enzymatic hydrolytic attack by microorganisms. These findings highlight the significance of optimizing the structural chain segments within aliphatic-aromatic copolyesters. By doing so, it is possible to significantly enhance their properties and performance, offering viable bio-based alternatives to petroleum-based polyesters such as polyethylene terephthalate (PET).

Compatibilization is crucial for the blending of immiscible polymers to develop high-performance composites; however, traditional compatibilization by copolymers (pre-made or in-situ generation) suffers from weak interface anchoring, and inorganic particles have gained extensive attention recently owing to their large interfacial desorption energy, while their low affinity to bulk components is a drawback. In this study, an interfacial atom transfer radical polymerization (ATRP) technique was employed to grow polystyrene (PS) and poly(2-hydroxyethyl methacrylate)(PHEMA) simultaneously on different hemispheres of Br-functionalized SiO₂ nanoparticles to stabilize a Pickering emulsion, whereby a brush-type Janus nanoparticle (SiO₂@JNP) was developed. The polymer brushes were well-characterized, and the Janus feature was validated by transmission electron microscope (TEM) observation of the sole hemisphere grafting of SiO₂-PS as a control sample. SiO₂@JNP was demonstrated to be an efficient compatibilizer for a PS/poly(methyl methacrylate) (PMMA) immiscible blend, and the droplet-matrix morphology was significantly refined. The mechanical strength and toughness of the blend were synchronously enhanced at a low content SiO₂@JNP optimized ~0.9 wt%, with the tensile strength, elongation at break and impact strength increased by 17.7%, 26.6% and 19.6%, respectively. This enhancement may be attributed to the entanglements between the grafted polymer brushes and individual components that improve the particle-bulk phase affinity and enforce interfacial adhesion.

The thioacetamide derivative (TD)-composite preservation system (TDCPS) exhibits superior preservation effects on natural rubber latex (NRL) and significantly enhances its vulcanization efficiency and mechanical properties. This study primarily investigated the principal chemical groups and mechanism of action of TDCPS in promoting NRL vulcanization through a comparative analysis. The results indicated that the key functional groups (thioamide and pyridine) in TDCPS synergistically accelerated crosslinking, reducing the vulcanization time by 41.18% compared to the high-ammonia (HA) preservation system. At an optimal TDCPS dosage of 5 mmol·L⁻¹, vulcanized films achieved a tensile strength of 34.18 MPa, with a sulfur content of 1.5 phr further improving the strength by 42.26%. TD outperformed the conventional accelerators 2-imidazolidinethione (ETU) and 3-hydroxypyridine (3-Hp) in promoting the crosslinking density and mechanical performance while eliminating ammonia-related environmental risks. This eco-friendly system demonstrates the industrial potential for sustainable rubber production.