Chinese Journal of Polymer Science最新文献

To simultaneously endow thermal conductivity, high glass transition temperature (T_g) and healing capability to glass fiber/epoxy (GFREP) composite, dynamic crosslinked epoxy resin bearing reversible β-hydroxyl ester bonds was reinforced with boron nitride nanosheets modified glass fiber cloth (GFC@BNNSs). The in-plane heat conduction paths were constructed by electrostatic self-assembly of polyacrylic acid treated GFC and polyethyleneimine decorated BNNSs. Then, the GFC@BNNSs were impregnated with the mixture of lower concentration (3-glycidyloxypropyl) trimethoxysilane grafted BN micron sheets, 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate and hexahydro-4-methylphthalic anhydride, which accounted for establishing the through-plane heat transport pathways and avoiding serious deterioration of mechanical performances. The resultant GFREP composite containing less boron nitride particles (17.6 wt%) exhibited superior in-plane (3.29 W·m⁻¹·K⁻¹) and through-plane (1.16 W·m⁻¹·K⁻¹) thermal conductivities, as well as high T_g of 204 °C (T_g of the unfilled epoxy=177 °C). The reversible transesterification reaction enabled closure of interlaminar cracks within the composite, achieving decent healing efficiencies estimated by means of tensile strength (71.2%), electrical breakdown strength (83.6%) and thermal conductivity (69.1%). The present work overcame the disadvantages of conventional thermally conductive composites, and provided an efficient approach to prolong the life span of thermally conductive GFREP laminate for high-temperature resistant integrated circuit application.

Abstract

In this study, a novel iron-based catalyst system, Fe(acac)₃/(isocyanoimino) triptenylphosphorane (IITP)/AlR₃, was employed for the synthesis of syndiotactic 1,2-polybutadiene in hexane. This catalyst system exhibits remarkably high catalytic activity, achieving a polymerization activity of 762 kg_polymer·mol_catalyst⁻¹·h⁻¹ at 50 °C with a [BD]/[Fe] molar ratio of 20000. Furthermore, living polymerization characteristic were observed during the investigation of the polymerization kinetics of 1,3-butadiene polymerization. These characteristics were well demonstrated by a narrow molecular weight distribution (PDI≈2.0) of the resulting polybutadiene and a linear relationship between–ln(1 − c) and polymerization time as well as number average molecular weight and polymer yield. The resultant polymer showed a 1,2-selectivity of approximately 76% and stereoregularity ranging from 62% to 73%(rrrr). Additionally, through kinetic studies on polymerization reaction, an apparent activation energy E_a value of this catalytic system was calculated to be 84.98 kJ·mol⁻¹, which suggests that high polymerization temperature favors efficient polymerization.

We investigate the solution self-assembly of a mixture of positively charged homopolymers and AB diblock copolymers, in which the A blocks are negatively charged, and the B blocks are neutral. The electrostatic complexation between oppositely charged polymers drives the formation of many ordered phases. The microstructures and phase diagrams are calculated using self-consistent field theory (SCFT) based on an ion-pair model with an equilibrium constant K to characterize the strength of binding between positively and negatively charged monomers. The effects of the charge ratio, representing the ratio of charges from the homopolymer over all charges from polymers in the system, on the ordered structure are systematically studied, both for hydrophobic and hydrophilic A blocks. The charge ratio plays an important role in determining the phase boundaries in the phase diagram of salt concentration versus polymer concentration. We also provide information about the varying tendency of the domain spacing and core size of the spherical phase when the charge ratio is changed, and the results are in good agreement with experiments. These studies provide a deep understanding of the self-assembled microstructures of oppositely charged diblock copolymer-homopolymer systems.

In unit cell simulations, identification of ordered phases in block copolymers (BCPs) is a tedious and time-consuming task, impeding the advancement of more streamlined and potentially automated research workflows. In this study, we propose a scattering-based automated identification strategy (SAIS) for characterization and identification of ordered phases of BCPs based on their computed scattering patterns. Our approach leverages the scattering theory of perfect crystals to efficiently compute the scattering patterns of periodic morphologies in a unit cell. In the first stage of the SAIS, phases are identified by comparing reflection conditions at a sequence of Miller indices. To confirm or refine the identification results of the first stage, the second stage of the SAIS introduces a tailored residual between the test phase and each of the known candidate phases. Furthermore, our strategy incorporates a variance-like criterion to distinguish background species, enabling its extension to multi-species BCP systems. It has been demonstrated that our strategy achieves exceptional accuracy and robustness while requiring minimal computational resources. Additionally, the approach allows for real-time expansion and improvement to the candidate phase library, facilitating the development of automated research workflows for designing specific ordered structures and discovering new ordered phases in BCPs.

In this study, we proposed a novel method that integrates density functional theory (DFT) with the finite field method to accurately estimate the polarizability and dielectric constant of polymers. Our approach effectively accounts for the influence of electronic and geometric conformation changed on the dielectric constant. We validated our method using polyethylene (PE) and polytetrafluoroethylene (PTFE) as benchmark materials, and found that it reliably predicted their dielectric constants. Furthermore, we explored the impact of conformation variations in poly(vinylidene fluoride) (PVDF) on its dielectric constant and polarizability. The resulting dielectric constants of α- and γ-PVDF (3.0) showed excellent agreement with crystalline PVDF in experiments. Our findings illuminate the relationship between PVDF’s structural properties and its electrical behavior, offering valuable insights for material design and applications.

Water-soluble copolymers of p-methacrylamidobenzoic acid (MABA) with neutral comonomers (N-vinylpyrrolidone (VP), N-methyl-N-vinylacetamide (MVAA), N-methacryloyl glucosamine (MAG)) and anionic comononer sodium styrene sulfonate (NaSS) were synthesized by radical copolymerization. The interactions between the prepared copolymers and Tb³⁺ ions in aqueous solutions were studied; the significant influence of chemical structure of a comonomer on luminescence intensity of Tb³⁺ complexes with the copolymers was revealed. The luminescence intensity of Tb³⁺ complexes with the copolymers containing N-vinylamide units (VP, MVAA) is three times more intense than that observed for the complexes between Tb³⁺ and MAG-containing copolymers. In the case of NaSS-containing copolymers, the luminescence intensity is controlled by the values of binding constants between Tb³⁺ and MABA and the content of MABA units in a copolymer. The studied copolymers and their complexes with Tb³⁺ have low cytotoxicity and a pronounced antiviral activity against human respiratory syncytial virus.

There is an urgent imperative to discover practical and efficacious artificial catalysts for the expeditious decontamination of toxic organophosphates. Herein, we propose a novel molecularly imprinted approach utilizing electrospun fiber scaffolds. Specifically, an amidoxime-based functional polymer (PMAOX) has been synthesized, which contains amidoxime groups that can act as nucleophiles and ligands for the formation of catalytic active sites. This polymer was blended with polyacrylonitrile (PAN), a well-processable material, to prepare a nanofiber mat using electrospinning techniques. Then, the amidoxime side groups on fiber surface were further cross-linked after the molecular coordination of templates to complete the molecularly imprinting process. This approach can not only enhance the content of functional molecularly imprinted polymers without affecting structural stability, but also combines surface MI technology to fully expose and leverage the advantages of active sites. The as prepared molecularly imprinted electrospun nanofibers MIF-Zn-PMAOX/PAN-6/4 catalyzes the degradation of paraoxon with a half-life of 32 min, and MIF-Ag-PMAOX/PAN catalyzes the degradation of parathion with a half-life of 18 min. The maximum catalytic rate evidence rate enhancements nearly 3700-fold of the self-hydrolysis. Thus, the mono-amidoxime based molecularly imprinted fibers demonstrate the versatility and superiority as self-detoxifying for organophosphates.

High speed sintering, a new powder-bed fusion additive manufacturing technology, utilizes infrared lights (IR) to intensely heat and melt polymer powders. The presence of defects such as porosity, which is associated with particle coalescence, is highly dependdent on the level of energy input. This study investigate the influcence of energy input on porosity and its subsequent effects on the mechanical properties and microstructures of PEBA parts. The parts were manufactured with a variety of lamp powers, resulting in a range of energy input levels spanning from low to high. Subsequebtly, they underwent testing using Archimedes’ method, followed by tensile testing. The porosity, mechanical characteristics, and energy input exhibit a strong correlation; inadequate energy input was the primary cause of pore formation. Using the reduced IR light power resulted in the following outcomes: porosity, ultimate tensile strength, and elongation of 1.37%, 7.6 MPa, and 194.2%, respectively. When the energy input was further increased, the porosity was reduced to as low as 0.05% and the ultimate tensile strength and elongation were increased to their peak values of 233.8% and 9.1 MPa, respectively.

Polymer/conductive filler composites have been widely used for the preparation of self-limiting heating cables with the positive temperature coefficient (PTC) effect. The control of conductive filler distribution and network in polymer matrix is the most critical for performance of PTC materials. In order to compensate for the destruction of the filler network structure caused by strong shearing during processing, an excessive conductive filler content is usually added into the polymer matrix, which in turn sacrifices its processability and mechanical properties. In this work, a facile post-treatment of the as-extruded cable, including thermal and electrical treatment to produce high-density polyethylene (HDPE)/carbon black (CB) cable with excellent PTC effect, is developed. It is found for the as-extruded sample, the strong shearing makes the CB particles disperse uniformly in HDPE matrix, and 25 wt% CB is needed for the formation of conductive paths. For the thermal-treated sample, a gradually aggregated CB filler structure is observed, which leads to the improvement of PTC effect and the notable reduction of CB content to 20 wt%. It is very interesting to see that for the sample with combined thermal and electrical treatment, CB particles are agglomerated and oriented along the electric field direction to create substantial conductive paths, which leads to a further decrease of CB content down to 15 wt%. In this way, self-limiting heating cables with excellent processability, mechanical properties and PTC effect have simultaneously been achieved.