Chinese Journal of Polymer Science最新文献

Due to the mechanical stability of PP layer, the PP/HDPE double-layer microporous membrane could be prepared at a higher heat-setting temperature than that of PE monolayer membrane. In this work, the effects of heat-setting temperature on the pore structure and properties of PP/HDPE double-layer membrane were studied. With the increase of heat-setting temperature from 120 °C to 130 °C, the length of connecting bridge crystal and crystallinity in the PE layer increase due to the melting of thin lamellae and the stability of connecting bridge structure during heat-setting. The corresponding air permeability, porosity, wettability of liquid electrolyte and mechanical property of the heat-set microporous membrane increase, exhibiting better electrochemical performance. However, when the heat-setting temperature is further increased to 140 °C, higher than the melting point of PE resin, some pores are closed since the lamellae and connecting bridges melt and shrink during heat-setting, resulting in a decrease of air permeability and porosity. In contrast, there is negligible change in the PP layer within the above heat-setting temperature region. This study successfully builds the relationship between the stable pore structure and property of microporous membrane during heat-setting, which is helpful to guide the production of high-performance PP/PE/PP lithium batteries separator.

Shear-thinning hydrogels have emerged for endoscopic submucosal dissection, while wound intervention after surgery has rarely been mentioned. Herein, a catechol-modified chitosan hydrogel with shear-thinning property was developed for simultaneously facilitating endoscopic submucosal dissection and postoperative wound healing. Benefiting from the shear-thinning and self-healing characteristics, the asprepared hydrogel showed easily endoscopic injectability. It also performed very well as submucosal cushion, which could remain above 70% after injection for 120 min in ex vivo porcine large intestine model. In fact, the cushion height of normal saline dramatically decreased to 46% of the initial height at 30 min. Ag nanoparticles encapsulated into the network endowed the hydrogel with almost reached 100% antibacterial effect against E. coli and S. aureus. The hemolysis ratio of the hydrogel was calculated to be as low as 0.8%. Combined with good hemocompatibility and cytocompatibility, the as-prepared hydrogel displayed much higher in vivo wound closure and healing efficacy than normal saline. These results demonstrated the superiority of the shear-thinning chitosan hydrogel in facilitating clinical endoscopic submucosal dissection surgery.

Toughening the petroleum-based epoxy resin blends with bio-based modifiers without compromising their modulus, mechanical strength, and other properties is still a big challenge in view of the sustainability. In this study, a bio-based liquid crystal epoxy resin (THMT-EP) with an s-triazine ring structure was utilized to modify a petroleum-based bisphenol A epoxy resin (E51) with 4,4′-diaminodiphenylsulfone (DDS) as a curing agent, and the blended systems were evaluated for their thermal stability, mechanical properties, and flame retardancy. The results showed that the impact strength of the blended system initially increased and then decreased with the increase in THMT-EP content, and it reached the a maximum value of 26.5 kJ/m² when the THMT-EP content was 5%, which was 31.2% higher than that of E51/DDS. Notably, the flexural strength, modulus, and glass transition temperature of the blended system were all simultaneously improved with the addition of THMT-EP. At the same time, the addition of THMT-EP enhanced the flame retardancy of the system by increasing the char yield at 700 °C and decreasing the peak heat release rate and total heat release rate. This work paves the way for a more sustainable improvement in the comprehensive performance of epoxy resin.

Plasma treatment is necessary to optimize the performance of biomaterial surfaces. It enhances and regulates the performance of biomaterial surfaces, creating an effective interface with the human body. Plasma treatments have the ability to modify the chemical composition and physical structure of a surface while leaving its properties unaffected. They possess the ability to modify material surfaces, eliminate contaminants, conduct investigations on cancer therapy, and facilitate wound healing. The subject of study in question involves the integration of plasma science and technology with biology and medicine. Using a helium plasma jet source, applying up to 18 kV, with an average power of 10 W, polymer foils were treated for 60 s. Plasma treatment has the ability to alter the chemical composition and physical structure of a surface while maintaining its quality. This investigation involved the application of helium plasma at atmospheric pressure to polyamide 6 and polyethylene terephthalate sheets. The inquiry involves monitoring and assessing the plasma source and polymer materials, as well as analyzing the impacts of plasma therapy. Calculating the mean power of the discharge aids in assessing the economic efficacy of the plasma source. Electric discharge in helium at atmospheric pressure has beneficial effects in technology, where it increases the surface free energy of polymer materials. In biomedicine, it is used to investigate cytotoxicity and cell survival, particularly in direct blood exposure situations that can expedite coagulation. Comprehending the specific parameters that influence the plasma source in the desired manner for the intended application is of utmost importance.

The thermochromic mechanism and the structure-property regulation principle of reversible thermochromic polydiacetylene (PDA) materials have always been a challenging issue. In this work, a series of diacetylene monomers (m-PCDA) containing phenyl and amide or carboxyl groups were synthesized from 10,12-pentacosadiynoic acid (PCDA) through the esterification or amidation reactions. The effects of the number and the distribution of the functional groups in m-PCDA molecules on their solid-state polymerization capability, and the thermochromic mechanism of their corresponding polymers (m-PDA) were investigated and discussed in detail. The results show that the m-PCDA monomers containing both benzene ring and groups that can form hydrogen bonding interactions have strong intermolecular interaction, and are easy to carry out the solid phase polymerization under 254-nm UV irradiation to obtain the corresponding new thermochromic m-PDA materials. The thermochromic behavior of m-PDA depends on its melting process. The initial color-change temperature (blue to red) is determined by the onset melting temperature, and the temperature range in which reversible color recovery can be achieved by repeat heating-cooling treatment is determined by its melting range. According to the proposed thermochromic mechanism of PDA, various new PDA materials with precise thermochromic temperatures and reversible thermochromic temperature ranges can be designed and synthesized through the appropriate introduction of benzene ring and groups that can form hydrogen bonding interactions into the molecular structure of linear diacetylene monomer. This work provides a perspective to the precise molecular structure design and the property regulation of the reversible thermochromic PDA materials.

With the rapid development of high-power-density electronic devices, interface thermal resistance has become a critical barrier for effective heat management in high-performance electronic products. Therefore, there is an urgent demand for advanced thermal interface materials (TIMs) with high cross-plane thermal conductivity and excellent compressibility to withstand increasingly complex operating conditions. To achieve this aim, a promising strategy involves vertically arranging highly thermoconductive graphene on polymers. However, with the currently available methods, achieving a balance between low interfacial thermal resistance, bidirectional high thermal conductivity, and large-scale production is challenging. Herein, we prepared a graphene framework with continuous filler structures in in-plane and cross-plane directions by bonding corrugated graphene to planar graphene paper. The interface interaction between the graphene paper framework and polymer matrix was enhanced via surface functionalization to reduce the interface thermal resistance. The resulting three-dimensional thermal framework endows the polymer composite material with a cross-plane thermal conductivity of 14.4 W·m⁻¹·K⁻¹ and in-plane thermal conductivity of 130 W·m⁻¹·K⁻¹ when the thermal filler loading is 10.1 wt%, with a thermal conductivity enhancement per 1 wt% filler loading of 831%, outperforming various graphene structures as fillers. Given its high thermal conductivity, low contact thermal resistance, and low compressive modulus, the developed highly thermoconductive composite material demonstrates superior performance in TIM testing compared with TFLEX-700, an advanced commercial TIM, effectively solving the interfacial heat transfer issues in electronic systems. This novel filler structure framework also provides a solution for achieving a balance between efficient thermal management and ease of processing.

Passive daytime radiative cooling (PDRC) is an innovative and sustainable cooling technology that holds immense potential for addressing the energy crisis. Despite the numerous reports on radiative coolers, the design of a straightforward, efficient, and readily producible system remains a challenge. Herein, we present the development of a hierarchical aligned porous poly(vinylidene fluoride) (HAP-PVDF) film through a freeze-thaw-promoted nonsolvent-induced phase separation strategy. This film features oriented microporous arrays in conjunction with random nanopores, enabling efficient radiative cooling performance under direct sunlight conditions. The incorporation of both micro- and nano-pores in the HAP-PVDF film results in a remarkable solar reflectance of 97% and a sufficiently high infrared thermal emissivity of 96%, facilitating sub-environmental cooling at 18.3 °C on sunny days and 13.1 °C on cloudy days. Additionally, the HAP-PVDF film also exhibits exceptional flexibility and hydrophobicity. Theoretical calculations further confirm a radiative cooling power of 94.8 W·m⁻² under a solar intensity of 1000 W·m⁻², demonstrating a performance comparable to the majority of reported radiative coolers.

The antioxidant N-isopropyl-N′-phenyl-p-phenylenediamine (4010NA) was dissolved in ethanol and impregnated into silica aerogel (SAG) via vacuum-pressure cycles, yielding composite particles (A-N) with enhanced sustained-release and reinforcing capabilities. The effect of A-N on the mechanical properties and thermal-oxidative aging resistance of styrene-butadiene rubber (SBR) vulcanizates was investigated. TGA and BET assessments indicated that the loading efficiency of 4010NA in SAG reached 14.26% within ethanol’s solubility limit. Incorporating A-N into SBR vulcanizates significantly elevated tensile strength by 17.5% and elongation at break by 41.9% over those with fumed silica and free 4010NA. Furthermore, A-N notably enhanced the thermal-oxidative aging resistance of SBR. After aging for 96 h at 100 °C, the tensile strength and elongation at break of SBR with A-N sustained 70.09% and 58.61% of their initial values, respectively, with the retention rate of elongation at break being 62.8% higher than that of SBR with fumed silica and free antioxidant. The study revealed that A-N composite particles significantly inhibited the crosslinking in SBR’s molecular chains, reducing hardening and embrittlement during later thermal-oxidative aging stages.