Journal of Polymer Science Part A: Polymer Chemistry最新文献

The polymer/solvent/nonsolvent ternary solutions have been previously used for fabricating electrospun macroporous fibers, in which the nonsolvent was expected to induce a liquid–liquid phase separation that leads to formation of pores after drying. In this study, we demonstrate that the poly(styrene-co-acrylonitrile) (SAN)/chlorobenzene (CB)/dimethyl sulfoxide (DMSO) system can be successfully electrospun into highly uniform macroporous fibers with pore size >50 nm at CB/DMSO volume ratio ~7/3 though both CB and DMSO are good solvents to SAN. The results imply that a premixed nonsolvent is not necessary for the formation of macropores. We find that it is the water droplets condensed from the atmosphere that work as the nucleation sites to trigger the phase separation while water-miscible DMSO plays a supporting role to expand the solvent-rich phase and the resultant pore size. Instead of solvent quality, the distinct volatilities and water miscibilities of the solvents are the keys. The macropores throughout the fibers provide high surface areas and large openings on surface such that the fibers show a significant improvement in oil adsorption capacity in comparison to the smooth and mesoporous ones.

Cerium-containing metal organic framework defined as Ce-MOF was prepared and then combined with piperazine pyrophosphate (PAPP) for preparing flame retardant ethylene vinyl acetate (EVA) copolymer composites. The samples of EVA/PAPP/Ce-MOF achieved UL-94 V-0 rating with the limiting oxygen index (LOI) value of 31.3% when 17 wt% PAPP/Ce-MOF with the mass fraction of 97:3 was introduced. Under the same loading amount of PAPP, the EVA/PAPP only obtained UL-94 V-1 rating with the LOI value of 26.9%. Cone calorimeter test confirmed that the total heat release and total smoke production of EVA/PAPP/Ce-MOF significantly reduced from 132.8 MJ m⁻² and 11.5 m² for EVA/PAPP to 98.8 MJ m⁻² and 7.3 m², with a reduction of 25.6% and 36.5%, respectively. Besides, the maximum smoke density decreased from 488.8 and 375.9 for EVA and EVA/PAPP to 177.5 for EVA/PAPP/Ce-MOF. It indicated that the addition of Ce-MOF and PAPP effectively exerted synergistic flame retardant and smoke inhibition effect for EVA. Moreover, the addition of Ce-MOF enhanced the compatibility of PAPP with EVA matrix, and water resistance of EVA/PAPP/Ce-MOF was higher than that of EVA/PAPP. The x-ray photoelectron spectroscopy texts of residual char of EVA composites indicated that the cerium ion complexed with phosphoric acid and polyphosphate generated by the thermal decomposition of PAPP and then more phosphorus elements remained in condensed phase. As a result, the sufficient, crosslinking and dense char layer with excellent intensity was formed, and the heat, combustible gas and smoke were efficiently inhibited. Consequently, the EVA materials were endowed excellent fire safety as well as low heat and smoke release.

Over the last 2 decades, high throughput genome-wide molecular profiling has revealed characteristic genetic and epigenetic alterations associated with different types of central nervous system (CNS) tumors. DNA methylation profiling has emerged as an important molecular platform for CNS tumor classification with improved diagnostic accuracy and patient risk stratification in comparison to the standard of care histopathological analysis and any single molecular tests. The emergence of DNA methylation arrays have also played a crucial role in refining existing types and the discovery of new tumor types or subtypes. The adoption of methylation data into neuro-oncology has been greatly aided by the development of a freely accessible machine learning-based classifier. In this review, we discuss methylation workflow, address the utility of DNA methylation profiling in CNS tumors in a routine diagnostic setting, and provide an overview of the methylation-based tumor types and new types or subtypes identified with this platform.

Rigid amorphous fraction (RAF) in bulk and thin-film states of isotactic polystyrene (iPS) was studied as a function of crystalline fraction (CF). The CF increased with isothermal cold crystallization in initially amorphous, melt-quenched bulk iPS samples. Assessed by differential scanning calorimetry, RAF in bulk iPS increased and then decreased with increasing crystallization time and CF. Specific RAF, that is, RAF/CF, decreased with increasing CF. Using ellipsometry, similar behaviors of RAF and specific RAF as functions of CF were observed in initially amorphous iPS thin films. These results indicate that specific RAF in iPS exhibits a continuous decrease from slightly below 2 at very low CF to ~0.2 at the maximum CF, independent of sample type and characterization method. This trend of decreasing specific RAF is consistent with a progression of crystal perfection during cold crystallization which is associated with lamellae thickening and decoupling between crystalline and amorphous regions. Qualitatively similar behaviors of RAF and specific RAF have been reported in other semi-crystalline polymers and in our recent studies of syndiotactic polystyrene, indicating that this trend of decreasing specific RAF with increasing CF is general for many semi-crystalline polymers. Finally, maximum CF is strongly reduced by nanoscale confinement in thin iPS films.

In this study, we report the synthesis of a new fluorinated vinyl monomer, that is, pentafluorophenyl vinyl ketone [1-(pentafluorophenyl)prop-2-en-1-one], its radical polymerization and copolymerization with styrene, methyl vinyl ketone, or phenyl vinyl ketone. The obtained homo- and co-polymers were subjected to thermal analysis, contact angle measurement, and an assay of resistance to UV irradiation. The results showed that the poly(pentafluorophenyl vinyl ketone) has a slightly greater contact angle and a lower temperature of the maximum decomposition rate when compared to the nonfluorinated analog: poly(phenyl vinyl ketone).

This article aims to outline the current progress in the field of energetic copolymer binders for composite solid propellants (CSPs). Propellants, which are a type of energetic material, are used to generate thrust in rockets and missiles, and they are generally less sensitive than explosives. The common formulations of CSPs contain several different chemical compounds that are typically bound together by a polymeric matrix to form a continuous solid. The use of inert polymers, however, does not enhance the overall specific impulse of the propellant. Energetic copolymers have emerged as a compelling category of binders for CSPs in recent years, offering potential advantages over traditional binders such as improved performance, enhanced safety, and increased manufacturing efficiency. The paper reviews the various types of energetic copolymer binders that have been developed, their potential advantages and drawbacks, and the current challenges and opportunities in the field. It suggests directions for future research and development and aims to provide a useful resource for researchers and practitioners interested in the use of energetic copolymer binders toward CSPs.

Aiming at obtaining high toughness polypropylene (PP) products, in this work, using high density polyethylene (HDPE) and styrene-ethylene-butylene-stryrene (SEBS) as toughening agents, PP/SEBS/HDPE blends were successfully fabricated by melt-blending method, and the microstructure, mechanical, thermodynamics, and rheological properties of the blends were investigated. The results revealed the core-shell structure particles with HDPE as the core and SEBS as the shell were dispersed in PP in the PP/SEBS/HDPE blends. The core-shell structure particles played good roles in toughening PP matrix, and the PP/SEBS/HDPE blends underwent brittle-tough transition at 15 wt% SEBS and 5 wt% HDPE. The impact toughness of PP/SEBS/HDPE blends with 15 wt% SEBS and 15 wt% HDPE reached 60.1 kJ/m², which was almost 1441.0% that of pure PP. The formation of core-shell particles in the system led to an increase in the degree of chain entanglement between the dispersed phase and PP, which enhanced the interfacial adhesion. In addition, based on the experimental results, the relationship between the viscosity and the material toughness was proposed, revealing the brittle-ductile transition behavior and the toughening mechanism.

It is still a serious challenge to construct a water-soluble polymer-based air filtration membrane with high efficiency and good mechanical properties by electrospinning. In the study, using polyvinyl alcohol (PVA) and polyacetylimide (PEI) as the main materials, both nanocellulosic crystal (CNC) and zinc oxide (ZnO) as the synergistic reinforcers and methyltrimethoxysilane (MTMS) as the hydrophobic modifier, the electrospun PVA/PEI/CNC/ZnO composite nanofibrous membrane with dual air filtration mechanisms was established. One of the mechanisms was the interception of the three-dimensional network structure built by the composite nanofibrous membrane, the other was the electrostatic adsorption provided by CNC. Based on the dual air filtration mechanisms, the filtration efficiency of particulate matter 2.5 (PM2.5) reached 98.20%. Moreover, the composite nanofibrous membrane displayed a good thermal stability and could still maintain more than the filtration efficiency of 83% and low-pressure drop after treatment at 200 °C for 1 h. Moreover, the composite nanofibrous membrane could still maintain the filtration efficiency (97.3%) and low-pressure drop (110.7 Pa) after five washing cycles after filtration, reflecting good reusability. Interestingly, the PVA/PEI/CNC/ZnO composite nanofibrous membrane was simple to produce and demonstrated excellent filtration efficiency, as well as excellent thermal stability, which could be an effective barrier against PM2.5 invasion.

Development of water-soluble polymer air filtration materials attracts considerable attentions due to their environmentally friendly performance and high efficiency, but the balance of mechanical strength, efficiency and pressure drop still is a severe challenge. Focusing on this issue, polyvinyl alcohol (PVA), bamboo activated carbon (BAC) and sodium lignosulfonate (Ls) were combined to construct an electrospinning system with two filtration functions. In the PVA@Ls@BAC system, the 3D network constructed by the electrospun PVA based nanofibrous could effectively intercept PM2.5, and the introduced Ls enhanced the mechanical strength of PVA nanofibrous due to its good rigidity. In addition, the added negatively charged BAC facilitated the electrostatic adsorption of PM2.5 while also improved the heat resistance of the system. Moreover, polydimethylsiloxane (PDMS) was introduced to enhance the water resistance of the system. The resulting electrospun PVA@Ls@BAC@PDMS composite nanofibrous air filtration membrane exhibited excellent air filtration performance (98.67%), water repellency (123.7° of WCA), and reusable performance, as well as having good mechanical property and the tensile fracture strain reaching 112%. Because of its good performance and simple preparation process, the electrospun PVA@Ls@BAC@PDMS composite nanofibrous air filtration membrane has great application space.

The cover image shows that a bacterial infection may occur in a wound, which delays the healing process. Therefore, in the modern day, a nature-inspired smart wound dressingis required to facilitate each step of wound healing. This image displays the different sources of natural polymers that are used in the development of dressing materials such as hydrogels, nanofibers, sponges, films, and various other types of scaffolds that aid in the complicated process of healing a wound. Bharti Sheokand, Monika Vats, Anand Kumar, Chander Mohan Srivastava, Indra Bahadur, and Seema R. Pathak contributed equally to the artwork. (DOI: 10.1002/pol.20220734)