ACS polymers Au最新文献

Polyacrylonitrile (PAN) fibers, widely recognized for their exceptional carbonization and graphitization at higher processing temperatures, serve as precursors for high-performance carbon fiber production. This study explores the fabrication of PAN control fibers and PAN-CNT composites via fiber spinning, a process influenced by solution behavior, macromolecular extension, and crystallizations. The polymer chain morphologies, along with pore nucleation and growth, play a critical role in determining fiber microstructure and mechanical properties. Comprehensive characterization like wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) was conducted for PAN control and PAN-CNT composite fibers at polymer concentrations of 9, 10, and 11 wt % with specific CNT loading. This study highlights the enhanced performance of PAN fibers and PAN/CNT composite fibers fabricated at polymer concentrations of 9, 10, and 11 wt %. Additionally, the effects of carbon nanotubes (CNTs) on the polymer microstructure and properties, including crystallinity and thermal stability, were analyzed and compared.

Photoinduced anionic curing of epoxides by thiols offers many advantages over traditional (cationic and radical) photochemical cross-linking processes. This includes insensitivity to air and moisture, low volume shrinkage, good adhesion to substrates through β-hydroxy thioether linkages, and often no requirement for a postexposure baking step. Thus, interest in the thiol-epoxy 'click' reaction for photopolymerization purposes has been growing steadily. In this regard, photolatent catalysts have been developed with the capability to generate strong organic bases (superbases) under illumination from UV to the visible and near-infrared range. Besides bulk polymerizations, the base-catalyzed ring-opening reaction can also be harnessed for lithography purposes to fabricate micro- and nanosized patterns. Use of hydrophilic monomers can lead to the preparation of hydrogels. The cross-linked networks can be incorporated with photosensitive monomers to afford photoactive properties. Alternatively, the thioether linkages can be addressed through sulfur alkylation. This post-cross-linking modification reaction transforms the neutral thermosets into zwitterionic sulfonium/carboxylate or cationic sulfonium salts. The former endows the materials with antibiofouling properties, while the latter endows them with antibacterial surface properties. Postfabrication transesterification reactions within the material, on the other hand, bring vitrimer properties to the network and allow for object reshaping. The concepts of shape memory polymers and 3D printing have also been established. The aim of this Perspective is to review this nascent but growing area of research with the help of key literature examples.

To determine the impact of the interface material properties on hydrodynamic interactions and transport, we have investigated how "soft" gel surfaces influence the local diffusion of polystyrene nanoparticles in deionized water in convex lens-induced confinement (CLiC). The gel coatings are created by polymerizing polyacrylamide onto glass surfaces, resulting in surfaces with varying moduli of 60, 1300, 2620, and 8400 Pa that are 30-100 nm in height. We analyze the diffusion using differential dynamic microscopy (DDM) as a function of proximity to the surface. We find that diffusion depends on the material properties of the surface. The gel layers are too thin to impact the hydrodynamic interactions experienced on the surface, mirroring the contact angle measurements. However, near softer, more hydrated layers, the nanoparticles can permeate into or between the gel surfaces. As the modulus increases, the partition into the gel is lower, and we observe absorption of the particles into the gel, but no discernible motion in the gel layers. No additional effects are observed as a function of the height of the surface coatings within the experimental range. We postulate that these findings contribute to understanding polymer dynamics at complex interfaces and can potentially lead to a transformative understanding of biofouling and polymer-based separations.

This perspective offers an in-depth guide to photopolymerizations mediated with thiocarbonylthio compounds, with a particular focus on photoiniferter and photoinduced energy/electron transfer RAFT (PET-RAFT) polymerizations, focusing on practical considerations. It is designed to provide both newcomers and experts with the practical knowledge needed to harness light-mediated polymerizations for innovative applications. The discussion begins with an overview of conventional RAFT polymerization and proceeds to highlight the distinctive advantages of the photomediated processes. The photochemical behavior of thiocarbonylthio compounds, along with the selection of appropriate light wavelengths, is critically examined for its impact on polymerization kinetics and optimization of polymer properties. Key parameters influencing polymerization successsuch as catalyst selection, solvent choice, light intensity, and temperatureare explored in detail. The importance of oxygen tolerance and end-group fidelity is also addressed, as these factors are essential for achieving well-defined polymers. Additionally, reactor configurations are reviewed, focusing on the roles of light sources, reactor geometry (batch versus flow systems), and temperature control in optimizing the reaction efficiency. The article concludes by integrating these concepts into a comprehensive framework for optimizing photoiniferter and PET-RAFT polymerizations.