Thermo-Responsive Membranes from Blends of PVDF and PNIPAM-b-PVDF Block Copolymers with Linear and Star Architectures

The Effect of Colloidal Nanoparticles on Phase Separation of Block and Heteroarm Star Copolymers Confined between Polymer Brushes

The effect of colloidal nanoparticles on the phase changes of the amphiphilic AB linear diblock, A1A2B, and A2B heteroarm star copolymers confined between two polymer brush substrates was investigated by using a real-space self-consistent field theory. By changing the concentrations of nanoparticles and polymer brushes, the phase structure of the amphiphilic AB copolymer transforms from lamellar to core-shell hexagonal phase to cylinder phase. The pattern of A2B heteroarm star copolymer changes from core-shell hexagonal phases to lamellar phases and the layer decreases when increasing the density of the polymer brushes. The results showed that the phase behavior of the system is strongly influenced by the polymer brush architecture and the colloidal nanoparticle numbers. The colloidal nanoparticles and the soft confined surface of polymer brushes make amphiphilic AB copolymers easier to form ordered structures. The dispersion of the nanoparticles was also investigated in detail. The soft surfaces of polymer brushes and the conformation of the block copolymers work together to force the nanoparticles to disperse evenly. It will give helpful guidance for making some new functional materials by nano etching technology, nano photoresist, and nanoprinting.

Advanced stimuli-responsive membranes for smart separation

Membranes have been extensively studied and applied in various fields owing to their high energy efficiency and small environmental impact. Further conferring membranes with stimuli responsiveness can allow them to dynamically tune their pore structure and/or surface properties for efficient separation performance. This review summarizes and discusses important developments and achievements in stimuli-responsive membranes. The most commonly utilized stimuli, including light, pH, temperature, ions, and electric and magnetic fields, are discussed in detail. Special attention is given to stimuli-responsive control of membrane pore structure (pore size and porosity/connectivity) and surface properties (wettability, surface topology, and surface charge), from the perspective of determining the appropriate membrane properties and microstructures. This review also focuses on strategies to prepare stimuli-responsive membranes, including blending, casting, polymerization, self-assembly, and electrospinning. Smart applications for separations are also reviewed as well as a discussion of remaining challenges and future prospects in this exciting field. This review offers critical insights for the membrane and broader materials science communities regarding the on-demand and dynamic control of membrane structures and properties. We hope that this review will inspire the design of novel stimuli-responsive membranes to promote sustainable development and make progress toward commercialization.

Physical, Electrochemical, and Solvent Permeation Properties of Amphiphilic Conetwork Membranes Formed through Interlinking of Poly(vinylidene fluoride)-Graft-Poly[(2-dimethylamino)ethyl Methacrylate] with Telechelic Poly(ethylene glycol) and Small Molecular Weight Cross-Linkers

We report the preparation of dense and porous amphiphilic conetwork (APCN) membranes through the covalent interconnection of poly(vinylidene fluoride)-graft-poly[(2-dimethylamino)ethyl methacrylate] (PVDF-g-PDMAEMA) copolymers with telechelic poly(ethylene glycol) (PEG) or α,α-dichloro-p-xylene (XDC). The dense APCN membranes exhibit varying solvent swelling and mechanical properties depending on the compositions and overall crystallinity. The crystallinity of both PVDF (20-47%) and PEG (9-17%) is significantly suppressed in the dense APCNs prepared through the interconnection of PVDF-g-PDMAEMA with reactive PEG as compared to the APCN membranes (48-53%) prepared with XDC as well as mechanical blend of PVDF-g-PDMAEMA plus nonreactive PEG. The dense APCN membranes exhibit a good transport number of monovalent ions and ionic conductivity. The APCN membrane interconnected with PEG and containing binary ionic liquids exhibits a room-temperature lithium ion conductivity of 0.52 mS/cm. On the other hand, APCN ultrafiltration (UF) membranes exhibit organic solvent-resistant behavior. The UF membrane obtained by interconnecting PVDF-g-PDMAEMA with telechelic PEG shows low protein fouling propensity, higher hydrophilicity, and water flux as compared to membranes prepared using XDC as the interconnecting agent. The significant effect of the covalent interconnection of the amphiphilic graft copolymers with telechelic PEG or XDC on the overall properties provides a good opportunity to modulate the properties and performance of APCN membranes.