Synthesis and characterization of chiral and thermo responsive amphiphilic conetworks

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.

Advances in versatile anti-swelling polymer hydrogels

Swelling is ubiquitous for traditional as-prepared hydrogels, but is unfavorable in many situations, especially biomedical applications, such as tissue engineering, internal wound closure, soft actuating and bioelectronics, and so forth. As the swelling of a hydrogel usually leads to a volume expansion, which not only deteriorates the mechanical property of the hydrogel but can bring about undesirable oppression on the surrounding tissues when applied in vivo. In contrast, anti-swelling hydrogels hardly alter their volume when applied in aqueous environment, therefore reserving the original mechanical performance and size-stability and facilitating their potential application. In the past decade, with the development of advanced hydrogels, quite a number of anti-swelling hydrogels with versatile functions have been developed by researchers to meet the practical applications well, through integrating anti-swelling property with certain performance or functionality, such as high strength, self-healing, injectability, adhesiveness, antiseptics, etc. However, there has not been a general summary with regard to these hydrogels. To promote the construction of anti-swelling hydrogels with desirable functionalities in the future, this review generalizes and analyzes the tactics employed so far in the design and manufacture of anti-swelling hydrogels, starting from the viewpoint of classical swelling theories. The review will provide a relatively comprehensive understanding of anti-swelling hydrogels and clues to researchers interested in this kind of materials to develop more advanced ones suitable for practical application.

Stereocomplex Poly(Lactic Acid) Amphiphilic Conetwork Gel with Temperature and pH Dual Sensitivity

A novel stereocomplex poly(lactic acid) amphiphilic conetwork gel with temperature and pH dual sensitivity was synthesized by ring-opening polymerization (ROP) and free radical copolymerization. The chemical structure and composition of hydrogel were characterized by Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (1H NMR) and X-ray diffraction (XRD). The temperature and pH sensitivity and good amphiphilicity of hydrogel were studied using digital photos, the swelling ratios and a scanning electron microscope (SEM). The thermal stability and mechanical properties of hydrogel were studied by differential scanning calorimeter (DSC) and dynamic viscoelastic spectrometer. The results indicated that the hydrogel has amphiphilicity, temperature and pH sensitivity, good thermal stability and mechanical strength.

Porous Surface Films With Tunable Morphologies and Hydrophobic Properties Based on Block Copolymer Under the Effects of Thermal Annealing

The fabrication of porous-structured polymer films with patterned surface structures has recently attracted increased interest within the material science field. In this work, a series of microstructure scale patterned polymer films were obtained via breath figure methods (BF) with hydrophobic surface films based on self-assembled diblock copolymers by atom-transfer radical polymerization (ATRP). The surface characteristics and morphological properties, pore size, roughness, thickness, and wettability of the block copolymer films was studied in response to variation of the hydrophilic co-monomer structures. A significant improvement of the quality and order of the hydrophobic films was observed in response to thermal annealing and a consequent optimization of the assembly process.

Swelling properties of thermoresponsive/hydrophilic co-networks with functional crosslinked domain structures

We focused on the monomer/crosslinker sequence in a gel network and designed novel thermoresponsive/hydrophilic amphiphilic co-networks with crosslinked domain structures.

Synthesis of thermo- and photo-responsive polysiloxanes with tunable phase separationviaaza-Michael addition

Two kinds of thermo- and photo-dual-responsive polysiloxanes were synthesized through a facile, effective, and catalyst-free aza-Michael addition.

Reversible Self-Actuated Thermo-Responsive Pore Membrane

Smart membranes, which can selectively control the transfer of light, air, humidity and temperature, are important to achieve indoor climate regulation. Even though reversible self-actuation of smart membranes is desirable in large-scale, reversible self-regulation remains challenging. Specifically, reversible 100% opening/closing of pore actuation showing accurate responsiveness, reproducibility and structural flexibility, including uniform structure assembly, is currently very difficult. Here, we report a reversible, thermo-responsive self-activated pore membrane that achieves opening and closing of pores. The reversible, self-actuated thermo-responsive pore membrane was fabricated with hybrid materials of poly (N-isopropylacrylamide), (PNIPAM) within polytetrafluoroethylene (PTFE) to form a multi-dimensional pore array. Using Multiphysics simulation of heat transfer and structural mechanics based on finite element analysis, we demonstrated that pore opening and closing dynamics can be self-activated at environmentally relevant temperatures. Temperature cycle characterizations of the pore structure revealed 100% opening ratio at T = 40 °C and 0% opening ratio at T = 20 °C. The flexibility of the membrane showed an accurate temperature-responsive function at a maximum bending angle of 45°. Addressing the importance of self-regulation, this reversible self-actuated thermo-responsive pore membrane will advance the development of future large-scale smart membranes needed for sustainable indoor climate control.

A clean synthesis approach to biocompatible amphiphilic conetworks via reversible addition–fragmentation chain transfer polymerization and thiol–ene chemistry

A series of APCNs from amphiphilic clickable pentablock copolymers with narrow polydispersity were synthesized via RAFT polymerization. The resulting APCNs exhibit unique amphiphilic characters, and can be potentially employed in some biomaterial applications.

High-sensitivity stimuli-responsive polysiloxane synthesized via catalyst-free aza-Michael addition for ibuprofen loading and controlled release

High-sensitive stimuli-responsive polysiloxanes with high sensitive respond to three changes of thermo-, pH-, and salinity were synthesized via a facile, highly efficient, catalyst-free aza-Michael addition of poly(aminopropylmethylsiloxane) with N-isopropylacrylamide.

Chiral porous hybrid particles constructed by helical substituted polyacetylene covalently bonded organosilica for enantioselective release

A new type of chiral porous hybrid particle was successfully prepared and applied in enantioselective release.

Unexpected thermal decomposition behavior of poly(N-vinylimidazole)-l-poly(tetrahydrofuran) amphiphilic conetworks, a class of chemically forced blends

The underlying chemical processes of the unexpected thermal decomposition behavior of poly(N-vinylimidazole)-l-poly(tetrahydrofuran) amphiphilic conetworks were investigated by thermogravimetric analysis and thermogravimetry-mass spectrometry.

Amphiphilic conetworks and gels physically cross-linked via stereocomplexation of polylactide

Amphiphilic conetworks (APCNs), consisting of hydrophilic poly[poly(ethylene glycol) methyl ester acrylate] (PPEGMEA) and hydrophobic stereocomplex of poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA), were prepared by free radical copolymerization of PEGMEA with acrylate macromonomer of the PLA stereocomplex. The effects of stereocomplexation and the amount of PLA stereocomplex on the rheology properties of APCNs were investigated. The results indicated that the APCNs was stronger in the presence of stereocomplexation compared with the that of nonstereocomplex system, and the strength of the APCNs increased with the increasing of the amount of PLA stereocomplex. The storage modulus of the APCNs could be easily tuned from 1200 to 4300 Pa by incorporating 2-10% of stereocomplex PLA. On the other hand, the swelling behavior of APCNs decreased with the increasing content of hydrophobic PLA cross-linker.

Investigations on diffusion limitations of biocatalyzed reactions in amphiphilic polymer conetworks in organic solvents

The use of enzymes as biocatalysts in organic media is an important issue in modern white biotechnology. However, their low activity and stability in those media often limits their full-scale application. Amphiphilic polymer conetworks (APCNs) have been shown to greatly activate entrapped enzymes in organic solvents. Since these nanostructured materials are not porous, the bioactivity of the conetworks is strongly limited by diffusion of substrate and product. The present manuscript describes two different APCNs as nanostructured microparticles, which showed greatly increased activities of entrapped enzymes compared to those of the already activating membranes and larger particles. We demonstrated this on the example of APCN particles based on PHEA-l-PDMS loaded with α-Chymotrypsin, which resulted in an up to 28,000-fold higher activity of the enzyme compared to the enzyme powder. Furthermore, lipase from Rhizomucor miehei entrapped in particles based on PHEA-l-PEtOx was tested in n-heptane, chloroform, and substrate. Specific activities in smaller particles were 10- to 100-fold higher in comparison to the native enzyme. The carrier activity of PHEA-l-PEtOx microparticles was tenfold higher with some 25-50-fold lower enzyme content compared to a commercial product.

Amphiphilic co-networks with moisture-induced surface segregation for high-performance nonfouling coatings

Herein we report the design of a photocurable amphiphilic co-network consisting of perfluoropolyether and poly(ethylene glycol) segments that display outstanding nonfouling characteristics with respect to spores of green fouling alga Ulva when cured under high humidity conditions. The analysis of contact angle hysteresis revealed that the poly(ethylene glycol) density at the surface was enhanced when cured under high humidity. The nonfouling behavior of nonbiocidal surfaces against marine fouling is rare because such surfaces usually reduce the adhesion of organisms rather than inhibit colonization. We propose that the resultant surface segregation of these materials induced by high humidity may be a promising strategy for achieving nonfouling materials, and such an approach is more important than simply concentrating poly(ethylene glycol) moieties at an interface because the low surface energy has been maintained in our work.