Amphiphilic polymer conetworks as chiral separation membranes

Dynamic Covalent Amphiphilic Polymer Conetworks Based on End-Linked Pluronic F108: Preparation, Characterization, and Evaluation as Matrices for Gel Polymer Electrolytes

We present the development of a platform of well-defined, dynamic covalent amphiphilic polymer conetworks (APCN) based on an α,ω-dibenzaldehyde end-functionalized linear amphiphilic poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol) (PEG-b-PPG-b-PEG, Pluronic) copolymer end-linked with a triacylhydrazide oligo(ethylene glycol) triarmed star cross-linker. The developed APCNs were characterized in terms of their rheological (increase in the storage modulus by a factor of 2 with increase in temperature from 10 to 50 °C), self-healing, self-assembling, and mechanical properties and evaluated as a matrix for gel polymer electrolytes (GPEs) in both the stretched and unstretched states. Our results show that water-loaded APCNs almost completely self-mend, self-organize at room temperature into a body-centered cubic structure with long-range order exhibiting an aggregation number of around 80, and display an exceptional room temperature stretchability of ∼2400%. Furthermore, ionic liquid-loaded APCNs could serve as gel polymer electrolytes (GPEs), displaying a substantial ion conductivity in the unstretched state, which was gradually reduced upon elongation up to a strain of 4, above which it gradually increased. Finally, it was found that recycled (dissolved and re-formed) ionic liquid-loaded APCNs could be reused as GPEs preserving 50-70% of their original ion conductivity.

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.

In situ fabrication of chiral covalent triazine frameworks membranes for enantiomer separation

Rapid and high-flux enantiomer separation is significant for drug development. Membrane separation technology provides promising approaches for enantiomer separations. Porous membrane with good selectivity and high permeability is an ideal choice for enantiomer separations. Herein, we demonstrate the preparation of a novel two-dimensional chiral covalent triazine frameworks (CCTF) membrane by "in situ growth" method. Inheriting the strong chirality and specific interactions from CCTF, the CCTF membranes exhibited good enantioselectivity for drug intermediates and drug, including (R)/(S)-1-phenylethanol, (R)/(S)-1,1'-binaphthol and (R)/(S)-ibuprofen. Under optimal separation conditions, the enantiomeric excess value (e.e %) was above 21.7 % for (R)/(S)-1-phenylethanol, 12.0% for (R)/(S)-1,1'-binaphthol and 9.7 % for (R)/(S)-ibuprofen. The mechanism of the CCTF recognizing enantiomers were simulated by quantum mechanical calculations. In addition, the mechanism was also proved by the separation of enantiomers using this CCTF-modified silica column in liquid chromatography. The CCTF membrane may bring about the potentially application for large-scale production of chiral compounds. Meanwhile, this work provides a theoretical guidance for the application of CCOFs in enantiomer separation.

Enantioselective Mixed Matrix Membranes for Chiral Resolution

Most pharmaceuticals are stereoisomers that each enantiomer shows dramatically different biological activity. Therefore, the production of optically pure chemicals through sustainable and energy-efficient technology is one of the main objectives in the pharmaceutical industry. Membrane-based separation is a continuous process performed on a large scale that uses far less energy than the conventional thermal separation process. Enantioselective polymer membranes have been developed for chiral resolution of pharmaceuticals; however, it is difficult to generate sufficient enantiomeric excess (ee) with conventional polymers. This article describes a chiral resolution strategy using a composite structure of mixed matrix membrane that employs chiral fillers. We discuss several enantioselective fillers, including metal-organic frameworks (MOFs), covalent organic frameworks (COFs), zeolites, porous organic cages (POCs), and their potential use as chiral fillers in mixed matrix membranes. State-of-the-art enantioselective mixed matrix membranes (MMMs) and the future design consideration for highly efficient enantioselective MMMs are discussed.

Solvent Effect on the Self-Assembly of a Thin Film Consisting of Y-Shaped Copolymer

The self-assembly of an amphiphilic Y-shaped copolymer consisting of two hydrophilic branches and one hydrophobic branch in a thin film is investigated under different conditions by virtue of mesoscopic computer modelling, accompanied by doping with a single solvent, doping with a binary solvent, and those solvent environments together with the introduction of confinement defined by various acting distances and influencing regions. A cylindrical micellar structure is maintained, as it is in the thin film with the doping of either 10% hydrophobic solvent or 10% hydrophilic solvent, whose structure consists of the hydrophobic core and hydrophilic shell. Attributed to the hydrophobicity/hydrophilia nature of the solvents, different solvents play an obvious role on the self-assembled structure, i.e., the hydrophobic solvent presents as a swelling effect, conversely, the hydrophilic solvent presents as a shrinking effect. Further, the synergistic effect of the binary solvents on the self-assembly produces the lowest values in both the average volumetric size and free energy density when the quantity of hydrophobic solvent and hydrophilic solvent is equivalent. Interestingly, the solvent effect becomes more pronounced under the existent of a confinement. When a lateral-oriented confinement is introduced, a periodically fluctuating change in the cylindrical size occurs in two near-wall regions, but the further addition of either hydrophobic or hydrophilic solvent can effectively eliminate such resulting hierarchical-sized cylinders and generate uniform small-sized cylinders. However, with the introduction of a horizontal-orientated confinement, the copolymers self-assemble into the spherical micellar structure. Moreover, the further addition of hydrophobic solvent leads to a decrease in the average size of micelles via coalescence mechanism, in contrast, the further addition of hydrophilic solvent causes an increase in the average size of micelles via splitting mechanism. These findings enrich our knowledge of the potential for the solvent effect on the self-assembly of amphiphilic copolymer system, and then provide theoretical supports on improving and regulating the mesoscopic structure of nanomaterials.

Swelling and mechanical properties of thermoresponsive/hydrophilic conetworks with crosslinked domain structures prepared from various triblock precursors

Thermoresponsive conetworks with crosslinked domain structures were designed by the crosslinking of triblock polymers for responsive gel functioning without external water.

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.

Nanophasic morphologies as a function of the composition and molecular weight of the macromolecular cross-linker in poly(N-vinylimidazole)-l-poly(tetrahydrofuran) amphiphilic conetworks: bicontinuous domain structure in broad composition ranges

Compositionally asymmetrical morphologies and cocontinous nanophase-separated structures are formed over a broad composition range, affected by composition and the molecular weights of macromonomers.

Mechanistic investigations of confinement effects on the self-assembly of symmetric amphiphilic copolymers in thin films

The self-assembly of a copolymer thin film, whose molecular structure is composed of one hydrophobic branch (denoted in green) and two hydrophilic branches (denoted in red), gives (a) cylindrical structure, (b) micellar structure, and (c) lamellar structure.

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.

Poly(N-vinylimidazole)-l-poly(propylene glycol) amphiphilic conetworks and gels: molecularly forced blends of incompatible polymers with single glass transition temperatures of unusual dependence on the composition

New molecularly forced blends of incompatible poly(N-vinylimidazole) and poly(propylene glycol) polymers with single glass transition temperatures.

Self-Sealing and Puncture Resistant Breathable Membranes for Water-Evaporation Applications

Breathable and waterproof membranes that self-seal damaged areas are prepared by modifying a poly(ether ester) membrane with an amphiphilic polymer co-network. The latter swells in water and the gel closes punctures. Damaged composite membranes remain water tight up to pressures of at least 1.6 bar. This material is useful for applications where water-vapor permeability, self-sealing properties, and waterproofness are desired, as demonstrated for a medical cooling device.

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.

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.