Properties and Applications of Poly(dimethylsiloxane) Containing Poly(meth)acrylate-Based Thermoplastic Elastomer/Clay Nanocomposites

The beneficial effect of covalent attachment of a moderate amount (8–16 wt %) of poly­(dimethylsiloxane) (PDMS) into poly­(meth)­acrylate-based thermoplastic elastomers (TPEs) toward clay nanocomposite (NC) formation with improved mechanical properties, thermal properties, and tunable hydrophobic drug release behavior is reported. XRD and TEM analyses suggest that the covalent attachment of PDMS enhances the NC formation with both exfoliated and intercalated structures. With increasing amount of attached PDMS, the <i>d</i>-spacing of the intercalated clay part increases and the copolymer forms exclusively exfoliated structure at nearly 16 wt % PDMS content. Hence, clay NCs of a wide range of well-defined block copolymers of PDMS and poly­(meth)­acrylates can conveniently be prepared by this technique. The surface characterizations revealed comparatively more hydrophobic surface of PDMS-containing poly­(meth)­acrylate-based TPE/clay NCs than the corresponding neat poly­(meth)­acrylate-based TPE/clay NC. The improved thermal stability, improved mechanical properties, and sustained drug eluting behavior together with preferential surface coverage by biocompatible and biostable PDMS might provide further opportunities for the use of PDMS-containing poly­(meth)­acrylate-based TPE/clay NCs in possible biomedical applications

Physical, Electrochemical, and Solvent Permeation Properties of Amphiphilic Conetwork Membranes Formed through Interlinking of Poly(vinylidene fluoride)-<i>Graft</i>-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

Effect of Polyethylene Glycol on Properties and Drug Encapsulation–Release Performance of Biodegradable/Cytocompatible Agarose–Polyethylene Glycol–Polycaprolactone Amphiphilic Co-Network Gels

We synthesized agarose–polycaprolactone (Agr-PCL) bicomponent and Agr–polyethylene glycol–PCL (Agr-PEG-PCL) tricomponent amphiphilic co-network (APCN) gels by the sequential nucleophilic substitution reaction between amine-functionalized Agr and activated halide terminated PCL or PCL-<i>b</i>-PEG-<i>b</i>-PCL copolymer for the sustained and localized delivery of hydrophilic and hydrophobic drugs. The biodegradability of the APCNs was confirmed using lipase and by hydrolytic degradation. These APCN gels displayed good cytocompatibility and blood compatibility. Importantly, these APCN gels exhibited remarkably high drug loading capacity coupled with sustained and triggered release of both hydrophilic and hydrophobic drugs. PEG in the APCNs lowered the degree of phase separation and enhanced the mechanical property of the APCN gels. The drug loading capacity and the release kinetics were also strongly influenced by the presence of PEG, the nature of release medium, and the nature of the drug. Particularly, PEG in the APCN gels significantly enhanced the 5-fluorouracil loading capacity and lowered its release rate and burst release. Release kinetics of highly water-soluble gemcitabine hydrochloride and hydrophobic prednisolone acetate depended on the extent of water swelling of the APCN gels. Cytocompatibility/blood compatibility and pH and enzyme-triggered degradation together with sustained release of drugs show great promise for the use of these APCN gels in localized drug delivery and tissue engineering applications

Self-Assembly of Partially Alkylated Dextran-<i>graft</i>-poly[(2-dimethylamino)ethyl methacrylate] Copolymer Facilitating Hydrophobic/Hydrophilic Drug Delivery and Improving Conetwork Hydrogel Properties

Key issues of injectable hydrogels are incapability of loading hydrophobic drugs due to insolubility of drugs in aqueous prepolymer solution as well as in hydrogel matrix, and high water swelling, which leads to poor mechanical and bioadhesive properties. Herein, we report that self-assembly of partially long-chain alkylated dextran-<i>graft</i>-poly­[(2-dimethylamino)­ethyl methacrylate] copolymer in aqueous solution could encapsulate pyrene, a hydrophobic probe, griseofulvin, a hydrophobic antifungal drug, and ornidazole, a hydrophilic antibiotic. Addition of activated chloride terminated poly­(ethylene glycol) (PEG) into the guest molecules loaded copolymer solution produced an injectable dextran-<i>graft</i>-poly­[(2-dimethylamino)­ethyl methacrylate]-linked-PEG conetwork hydrogel. The alkylated hydrogels exhibited zero order release kinetics and were mechanically tough (50–54 kPa storage modulus) and bioadhesive (8–9 kPa). The roles of alkyl chains and dextran on the drug loading-release behavior, degradation behavior, gelation time, and the mechanical property of the hydrogels have been studied in details. Additionally, DNA hybrid composite hydrogel was formed owing to the cationic nature of the prepolymer solution and the hydrogel. Controlled alkylation of a prepolymer thus highlights the potential to induce and enhance the hydrogel property

Multifunctionalization of Poly(vinylidene fluoride)/Reactive Copolymer Blend Membranes for Broad Spectrum Applications

Simultaneous immobilization and cross-linking of antifouling/low toxic polymers, e.g., poly­(ethylenimine) (PEI), dextran (Dex), agarose (Agr), poly­(ethylene glycol) (PEG), PEI–Dex, and PEI–PEG conjugates, and stimuli-responsive copolymers on a porous membrane surface in mild reaction conditions is desirable for the enhancement of hydrophilicity, antifouling character, cytocompatibility, and inducing stimuli-responsive behavior. Grafting to technique is required since the precursors of most of these macromolecules are not amenable to surface-initiated polymerization. In this work, we report a versatile process for the simultaneous immobilization and cross-linking of a library of macromolecules on and into the blend membrane (PVDF-blend) of poly­(vinylidene fluoride) and poly­(methyl methacrylate)-<i>co</i>-poly­(chloromethyl­styrene). Sequential nucleophilic substitution reaction between activated halide moieties of the copolymer and amine groups of different macromolecules readily provided series of modified membranes. These membranes exhibited antifouling property superior to that of the unmodified membrane. The effectiveness of this technique has been demonstrated by the immobilization of pH or both pH- and temperature-responsive copolymer on PVDF-blend membrane for responsive separation of poly­(ethylene oxide) and bovine serum albumin. Silver nanoparticles were also anchored on the select modified membranes surfaces for the enhancement of antibiofouling property. Our approach is useful to obtain verities of functional membranes and selection of membrane for a particular application