Three imidazolium-based ionic liquid (IL) monomers, namely, 3-(1-ethyl imidazolium-3yl)propylmethacrylamido bromide (IL-1), 2-(1-methylimidazolium-3-yl)ethyl methacrylate bromide (IL-2), and 2-(1-ethylimidazolium-3-yl)ethyl methacrylate bromide (IL-3), and methacrylic acid (MAA) were polymerized by the reversible addition fragmentation chain transfer (RAFT) process in methanolic solutions at 70 °C, using either 2-cyanopropyl dithiobenzoate (CTA-1) or (4-cyanopentanoic acid)-4-dithiobenzoate (CTA-2) as chain transfer agents (CTAs). Under these conditions, polymers exhibited molar masses predetermined by the initial molar ratio of the monomers to the dithioester precursor, as evidenced by 1 H NMR spectroscopy from chain ends analysis. These hydrophilic polymers were subsequently used as macro-CTAs in chain extension experiments in aqueous or in alcoholic solutions, affording IL-based double hydrophilic block copolymers (DHBCs) of the type PIL-1-b-PAm, PMAA-b-PIL-2 and PMAA-b-PIL-3, where PAm and PIL stand for polyacrylamide and polymeric ionic liquid. These DHBCs could be further manipulated and made to self-assemble in micelle-like structures in water by exchanging the bromide (Br -) counteranion of IL blocks for -N(SO 2 CF 3 ) 2 . This anion exchange indeed turned the solution properties of the PIL blocks from hydrophilic to hydrophobic, as verified on the corresponding IL-based homopolymers which were immiscible with water after the anion switch. Investigations by 1 H NMR evidenced that the diblock copolymers exhibited salt-responsive behavior in aqueous solutions: anion exchange induced the formation of water-soluble micellar aggregates consisting of hydrophobic -N(SO 2 CF 3 ) 2 -based IL blocks at the core stabilized by water-soluble PAm or PMAA at the shell.

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- graft-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- graft-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.

We report the preparation of a novel cross-linked anion exchange membrane (AEM) from poly(acrylonitrile)-co-poly(2-dimethylamino)ethyl methacrylate (PAN-co-PDMA) copolymer by quaternizing the DMA moieties followed by cross-linking of -CN groups. This process avoids the use of the carcinogenic reagent, chloromethyl ether (CME) which is widely employed for the chloromethylation reaction in the preparation of AEMs. Key parameters were evaluated via electrodialysis (ED) during water purification and revealed that a copolymer containing 28 wt% PDMA possesses all the required properties of a high performance AEM, such as, reasonable water uptake (21%), good ion-exchange capacity (IEC ¼ 1.30 m eq g À1 ), high ionic conductivity (K m ¼ 2.22 mS cm À1 ), a high transport number (t À ¼ 0.88) and good mechanical properties (9.2 MPa of tensile stress at break and 2.4 Kg cm À2 of burst strength in the water wet state). The AEM was directly tested in an ED unit in the recirculation mode by varying the concentration of the NaCl feed and the applied potential, showing a current efficiency as high as 80%. Such combination of physical and electrochemical properties of the membrane is attributed to its co-continuous morphology and its low degree of phase separation as confirmed by swelling, differential scanning calorimetry, the homogeneous distribution of oppositely charged dye and by the transparency of the membrane in both the dry and swelled states.

Atom transfer radical polymerization (ATRP) of acrylamide has been carried out in water or in glycerol-water (1:1 v/v) medium at 130 °C using water-soluble initiators, viz. 2-chloropropionamide (2-Cl-PA) or 2-bromopropionamide (2-Br-PA) and CuX (X ) Cl, Br) bipyridine complex as catalyst. Extraneous addition of CuX 2 (20 mol % of CuX) and/or excess Xions (1 M alkali halide) in the reaction mixture helps to reduce molecular weight polydispersity (PDI). However, even under the best conditions (using both CuX 2 and Xion additives), the PDI is high, ca. 1.6-1.7. Also, the GPC traces show shoulders. The chain extension experiment, however, confirms the living nature of the polymers. Replacement of glycerol-water with water as the medium results in sluggish polymerization. The ln M 0/M vs t plots are curved to start with but become linear after polymerization proceeds to variable extents depending on the additives used. The molecular weights tend to agree with the theoretical values as conversion increases. A method of selecting the appropriate ligand for ATRP has been proposed on the basis of the premise that a high rate of deactivation is one of the primary requirements for ATRP to succeed. A relative measure of the deactivation rate for various ligands has been obtained from the molecular weights (GPC) of polymers formed in a CuX 2Lx deactivated polymerization initiated by an azo initiator at 90 °C. A ligand that leads to the highest deactivation rate has been proposed to be chosen.

PEG-based dually crosslinked injectable hydrogels have been developed through extremely simple chemistry which avoids use of small molecular weight crosslinker, formation of by-products and involved low heat change. The hydrogels are useful for wound healing and soft tissue regeneration.

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-b-PEG-b-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.

No abstract

Novel segmented polyurea elastomers containing soft polyisobutylene (PIB) segments were synthesized and characterized. The key ingredient, primary amine‐telechelic PIB oligomers (NH2‐PIB‐NH2) with number average molecular weights of 2500 and 6200 g/mol were synthesized. PIB‐based polyureas were prepared by using various aliphatic diisocyanates and diamine chain extenders with hard segment contents between 9.5 and 46.5% by weight. All copolymers displayed microphase morphologies as determined by dynamic mechanical analysis. Tensile strengths of nonchain‐extended and chain‐extended polyureas showed a linear dependence on the urea hard segment content. PIB‐based polyureas prepared with NH2‐PIB‐NH2 of Mn = 2500 g/mol, 4,4′‐methylendbis(cyclohexylisocyantate), and 1,6‐diaminohexane containing 45% hard segment exhibited 19.5 MPa tensile strength which rose to 23 MPa upon annealing at 150 °C for 12 h. With increasing hard segment content, elongation at break decreased from ∼ 450% to a plateau of 110%. The hydrolytic and oxidative stability of PIB‐based polyureas were unprecedented. Although commercial “oxidatively resistant” thermoplastic polyurethanes degraded severely upon exposure to boiling water or concentrated nitric acid, the experimental polyureas survived without much degradation in properties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 38–48, 2009