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Multi-responsive composite microspheres were synthesized via an in situ free radical polymerization of thermo-responsive poly( N -isopropylacrylamide) (poly(NIPAAm)) in the presence of carboxymethylchitosan (CMC) and magnetite nanoparticles (MNPs) followed by glutaraldehyde crosslinking. Formulation conditions of the composite microspheres were tuned such that spherical microspheres with narrow size distributions were obtained (30.0 ± 1.0 μm in diameter). They responded well to an applied magnetic field and showed water swelling responses to the change in solution pH and temperature. The release of an entrapped indomethacin model drug was accelerated when the solution temperature was above its lower critical solution temperature (LCST) (50 °C) or when the solution pH was in basic conditions (pH 11). These responsive properties can be used as triggering mechanisms for releases of the entrapped drugs from the microspheres, indicating their great potentials for use in controlled release applications. [ABSTRACT FROM AUTHOR]

Abstract: Preparation and properties of polydimethylsiloxane (PDMS)-modified chitosan are discussed herein. A series of PDMS with systematically varied molecular weights were first prepared via acid-catalyzed ring opening polymerization of octamethylcyclotetrasiloxane (D4) to obtain PDMS prepolymers. They were subsequently functionalized with allyl glycidyl ether to obtain epoxy functional groups at PDMS terminals. Their chemical structures and molecular weights were characterized using1H NMR,13C NMR and FTIR, and thermal properties were determined by DSC. The reaction of the epoxidized PDMS and chitosan was carried out in an acidic aqueous solution. Increasing the molecular weights of PDMS and/or its concentrations improved flexibility and water swellability due to the formation of PDMS microphase. Water contact angle and water vapor permeability measurements indicated that incorporation of the PDMS enhanced its hydrophobicity as compared to the unmodified one. [Copyright &y& Elsevier]

Abstract: Synthesis and properties of semi-interpenetrating polymer networks (semi-IPNs) based on polydimethylsiloxane (PDMS)/poly(ethylene glycol) (PEG)-modified chitosan were studied. 1–20wt% of PDMS or PEG was interpenetrated into chitosan hydrogels having 10wt% of hexamethylene-1,6-di-(aminocarboxysulfonate) (HDA) as a water-soluble crosslinker. PDMS prepolymer was synthesized via acid-catalyzed ring-opening polymerization of octamethylcyclotetrasiloxane (D4), followed by hydrosilylation reaction with allyl alcohol to obtain hydroxyl-terminated PDMS. Effect of PDMS/PEG contents (1–20wt%) and their molecular weights (2000 and 8000g/mol) in chitosan semi-IPNs on percent crosslinking, water swelling properties, thermal stability, surface properties, water vapor permeability and tensile properties were investigated. Percent crosslinking of the PDMS/PEG-chitosan semi-IPNs ranged between 42% and 74% depending on molecular weight and percent of PDMS/PEG added. PDMS and PEG in the semi-IPNs enhanced water swellability and water vapor permeability of the films. Also, PDMS/PEG in chitosan semi-IPNs enhanced their thermal stability and surface hydrophobicity, while their tensile properties were sacrificed. [Copyright &y& Elsevier]

Abstract: Preparation and properties of carboxymethylchitosan (CMC) modified with polyurethane (PU) containing poly(ethylene adipate) (PEA) as a soft segment is described. Urethane prepolymer was first synthesized by the reaction of PEA with an excess of 1,6-hexamethylene diisocyanate (HDI) to terminate its ends with isocyanate functional groups, followed by chain extension reaction using ethylene glycol as a chain extender. Its chemical structure was characterized by 1H NMR and FTIR, molecular weight by GPC, and thermal behavior by DSC. To prepare PU-modified CMC (CMC-PU), 1–60wt% of PU were introduced into the CMC solution of THF:H2O mixture (50:50 v/v) in the presence of 10wt% of hexamethylene-1,6-di-(aminocarboxysulfonate) (HDA) to increase network density. Formation of the network structure was confirmed by investigating percent crosslinking and water swelling properties of CMC-PU compared to CMC network without PU. When percent of PU increased from 1 to 60wt%, percent crosslinking of CMC-PU gradually increased up to 82%, whereas equilibrium water content (EWC) dropped and retained at 1000%. SEM showed microphase separation of PU (10–50μm) thoroughly dispersed in CMC surface and in the bulk. In addition, CMC-PU exhibited a slight enhancement in toughness properties. Cytotoxicity and biocompatibility tests indicated that CMC-PU was non-toxic. [Copyright &y& Elsevier]