The overall goal of this study was to synthesize semicrystalline poly(ε-caprolactone) (PCL) copolymer networks with stimuli-responsive shape memory behavior. Herein, we investigate the influence of a cinnamoyl moiety to design shape memory polymer networks with tunable transition temperatures. The effect of various copolymer architectures (random or ABA triblock), the molecular weight of the crystalline domains, PCL diol, (M(w) 1250 or 2000 g mol(-1)) and its composition in the triblock (50 or 80 mol %) were also investigated. The polymer microstructures were confirmed by NMR, DSC, WAXS and UV-vis spectroscopic techniques. The thermal and mechanical properties and the cross-linking density of the networks were characterized by DSC, tensile testing and solvent swelling, respectively. Detailed thermomechanical investigations conducted using DMA showed that shape memory behavior was obtained only in the ABA triblock copolymers. The best shape memory fixity, R(f) of ~99% and shape recovery, R(r) of ~99% was obtained when PCL diol with M(w) 2000 g mol(-1) was incorporated in the triblock copolymer at a concentration of 50 mol %. The series of triblock copolymers with PCL at 50 mol % also showed mechanical properties with tunable shape memory transition temperatures, ranging from 54 °C to close to body temperature. Our work establishes a general design concept for inducing a shape memory effect into any semicrystalline polyester network. More specifically, it can be applied to systems which have the highest transition temperature closest to the application temperature. An advantage of our novel copolymers is their ability to be cross-linked with UV radiation without any initiator or chemical cross-linker. Possible applications are envisioned in the area of endovascular treatment of ischemic stroke and cerebrovascular aneurysms, and for femoral stents.

Microwave-, photo- and thermo-responsive polymer microgels that range in size from 500 to 800 microm and are swollen with water were prepared by a novel microarray technique. We used a liquid-liquid dispersion technique in a system of three immiscible liquids to prepare hybrid PNIPAm- co-AM core-shell capsules loaded with AuNPs. The spontaneous encapsulation is a result of the formation of double oil-in-water-in-oil (o/w/o) emulsion. It is facilitated by adjusting the balance of the interfacial tensions between the aqueous phase (in which a water-soluble drug may be dissolved), the monomer phase and the continuous phase. The water-in-oil (w/o) droplets containing 26 wt% NIPAm and Am monomers, 0.1 wt% Tween-80 surfactant, FITC fluorescent dye and colloidal gold nanoparticles spontaneously developed a core-shell morphology that was fixed by in situ photopolymerization. The results demonstrate new reversibly swelling and deswelling AuNP/PNIPAm hybrid core-shell microcapsules and microgels that can be actuated by visible light and/or microwave radiation (

A versatile new concept is presented for the synthesis of Janus colloids composed of Laponite nanoclay armored poly(divinylbenzene) with an anisotropic surface potential via a double Pickering emulsion template. First, polystyrene or poly(divinylbenzene) colloids stabilized with Laponite nanoclay are synthesized via a Pickering miniemulsion approach. These nanoparticle-stabilized colloids were then templated at a wax-water interface in a second Pickering emulsion in order to chemically modify one hemisphere of the colloids. Janus modification of the colloids was accomplished by cation exchange of sodium ions, originally present on the surface of the Laponite with various salts of modifying ions (Ca(2+), Fe(2+), and Fe(3+)) in the suspension. The zeta potential of the chemically modified and unmodified colloids was compared. The maximum change in the zeta potential was given by the calcium ions, Ca(2+)-adsorbed modified colloids as compared to unmodified sodium ions, Na(+)-adsorbed colloids. The distribution of charges on the Janus colloids results in a nonuniform zeta potential. XPS and optical microscopy were used to verify the successful chemical modification by the cation exchange of Na(+) for Ca(2+) ions on one hemisphere of the Janus colloids.

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