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首页> 外文会议>Silicones and silicone-modified materials symposium >An Investigation into the Influence of Crosslinker Type and Solvent Composition on Physical Properties and Phase Transition Behavior of Poly(N-isopropylacrylamide) Hydrogels
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An Investigation into the Influence of Crosslinker Type and Solvent Composition on Physical Properties and Phase Transition Behavior of Poly(N-isopropylacrylamide) Hydrogels

机译：交联剂类型和溶剂组成对聚（N-异丙基丙烯酰胺）水凝胶物理性质和相变行为的影响的研究

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Poly(N-isopropylacrylamide) (PNIPAAm) hydrogels have been synthesized by free radical polymerization in 1,4-Dioxane using N,N'-methylenebisacrylamide (BIS) and α,ω-acryloxyorganofunctional poly(dimethylsiloxane) (VTPDMS) as crosslinkers. The disc samples equilibrated by swelling in water, water-methanol mixtures and methanol were examined by volumetric and stress-compression measurements to afford the values of swelling ratio (V/ V_o), polymer-solvent interaction parameter (χ), compression modulus (G) and effective crosslinking density (v_e). It was observed that the incorporation of hydrophobic VTPDMS chains, instead of hydrophilic BIS molecules, as crosslinker into the structures of neutral NIPAAm hydrogels improved their mechanical strengths. The values of v_e, being greater than v_t (theoretical crosslinking density) also indicated the presence of hydrophobic physical interactions, i.e., physical crosslinkings, between dimethyl siloxane groups in the PNIPAAm hydrogels crosslinked with VTPDMS. Further, the G-, χ- and v_e-solvent composition curves of both NIPAAm/VTPDMS and NIPAAm/BIS hydrogels swollen to equilibrium in water/methanol mixtures (80/20, 50/50 and 20/80, in v/v %) at 23°C showed maxima corresponding to 0.20 and 0.50 of methanol volume fractions, respectively. It was assumed that the maxima on G, v_e and χ versus solvent composition curves resulted from the competitions between interaction of methanol and water together versus their individual interactions with PNIPAAm/VTPDMS and PNIPAAm/BIS polymers.
机译：聚（N-异丙基丙烯酰胺）（PNIPAAm）水凝胶是通过使用N，N'-亚甲基双丙烯酰胺（BIS）和α，ω-丙烯酰氧基有机官能聚（二甲基硅氧烷）（VTPDMS）作为交联剂在1,4-二恶烷中进行自由基聚合反应合成的。通过体积和应力压缩测量检查通过在水，水-甲醇混合物和甲醇中溶胀平衡的圆盘样品，以提供溶胀比（V / V_o），聚合物-溶剂相互作用参数（χ），压缩模量（G）的值）和有效的交联密度（v_e）。观察到，疏水性VTPDMS链而不是亲水性BIS分子的掺入作为交联剂进入中性NIPAAm水凝胶的结构，提高了它们的机械强度。大于v_t（理论交联密度）的v_e值还表明在与VTPDMS交联的PNIPAAm水凝胶中二甲基硅氧烷基团之间存在疏水性物理相互作用，即物理交联。此外，NIPAAm / VTPDMS和NIPAAm / BIS水凝胶在水/甲醇混合物中溶胀至平衡（80 / 20、50 / 50和20/80，v / v％）的G，χ和v_e溶剂组成曲线）在23°C时的最大值分别对应于甲醇体积分数的0.20和0.50。假设G，v_e和χ相对于溶剂组成曲线的最大值是甲醇和水之间相互作用的竞争以及它们与PNIPAAm / VTPDMS和PNIPAAm / BIS聚合物的相互作用之间的竞争所致。

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