Poly(N-isopropylacrylamide) (PNIPAAm) hydrogels containing N-[3-(N,N-dimethylamino)propyl]methacrylamide (DMAPMAAm), 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA) and [3-(methacryloylamino)propyl]trimethylammonium chloride (MAPTAC) as cationic monomers were cross-linked with N,N’-methylenebisacrylamide (BIS) and tetraallylammonium bromide (TAB). The swelling degrees, uniaxial compression moduli and L-ascorbic acid (L-AA) releases of these cationic PNIPAAm hydrogels synthesized in 1,4-dioxane were compared with the one prepared in distilled–deionized water (DDW) and in aqueous sodium hydroxide solution (0.1 N NaOH). P(NIPAAm-co-MAPTAC)/BIS and P(NIPAAm-co-DMAEMA)/BIS hydrogels at 37 °C in DDW and at 37 °C/pH 4 exhibited higher gel strengths and compressive moduli than all the others cross-linked and copolymerized with TAB and DMAPMAAm, respectively. All the observations indicated that the physical cross-linking points created by ionomer pairs of MAPTA⁺Cl⁻ units and the hydrophobic contributions of ester groups in the DMAEMA units might be a reason of their improved mechanical properties in DDW at 37 °C. Further, the charge screening effect of chloride ions in the swelling medium at pH 4 also resulted in the improved compressive moduli compared to the ones in DDW. The water diffusion into/from all the copolymeric PNIPAAm hydrogels during the swelling/deswelling processes at 25 °C/37 °C in DDW and their L-AA releases at 37 °C in DDW also revealed the importance of these ionic and hydrophobic effects. Water transport through the ones cross-linked with TAB was controlled by non-Fickian process due to the repulsive forces between the quaternized ammonium groups on the chemical cross-links while in the case of P(NIPAAm-co-MAPTAC)/BIS, water transport followed Fickian diffusion because the multiplet formations behaved as additional cross-links. Furthermore, P(NIPAAm-co-MAPTAC)/BIS hydrogel due to the ionomer-multiplet transitions at 37 °C in DDW has exhibited less-Fick diffusion that resulted in a lower diffusion coefficient during the release of L-AA as compared to the others.

中文翻译：

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离聚物/多重形成对DMAEMA，DMAPMAAm和MAPTAC共聚的PNIPAAm水凝胶的力学性能和抗坏血酸释放行为的影响

聚（Ñ -isopropylacrylamide酰胺）（PNIPAAm）水凝胶含有ñ - [3-（N，N-二甲基氨基）丙基]甲基丙烯酰胺（DMAPMAAm），2-（N，N-二甲基氨基）乙基甲基丙烯酸酯（DMAEMA）和[3-（甲基丙烯酰氨基作为阳离子单体的）]丙基]三甲基氯化铵（MAPTAC）与N，N'-亚甲基双丙烯酰胺（BIS）和四烯丙基溴化铵（TAB）交联。将这些在1,4-二恶烷中合成的阳离子PNIPAAm水凝胶的溶胀度，单轴压缩模量和L-抗坏血酸（L -AA）释放与在蒸馏去离子水（DDW）和氢氧化钠水溶液中制备的阳离子进行比较。 （0.1 N NaOH）。P（NIPAAm- co-MAPTAC）/ BIS和P（NIPAAm- co -DMAEMA）/ BIS水凝胶在DDW和37°C / pH 4下在37°C时显示出比所有其他与TAB交联和共聚的凝胶强度和压缩模量更高的凝胶强度和压缩模量分别为DMAPMAAm。所有的观察表明的物理交联点由离聚物对MAPTA的创建⁺氯^-单元和DMAEMA单元中酯基团的疏水作用可能是其在DDW中于37°C下改善的机械性能的原因。此外，与DDW相比，溶胀介质在pH 4时氯离子的电荷屏蔽作用还导致压缩模量提高。在DDW中在25°C / 37°C的溶胀/溶胀过程中，水扩散到所有PNIPAAm共聚水凝胶中/从其中扩散，以及在DDW中在37°C的L -AA释放过程中，也揭示了这些离子和疏水作用的重要性。由于P（NIPAAm- co-MAPTAC）/ BIS，水的运输遵循Fickian扩散，因为多重峰的形成表现为额外的交联。此外，由于DDW中37°C的离聚物-多跃迁，P（NIPAAm- co -MAPTAC）/ BIS水凝胶的Fick扩散较少，与L- AA释放相比，扩散系数较低。其他。