Department of Chemistry, University of Tennessee , Knoxville, Tennessee 37996, United States.
Langmuir. 2014 Mar 11;30(9):2541-50. doi: 10.1021/la4049924. Epub 2014 Feb 26.
This Article reports on the synthesis of a series of well-defined, tertiary-amine-containing ABA triblock copolymers, composed of a poly(ethylene oxide) (PEO) central block and thermo- and pH-sensitive outer blocks, and the study of the effect of different tertiary amines on thermally induced sol-gel transition temperatures (T(sol-gel)) of their 10 wt % aqueous solutions. The doubly responsive ABA triblock copolymers were prepared from a difunctional PEO macroinitiator by atom transfer radical polymerization of methoxydi(ethylene glycol) methacrylate and ethoxydi(ethylene glycol) methacrylate at a feed molar ratio of 30:70 with ∼5 mol % of either N,N-diethylaminoethyl methacrylate (DEAEMA), N,N-diisopropylaminoethyl methacrylate, or N,N-di(n-butyl)aminoethyl methacrylate. The chain lengths of thermosensitive outer blocks and the molar contents of tertiary amines were very similar for all copolymers. Using rheological measurements, we determined the pH dependences of T(sol-gel) of 10 wt % aqueous solutions of these copolymers in a phosphate buffer. The T(sol-gel) versus pH curves of all polymers exhibited a sigmoidal shape. The T(sol-gel) increased with decreasing pH; the changes were small on both high and low pH sides. At a specific pH, the T(sol-gel) decreased with increasing the hydrophobicity of the tertiary amine, and upon decreasing pH the onset pH value for the T(sol-gel) to begin to increase noticeably was lower for the more hydrophobic tertiary amine-containing copolymer. In addition, we studied the effect of different tertiary amines on the release behavior of FITC-dextran from 10 wt % micellar gels in an acidic medium at 37 and 27 °C. The release profiles for three studied hydrogels at 37 °C were essentially the same, suggesting that the release was dominated by the diffusion of FITC-dextran. At 27 °C, the release was significantly faster for the DEAEMA-containing copolymer, indicating that both diffusion and gel dissolution contributed to the release at this temperature.
这篇文章报道了一系列具有明确结构的、含叔胺的 ABA 三嵌段共聚物的合成，这些共聚物由聚（环氧乙烷）（PEO）中心嵌段和热响应性及 pH 响应性的外嵌段组成，并研究了不同叔胺对其 10wt%水溶液的热诱导溶胶-凝胶转变温度（T(sol-gel)）的影响。通过原子转移自由基聚合，由双官能 PEO 大分子引发剂引发甲氧基二（乙二醇）甲基丙烯酸酯和乙氧基二（乙二醇）甲基丙烯酸酯共聚，进料摩尔比为 30:70，并用约 5mol%的 N,N-二乙基氨基乙基甲基丙烯酸酯（DEAEMA）、N,N-二异丙基氨基乙基甲基丙烯酸酯或 N,N-二（正丁基）氨基乙基甲基丙烯酸酯作为叔胺，制备了双重响应性的 ABA 三嵌段共聚物。所有共聚物的热敏感外嵌段的链长和叔胺的摩尔含量非常相似。通过流变学测量，我们在磷酸盐缓冲液中测定了这些共聚物 10wt%水溶液的 T(sol-gel)随 pH 值的变化。所有聚合物的 T(sol-gel)与 pH 值曲线均呈 S 形。随着 pH 值的降低，T(sol-gel)增加；在高 pH 值和低 pH 值两侧变化都很小。在特定 pH 值下，T(sol-gel)随叔胺疏水性的增加而降低，并且随着 pH 值的降低，T(sol-gel)开始显著增加的起始 pH 值对于疏水性更强的含叔胺共聚物越低。此外，我们还研究了不同叔胺对 FITC-葡聚糖在酸性介质中从 10wt%胶束凝胶中的释放行为的影响，实验温度分别为 37°C 和 27°C。在 37°C 下，三种研究水凝胶的释放曲线基本相同，表明释放主要受 FITC-葡聚糖的扩散控制。在 27°C 下，含 DEAEMA 的共聚物的释放速度明显更快，表明在该温度下，扩散和凝胶溶胀都对释放有贡献。
