Key Laboratory for Advanced Materials and Department of Chemistry, East China University of Science & Technology, Shanghai 200237, China.
Langmuir. 2013 Jan 29;29(4):1024-34. doi: 10.1021/la3036874. Epub 2013 Jan 15.
A series of poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA) homopolymers and poly(2-(dimethylamino)ethyl methacrylate)-b-poly(acrylic acid) (PDMAEMA-b-PAA) diblock copolymers were synthesized by atomic transfer radical polymerization. Thanks to a fine-tuning of the hydrophobic-hydrophilic balance by varying the molecular weight of the polymers and the pH of the aqueous solutions, as well as the composition for the block copolymers, the lower critical solution temperature (LCST) and the aggregation-dissolution kinetics of PDMAEMA homopolymers and PDMAEMA-b-PAA block copolymers can be adjusted. For the block copolymers, the results show that larger relative size of the PDMAEMA blocks leads to an increasing tendency to form micellar aggregates and a decrease of the LCST of the aqueous solution, which is consistent with the increasing copolymer hydrophobicity. A significant difference of the stimuli-responsive behavior between PDMAEMA-rich and PAA-rich copolymers is observed, because the former exhibit thermo-responsive behavior in a broad temperature range of 40-60 °C in basic media, while the pH-responsive behavior is dominant, and only a weak thermo-responsive behavior is exhibited around the specific isoelectric point (IEP) in the latter case. The aggregation rate is strongly influenced by temperature, molecular weight, structure, and composition of the polymer. Specifically, temperature has a stronger effect than the molar ratio of the PDMAEMA segment in the copolymer (related to its hydrophobicity) and the chain molecular weight, although the PDMAEMA-b-PAA copolymers show faster aggregation rate than do the PDMAEMA homopolymers.
一系列聚（2-（二甲氨基）乙基甲基丙烯酸酯）（PDMAEMA）均聚物和聚（2-（二甲氨基）乙基甲基丙烯酸酯）-b-聚（丙烯酸）（PDMAEMA-b-PAA）嵌段共聚物通过原子转移自由基聚合合成。通过精细调整聚合物的分子量和水溶液的 pH 值以及嵌段共聚物的组成，来调整 PDMAEMA 均聚物和 PDMAEMA-b-PAA 嵌段共聚物的低临界溶液温度（LCST）和聚集-溶解动力学。对于嵌段共聚物，结果表明，PDMAEMA 块的相对尺寸越大，形成胶束聚集的趋势就越大，水溶液的 LCST 就越低，这与共聚物疏水性的增加是一致的。观察到 PDMAEMA 丰富和 PAA 丰富的共聚物之间的刺激响应行为存在显著差异，因为前者在碱性介质中 40-60°C 的较宽温度范围内表现出热响应行为，而后者的 pH 响应行为占主导地位，仅在特定等电点（IEP）附近表现出较弱的热响应行为。聚集速率强烈受到温度、聚合物的分子量、结构和组成的影响。具体来说，温度的影响比共聚物中 PDMAEMA 段的摩尔比（与疏水性有关）和链分子量更强，尽管 PDMAEMA-b-PAA 共聚物的聚集速率比 PDMAEMA 均聚物更快。
