Van Guyse Joachim F R, Bera Debaditya, Hoogenboom Richard
Supramolecular Chemistry Group, Centre of Macromolecular Chemistry (CMaC), Department of Organic and Macromolecular Chemistry, Ghent University, Krijgslaan 281-S4, B-9000 Ghent, Belgium.
Polymers (Basel). 2021 Jan 26;13(3):374. doi: 10.3390/polym13030374.
Smart or adaptive materials often utilize stimuli-responsive polymers, which undergo a phase transition in response to a given stimulus. So far, various stimuli have been used to enable the modulation of drug release profiles, cell-interactive behavior, and optical and mechanical properties. In this respect, molecular recognition is a powerful tool to fine-tune the stimuli-responsive behavior due to its high specificity. Within this contribution, a poly(2-oxazoline) copolymer bearing adamantane side chains was synthesized via triazabicyclodecene-catalyzed amidation of the ester side chains of a poly(2-ethyl-2-oxazoline--2-methoxycarbonylpropyl-2-oxazoline) statistical copolymer. Subsequent complexation of the pendant adamantane groups with sub-stoichiometric amounts (0-1 equivalents) of hydroxypropyl β-cyclodextrin or β-cyclodextrin enabled accurate tuning of its lower critical solution temperature (LCST) over an exceptionally wide temperature range, spanning from 30 °C to 56 °C. Furthermore, the sharp thermal transitions display minimal hysteresis, suggesting a reversible phase transition of the complexed polymer chains (i.e., the β-cyclodextrin host collapses together with the polymers) and a minimal influence by the temperature on the supramolecular association. Analysis of the association constant of the polymer with hydroxypropyl β-cyclodextrin via H NMR spectroscopy suggests that the selection of the macrocyclic host and rational polymer design can have a profound influence on the observed thermal transitions.
智能或自适应材料通常利用刺激响应性聚合物，这类聚合物会响应给定刺激而发生相变。到目前为止，已使用各种刺激来实现对药物释放曲线、细胞相互作用行为以及光学和机械性能的调节。在这方面，分子识别因其高特异性而成为微调刺激响应行为的有力工具。在本论文中，通过三氮杂双环癸烯催化的聚（2-乙基-2-恶唑啉-2-甲氧基羰基丙基-2-恶唑啉）统计共聚物酯侧链的酰胺化反应，合成了带有金刚烷侧链的聚（2-恶唑啉）共聚物。随后，使侧链金刚烷基团与亚化学计量量（0 - 1当量）的羟丙基β-环糊精或β-环糊精进行络合，能够在从30℃到56℃的异常宽的温度范围内精确调节其低临界溶液温度（LCST）。此外，急剧的热转变显示出最小的滞后现象，这表明络合聚合物链发生了可逆的相变（即β-环糊精主体与聚合物一起塌陷），并且温度对超分子缔合的影响最小。通过核磁共振氢谱对聚合物与羟丙基β-环糊精的缔合常数进行分析表明，大环主体的选择和合理的聚合物设计对观察到的热转变可能有深远影响。
