Department of Biological Sciences, Department of Biomedical Engineering, and Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois, USA.
Soft Matter. 2017 Sep 27;13(37):6322-6331. doi: 10.1039/c7sm01538k.
Herein, we develop a molecular theory to examine a class of pH and temperature-responsive tethered polymer layers. The response of pH depends on intramolecular charge repulsion of weakly acidic monomers and the response of temperature depends on hydrogen bonding between polymer monomers and water molecules akin to the behavior of water-soluble polymers such as PEG (poly-ethylene glycol) or NIPAAm (n-isopropylacrylamide). We investigate the changes in structural behavior that result for various end-tethered copolymers: pH/T responsive monomers alone, in alternating sequence with hydrophobic monomers, and as 50/50 diblocks with hydrophobic monomers. We find that the sequence and location of hydrophobic units play a critical role in the thermodynamic stability and structural behavior of these responsive polymer layers. Additionally, the polymers exhibit tunable collapse when varying the surface coverage, location and sequence of hydrophobic units as a function of temperature and pH. As far as we know, our results present the first molecularly detailed theory for end-tethered polymers that are both pH and temperature-responsive via hydrogen bonding. We propose that this work holds predictive power for the guided design of future biomaterials.
在这里，我们发展了一种分子理论来研究一类 pH 值和温度响应的接枝聚合物层。pH 值的响应取决于弱酸性单体的分子内电荷排斥，而温度的响应则取决于聚合物单体与水分子之间的氢键，类似于水溶性聚合物如 PEG（聚乙二醇）或 NIPAAm（N-异丙基丙烯酰胺）的行为。我们研究了各种端接共聚物的结构行为变化：单独的 pH/T 响应单体、与疏水性单体交替序列以及与疏水性单体的 50/50 嵌段共聚物。我们发现，疏水性单元的序列和位置在这些响应聚合物层的热力学稳定性和结构行为中起着关键作用。此外，当作为温度和 pH 的函数改变疏水性单元的表面覆盖率、位置和序列时，聚合物表现出可调节的塌陷。据我们所知，我们的结果首次提出了一种通过氢键实现 pH 值和温度响应的端接聚合物的分子详细理论。我们提出，这项工作为未来生物材料的设计提供了有预测能力的指导。
