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.

中文翻译：

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具有竞争性的温度和pH响应系留聚合物层的结构行为

在本文中，我们发展了一种分子理论来研究一类pH和温度响应的拴系聚合物层。pH值的响应依赖于弱酸性单体的分子内电荷斥力和温度的响应类似于聚合物的单体和水分子之间的依赖于氢键的水溶性聚合物的行为，如PEG（聚乙二醇）或的NIPAAm（ñ -异丙基丙烯酰胺）。我们调查了各种末端连接的共聚物导致的结构行为的变化：pH / T单独的响应性单体，与疏水性单体的交替顺序，以及与疏水性单体的50/50二嵌段。我们发现疏水单元的顺序和位置在这些响应性聚合物层的热力学稳定性和结构行为中起着关键作用。另外，当根据温度和pH改变疏水单元的表面覆盖率，位置和顺序时，聚合物表现出可调的塌陷。据我们所知，我们的结果提出了第一个分子详细的理论，用于末端连接的聚合物，该聚合物通过氢键具有pH值和温度响应性。我们建议这项工作对未来生物材料的指导设计具有预测力。