Hydrophobic and Electrostatic Driving Forces for Ion Adsorption to Polymers and Extended Interfaces

化学系的大分子、超分子和纳米化学项目支持宾夕法尼亚州立大学Paul S. Cremer教授和他的学生探索盐影响溶解在水中的油性聚合物分子的方式。油和水不易混合。例如，在沙拉酱中，油层通常漂浮在水基层之上。此外，溶解盐主要存在于水相而不是油相中。具体来说，这项研究有助于确定带负电荷或正电荷的离子何时与聚合物分子相互作用或分离。聚合物对水中盐的吸引力决定了聚合物是否能保持溶解在溶液中或从溶液中以固体形式沉积。聚合物在盐水中的溶解度在从生物和食品科学到大气化学、新材料的自组装，甚至是洗衣的清洁等广泛的领域都很重要。这项研究不仅揭示了与社会直接相关的问题，而且还培养了涉及化学、生物学、材料科学和工程等跨学科领域的学生。克雷默教授和他的团队正在与高中化学老师合作，为10年级和11年级的学生制作廉价且容易操作的实验。讲师将开发有关聚合物溶解原理和盐离子在日常生活中的核心作用的教学模块。Cremer小组正在探索弱水合阴离子，强水合阳离子，以及水合氢离子和氢氧化物如何影响水溶液中热敏聚合物的行为。他们的实验方法涉及将离子结合和疏水坍塌行为与水化壳的光谱特征联系起来。这些信息可以通过拉曼多变量曲线分辨率光谱和振动和频率光谱等技术获得。这些热力学和光谱实验是与进行分子动力学模拟的理论家合作进行的。测量是在散装溶液和表面活性剂单层在空气/水界面。例如，正在探索结果与大分子的大小、它们的净电荷和特定带负电荷和正电荷的官能团的存在之间的函数关系。特别关注的是溶液中的离子是否可以通过接触离子对或溶剂共享离子对与聚合物分子相互作用。此外，在其中带电的部分被提出的背景下进行了探讨。这些研究提供了关于带电部分的数量密度以及周围疏水位点的配置如何影响离子-聚合物相互作用的信息。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The Macromolecular, Supramolecular, and Nanochemistry Program in the Chemistry Division supports Professor Paul S. Cremer and his students at the Pennsylvania State University to explore the ways that salts influence oily polymer molecules dissolved in water. Oil and water do not readily mix. In salad dressing, for example, an oily layer is typically found floating on top of a water-based layer. Moreover, dissolved salts reside primarily within the water phase rather than in the oil phase. Specifically, this study helps to determine when negatively or positively charged ions interact with polymer molecules or separate from them. The attraction of the polymer for salts in water dictates whether the polymers can remain dissolved in solution or deposit as a solid from the solution. The solubility of polymers in salt water is important in a surprisingly wide variety of areas ranging from the biological and food sciences to atmospheric chemistry, the self-assembly of novel materials, and even the cleaning of laundry. This research not sheds light on problems of direct relevance to society, but also trains students in interdisciplinary fields involving chemistry, biology, materials science, and engineering. Professor Cremer and his group are working with high school chemistry teachers to create inexpensive and easily accessible experiments for 10th and 11th graders. The instructors will develop teaching modules on principles of polymer solubility and the central role of salt ions in everyday life.The Cremer group is exploring how weakly hydrated anions, strongly hydrated cations, as well as hydronium and hydroxide influence the behavior of thermoresponsive polymers in aqueous solutions. Their experimental approach involves correlating ion binding and hydrophobic collapse behavior with spectroscopic signatures of the hydration shell. This information can be obtained by using techniques like Raman multivariate curve resolution spectroscopy and vibrational sum frequency spectroscopy. These thermodynamic and spectroscopic experiments are performed in collaboration with theoreticians performing molecular dynamic simulations. Measurements are made in bulk solution and with surfactant monolayers at the air/water interface. For example, results are being explored as a function of the size of the macromolecules as well as their net charges and the presence of specific negatively and positively charged functional groups. Special attention is focused on whether ions in solution can interact with polymer molecules via contact ion pairing or through solvent shared ion pairing. Moreover, the context in which charged moieties are presented is explored. These studies provide information as to how the number density of charged moieties as well as the configuration of surrounding hydrophobic sites influence ion-polymer interactions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.