MWN: Thermal Transitions in Polyelectrolyte Multilayers and Complexes

技术概述：聚电解质复合物和多层膜（分别为佩奇和PEM）都是由带相反电荷的聚合物形成的，并且在结构和性能方面具有许多相似之处。佩奇和PEM对于从水下粘合剂到药物输送和生物材料的应用越来越重要。Lutkenhaus小组最近的工作发现，PEM在水的存在下加热时会发生二级玻璃化转变。尽管Lutkenhaus观察到的热转变具有玻璃化转变的所有经典特征，但其确切性质仍然难以捉摸。PEM通常近似为PEC，并与佩奇进行比较，因为它们都使用离子配对和熵相互作用来控制它们的形成。合理地说，佩奇可以用作实验和模拟的平台，以近似PEM中水合作用、离子强度和温度的作用。因此，PI建议使用水合作用、离子强度和离子种类以及温度作为调整参数，将佩奇作为PEM的近似值进行研究。在国家科学基金会材料研究部门和芬兰科学院自然科学和工程研究部门的财政支持下，材料世界网络项目将通过实验和模拟方法进行研究，美国和芬兰团队分别拥有专业知识。团队将举行学生和教师交流，以促进国际合作。非技术性总结：聚电解质复合物是由带相反电荷的聚合物之间的相互作用形成的，在从水下粘合剂到药物输送和生物材料的应用中越来越重要。复合物是否形成取决于几个参数：盐的类型，盐的类型，浓度，水合作用和温度。最近，Lutkenhaus小组观察到，被认为类似于复合物的多层膜在高温下经历了独特的热转变。这种转变的本质还没有被完全理解，但这对未来复合物和多层结构的创新至关重要。因此，本材料世界网络项目将研究上述参数对金属络合物的形成和热转变的影响。计划在美国和芬兰团队之间进行学生交流。聚电解质络合演示计划为德克萨斯A M大学的化学开放日，每年一度的活动向公众开放。计划对本科生和研究生进行研究指导，并对中学教师进行指导。

TECHNICAL SUMMARY:Polyelectrolyte complexes and multilayers (PECs and PEMs, respectively) are both formed from oppositely charged polymers, and share many similarities in structure and properties. Both PECs and PEMs are increasingly important for applications ranging from underwater adhesives to drug delivery and biomaterials. Recent work by the Lutkenhaus group has discovered that PEMs undergo a second-order, glass transition-like thermal transition upon heating in the presence of water. Even though the thermal transition observed by Lutkenhaus has all the classic features of a glass transition, its exact nature remains elusive. PEMs are often approximated as, and compared to, PECs because they both use ion-pairing and entropic interactions to control their formation. Rationally, PECs can be used as a platform for both experiments and simulations to approximate the role of hydration, ionic strength, and temperature in PEMs. Therefore, the PIs propose to study PECs as an approximation of PEMs using hydration, ionic strength and ionic species, and temperature as tuning parameters. With financial support from the Division of Materials Research at the National Science Foundation and the Natural Sciences and Engineering Research Unit at the Academy of Finland, this Materials World Network project will approach the study through both experimental and simulational approaches, in which the U.S. and Finnish teams have expertise, respectively. Teams will hold student and faculty exchanges to foster the international collaboration.NON-TECHNICAL SUMMARY:Polyelectrolyte complexes, which are formed from the interactions between oppositely charged polymers, are increasingly important for applications ranging from underwater adhesives to drug delivery and biomaterials. Whether or not the complex forms depends on several parameters: polyelectrolyte type, salt type, concentration, hydration and temperature. Recently, the Lutkenhaus group has observed that polyelectrolyte multilayers, which have been proposed to be similar to complexes, undergo a unique thermal transition at elevated temperatures. The nature of this transition is not at all understood, but it is critically important to the future innovation of complexes and multilayers to do so. Therefore, this Materials World Network project will study the effects of the aforementioned parameters on the formation in and thermal transitions of polyelectrolyte complexes. Student exchanges are planned between U.S. and Finnish teams. Polyelectrolyte complexation demonstrations are planned for Texas A&M University's Chemistry Open House, an annual event open to the public. Undergraduate and graduate research mentoring, as well of mentoring of secondary school teachers is planned.