Formation and Theory of Self-Assembled Nanoscopic Structures in 2-Dimensions using Diblock Copolymers

将进行实验和理论研究，以更好地了解如何诱导两亲性两嵌段共聚物在液-气界面上形成规则的纳米结构，从而形成二维结构。聚苯乙烯-聚环氧乙烷的柔性两嵌段共聚物已被证明从快速蒸发的溶剂中扩散，形成点状、意大利面和大陆，这取决于溶液浓度和亲水嵌段的百分比。这些大分子的长度自然在几十到几百纳米的数量级。观察到的图案形成现象不是热力学上稳定的结果，而是溶液液滴扩散(从而分离聚合物)和由于蒸发(从而减少聚合物分离)而导致的溶液浓度增加之间的竞争，最终导致疏水链段的聚集。与麻省理工学院的Anette Hosoi博士合作，推导出了一个理论模型，该模型预测了这种动力学陷阱行为，而不使用拟合参数；只使用了系统的真实物理参数。这些研究现在将扩展到具有不同物理性质的两嵌段共聚物的实验观察和理论描述：不同的几何结构，而不是线性线圈-线圈链，以及由持续长度定义的不同刚性。将使用双嵌段和双嵌段与均聚物的二元混合物，以更好地控制亲水和疏水内容物的相对组成。通过这种方式，将检验该模型的普遍适用性。此外，将从实验和理论上探讨剪切对准意大利面结构所需的可能技术和力的大小。目标是在纳米尺度上创建结构，并对它们进行定向，以便提供具有地形和化学异质性的表面。非技术摘要：生物系统中的大多数结构通过一种称为自组装的过程在最小的长度尺度上自发组织。这项研究利用了许多与生物系统相同的力，即组织和分离单个大分子的亲水(亲水)和疏水(亲油)部分，在这种情况下是两嵌段共聚物。已观察到这些聚合物在制备技术中形成二维纳米结构，该制备技术涉及将聚合物铺展在水面上，并仅改变溶液的浓度或聚合物的亲水和疏水部分的相对尺寸。这项工作结合了理论和实验工作，以更好地理解和控制自组装中这些微小结构的创建。本研究以本科生为主要研究对象，积极指导和培养博士后研究人员。一个积极和吸引人的研究项目对本科生的影响对于鼓励和支持未来的科学家是重要的。

Experimental and theoretical investigations will be performed to better understand how amphiphilic diblock copolymers can be induced to form regular nanoscopic structures on the liquid-air interface, and thus in 2-dimensions. Flexible diblock copolymers of poly (styrene) -b- poly (ethylene oxide) have been shown to spread from a quickly evaporating solvent to form dots, spaghetti and continents depending on the solution concentration and % hydrophilic block. The length scales of these macromolecules are naturally on the order of tens to hundreds of nanometers. The phenomenon observed of pattern formation is not a thermodynamically stable result, but rather, a competition between the solution droplet spreading (and thus separating the polymers) and an increase in solution concentration due to evaporation (and thus decreasing polymer separation) that ultimately causes aggregation of the hydrophobic block. In collaboration with Dr. Anette Hosoi of MIT, a theoretical model was derived that predicts this kinetically trapped behavior without the use of fitting parameters; only the real physical parameters of the system are used. These studies will now be extended to the experimental observation and theoretical description of diblock copolymers with different physical properties: geometries other than linear coil-coil chains and different rigidities as defined by persistence length. Binary mixtures, of diblocks and of diblocks with homopolymers, will be used to better control the relative compositions of the hydrophilic and hydrophobic contents. In this manner, the general applicability of the model will be tested. Furthermore, the possible techniques and magnitudes of forces required to shear align the spaghetti structures will be probed both experimentally and theoretically. The goals are both to create structures on the nanoscale and to orient them in order to provide surfaces with both topographical and chemical heterogeneity.NON-TECHNICAL SUMMARY:Most structures in biological systems spontaneously organize on the smallest length scales by a process known as self-assembly. This research utilizes many of the same forces as biological systems, that is, the organization and separation of hydrophilic (water-loving) and hydrophobic (oil-loving) sections of a single large molecule, in this case a diblock copolymer. These polymers have been observed to form two-dimensional nanoscopic structures in a preparation technique that involves spreading the polymers on a water surface and changing only the concentration of the solution or the relative sizes of the hydrophilic and hydrophobic parts of the polymer. This work couples theoretical and experimental work to better understand and control the creation of these tiny structures in self-assembly. The research actively involves undergraduates as the key research participants with active mentoring and training of postdoctoral researchers. The impact of an active and engaging research program on undergraduates is important in encouraging and sustaining future scientists.