Research Initiation Award: Intermolecular Reactions in Flexible Polymer Solutions

大量的工业过程涉及化学反应 在连接到高分子量 柔性聚合物 实例包括：（1）生产线性 自由基聚合和缩聚形成的链; (2)橡胶弹性体和凝胶的制造， 通过化学方法或通过 高能辐射作用;（3）反应加工法 生产高强度复合材料。 虽然小分子反应 也发生在这些情况下，主要的困难涉及 大分子反应，因为反应性物种的能力，以满足 是由聚合物的动态和静态性能决定的 他们所依附的。 本研究的目的是 通过计算确定这些过程的基本机制 当两个长的未支化的聚合物各自 携带一个位于它们各自的沿着某处的活性基团 两个人，如果在一起， 他们彼此之间的距离（“捕获半径”）， 每单位时间内以一定的概率发生反应。 两个聚合物线圈 必须在空间中扩散，然后相互穿透 显著地在反应可以进行之前（典型的聚合物线圈和 捕获半径尺寸分别为300和10埃 分别）。 PI计划发展一种反应的分子理论 溶液中高分子量聚合物与 预测反应速率作为聚合物分子量的函数 和聚合物在稀、半稀（其中 聚合物强烈重叠， 效果）和稠密的解决方案（熔体）。 反应速率为 这取决于浓度，因为如果聚合物被稀释在 在单体背景下，线圈扩散相对较快 但在近距离接触时会强烈排斥 而如果链是密集的（在熔体中）和长的， 排斥被屏蔽，但扩散被大大减慢 被纠缠。 预期的另一个结果是， 研究是，它将增加知识的性质， 不可逆反应的平衡系统 （聚合物反应是非平衡热反应的一个例子。 系统）。

A large number of industrial processes involve chemical reactions between reactive groups which are attached to high molecular weight flexible polymers. Examples includes: (1) the production of linear chains by radical and condensation polymerization; (2) the manufacture of rubber elastomers and gels by cross-linking long polymer chains either chemically or through the action of high energy radiation; and (3) reactive processing methods producing high strength composites. While small molecule reactions also occur in these situations, the main difficulty concerns the macromolecular reactions since the ability of reactive species to meet is determined by the dynamical and static properties of the polymers to which they are attached. The objective of this research is to determine a fundamental mechanism for these processes by calculating reaction rates for the case when two long unbranched polymers each carrying one active group located somewhere along their respective backbones, such that if ever the two groups are brought to within a certain distance of one another ( the "capture radius") they will react with certain probability per unit time. The two polymer coils must diffuse through space and then penetrate one another significantly before reaction may proceed (typical polymer coil and capture radius dimensions are 300 Angstroms and 10 Angstroms respectively). The PI is planning to develop a molecular theory of reaction rates between high molecular weight polymers in solution and to predict reactions rates as a function of polymer molecular weight and concentration for polymers in dilute, semi-dilute (where polymers overlap strongly giving rise to some concentration effects) and dense solutions (melt). The reaction rates are dependent on concentration because if the polymers are dilute in a monomeric background, the coils diffuse relatively quickly through space but strongly repel one another on close encounter, while if the chains are dense (in a melt) and long, such repulsions are screened but diffusion is drastically slowed down by entanglements. An additional outcome expected of this research is that it will increase knowledge about the nature of an equilibrium system to which irreversible reactions are added (polymer reactions are an example of a non-equilibrium thermal system).