UNS: Time-lapse and Cure-on-Demand Polymerization using Autocatalytic Reactions

PI：Pojman，John提案编号：1510612按需固化聚合是“在您需要的时候获得您想要的东西。“换句话说，聚合只有在你选择开始的时候才能进行。氰基丙烯酸酯具有“按需固化”性质，因为当暴露于水分时发生聚合。这也适用于异氰酸酯粘合剂，如Gorilla胶水或硅酮密封剂。这些系统的问题是反应不完全在用户的控制之下。理想的情况是，材料不反应，直到提供外部刺激。光聚合表现出这种特征，但它们限于光可以穿透系统的情况。因此，光聚合对于高度填充的系统或当表面投射阴影而留下未固化的区域时是无用的。实现按需固化的一种可能是通过使用前沿聚合（FP），一种聚合方法，其中聚合在局部反应区中定向发生。热前沿聚合是由热传递和放热聚合反应速率的依赖性耦合而成的。FP的基本标准是系统在初始温度下必须具有极低的速率，但在前端温度下必须具有高的反应速率，使得产热速率超过热损失速率。换句话说，该体系必须在室温下缓慢反应或完全不反应，具有大的放热和高的活化能。大多数粘合剂和修补配方需要混合两种组分，然后开始反应，或者需要很长的时间来完成固化。PI将研究尿素酶催化的尿素水解，产生氨和二氧化碳。如果初始pH设定为4，则反应自催化进行，因为脲酶在pH 7时具有最佳反应性。该反应可以是时钟反应，在可编程的时间段之后pH突然上升，或者可以支持传播的碱性pH前沿。PI计划使用该系统触发硫醇与丙烯酸酯的Michael加成。他可以创造延时聚合和等温前沿聚合。在高浓度尿素的情况下，高的最终pH导致延迟的水解，这允许聚合物颗粒的可编程的临时粘合剂或可编程的降解。他计划使用一种自催化生成哌啶的有机系统来创造非水延时聚合和前沿聚合系统。这项研究可能会导致消费者使用的商业粘合剂。尿素-尿素酶-硫醇-丙烯酸酯系统可用于产生“按需固化”骨修复材料或程序化药物释放系统。系统的延时特性可用于产生可编程粘合剂，并且可降解特征可用于产生在确定时间之后将停止粘附的可编程粘合剂。使用瓜尔胶和硼酸盐，人们可能能够创造一种用于水力压裂的添加剂，这种添加剂只会在流体被泵入储层深处后才允许粘度增加。

PI: Pojman, JohnProposal #: 1510612Cure-on-demand polymerization is "getting what you want, when you want it." In other words, the polymerization only proceeds when you choose it to commence. Cyanoacrylates have a "cure-on-demand" property in that the polymerization occurs when exposed to moisture. This is also true for isocyanate adhesives such as Gorilla glue or silicone sealants. The problem with these systems is that the reaction is not completely under the control of the user. The ideal case is that the material does not react until an external stimulus is provided. Photopolymerizations exhibit this feature but they are limited to situations in which the light can penetrate the system. Therefore, photopolymerization is not useful for highly-filled systems or when a surface casts shadows that leave areas uncured. One possible was to accomplish cure-on-demand is by using frontal polymerization (FP), a polymerization process in which polymerization occurs directionally in a localized reaction zone. Thermal Frontal Polymerization results from the coupling of thermal transport and the dependence of the reaction rate of an exothermic polymerization. The essential criteria for FP is that the system must have an extremely low rate at the initial temperature but a high rate of reaction at the front temperature such that the rate of heat production exceeds the rate of heat loss. In other words, the system must react slowly or not at all at room temperature, have a large heat release and have a high energy of activation.Most adhesive and repair formulations require mixing two components, which then begin reacting, or require a lengthy time to complete the curing. The PI will study the urease-catalyzed hydrolysis of urea, which produces ammonia and carbon dioxide. If the initial pH is set to 4, the reaction proceeds autocatalytically because urease has optimal reactivity at pH 7. The reaction can be a clock reaction, with the pH abruptly rising after a programmable period of time or can support a propagating basic pH front. The PI plans to use this system to trigger the Michael addition of a thiol to an acrylate. He can create time-lapse polymerizations and isothermal frontal polymerization. With high concentration of urea, the high final pH results in a delayed hydrolysis that allows a programmable temporary adhesive or programmed degradation of a polymer particle. Using an organic system that autocatalytically produces piperidine, he plans to create nonaqueous time-lapse and frontal polymerization systems. This research could lead to commercial adhesives for consumer use. The urea-urease-thiol-acrylate systems could be used to create a "cure-on demand" bone repair material or a programmed drug release system. The time-lapse character of the system could be used to create a programmable adhesive and the degradable feature to create a programmed adhesive that will stop adhering after a determined time. Using Guar gum and borate, one may be able to create an additive for fracking that will allow the viscosity to increase only after the fluid is pumped deep into the reservoir.