Understanding rapid pseudo-solid state step-growth polymerization in micro-layers leading to ultra-high molecular weight polymers with unusual molecular structures

[1033071]本研究将研究在非晶聚合物微层的有限反应空间中快速生成高至超高分子量（MW）聚合物的伪固态阶梯生长聚合。伪固态聚合（p-SSP）具有在短反应时间内制备超高分子量聚合物的能力。最终聚合物的超高分子量和特殊性能只能与通过开环聚合生产的缩合聚合物相比，但p-SSP更经济可行，更环保。这种聚合技术包括将低毫瓦无定形聚合物前驱体与催化剂一起配制成聚合物微层的密闭反应空间，并在接近但低于聚合物熔点的减压和温度下进行聚合。初步实验结果表明，该反应的进行速度比传统的半结晶颗粒固态聚合快20倍以上，聚合物的分子量和多分散度明显超过了经典阶梯生长聚合理论的理论极限。在适当的反应时间，不溶性/不溶性结构与可溶性结构共存，最终聚合物表现出优异的光学清晰度。通过13C-NMR和1H-NMR，以及聚合物的流变学表征，证实了支链结构的存在。聚合物链在无定形状态下的高迁移率、缩聚副产物在微米级反应空间的高效去除、残余铸造溶剂热分解或裂解反应引起的自由基诱导分支反应、Fries重排、交换反应和高反应活性是聚合物分子量快速而罕见地增加和不溶性聚合物形成的主要原因。研究了三种模型体系：双酚a聚碳酸酯、聚l-乳酸和聚碳酸酯与聚二甲基硅氧烷的共聚物。预计该技术可以应用于许多其他缩聚体系，这表明p-SSP可以对步长聚合技术产生广泛的影响。通过实验和理论研究，该项目将发展对控制p- ssp过程的化学和物理现象的基本理解。智力价值：目标是通过实验和理论建模，对驱动p-SSP动力学的化学和物理现象进行新的定量理解。P-SSP不同于熔融聚合和传统的固态聚合，其动力学也偏离了传统的方法。综合实验和数学建模的集成将提供一种系统的方法来生产量身定制的缩合聚合物，用于各种需要高或超高mw，耐溶剂性和耐热性的特殊应用。拟议研究的更广泛影响：P-SSP是一种在短反应时间内生产超高MW缩合聚合物的方法。这项研究将为先进聚合工艺技术的发展提供基础数据和知识，特别是大规模生产，以及新的聚合物性能。例如，传统可溶聚合物的不溶性和不溶性结构的合成可以激发各种新的应用。研究结果有望应用于许多其他缩合聚合反应。研究成果将在相关的科学和工程领域发表。所有层次的本科生，不论种族背景和性别，都将被强烈鼓励以学期研究或暑期实习项目的形式参与提议的项目。在学术上有天赋的高中生也将被邀请参加马里兰大学女性工程项目（Women In Engineering， WIE）的暑期研究体验项目。我们将鼓励不同层次的学生开发创新的应用程序，并随着研究的进展对这些想法进行测试。

1033071ChoiThis research will investigate the pseudo-solid state step-growth polymerization in the confined reaction space of an amorphous polymer micro-layer where high to ultra-high molecular weight (MW) polymers are rapidly produced. Pseudo-solid state polymerization (p-SSP) has the ability to produce ultra-high MW polymers in short reaction times. The extraordinary high MWs and the exceptional properties of the final polymer can only be compared with condensation polymers produced via ring opening polymerization, but p-SSP is more economically feasible and environmentally friendly.This polymerization technique consists of formulating a low MW amorphous polymer precursor with catalyst into a confined reaction space of a polymer micro-layer, and carrying out the polymerization at reduced pressures and at temperatures close to but below the polymer melting point. Preliminary experimental results indicate that the reaction proceeds more than 20 times faster than conventional solid state polymerizations in semi-crystalline particles, and polymer MWs and polydispersities notably exceed the theoretical limits of the classical step-growth polymerization theory. At moderate reaction times, insoluble/infusible structures coexist with soluble structures, and the final polymer exhibits excellent optical clarity. The presence of branched structures has been confirmed by 13C-NMR and 1H-NMR, and the rheological characterization of the polymer. The relatively high mobility of polymer chains in the amorphous state, the efficient removal of polycondensation byproduct from the micron-sized reaction space, the radical-induced branching reactions via thermal decomposition of the residual casting solvent or via scission reactions, Fries rearrangement, interchange reactions, and high reactivities are hypothesized to be mainly responsible for the fast and unusual increase of the polymer MWs and the formation of insoluble polymer. Three model systems have been investigated: bisphenol-A polycarbonate, poly(L-lactic acid), and a copolymer of polycarbonate and poly(dimethylsiloxane). It is expected that the technique can be applied to many other condensation systems, suggesting that p-SSP can have a broad impact on step-growth polymerization technology. Through experimental and theoretical studies, this project will develop fundamental understandings of the chemical and physical phenomena that govern the p-SSPs process.The Intellectual Merit: The goal is to develop new quantitative understandings of the chemical and physical phenomena that drive the kinetics of p-SSP to unusual reaction behaviors through experimentation and theoretical modeling. P-SSP is different from melt and conventional solid-state polymerizations, and its kinetics deviates from the traditional approaches. Integration of comprehensive experimentation and mathematical modeling will provide a systematic way to produce tailor-made condensation polymers for a variety of special applications where high or ultra-high MWs, solvent resistance, and thermal resistance are required.The Broader Impacts of the Proposed Study: P-SSP is a method to produce ultra-high MW condensation polymers in short reaction times. This research will provide fundamental data and knowledge for the development of an advanced polymerization process technology, especially for large-scale mass production, as well as new polymer properties. For instance, the synthesis of insoluble and infusible structures for traditionally soluble polymers can inspire a variety of novel applications. The research results are expected to be applicable to many other condensation polymerizations. The results of the research will be presented at relevant scientific and engineering fields. Undergraduate students at all levels, regardless of ethnic background and gender, will be strongly encouraged to participate in the proposed project as semester research or summer internship programs. Academically talented high school students will also be invited to a summer research experience program through University of Maryland's Women In Engineering (WIE) program. The participating students at different levels will be encouraged to develop innovative applications and test the ideas as the research progresses.