Gelation Crystallization of Polymers from Supercritical Solution as a Route Toward Useful Materials

该方案研究的是溶解在超临界流体中的聚合物结晶过程中形成的物质。聚合物，如线性聚乙烯和聚丙烯，在超临界条件下与甲苯完全相容。当混合物冷却和降压时，聚合物晶体形成一个相互连接的网络。通过降压除去气态溶剂，使结晶网络保持不变。其结果是得到了结构均匀的无溶剂凝胶或泡沫，并且具有广泛的孔隙率和机械强度，可以根据结晶条件的不同而变化。该方法比液相结晶具有优势，在液相结晶中，溶剂的去除通常会破坏结晶网络。该提案将研究这些凝胶的机械强度和微观结构，这些凝胶由各种不同的聚合物前体形成，包括聚合物混合物。

This proposal studies the materials which are formed during the crystallization of polymers dissolved in a supercritical fluid. Polymers such as linear polyethylene and polypropylene are completely miscible with toluene under supercritical conditions. As the mixture is cooled and depressurized, polymer crystals form in a linked network. The gaseous solvent is removed by depressurization, leaving the crystalline network intact. The result is a solvent-free gel or foam of uniform structure, and with a broad range of porosities and mechanical strengths which can be varied depending upon the crystallization conditions. The process has the advantage over liquid phase crystallization where removal of the solvent usually destroys the crystalline network. The proposal will study the mechanical strength and microstructure of these gels formed from a variety of different polymer precursors, including polymer blends.