Nanogels and microgels: The new polymeric materials playground
Nanogels and microgels: The new polymeric materials playground
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DOI：
10.1351/pac199870061271
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发表时间：
1998-06-01
影响因子：
1.8
通讯作者：
Cameron, A
中科院分区：
文献类型：
--
作者：
Graham, NB;Cameron, A
微凝胶，或分子内交联大分子(ICM)，多年来一直被人们所知。它们是在多官能团前驱体聚合的过程中形成的，但在不完全反应时，形成了最初由Cartheres和Flory提出的凝胶理论预测的大凝胶化。这些凝胶化理论并没有预言这种多官能团反应溶液可以在完全反应和高浓度下制备这种微凝胶，而不需要凝胶化。然而，通过使用水或非水分散聚合，在其所包含的反应性基团完全转化时，已经成功和有效地制备了微凝胶，其中利用表面活性剂将聚合包含到孤立的亚微米尺寸的区域。向大凝胶化的进展受分散区域的最大尺寸的限制。本文论证了这种多官能团反应前驱体在溶剂中的宏观凝胶化不可能发生在临界凝胶化浓度(CGC)以下的一般观察结果，前提是聚合溶剂和形成的聚合物的溶剂溶解度参数经过精心选择才能匹配。在某些情况下，只需添加10%w/w的Ca10%的溶剂即可完全防止完全转化时的大凝胶化。此外，聚合反应产生的ICM的分子量可以简单可控的方式变化，从几千(纳米凝胶)到几百万(微凝胶)，只需选择它们的制备浓度即可。这些产品是一种截然不同的聚合物形式，与线性类似物有很大不同，几乎可以肯定的是，这些溶液制备的产品不同于通过水分散聚合技术形成的微凝胶。这一新的溶液技术为大量具有基本学术价值和潜在商业用途的定制球形聚合物的快速合成和设计提供了一种简单而通用的新方法。
Microgels, or intramolecularly crosslinked macromolecules (ICMs), have been known for a number of years. They are formed during the polymerization of polyfunctional precursors en-route, but at incomplete reaction, to the macrogelation predicted by the theories of gelation initially propounded by Carothers and Flory. These gelation theories did not predict that such microgels made in solution could be prepared from such polyfunctional reactive solutions at complete reaction and high concentrations, without gelation. Microgels have been successfully and usefully prepared, however, at complete conversion of their contained reactive groups by the use of either aqueous or non-aqueous dispersion polymerization in which surface active agents are utilized to contain the polymerization to isolated submicron-size domains. The progression towards macrogelation is constrained to the maximum size of the dispersed domains. This paper demonstrates the contrasting general observation that macrogelation in solvents of such polyfunctional reactive precursors cannot occur below a Critical Gelation Concentration (CGC) if a carefully selected match of solvent solubility parameters for the polymerization solvent and the formed polymer is made. In some cases the addition of only ca, ten percent w/w of solvent is required to completely prevent macrogelation at complete conversion. In addition polymerization the molecular weight of the produced ICMs may be varied in a simple controllable manner from the low thousands (nanogels) to many millions (microgels) simply by the choice of concentration at which they are prepared. The products are a distinct form of polymer which is quite different to the linear analogue and almost certainly these solution-prepared products are different to the microgels formed by aqueous dispersion polymerization techniques. This new solution technique provides a simple and general new method for the ready synthesis and design of an enormous range of bespoke globular polymers having both fundamental academic interest and potential commercial utility.