Synthese und Bildungsmechanismen vernetzter Polymerer

Abstract

Polymers with a high molecular weight can be obtained by multifunctional crosslinking reactions despite of possible side reactions which may seriously interfere with the formation of linear polymers. Synthesis of crosslinked polymers may procede by polymerisation with simultaneous crosslinking or by crosslinking of preformed linear polymers. As to certain properties, e.g. those characteristic for the gel state, it is appropriate not only to consider covalent bonds as crosslinks, but also ionic, complex and hydrogen bonds and even other intermolecular interactions.
The course of reaction and the kinetics of crosslinking polymerisation are similar to those of linear polymerisation in concentrated solutions or in substance, yet there are some differences to be noted which may be explained by the hindrance of translational diffusion in crosslinking systems.
There are several causes which may be responsible for structural heterogeneity of polymer networks, as dilution by inert solvents, fixation of growing radical chains at the network, special reactivity ratios of the monomers and phase separation during polymerisation. The occurrance of structural homogeneous networks seems to be rather an exceptional than the normal case.
Some possible ways for synthesizing polymer networks with definite inhomogeneous structure are indicated.