New crosslinking processes

Abstract

Synthesis of model-networks characterized by the quasi-constant length of the linear chain elements between two successive branch points has been carried out by anionic block copolymerization of two monomers, one being bifunctional. The influence of various parameters (concentration, temperature, number of molecules of bifunctional monomer added per active chain end) on the behaviour of the gels is discussed. This method can be applied to several systems.

Another method was successfully used to synthesize networks: reaction of α, ω-difunctional linear polymer chains with tri- or tetrafunctional molecules, in stoichiometric amount was shown to lead to gels in which both the length of the linear chain elements and the functionality of the branch points are controlled. Reactions of terminal carbon metal bonds with electrophilic groupings of various kinds were used, as well as reaction of silane end groups with allylic double bonds. The gels obtained were characterized by their swelling behaviour, in relation to the molecular weight of the chain elements and the functionality of the branch points.