Vinylogous urethane vitrimers

Vitrimers are a new class of polymeric materials with very attractive properties, since they can be reworked to any shape while being at the same time permanently cross-linked. As an alternative to the use of transesterification chemistry, we explore catalyst-free transamination of vinylogous urethanes as an exchange reaction for vitrimers. First, a kinetic study on model compounds reveals the occurrence of transamination of vinylogous urethanes in a good temperature window without side reactions. Next, poly(vinylogous urethane) networks with a storage modulus of approximate to 2.4 GPa and a glass transition temperature above 80 degrees C are prepared by bulk polymerization of cyclohexane dimethanol bisacetoacetate, m-xylylene diamine, and tris(2-aminoethyl) amine. The vitrimer nature of these networks is examined by solubility, stress-relaxation, and creep experiments. Relaxation times as short as 85 s at 170 degrees C are observed without making use of any catalyst. In addition, the networks are recyclable up to four times by consecutive grinding/compression molding cycles without signifi cant mechanical or chemical degradation