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C. Schnöll, C. Gorsche, N. Moszner, R. Liska:
"Debonding on Demand (DoD) via thermally induced gas formation using blocked isocyanates";
Poster: 4th European Symposium of Photopolymer Science, Leipzig; 11.09.2016 - 14.09.2016; in: "ESPS 2016", (2016), S. P-43.

Photocurable resins based on mono- and multifunctional methacrylates represent major components for dental adhesives and cements, which are used for temporary dental fixations.[1] However, the excellent adhesion of those materials to the tooth surface leads to one of their main drawbacks, which is the difficult removal after the temporary fixture is no longer needed.
Therefore, a suitable adhesive that enables "Debonding on Demand" (DoD) would be beneficial. With the incorporation of cleavable crosslinks into the polymer matrix the architecture and hence the mechanical properties of the network can be changed by an external stimulus (e.g. light or heat). Such cleavable crosslinks described in literature are for example based on retro-Diels-Alder reactions[2] or photocleavable groups.[3] However, the retro-Diels-Alder concept consequences in a reversible reaction. For the realization of DoD it is crucial that the cleaved crosslinks do not recombine and further strengthen the material. The homolytic cleavage of the photolabile group results in the formation of radicals, which bear the potential for post curing and recombination. For those reasons, both concepts have not been pursued for the realization of DoD in the field of dental applications.
To overcome the described challenges the concept of blocked isocyanates (BICs) as thermolabile crosslinks is introduced. Upon heating these compounds generate reactive moieties (isocyanates or ketens), which can further react with moisture present in the oral environment and decarboxylate. This results in an irreversible DoD mechanism via a thermally induced gas formation. A broad variety of BICs was synthesized and studied regarding their deblocking temperature. Moreover, the most promising compounds were tested towards their potential to realize DoD in a suitable polymer matrix.

biomedical applications, Debonding on Demand