A new silane precursor with reduced polymerization shrinkage

There is a growing interest in precursor molecules for the sol-gel process which allow the formation of inorganic-organic copolymers, the so-called ORMOCER^®s, with no or only low shrinkage. A new silane type, the spiro ortho ester silanes, which can be polymerized by a ring opening reaction has been developed in order to overcome problems associated with loss of precise dimension and poor cohesion or stresses in coatings or in bulk materials caused by shrinkage during the curing step. In this paper, the synthesis of the new reactive silane precursor, the incorporation into the sol-gel process and the ring-opening reaction that can be UV-induced, for instance, will be described. First investigations show that the last reaction step is accompanied by a volume change of only <0.30 vol. -%.