Open-cage silsesquioxane necklace polymers having closed-cage silsesquioxane pendants

Polyhedral oligomeric silsesquioxanes (POSSs) are promising building blocks for organic–inorganic hybrid materials. However, polymers containing POSS units in the main chains have been hardly studied because the synthesis of bifunctional POSS monomers is very difficult in general. In this work, a novel molecular design of a POSS monomer has been proposed; a completely condensed POSS (CC-POSS) was linked to one reaction site of an incompletely condensed POSS (IC-POSS), and the remaining two reaction sites of the IC-POSS were used for polymerization. Notably, substituents on the IC- and CC-POSSs can be widely varied based on the present molecular design. It has been demonstrated that the resulting polymers are suitable for optically transparent materials because of their high thermal stability and transparency and that the properties were controlled by the substituents of the POSSs and comonomers.