Synthesis of Network Polymers Containing Si-Vinylene Units by Mizoroki-Heck Reaction

Abstract

Network polymers containing Si-vinylene units have been synthesized by Mizoroki-Heck reaction of cyclic siloxane or cubic silsesquioxane compounds with vinyl groups, as joint molecules, and dibromo aryl compounds, as linker molecules, using a Pd catalyst. The reaction of 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane (TVMCTS) or octavinyloctasilsesquioxane (PVOSS) with o, m, p-dibromobenzene (DBB) or 4,4'-dibromobiphenyl (DBBP) yielded the corresponding network polymers, except TVMCTS-oDBB system. Optical properties of the network polymers were studied by UV-vis and photoluminescence spectroscopy, and absorption and emission derived from s-p conjugation of the Si-vinylene units were detected. Copolymerization of TVMCTS-DBB/bromobenzene yielded CHCl3 soluble fraction due to formation of the network fragments. The network polymers of TVMCTS or PVOSS with 2,7-dibromofluorene (BFl) or 9,9-dihexyl-2,7-dibromofluorene were synthesized by the same procedures. Scanning electron microscope image of TVMCTS-BFl network polymer indicated formation of porous structure. The network polymers have been also synthesized by the reactions of multifunctional aryl bromide, as the joint molecules, with divinyl or dially silane compounds, as the linker molecules. The molecular structure of the multifunctional aryl bromide affected the emission wavelengths of the network polymers. In the case of the 2,2’,7,7’-tetrabromo-9,9’-spirobifluorene-based network polymers, the emission spectra widely ranged from 450 to 500 nm, which were sensitive to molecular structure of the divinyl or dially silane compounds.