Preparation of Silicophosphate Alternating Hybrid Copolymers via Nonaqueous Acid-Base Reactions of Phosphoric Acid and Organo-Bridged Bis(chlorosilane)

A design of atomic and oligomer level structure in organic-inorganic hybrid materials is highly important for various applications. Nonaqueous acid-base reaction allows us to prepare silicophosphates with controlled inorganic networks (-(O-P-O-Si)_n) at atomic level because phosphorous and silicon-based precursors can react directly, resulting in an alternating copolymer network. Organic functionalization in those materials has been realized so far by using organic-modified phosphorous acid and/or organo-chlorosilane as precursors. In the present study, silicophosphate oligomers exhibiting inorganic-organic hybrid chains of (-(O-P-O-Si-R-Si)_n) (R: bridging organic functional groups), are prepared from phosphoric acid and organo-bridged bis(chlorosilane). The 1, 2-bis(chlorodimethylsilyl)ethane ((C₂H₄)(Me₂SiCl)₂) and 1, 4-bis(chlorodimethylsilyl)benzene ((C₆H₄)(Me₂SiCl)₂) were used as organo-bridged bis(chlorosilane). Different types of silicophosphate oligomers with different network structures and terminal groups (P-OH and/or Si-Cl) were prepared by changing the reaction temperature and molar ratio of precursors. The formation of low molecular weight oligomers of ring and cage morphologies (ring tetramer, cage pentamer, and ring hexamer) is suggested in the product prepared from phosphoric acid and (C₆H₄)(Me₂SiCl)₂ molecule at 150 °C. Those silicophosphate hybrid oligomers are expected to be used as building blocks of hybrid materials with well-defined network structures for desired functionalities.