The Synthesis of Silicon-containing Polyester Directly from SiO2 and Characterization of Its Structure
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The Synthesis of Silicon-containing Polyester Directly from SiO2 and Characterization of Its Structure Jianhua Song, Luyi Sun1, Anhua Liu and Kecheng Gong Polymer Structure & Modification Lab, South China University of Technology, Guangzhou, 510640, P. R. China 1 Department of Chemistry, University of Alabama, Tuscaloosa, AL 35487, U.S.A.
ABSTRACT A new approach to the synthesis of a novel silicon-containing polyester by noncarbothermal method directly from SiO2 was studied. At first, a high reactive pentacoordinate organic silicon compound (KSi(OCH2CH2O)2(OCH2CH2OH)) was prepared by the reaction of the fumed silica with ethylene glycol (EG) and KOH. Then, a novel double hydroxy tetracoordinate silicon monomer (OCH2CH2O)Si(OCH2CH2OH)(OCH2CH2OCH2CH2OH) was synthesized by the reaction of ClCH2CH2OH with reactive pentacoordinate silicon compound. Finally, a silicon-containing polyester was synthesized by low temperature solution condensation between tetracoordinate silicon compound and p-phthaloyl chloride in dimethyl sulfoxide (DMSO). The product was characterized by FTIR, TG, GPC, etc. The IR spectra of polyester exhibited a characteristic strong absorption band for ester carbonyl in the 1722.2cm-1. IR spectra also showed absorption at 1124.6cm-1 due to the O-Si-O group. TG analysis showed its good thermal stability. GPC analysis showed that the number average molecular weight of this siliconcontaining polyester was about ninety thousand. INTRODUCTION The formation and structure of hypervalent silicon compounds continues to be a hot research topic and has been regularly reviewed. Recently, R.M.Laine [1] and R.J.P.Corriu [2] have done a great deal of work on it respectively. It was reported that a novel hypervalent silicon species could be obtained directly from silica. What is worth noting is that aliphatic 1, 2-diols can react with SiO2 to form pentacoordinate silicon compounds when the reaction was performed with MOH (M=Li, Na, K, or Cs) and hexacoordinate silicon compound when the reaction was performed with BaO, respectively. Catechol was also an effective agent for the preparation of the hexacoordinate silicon compound directly from silica. But almost all the pentacoordinate silicon compounds were unstable and moisture sensitive, which also indicates their high reactivities. How to use their high reactivities to make the pentacoordinate silicon compounds to form the useful polymers was a key point of this work. Through the reaction of functional halogencontaining compounds with reactive pentacoordinate silicon compound, our lab has prepared varies of novel tetracoordinate silicon compounds [3]. Double hydroxyl tetracoordinate silicon KK8.16.1
monomer was one of the most attractive products. Through further solution condensation reaction of the tetracoordinate silicon monomer with bifunctional acyl chloride or diisocyanate, a novel silicon-containing polyester has been prepared. EXPERIMENTAL DETAILS Pentacoordinate silicon compound (the method similar as reference [1]) 7.5g SiO2, 7g KOH and 135ml EG were intro
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