A new family of organic-inorganic hybrid materials has been prepared by incorporating polystyrene structure units covalently into the SiO2 glass network via the sol-gel approach. The polymer precursors were synthesized by free-radical copolymerization of styrene with 3-(trimethoxysilyl)propyl methacrylate (MSMA) at various feeds. These copolymers were then hydrolyzed and co-condensed with tetraethyl orthosilicate in tetrahydrofuran at room temperature to afford monolithic polystyrene-SiO2 hybrid sol-gel materials having SiO2 contents of 15 to 84% by weight. The hybrid materials derived from the copolymers with MSMA contents greater than 22 mol% have excellent optical transparency. In these transparent hybrid materials, the polymer chains should be uniformly distributed in and covalently bonded to the amorphous SiO2 matrices. The bulk properties of these materials including density, refractive index, and hardness were found to be related to their molecular compositions and can be tailored by varying the polymer contents.

Photochemical synthesis of hybrid sol–gel materials is demonstrated for the first time. Photoacid‐catalyzed sol–gel reactions of tetraethyl orthosilicate with polymer precursors under ultraviolet radiation produce poly‐acrylate‐silica materials (shown schematically in the Figure). The effect of the concentrations of the photoacids and polymer precursors and the intensity of the radiation is discussed.

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IntroductionOne of the great advantages of the sol-gel method is that inorganic ceramics can be prepared at low temperatures, which makes it possible to incorporate organic compounds and polymers into inorganic matrices to form a new class of organicinorganic hybrid materials 2). A particularly interesting process consists of hydrolysis and co-condensation of metal alkoxides with polymers containing reactive functional groups to afford polymer-modified glasses or ceramics (so-called ceramers), in which the polymer chains are covalently bonded to the inorganic components. For examples, polymers, such as poly(dimethylsi1oxane) 3), poly(tetramethy1ene oxide) ' I , polyimide 5 ) , poly(ary1ene ether ketone) and poly(ary1ene ether sulfone) @, polymethacrylates 7-10), polystyrene 11), polyoxazolines 12), etc., have been successfully incorporated into SiO, and/or TiO, networks via the sol-gel approach. These hybrid materials show many unique physical properties.Polyacrylonitrile (PAN) is an important commercial polymer not only as a useful material itself but also as a most commonly used precursor for production of carbon fibers 13). In this communication, we present the first synthesis of polyacrylonitrilesilica hybrid sol-gel glasses, in which the polyacrylonitrile chains are uniformly distributed in and covalently bonded to the inorganic SiO, matrix. The polyacrylonitrile component employed was modified to contain trialkoxysilyl functional groups, which can be hydrolyzed and co-condensed with the metal alkoxides, e. g. tetraethyl orthosilicate, to form the hybrid sol-gel materials. We also report our preliminary results on pyrolysis of these hybrid materials to convert polyacrylonitrile into carbon fibers in the glass matrices. Experimental partMaterials and instrumentation: Acrylonitrile (AN) and 3-(trimethoxysily1)propyl methacrylate (MSMA) were purified by distillation under reduced pressure in a nitrogen atmosphere. Benzoyl peroxide (BPO) was purified by recrystallization from methyl alcohol. Benzene (HPLC (high pressure liquid chromatography) grade) was dried over 4 A molecular sieves. Tetraethyl orthosilicate (TEOS) and tetrahydrofuran (THF, HPLC grade) were used as received. All the chemicals were purchased from Aldrich. The 'H NMR spectra were recorded on a Bruker WM-250 FTNMR spectrometer. The infrared spectra were collected on a Perkin-Elmer Model 1600 FTIR spectrometer. Molecular weights were measured on a Waters gel-permeation chromatograph (GPC) Model IIA using THF eluant and polystyrene calibration. Thermogravimetry (TG) was performed on a DuPont 9900 TA System equipped with TGA Module 951 under air or nitrogen flow in a temperature range of = 30 to 800 "C at a heating rate of 20 "C/min. The samples

ABSTRACT:The first synthesis of poly (styrene-co-styrylethyltrimethoxysilane) [P(ST-STMS)] -silica hybrid materials has been achieved via the acid-catalyzed sol-gel reactions of P(ST-STMS) with tetraethyl orthosilicate. New sulfonated polystyrene-silica hybrid materials have been prepared by sulfonation of P(ST-STMS) -silica and poly [-styrene-co-3-(trimethoxysilyl)propyl methacrylate] -silica hybrids with concentrated or fuming sulfuric acid. The sulfonated materials exhibit cation exchange capacities ranging from 0.33 to 1.27 meq/g depending on the composition of the hybrid materials and on the sulfonation conditions.