Danliang Jin

A fast convenient method to prepare hybrid sol-gel materials with low volume-shrinkages

We present a simple and fast method for the synthesis of polyacrylates-silica hybrid materials with significantly low volume shrinkages through the sol-gel reactions of tetraethyl orthosilicate and 2-hydroxyethyl methacrylate along with the free-radical polymerization of the acrylate monomer. The volume shrinkage from the processible sol to the final product was about 6–20% for the hybrid materials having the silica contents up to about 50 wt-%. As a result of the low shrinkage, crack-free, transparent and monolithic hybrid materials of relatively large sizes can be prepared within a short period of 6 to 12 hours. The formation of covalent bonding between the organic and the silica components in the hybrid materials was demonstrated. Thermal stability of the polyacrylate component in the hybrid materials were found to be higher than that of the bulk polymer. Other vinyl polymers such as poly(methyl methacrylate) and polyacrylonitrile have also been incorporated into the inorganic silica sol-gel matrix by using this method.

Novel organic–inorganic chemical hybrid fillers for dental composite materials

A series of new polymethacrylate–silica chemical hybrid dental fillers has been prepared by the sol–gel reactions of poly[methyl methacrylate-co-3-(trimethoxysilyl) propyl methacrylate] or poly[3-(trimethoxysilyl)propyl methacrylate] with tetraethyl orthosilicate at various compositions. In these hybrid fillers, the polymethacrylate chains are uniformly distributed in and covalently bonded to the silica networks at molecular level without macroscopic organic–inorganic phase separation. The contact angle and surface tension parameters indicate that the hybrid fillers have better wetting properties with the 2,2-bis(p-2-hydroxy-3-methacryloxypropoxyphenyl)propane/triethyleneglycol dimethacrylate resin and stronger interfacial bonding with the polymer matrix than pure silica fillers. The compressive testing results demonstrate that the dental composites prepared with the hybrid fillers tend to have enhanced mechanical properties in comparison to those with the silane-treated fused silica and the pure sol-gel silica fillers at the same silica content. Scanning electron micrographic study reveals that upon compressive tests the dental composites with the hybrid fillers have fewer failures at the filler–matrix interface than those with pure silica fillers.

Synthesis of mesoporous aluminum oxide with aluminum alkoxide and tartaric acid

Mesoporous aluminum oxide with high specific surface area is synthesized using aluminum alkoxide and tartaric acid. It was found that the average pore size increases with increasing amount of tartaric acid. Moreover, the mesoporous structure is thermally stable up to 1273 K, indicating potential application as catalyst supports.

Organic-inorganic hybrid materials: relations of thermal and mechanical properties with structures

Abstract Two series of polymethacrylate-silica covalent hybrid materials, i.e., poly[methyl methacrylate-co-3-(trimethoxysilyl)propyl methacrylate]-silica (PMCM-SiO 2 ) and poly(2-hydroxyethyl methacrylate)-silica (PHEMA-SiO 2 ), have been synthesized via two different sol-gel routes. The materials are highly transparent to visible light. Rapid formation of covalent bonds between the polymer and silica components during the sol-gel reactions prevents thermodynamically induced organic-inorganic phase separation. The presence of organic components does not alter the condensations of silanol groups. When extracted with an organic solvent, compositions of the hybrid materials remained largely unchanged. Bulk density and hardness of the materials can be controlled between those of the pure silica and polymers by varying the compositions. The hardness is not significantly affected by the molecular weight of PMCM polymers. The glass transition of the polymer components in all the hybrid materials is much less pronounced than that of pure polymer, as indicated by lower Tan δ peak values and smaller changes in storage modulus. As the silica content is increased, the T g increases for the PHEMA-SiO 2 hybrids while it remains essentially the same for the PMCM-SiO 2 materials. As the silica content is increased, both the storage modulus and thermal stability of the hybrids are improved.

Synthesis of sulfonated polystyrene-silica hybrids and their application as ion exchange materials

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.