Epoxy-Silica Mesocomposites with Enhanced Tensile Properties and Oxygen Permeability
详细信息 查看全文
- 作者：In Park ; Hua-gen Peng ; David W. Gidley ; Siqi Xue ; and Thomas J. Pinnavaia
- 刊名：Chemistry of Materials
- 出版年：2006
- 出版时间：February 7, 2006
- 年：2006
- 卷：18
- 期：3
- 页码：650 - 656
- 全文大小：260K
- 年卷期：v.18,no.3(February 7, 2006)
- ISSN：1520-5002
文摘
As-made and calcined forms of large-pore (5.3 nm) mesostructured silica with a wormhole frameworkstructure, denoted MSU-J, have been used to form rubbery epoxy mesocomposites containing 1.0-12%(w/w) silica. The tensile modulus, strength, toughness, and extension-at-break for the mesocompositesformed from as-made and calcined forms of MSU-J silica are systematically reinforced by up to 4.8, 5.7,1.6, and 8.5 times, respectively, in comparison to the pure epoxy polymer. The composites represent thefirst examples wherein the reinforcement benefits provided by mesostructured silica particles arecomparable to those provided by exfoliated organoclay nanolayers at equivalent loadings. Moreover, thereinforcement benefits are realized without the need for organic modification of the silica surface, andthe increases in tensile properties occur with little or no sacrifice in optical transparency or thermalstability. The oxygen permeability of the mesocomposites prepared from as-made MSU-J silica increasesdramatically at loadings 
f">5.0% (w/w), whereas the compositions made from the calcined form of themesostructure show no permeation dependence on silica loading. For instance, the oxygen permeabilityof the mesocomposites containing 12% (w/w) as-made MSU-J silica is 6-fold higher than that of thesilica-free epoxy membrane. Positron annihilation lifetime spectroscopy established the absence of freevolume in the mesocomposites, thus precluding the possibility of facile oxygen diffusion through theframework pores of the silica. The increase in oxygen permeability is correlated with the partitioning ofcuring agent between the as-made mesostructure and the liquid prepolymer, which leads to coronas ofpermeable polymer with reduced chain cross-linking in the vicinity of the silica particles. Mesocompositesmade from calcined forms of the mesostructured silica do not allow for curing agent partitioning, andthe oxygen permeability is not significantly influenced by the silica loading.
f">5.0% (w/w), whereas the compositions made from the calcined form of themesostructure show no permeation dependence on silica loading. For instance, the oxygen permeabilityof the mesocomposites containing 12% (w/w) as-made MSU-J silica is 6-fold higher than that of thesilica-free epoxy membrane. Positron annihilation lifetime spectroscopy established the absence of freevolume in the mesocomposites, thus precluding the possibility of facile oxygen diffusion through theframework pores of the silica. The increase in oxygen permeability is correlated with the partitioning ofcuring agent between the as-made mesostructure and the liquid prepolymer, which leads to coronas ofpermeable polymer with reduced chain cross-linking in the vicinity of the silica particles. Mesocompositesmade from calcined forms of the mesostructured silica do not allow for curing agent partitioning, andthe oxygen permeability is not significantly influenced by the silica loading.