Preparation and properties of poly(vinyl acetate)/silica‐gel microhybrids

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Abstract
Poly(vinyl acetate) (PVAc) was incorporated into silica gel using the sol–gel process involving tetraethoxysilane (TEOS). In order to prepare silica‐gel microhybrids, two different processes were employed, and the physical properties of the resulting two sets of hybrids were compared. In the first method, PVAc was first mixed with TEOS in an acetone solution and then cured using HCI and H2O. In the second method, an acetone solution of a copolymer composed of vinyl acetate (VAc) and vinyl triethoxysilane (VTES) was first mixed with TEOS and then cured. This copolymer contained 10 mol % of VTES component and was bound covalently to silica‐gel molecules. When comparing the properties of the hybrids, the dynamic modulus, E′, increased with increasing amounts of TEOS over a wide temperature range: −20–120°C. E′ of a hybrid from PVAc was lower than that of a hybrid from the VAc/VTES copolymer. A sharp peak in the loss modulus, E″, of a PVAc hybrid occurred at 40°C, and its position did not change with TEOS content. In contrast, the E″, peak of a copolymer hybrid was broad and its position also shifted to a higher temperature as the TEOS content increased. The tensile strength of a PVAc hybrid increased as the amount of mixed TEOS increased, reaching a maximum of 30 MPa at 50 wt % of TEOS. However, the strength of a copolymer hybrid reached a maximum of 50 MPa at 50 wt % of TEOS. The differences in the physical properties between a PVAc hybrid and a copolymer hybrid arise from the difference in their structure. Organic polymer molecules in a copolymer hybrid combine covalently with silica‐gel molecules through the VTES component, while a PVAc hybrid has no bounding between PVAc and silica‐gel molecules. © 1994 John Wiley & Sons, Inc.