The relationships between the properties and structure are discussed for po
ly(vinyl alcohol)(PVA)/silica composites prepared through the sol-gel proce
ss. The composites became stiff and brittle with increasing the silica cont
ent. The properties of the composites were changed drastically at around th
e composition of PVA/silica = 70/30 wt %. For example, there was no large c
hange in the Young's modulus above 30 wt % Of silica content (Pure PVA: 31.
8 MPa, silica 30%: 52.6 MPa, silica 50%: 55.2 MPa). Consequently, it was co
nsidered that the three-dimensional network structure of silica could be fo
rmed in the composite with more than 30 wt % of silica in PVA. From this be
havior, it could be considered that the crystal growth of PVA was remarkabl
y inhibited by silica network. (C) 1999 John Wiley & Sons, Inc.