Viscoelastic behavior of the dilute solution of ultrahigh molecular weight
syndiotactic poly(vinyl alcohol) (UHMW s-PVA)/dimethyl sulfoxide (DMSO)/wat
er was investigated through rheological response. Below a critical temperat
ure, the dynamic storage modulus (G ') of the solution became greater than
the dynamic loss modulus (G ") and the viscoelastic exponent for G ' became
smaller than that for G " before macroscopic gelation, which indicates the
evolution of viscoelastic solid properties at the Sol state. Also, the los
s tangent (tan delta) of the solution below the critical temperature increa
sed with increasing frequency. Consequently, the dilute solution of UHMW s-
PVA/DMSO/water showed the rheological behaviors as can be observed in gener
al chemical or physical gel systems below the critical temperature. These r
esults suggest that solidlike heterogeneity prevailed in the solution befor
e macroscopic gelation with decreasing temperature. Such heterogeneity was
considered as phase-separated domains attributed to spinodal decomposition.
(C) 2001 John Wiley & Sons, Inc.