Viscoelastic Properties of Poly(vinyl chloride) Gels: Universality of Gel Elasticity

The equilibrium modulus G e of the poly(vinyl chloride) (PVC)/bis(2-ethylhexyl) phthalate (DOP) gels was examined at temperatures T ≥ 40 °C. Near the sol−gel transition temperature, G e decreased rapidly with increasing T . The normalized moduli G e M / cRT of the gels at different M, T, and/or c were universally dependent on the relative distance from the gelation point, ε, with c and M being the PVC concentration and molecular weight, respectively, and R being the gas constant. This result suggested that the mesh size of the gel network near the gelation point was universally determined by ε and M . The normalized moduli were smaller than unity, i.e., G e < cRT / M at low ε . This result suggested that the average mesh size near the gelation point was larger than the PVC chain size. Thus, several PVC chains appeared to be connected at cross-linking crystal domains to form a larger, effective mesh strand.