Dynamic viscoelasticity of a,o)-dimethyl silyl poly(propylene oxide) solutions was studied through the gelation process with end-linking. The gel point was determined as the reaction time, t = to, at which the storage and the loss shear moduli, G'(co) and G"(~o), respectively, both became proportional to ~o" over the whole co range measured, where ro is the angular frequency and n is a constant. Effects of polymer molecular weight M and concentration c on the steady-state viscosity r/ before the gel point and the equilibrium modulus Geq after the gel point were examined in terms of critical exponents, k and z, defined by power laws, ~/~(It- tcl/tc) -k ~e -k and G~q ~e =, respectively (~ being the relative distance from the gel point). The three exponents n, k and z were found to take universal values of n = 0.66 4- 0.02, k = 1.0 4- 0.1 and Z = 2.0 4- 0.1 irrespective of M and c for unentangled systems. In these systems, the reduced plot of G~q(~)/G~o versus gave a single composite curve in the range of 0.1 < ~ < 0.7, where G~o was the modulus for the ideal network in which all functional groups reacted. The presence of entanglement coupling in the prepolymer solutions made the critical behaviour of t/and Geq obscure and affected the exponent values. The results were briefly compared with theoretical predictions
Посилання на статтю:
Dynamic viscoelasticity of end-linking =,ta-dimethyl silyl poly(propylene oxide) solutions near the gel point / Akihiro Koike, Norio Nemoto*, Masaoki Takahashit and Kunihiro Osaki // Polymer. – 1994. – Vol 35. – P. 3005-3010.
