Abstract :
This paper studies sol/gel transition of associating polymers with multiple cross-link junctions. Paying special attention to the multiplicity and sequence length of the network junctions, we derive phase diagrams and analyze molecular structure of the networks. The conventional Eldridge–Ferry method is extended to evaluate multiplicity, as well as enthalpy, of the cross links, and applied to the experimental gel melting curves of poly(vinyl alcohol) in water. The effect of added surfactants on the formation of reversible gels in hydrophobically modified polymer solutions is also studied under the assumption of the existence of a minimum multiplicity required for stable cross-links. On the basis of the transient network model with temporal junctions, we calculate dynamic mechanical moduli, average lifetime of a junction, the number of elastically effective chains and of dangling ends as functions of the strength of the association constant, polymer concentration and the temperature. We compare the results with the experimentally measured moduli of hydrophobically modified poly(ethylene oxide).
