Dielectric study of miscibility in poly(methylacrylate)-poly(methyl methacrylate) sequential interpenetrating polymer networks

摘要

Polymer miscibility is determined by the composition dependence of the free energy of the blend due to thermodynamic equilibrium and stability criteria. The same criteria apply in the case of polymer networks but here, in addition, the constraintimposed by cross-links play an important role. A sequential IPN is formed by swelling a polymer network of component A in the monomer of component B and then polymerising the second network. If polymers A and B are immiscible and the cross-linking density of A is small, i.e., the number of monomeric units between cross-links is high, then during the polymerisation of network B, the growing B chains push apart the already existing A chains, and finally a phase separated IPN is obtained. But if thecross-linking density of A is high the positions of the A chains can hardly be changed and the B network grows actually interpenetrating the existing network A. Thus a homogeneous IPN can eventually be obtained, achieving a forced compatibilization ofboth polymers.In this work the miscibility of PMA/PMMA IPNs is studied as a function of the cross-linking density using dielectric and dynamic-mechanical techniques.