ملخص: We consider a polymer network G with fixed topology made of long polymer chains of common polymerization degree N. The network is assumed to be dissolved in a melt of short linear polymer chains of polymerization degree P P be any physical property (partition function, gyration radius, ...) associated with the network. The purpose is to investigate quantitatively the behavior of [Phi]p in the long-chain limit (N --> [infinity], at fixed P). Assume that the same physical quantity behaves for a low-molecular weight solvent (P=1) as: [Phi]1 NX+[sigma], where x is the critical exponent when G is ideal, and the additional one, [sigma], which is universal but it depends on the topology of G, characterizes the swelling of N-chains. We show that the asymptotic behavior of [Phi]P for a high-molecular weight solvent reads: [Phi]P ~ P-2[sigma]/(4-d)NX+[sigma], provided that N > P2/(4-d) (d =2, 3 is the space dimensionality and 4 is the critical dimension of the system). However, at dimension 3, when N 2, the network becomes ideal. Thus, a crossover between ideal and real networks occurs along the curve of equation N ~ P2 in the (P, N)-space. In dimension 2, we find that the network is always swollen by mobile chains, as long as N > P, which is the condition defining the system in the beginning. The main conclusion is that, in the presence of a high-molecular weight solvent, the asymptotic behavior is renormalized multiplicatively by a P[zeta]-factor, whose exponent [zeta] is related to the swelling exponent [sigma] relative to a solvent of small molecules through: [zeta] = -2[sigma]/(4-d). Finally, this unified description can be extended to polymer networks near interacting surfaces.

لغة: إنجليزية