Polymer networks swollen by a homopolymer solution

F. Brochard

We study the conformation of a polymer network (N monomers between crosslinks, volume fraction ϕN) in contact with a solution of the same polymer (P monomers per mobile chain, volume fraction ϕ extP). As a function of P/N and ϕ extP,we find three regimes : — Swollen unmixed (SUM) : the free chains do not penetrate. The internal concentration ϕ inP is exponentially small in the region occupied by the gel. The distance between crosslinks varies as N 3/5 — Swollen mixed (SM) : the mobile chains penetrate the region occupied by the gel but the gel is still swollen (R ~ N3/5/P1/5). — Ideal mixed (IM) : here again, the mobile chains penetrate the gel. The excluded volume interactions between monomers of the gel are strongly screened out. The gel is expected to reach a final state similar to what would be found in a θ solvent. In all the mixed cases, when starting from a swollen gel in contact with a polymer solution, the final state is reached only at very long times : it could be observed however on small gel particles immersed in the solvent mixture or with one labelled chain (N monomers) in a solution of P chains. All these results cease to be valid if the gel is even slightly chemically different from the mobile chains. In that case, the mobile chains are expelled out and the gel deswells as the concentration of the external polymer solution increases.

Mots clés: polymer solutions

Domaines: Articles anciens

F. Brochard. Polymer networks swollen by a homopolymer solution. Journal de Physique, 1981, 42 (3), pp.505-511. ⟨10.1051/jphys:01981004203050500⟩. ⟨jpa-00209036⟩