Mean field theory for a reversibly crosslinked polymer network

Abstract

We present a mean field theory for melts and solutions of reversibly crosslinked polymers. In our model, crosslinks are considered as local bonds between two monomers. For a blend of ABAB polymers, we assume reversible crosslinks between the copolymers AB with a crosslink strength z and interaction weights ω A and ω B for monomers of type A and B, respectively. The usual mean field model for polymer blends without reversible crosslinks is recovered if z vanishes. With or without crosslinks, the A+B+AB blend can form a lamellar phase with A and B rich regions. If reversible crosslinks are enabled and ω A differs strongly from ω B, the lamellar nanophase separation of A and B monomers is accompanied by a similar segregation of crosslinked and noncrosslinked polymers. If ω A and ω B are equal, crosslinked copolymers are well mixed with the homopolymers. For a homopolymer solution with reversible crosslinks between the polymers, our calculations show that polymers and solvent molecules are separated macroscopically if the Flory-Huggins interaction parameter and the crosslink strength are suitably high or if the volume fraction of polymers or the chain length are suitably low. © 2012 American Institute of Physics.