Structural properties and swelling behavior of randomly crosslinked polymer networks: A monte carlo study

The structural properties as well as some aspects of the swelling behavior of randomly crosslinked polymer networks obtained by lattice Monte Carlo simulations are investigated.

For a crosslink density of about 10 crosslink points per precursor chain, unusual structural properties are observable on scales well beyond the mesh size. For scales of order of the averaged mesh size an inner dimension of d_i ≅ 1.15 and for scales up to the lattice size d_i ⋍ 2.2 can be obtained. For the autocorrelation function of a random walker placed on the network topology, these properties can be reproduced.

In the case of athermal swelling of the network structure inhomogeneous deformation of the individual network chains can be observed. Additionally the average network chain deformation is considerably less than the macroscopic swelling ratio.

The swelling pressure of the network shows a scaling behavior different from the corresponding uncrosslinked system. This can be related to the fractal properties of the network within the correlation length by applying the well known scaling theory for the osmotic pressure for semidiluted polymers to fractal objects. This explains the swelling anomalies for polymer network even in the case of athermal swelling.