Study of three-dimensional polystyrene networks containing linear chains: 1. Influence of free chains on the volume fraction of crosslinked chains

Abstract

A ternary system, crosslinked polystyrene-linear polystyrene in swelling equilibrium in benzene or cyclohexane, has been prepared by anionic polymerization in dilute solution (7.5%). By swelling ratios and modulus measurements we proposed to show the specific influence of linear polystyrene chains of high molecular weight, maintained inside the network, and to compare this behaviour with the behaviour of an ‘ideal’ polystyrene network. It may be concluded that: (i) the calculated number of elastic chains is independent of the swelling solvent, but the presence of free chains in the polymerization and crosslinking process produces a non-negligible number of free and pendant chains; (ii) for the same number of elastic chains, the two types of networks have the same swelling ratio, but the introduction of free chains into the networks leads to a decrease in the volume fraction of crosslinked chains, and thus to an increase in the swelling rate of the network. However, these values are consistent with the Gaussian theory; (iii) the values of functionality are lower than those found for ‘ideal’ networks; this result confirms the presence of pendant chains; (iv) the Flory-Huggins parameters are the same for the two types of networks.