Investigation of Mechanical Properties and Swelling of Scale-Free Polymer Networks

We studied experimentally and theoretically how the network topology influences the mechanical properties and swelling of polymer networks. The properties of monofunctional and polyfunctional networks were compared. The cross-link functionality distribution of the polyfunctional networks is a power function. Such networks are also called scale-free networks. The ultimate tensile strength and ultimate tensile strain of a polyfunctional network appeared to be 1.4 and ~2 times as high as the respective parameters for a monofunctional network. For assessing the long-term strength of polymer networks, we used cyclic straining. The number of cycles from the onset of an experiment to the breakdown of the test sample for a scale-free polymer network was 56 to 60 times the number of cycles for a monofunctional network. We used the lattice-type model of solutions and derived an equation relating the chemical potential of the solvent or plasticizer in a swollen scale-free polymer network to the network parameters and the volume fraction of the polymer. The experimental results verified the validity of our theoretical analysis.