Molecular simulation of networks formed by end-linking of tetra-arm star polymers: Effects of network structures on mechanical properties

The structures and the mechanical properties of networks formed by end-linking of two types of tetra-arm star polymers are studied by a coarse-grained molecular dynamics simulation. The formation efficiency of elastically effective chains is improved by increasing the length of the arms and the volume fraction of the star polymers at the preparation stage. When the uniaxial elongation is applied to the networks in the as-prepared state, the shear modulus is proportional to the number density of the elastically effective chains and indicates an intermediate value between the phantom and affine network models. In the equilibrium swollen state, the shear moduli of the networks prepared at high volume fractions are significantly enhanced by trapped entanglements. The networks formed from the tetra-arm star polymers show higher number densities of the elastically effective chains than networks consisting of telechelic functional polymers and cross-linkers.