Microscopic mechanism of distinct mechanical properties of divinylbenzene reinforced cross-linked polystyrene revealed by molecular dynamics simulations

Molecular dynamics method was employed to establish the model of three-dimensional cross-linked polystyrene (PS) formed by divinylbenzene (DVB) and PS chains. Density, radial distribution function, free volume fraction, mean square displacement of systems with different cross-linking degrees (DVB contents of 0%, 3.8%, 7.1% and 11.1%) were studied, as well as macroscopic properties such as glass transition temperature, elastic mechanical properties, uniaxial tensile deformation. The results showed that cross-linking algorithm proposed was feasible for constructing cross-linked PS. With the increase of cross-linking degree, cross-linked PS became denser, and glass transition temperature increased, indicating an increase of heat resistance. Compared with uncross-linked PS, elastic modulus of three cross-linked systems increased by 19.26%, 29.56% and 40.19%; bulk modulus increased by 2.9%, 20.98% and 44.03%; and shear modulus increased by 21.05%, 29.82% and 42.98%. Tensile stress-strain curves showed that network structure formed by adding DVB improved yield stress and tensile resistance of PS.