Dynamic mechanical properties of oriented polymer networks

For the isotropic and oriented polymer networks prepared via radiation-indu ced crosslinking of the polymer-oligomer systems based on low-molecular-mas s and high-molecular-mass polystyrene and trioxyethylene dimethacrylate, a comparative study of the dynamic mechanical properties was carried out. In the case of isotropic and oriented networks, as molecular mass of polymer i s increased, one may observe an increase in both storage modulus and temper ature at which storage modulus dramatically decreases. As compared with the isotropic networks, in the case of the oriented networks, the temperature corresponding to the peak of mechanical loss tangent is shifted to lower te mperatures by 7 K, independently of the molecular mass and molecular mass d istribution of polymer. As orientation is increased, the peak of mechanical losses related to glass transition decreases its intensity and narrows dow n. In the case of the compositions based on high-molecular-mass polystyrene with a narrow molecular mass distribution, the results of dynamic mechanic al tests suggest the development of the oriented network with a higher dens ity of intermolecular crosslinking and a low degree of structural heterogen eity.