Glass Transition Parameters of Polyisoprene Rubbers: Differential Scanning Calorimetry Study

Natural rubber and synthetic polyisoprene rubbers synthesized using titanium-, neodymium-, and gadolinium-containing catalytic systems are studied by DSC, NMR spectroscopy (700 MHz), and GPC. According to DSC thermograms, glass transition parameters, such as the temperature and width of transition and heat capacity jump, are determined. The dependence of the transition temperature on the configurational and isomeric composition of polyisoprenes with a high content of cis-units is examined. It is demonstrated that, when considering the dependence on isomeric composition, natural rubber cannot be used as a quantitative standard corresponding to the reference position of “all (100%) cis-polyisoprene” with the lowest transition temperature.