The synthesis of a multi(alpha-methyl styrene) oligomer containing a polybutadienic chain was achieved from the condensation of hydroxytelechelic polybutadiene (HTPB) with meta isopropenyl-alpha,alpha'-methyl benzyl isocyanate (TMI). Then, formulations from modified HTPB with various acrylic reactive diluents containing lauryl acrylate and hexane-1,6-diol diacrylate (HDDA) were investigated and compared with classical polyurethanes. Various physical properties (viscosity, shore hardness and gel time) and thermal properties (glass transition and degradation temperatures) were studied and discussed.