We investigated the acoustic and thermal features of a polymeric system by a heterodyne detected transient grating technique. We studied two polymers characterized by different molecular weights. Transient grating experiments could reveal a reliable series of information on sound velocity, acoustic damping time, and thermal diffusion of the polymers. The temperature and molecular weight dependence of the polymer acoustic and thermal properties are reported. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 685-690, 2011