Polymer matrix composite comprising a porous polymeric network; and a plurality of thermally conductive particles distributed within the polymeric network structure; wherein the thermally conductive particles are present in a range from 15 to 99 weight percent, based on the total weight of the thermally conductive particles and the polymer (excluding the solvent); and wherein the polymer matrix composite has a density of at least 0.3 g/cm3; and methods for making the same. The polymer matrix composites are useful, for example, in electronic devices.