Polymer matrix composite comprising a porous polymeric network; and a plurality of intumescent particles distributed within the polymeric network structure; wherein the intumescent particles are present in a range from 15 to 99 weight percent, based on the total weight of the intumescent particles and the polymer (excluding the solvent); and wherein the polymer matrix composite volumetrically expands at least 2 times its initial volume when exposed to at least one temperature greater than 135° C.; and methods for making the same. The polymer matrix composites are useful, for example, as fillers, thermally initiated fuses, and fire stop devices.