A thermally imagable article comprises a substrate on which is coated a positive working heat-sensitive composition comprising a hydroxyl group-containing polymer and a heat-labile moiety which decreases the developer solubility of the composition as compared to the developer solubility of the composition without the heat-labile moiety, wherein the heat-sensitive composition does not comprise an acid generating moiety. The invention also provides novel positive working compositions comprising heat-labile moieties, and imagable articles comprising said compositions.