An imaging member, such as a negative-working printing plate, can be prepared using a hydrophilic imaging layer comprised of a heat-sensitive hydrophilic polymer having a positively charged moiety, and optionally a photothermal conversion material. The heat-sensitive polymer has recurring units containing an N-alkylated aromatic heterocyclic group or an organoonium group that reacts to provide increased oleophilicity in areas exposed to energy that provides or generates heat. For example, heat can be supplied by laser irradiation in the IR region of the electromagnetic spectrum. Thus, the heat-sensitive polymer is considered "switchable" in response to heat, and provides an imaging means without wet processing.