A positive-working imageable element comprises inner and outer layers and a radiation absorbing compound such as an IR absorbing dye. The inner layer includes a first polymeric material. The ink receptive outer layer includes a second polymeric binder comprising a polymer backbone and an --X--C(.dbd.T)--NR--S(.dbd.O).sub.2-- moiety that is attached to the polymer backbone, wherein --X-- is an oxy or --NR'-- group, T is O or S, R and R' are independently hydrogen, halo, or an alkyl group having 1 to 6 carbon atoms. After thermal imaging, the element can be developed using an alkaline developer. Use of the particular second polymeric binder reduces sludging in the developer. Its dissolution rate in the developer is slow enough to resist developer attack in the non-imaged areas of the outer layer but rapid enough for the second polymeric binder to be quickly loosened from imaged areas and kept suspended or dissolved for a considerable time.