Temperature- and pH-sensitive polymers and block copolymers have been synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. Thiocarbonylthio compounds used as chain transfer agents in the polymerization lead to end-functionalized polymers that give the corresponding thiols upon hydrolysis. Both block copolymers with short blocks of oligo(active ester)s and thiol-terminated polymers can be used for polymer-protein conjugation. 2-Vinyl-4,4-dimethyl-5-oxazolone (VO), N-hydroxysuccinimide methacrylate (NHSM), diacetone acrylamide (DAA), N-iso-propylacrylamide (NIPAAm), and acrylic acid (AA) have been polymerized to homo- and block copolymers with narrow MWD in most cases, and their conjugation to model peptides has been investigated. Block copolymers of NIPAAm and AA were investigated for their response to combined external stimuli. Thus, thermo- and pH-responsive systems can be created for control of enzyme activity or molecular recognition processes.