The lower critical solution temperature (LCST) behavior of novel poly(ethylene glycol) (PEG)-based copolymers bearing multiple functional groups, obtained by anionic ring-opening (co)polymerization (AROP), has been investigated. Variable comonomer ratios of ethylene oxide (EO) and the corresponding oxiranes isopropylidene glyceryl glycidyl ether (IGG), ethoxyl vinyl glycidyl ether (EVGE), allyl glycidyl ether (AGE), or N,N-dibenzyl amino glycidyl (DBAG), particularly designed to implement functional groups at the PEG backbone, were found to influence the LCST behavior. Sharp transitions from translucent to opaque solutions, comparable to other well-established stimuli-responsive polymers, were observed at temperatures ranging from 9 to 82 degrees C. The influence of the side group hydrophobicity could be quantified by the comparison of the different copolymer systems observed.