We used initiation solutions of DBU and different thiols for the controlled ring-opening homo- and copolymerization of ethoxy ethyl thio glycidyl ether (EETGE) and allyl thio glycidyl ether (ATGE) to side-chain multifunctional polysulfides. Optimized preparation conditions allow the syntheses of monomodal homopolysulfides and monomodal polysulfide-block-mPEG copolymers. Furthermore, copolymers of EETGE and mPEG are firstly synthesized, characterized, and finally deprotected to yield intact poly(thio glycidol)-block-poly(ethylene glycol) copolymers. These amphiphiles are suitable to form particles in aqueous solutions as confirmed by DLS and cryo-SEM measurements.