Poly(ethylene oxide)-poly(2-methoxyethyl acrylate) diblock copolymers (PEO-b-PMEA) are synthesized by RAFT aqueous dispersion polymerization of MEA using poly(ethylene oxide) macromolecular chain transfer agent as a reactive steric stabilizer. Both segments are well-known to be bio-and blood-compatible polymers. This formulation enables the production of various particle morphologies such as spheres, worms, and vesicles from the same block copolymer in water. The synthesis starts when both the reactive steric stabilizer and MEA monomer are dissolved in water; however, the growing polymer is not water-soluble and begins to form nano-objects. In the case of the synthesis of PEO 113-b-MEA 300 diblock copolymers, the nano-objects change from spheres into larger aggregates of worms when the solids concentration in the polymerization increases from 5 to 15 wt% at full monomer conversion. The morphology finally turns into vesicles as the solids concentration increases to 20 wt%. The final block copolymer morphology at full monomer conversion is dictated by not only degree of polymerization of MEA but also the solids concentration in the polymerization mixture.

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Different types of novel xanthates containing a vinyl ether moiety, S-benzyl O-2-(vinyloxy)ethyl carbonodithioate (Xanthate 1) and S-1-(ethoxycarbonyl)ethyl O-2-(vinyloxy)ethyl carbonodithioate (Xanthate 2) were synthesized. In particular, the Xanthate 2 enabled to design polyvinyl alcohol (PVA) stereoblock copolymer via the combination of living cationic vinyl polymerization and RAFT/MADIX polymerization. For cationic polymerization of isobutyl vinyl ether (IBVE) and tert-butyl vinyl ether (TBVE), the polymerizations were conducted under Xanthate 1-HCl adduct/SnCl 4 and Xanthate 1 or 2-CF 3 COOH adduct/EtAlCl 2 initiating system in the presence of ethyl acetate. Both systems proceeded in living polymerization fashion because the calculated M n of both poly(IBVE) and poly(TBVE) matches with the M n polymerized assuming that one polymer chain is formed per one molecule of the Xanthate 1 or 2. The resulting poly(TBVE) had a high number average α-end functionality as determined by MALDI-TOF-MS spectrometry. Xanthate 2 is more efficient for the following RAFT/MADIX polymerization of vinyl acetate (VAc). The RAFT/MADIX polymerization of vinyl acetate (VAc) using azobis(isobutyronitrile) (AIBN) at 60 °C was conducted using either poly(IBVE) or poly(TBVE) macro-CTA. The poly(TBVE) macro-CTAs synthesized from the Xanthate 2 were able to polymerize VAc smoothly via RAFT/MADIX polymerization, to prepare well-defined diblock copolymer, poly(TBVE)-b-poly(VAc). The resulting block copolymer was then hydrolyzed using KOH in methanol and followed by acid hydrolysis using HBr gas bubbling. The resulting polymer is inherently stereoblock like copolymer, isotactic rich PVA-b-atactic PVA (iPVA-b-aPVA). From the DSC measurement, the iPVA-b-aPVA has one glass transition at 69.5 °C and two melting points according to iPVA and aPVA at 237.9 and 3 198.1 °C, respectively. Thus, it can be suggested that the obtained PVA has two different geometries by the combination of living cationic polymerization and RAFT/MADIX polymerization.