No abstract

The living free radical polymerizations of three “less activated” monomers (LAMs), vinyl acetate, N‐vinylcarbazole, and N‐vinylpyrrolidone, were successfully achieved in the presence of a disulfide, isopropylxanthic disulfide (DIP), using 2,2′‐azoisobutyronitrile (AIBN) as the initiator. The living behaviors of polymerizations of LAMs are evidenced by first‐order kinetic plots and linear increase of molecular weights (Mns) of the polymers with monomer conversions, while keeping the relatively low molecular weight distributions, respectively. The effects of reaction temperatures and molar ratios of components on the polymerization were also investigated in detail. The polymerization proceeded with macromolecular design via interchange of xanthate process, where xanthate formed in situ from reaction of AIBN and DIP. The architectures of the polymers obtained were characterized by GPC, 1H NMR, UV–vis, and MALDI‐TOF‐MS spectra, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010

Three tetrafunctional bromoxanthate agents (Xanthate3‐Br, Xanthate2‐Br2, and Xanthate‐Br3) were synthesized. Initiative atom transfer radical polymerizations (ATRP) of styrene (St) or reversible addition fragmentation chain transfer (RAFT) polymerizations of vinyl acetate (VAc) proceeded in a controlled manner in the presence of Xanthate3‐Br, Xanthate2‐Br2, or Xanthate‐Br3, respectively. The miktoarm star‐block copolymers containing polystyrene (PS) and poly(vinyl acetate) (PVAc) chains, PSn‐b‐PVAc4‐n (n = 1, 2, and 3), with controlled structures were successfully prepared by successive RAFT and ATRP chain‐extension experiments using VAc and St as the second monomers, respectively. The architecture of the miktoarm star‐block copolymers PSn‐b‐PVAc4‐n (n = 1, 2, and 3) were characterized by gel permeation chromatography and 1H NMR spectra. Furthermore, the results of the cleavage of PS3‐b‐PVAc and PVAc2‐b‐PS2 confirmed the structures of the obtained miktoarm star‐block copolymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010

A novel functional dithiocarbamate, ClBTD, comprising both chloromethyl and thiocarbonyl groups, was successfully synthesized and used to mediate the RAFT polymerizations of St and MA. The obtained polymer was functionalized with chloromethyl and thiocarbonyl groups at the α‐ and ω‐ends of the polymer chain, respectively. The obtained polymer was directly used as macroinitiator to conduct ATRP chain extension experiment with NIPAAM as the second monomer, which resulted in poor control of the polymerization. After the thiocarbonyl group in the polymer chain end was fully removed by reaction with excess of AIBN, the recovered polymer was successfully used as macroinitiator in St/NIPAAM block copolymerization.