Well-defined higher-molecular-weight polyacrylonitrile via RAFT technique in the presence of disulfide compounds as a source of chain transfer agent
ABSTRACT Well-defined polyacrylonitrile with a higher number-average molecular weight () up to 200,000 and a lower polydispersity index (PDI, 1.7–2.0) was firstly obtained via reversible addition–fragmentation chain transfer (RAFT) process. This was achieved by selecting a stable, easy way to prepare disulfide compound intermediates including bis(thiobenzoyl) disulfide (BTBDS) and bis(thiophenylacetoyl) disulfide (BTPADS) to react with azobis(isobutyronitrile) to directly synthesize RAFT agents in situ. The polymerization of acrylonitrile (AN) displays the characteristics of controlled/living radical polymerization as evidenced by pseudo first-order kinetics of polymerization, linear evolution of molecular weight with increasing monomer conversion, and narrow PDIs. The polymerization rate and the efficiency for producing RAFT agent of BTPADS system are obviously higher than those of BTBDS system, whereas the control of the latter over the polymerization is superior to that of the former. 1H NMR analysis has confirmed the dithioester chain-end functionality of the resultant polymer. The RAFT copolymerizations of AN and the comonomers including methyl acrylate, itaconic acid, methyl methacrylate, n-butyl acrylate, 2-hydroxyethyl acrylate, and acrylamide were also successfully carried out using the same polymerization system.
- Journal of Polymer Science Part A Polymer Chemistry 11/2005; 44(1):490 - 498. · 3.54 Impact Factor
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ABSTRACT: Free radical polymerization with reversible addition–fragmentation chain transfer (RAFT polymerization) is discussed with a view to answering the following questions: (a) How living is RAFT polymerization? (b) What controls the activity of thiocarbonylthio compounds in RAFT polymerization? (c) How do rates of polymerization differ from those of conventional radical polymerization? (d) Can RAFT agents be used in emulsion polymerization? Retardation, observed when high concentrations of certain RAFT agents are used and in the early stages of emulsion polymerization, and how to overcome it by appropriate choice of reaction conditions, are considered in detail. Examples of the use of thiocarbonylthio RAFT agents in emulsion and miniemulsion polymerization are provided.© 2000 Society of Chemical IndustryPolymer International 08/2000; 49(9):993 - 1001. · 2.13 Impact Factor
- Macromolecular Rapid Communications 11/2002; 23(16):952 - 956. · 4.93 Impact Factor