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.
[Show abstract][Hide abstract] ABSTRACT: In this paper, we describe a method for effectively expressing spatial geometric data in spatial database systems. The hyperplane is used to split a space into convex polytopes, each having a position vector. These position vectors are used to evaluate the spatial operations: the intersection, the union and the difference between two complexes of convex polytopes in any dimension. First, we explain the idea to represent a spatial object as a set of polytopes induced by hyperplanes, which must be stored in databases. We then present the conversion algorithms between position vectors and sign vectors of the complex model in any dimension. Next, we propose algorithms for compressing and uncompressing the sign vector to be stored in the database data. These algorithms are invoked when evaluating spatial operations. The above algorithms are implemented on an object database system. We also present the results of experimental tests to evaluate the data size of the spatial database.
TENCON 2004. 2004 IEEE Region 10 Conference; 12/2004
[Show abstract][Hide abstract] ABSTRACT: This paper provides a second update to the review of reversible deactivation radical polymerization achieved with thiocarbonylthio compounds (ZC(=S)SR) by a mechanism of reversible additionfragmentation chain transfer (RAFT) that was published in June 2005 (Aust. J. Chem. 2005, 58, 379410). The first update was published in November 2006 (Aust. J. Chem. 2006, 59, 669692). This review cites over 500 papers that appeared during the period mid-2006 to mid-2009 covering various aspects of RAFT polymerization ranging from reagent synthesis and properties, kinetics and mechanism of polymerization, novel polymer syntheses and a diverse range of applications. Significant developments have occurred, particularly in the areas of novel RAFT agents, techniques for end-group removal and transformation, the production of micro/nanoparticles and modified surfaces, and biopolymer conjugates both for therapeutic and diagnostic applications.
Australian Journal of Chemistry 01/2009; 62(11). DOI:10.1071/CH09311 · 1.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A simple, versatile, and one-step atom transfer radical addition−fragmentation (ATRAF) technique is reported for the synthesis of chain transfer agents (CTA) containing dithio groups (dithiobenzoate, dithiocarbamate, and xanthate), with various alkyl substituents, in the presence of copper catalyst, alkyl halide, and bis(thiocarbonyl) disulfide. The ATRAF procedure is efficient and selective, leading to almost quantitative conversion of alkyl halide initiators and formation of CTAs in high isolated yield under stoichiometric conditions as well as in the presence of catalytic amounts of copper(I) species. The CTAs synthesized by this process were used for reversible addition−fragmentation chain transfer (RAFT) polymerizations of styrene and methyl methacrylate without any further column purification, producing well-controlled polymers with low polydispersity, thereby demonstrating the effectiveness of ATRAF. Moreover, a simple one-pot, two-step RAFT polymerization was successful, starting from CTA synthesized in situ via ATRAF, followed directly by the addition of a monomer.
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.