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Branched Structure (branched + structure)
Selected AbstractsBranched polystyrene with abundant pendant vinyl functional groups from asymmetric divinyl monomerJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2008Zhong-Min Dong Abstract Branched polystyrenes with abundant pendant vinyl functional groups were prepared via radical polymerization of an asymmetric divinyl monomer, which possesses a higher reactive styryl and a lower reactive butenyl. Employing a fast reversible addition fragmentation chain transfer (RAFT) equilibrium, the concentration of active propagation chains remained at a low value and thus crosslinking did not occur until a high level of monomer conversion. The combination of a higher reaction temperature (120 °C) and RAFT agent cumyl dithiobenzoate was demonstrated to be optimal for providing both a more highly branched architecture and a higher polymer yield. The molecular weights (Mws) increased with monomer conversions because of the controlled radical polymerization characteristic, whereas the Mw distributions broadened showing a result of the gradual increase of the degree of branching. The evolution of branched structure has been confirmed by a triple detection size exclusion chromatography (TRI-SEC) and NMR technique. Furthermore, the double bonds in the side chains were successfully used for chemical modification reactions. 1H NMR and FTIR measurements reveal that the great mass of pendant vinyl groups were converted to the corresponding objective end-groups. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6023,6034, 2008 [source] Star polystyrenes by anionic star,star coupling reactions with divinylbenzeneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2006Hyung-Jae Lee Abstract The incremental addition of divinylbenzene was used to generate star polystyrenes in a nearly full conversion of a living polystyrenyl anion. The dramatic increase in the molecular weight of the star polystyrenes with a limited supply of the living polystyrene supported the formation of gradient-star polystyrenes through star,star coupling. The stoichiometric analysis of the star polymers revealed that their connection polymer had a shorter length than their branch polymer. The measured solution viscosity of the gradient-star polymers greatly deviated from a linear correlation with the molecular weight and was in parallel to a theoretical simulation based on a highly branched structure of the gradient-star polymer. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2579,2586, 2006 [source] Processability and mechanical properties of commercial PVC plastisols containing low-environmental-impact plasticizersJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 3 2009Paola Persico Preliminary results are presented concerning the use of less-toxic plasticizers such as dioctyl adipate (DOA) and acetyl tributyl citrate (ATBC) in plastisol formulations for rotational molding technology. The DOA and ATBC plasticizers have been studied by comparing the effects of their content, molecular architecture, and polarity on the rheological behavior of liquid plastic systems and on the mechanical properties of the ultimate products prepared with PVCs having different particle sizes and molecular-weight distributions. Rheological tests have confirmed the differences in solvent power of the diethylhexyl phthalate (DOP), DOA, and ATBC plasticizers. The glass transition temperatures measured on rotomolded samples have shown that the use of ATBC leads to a more nearly rigid system as a consequence of the branched structure and polarity of this plasticizer when compared with DOA. Mechanical tests carried out on final products after natural and forced environmental aging revealed a slight decrease in their performance. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers [source] "New" branched structures of mechanical systems as result of synthesis of selected class of dynamical characteristicsPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2006Andrzej Buchacz In this paper the problem of synthesis has been formulated and its basics has been formalized, according to the discrete mechanical systems with branched structure represented by graphs. In this case the essential field of basic conceptions according to the concerned class of structures and used graphs has been described. The way of receiving "new" structures as a result of synthesis of characteristics into partial fraction has been presented farther on. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||