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AB Block Copolymer (ab + block_copolymer)
Selected AbstractsCharacterization and rheological properties of model alkali-soluble rheology modifiers synthesized by reversible addition,fragmentation chain-transfer polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2003E. Sprong Abstract Model alkali-soluble rheology modifiers of different molar masses were synthesized by the reversible addition,fragmentation chain-transfer polymerization of methyl methacrylate, methacrylic acid, and two different associative macromonomers. The polymerization kinetics showed good living character including well-controlled molar mass, molar mass linearly increasing with conversion, and the ability to chain-extend by forming an AB block copolymer. The steady-shear and dynamic properties of a core-shell emulsion, thickened with the different model alkali-soluble rheology modifiers, were measured at constant pH and temperature. The steady-shear data for latex solutions with conventional rheology modifiers exhibited the expected thickening, whereas the associative rheology modifiers showed contrasting rheology behavior. The dynamic measurements revealed that the latex solutions thickened with the conventional rheology modifiers exhibit solid-like (dominant G,) behavior as compared with the associative rheology modifiers that give the latex solution a liquid-like (dominant G,) character. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 223,235, 2003 [source] AB-Block Copolymer with Moving B Blocks as a Model for Interpolymer ComplexesMACROMOLECULAR THEORY AND SIMULATIONS, Issue 5 2010Olga S. Pevnaya Abstract The conformational behavior of a single AB block copolymer is studied by Monte Carlo simulation. The A-A and A-B interactions have the character of excluded volume interactions while the B units attract each other; the attractive B blocks can move along the chain. The collapse transition of the chain with increasing attraction between the B units is analyzed. Intrachain separation of the A and B units takes place in the course of the chain collapse with the formation of "globule with a tail" conformations. The globule is formed by the attractive moving B blocks while the tail consists of the swollen A segments. The model of AB block copolymer with moving B blocks can describe the behavior of interpolymer complexes between a long macromolecule and shorter polymer chains. [source] Synthesis and characterization of core,shell-type polymeric micelles from diblock copolymers via reversible addition,fragmentation chain transferJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2006Ping Zhang Abstract A method was developed to enable the formation of nanoparticles by reversible addition,fragmentation chain transfer polymerization. The thermoresponsive behavior of polymeric micelles was modified by means of micellar inner cores and an outer shell. Polymeric micelles comprising AB block copolymers of poly(N -isopropylacrylamide) (PIPAAm) and poly(2-hydroxyethylacrylate) (PHEA) or polystyrene (PSt) were prepared. PIPAAm- b -PHEA and PIPAAm- b -PSt block copolymers formed a core,shell micellar structure after the dialysis of the block copolymer solutions in organic solvents against water at 20 °C. Upon heating above the lower critical solution temperature (LCST), PIPAAm- b -PHEA micelles exhibited an abrupt increase in polarity and an abrupt decrease in rigidity sensed by pyrene. In contrast, PIPAAm- b -PSt micelles maintained constant values with lower polarity and higher rigidity than those of PIPAAm- b -PHEA micelles over the temperature range of 20,40 °C. Structural deformations produced by the change in the outer polymer shell with temperature cycles through the LCST were proposed for the PHEA core, which possessed a lower glass-transition temperature (ca. 20 °C) than the LCST of the PIPAAm outer shell (ca. 32.5 °C), whereas the PSt core with a much higher glass-transition temperature (ca. 100 °C) retained its structure. The nature of the hydrophobic segments composing the micelle inner core offered an important control point for thermoresponsive drug release and the drug activity of the thermoresponsive polymeric micelles. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3312,3320, 2006 [source] RAFT Synthesis and Solution Properties of pH-Responsive Styrenic-Based AB Diblock Copolymers of 4-Vinylbenzyltrimethylphosphonium Chloride with N,N -DimethylbenzylvinylamineMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 21 2007Andrew B. Lowe Abstract The RAFT synthesis and solution properties of AB block copolymers of 4-vinylbenzyltrimethylphosphonium chloride (TMP) and N,N -dimethylbenzylvinylamine (DMBVA) is described. The pH-dependent self-assembly properties of the AB diblock copolymers were examined using of 1H NMR, DLS, and fluorescence spectroscopy. The size of the polymeric aggregates depends on the block copolymer composition/molecular mass. The self assembly is completely reversible, as predicted from the tunable hydrophilicity/hydrophobicity of the DMBVA residues. The AB diblock copolymers can be effectively locked in the self-assembled state using a straightforward core crosslinking reaction between the tertiary amine residues of DMBVA and difunctional 1,4-bis(bromomethyl)benzene. [source] | ||||||||||