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AB Diblock Copolymer (ab + diblock_copolymer)
Selected AbstractsRAFT 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] A doubly responsive AB diblock copolymer: RAFT synthesis and aqueous solution properties of poly (N -isopropylacrylamide- block -4-vinylbenzoic acid)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2007Andrew B. Lowe Abstract We describe herein the synthesis and self-assembly characteristics of a doubly responsive AB diblock copolymer comprised of N -isopropylacrylamide (NIPAM) and 4-vinylbenzoic acid (VBZ). The AB diblock copolymer was prepared via reversible addition-fragmentation chain transfer (RAFT) radical polymerization in DMF employing a trithiocarbonate-based RAFT agent. PolyNIPAM was employed as the macroRAFT agent. The NIPAM homopolymerization was shown to possess all the characteristics of a controlled process, and the blocking with VBZ was judged, by size exclusion chromatography, to be essentially quantitative. The NIPAM-VBZ block copolymer was subsequently demonstrated to be able to form normal and inverse micelles in the same aqueous solution by taking advantage of the stimuli responsive characteristics of both building blocks. Specifically, and as judged by NMR spectroscopy and dynamic light scattering, raising the temperature to 40 °C (above the lower critical solution temperature of the NIPAM block), while at pH 12 results in supramolecular self-assembly to yield nanosized species that are composed of a hydrophobic NIPAM core stabilized by a hydrophilic VBZ corona. Conversely, lowering the solution pH to 2.0 at ambient temperature results in the formation of aggregates in which the VBZ block is now hydrophobic and in the core, stabilized by the hydrophilic NIPAM block. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5864,5871, 2007 [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] Simulated Annealing Study of Self-Assembly of Symmetric ABA Triblock Copolymers Confined in Cylindrical NanoporesMACROMOLECULAR THEORY AND SIMULATIONS, Issue 2-3 2008Zheng Wang Abstract We report a simulated annealing study of the self-assembly of symmetric lamella-forming ABA triblock copolymers confined in cylindrical nanopores. We systematically examine the dependence of the self-assembled morphologies and structural parameters on the degree of confinement and the strength of the surface preference. We find that the confined morphologies for the symmetric ABA triblocks with fA,=,1/2 are similar to those for the symmetric or nearly symmetric AB diblock copolymers under the same confinement. We also find that different structural parameters can reflect different information. The predicted bridging fraction value for the bulk phase is in good agreement with previously established values, whereas the predicted values for the confined morphologies change with both the degree of confinement and the strength of the surface preference. We further explore the self-assembling process by examining the morphology and various ensemble-averaged thermodynamic quantities and structure parameters as a function of the reduced temperature. [source] | ||||||||||