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Sequential Anionic Polymerization (sequential + anionic_polymerization)

Distribution by Scientific Domains

Polymers and Materials Science	100%

Selected Abstracts

Two-Dimensional Chromatography of Complex Polymers, 7 , Detailed Study of Polystyrene- block -Polyisoprene Diblock Copolymers Prepared by Sequential Anionic Polymerization and Coupling Chemistry

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 19 2008
Valentina Mass
Abstract Two-dimensional chromatographic methods were developed using LC-CC in the first and SEC in the second dimension. These methods were applied for the investigation of PS- b -PI diblock copolymers synthesized by different approaches: sequential living anionic polymerization and coupling of living precursor blocks. The first dimension separates according to the individual block length of PS or PI blocks, whereas the second dimension separates with respect to the total molar masses of components. 2D-LC analysis provides information on the purity of the reaction products, the presence of by-products, the chemical compositions and the molar masses of all product components. The accuracy and selectivity of 2D-LC is discussed. [source]

Synthesis and characterization of poly[styrene- b -methyl(3,3,3-trifluoropropyl)siloxane] diblock copolymers via anionic polymerization

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2005
Lingmin Yi
Abstract A series of narrow molecular weight distribution (MWD) polystyrene- b -poly[methyl(3,3,3-trifluoropropyl)siloxane] (PS- b -PMTFPS) diblock copolymers were synthesized by the sequential anionic polymerization of styrene and trans -1,3,5-trimethyl-1,3,5-tris(3,,3,,3,-trifluoropropyl)cyclotrisiloxane in tetrahydrofuran (THF) with n -butyllithium as the initiator. The diblock copolymers had narrow MWDs ranging from 1.06 to 1.20 and number-average molecular weights ranging from 8.2 × 103 to 37.1 × 103. To investigate the properties of the copolymers, diblock copolymers with different weight fractions of poly[methyl(3,3,3-trifluoropropyl)siloxane] (15.4,78.8 wt %) were prepared. The compositions of the diblock copolymers were calculated from the characteristic proton integrals of 1H NMR spectra. For the anionic ring-opening polymerization (ROP) of 1,3,5-trimethyl-1,3,5-tris(3,,3,,3,-trifluoropropyl)cyclotrisiloxane (F3) initiated by polystyryllithium, high monomer concentrations could give high polymer yields and good control of MWDs when THF was used as the polymerization solvent. It was speculated that good control of the block copolymerization under the condition of high monomer concentrations was due to the slowdown of the anionic ROP rate of F3 and the steric hindrance of the polystyrene precursors. There was enough time to terminate the ROP of F3 when the polymer yield was high, and good control of block copolymerization could be achieved thereafter. The thermal properties (differential scanning calorimetry and thermogravimetric analysis) were also investigated for the PS- b -PMTFPS diblock copolymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4431,4438, 2005 [source]

Synthesis of a model cyclic triblock terpolymer of styrene, isoprene, and methyl methacrylate

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2002
Dimitris Pantazis
Abstract The synthesis of a model cyclic triblock terpolymer [cyclic(S- b -I- b -MMA] of styrene (S), isoprene (I), and methyl methacrylate (MMA) was achieved by the end-to-end intramolecular amidation reaction of the corresponding linear ,,,-amino acid precursor [S- b -I- b -MMA] under high-dilution conditions. The linear precursor was synthesized by the sequential anionic polymerization of S, I, and MMA with 2,2,5,5-tetramethyl-1-(3-lithiopropyl)-1-aza-2,5-disilacyclopentane as an initiator and amine generator and 4-bromo-1,1,1-trimethoxybutane as a terminator and carboxylic acid generator. The separation of the unreacted linear polymer from the cyclic terpolymer was facilitated by the transformation of the unreacted species into high molecular weight polymers by the evaporation of the reaction solvent and the continuation of the reaction under high-concentration conditions. The intermediate materials and the final cyclic terpolymer, characterized by size exclusion chromatography, vapor pressure osmometry, thin-layer chromatography, IR and NMR spectroscopy, exhibited high molecular weight and compositional homogeneity. Dilute-solution viscosity measurements were used as an additional proof of the cyclic structure. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1476,1483, 2002 [source]

Thermo- and pH-Responsive Micelles of Poly(acrylic acid)- block -Poly(N,N -diethylacrylamide)

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 7 2005
Xavier André
Abstract Summary: The bis-hydrophilic block copolymer, poly(acrylic acid)45 - block -poly(N,N -diethylacrylamide)360, was obtained after hydrolysis of poly(tert -butyl acrylate)45 - block -poly(N,N -diethylacrylamide)360, synthesized by sequential anionic polymerization of tert -butyl acrylate (tBA) and N,N -diethylacrylamide (DEAAm) in the presence of Et3Al. The polymer is stimuli-sensitive with respect to both pH and temperature in aqueous solution, reversibly forming spherical crew-cut micelles with PDEAAm-core (,Rh,z,=,21.5 nm) under alkaline conditions for T,>,35,°C as well as inverse star-like micelles with an expanded PAA-core (,Rh,z,=,43.8 nm) under acidic conditions for T,<,35,°C, as indicated by dynamic light scattering. Modes of micelle formation for poly(acrylic acid)45 - block -poly(N,N -diethylacrylamide)360 in aqueous solution depending on the pH and temperature. [source]