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DLS Measurements (dl + measurement)

Distribution by Scientific Domains
Polymers and Materials Science100%

Selected Abstracts

Synthesis and characterization of the PEG-based nonionic surfactants endowed with carboxylic acid moiety at the hydrophobic terminal

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2008
Hiroshi Morikawa
As a new class of stimulus-responsive surfactants, a series of ,-methyl-,-alkyl PEGs endowed with a carboxylic acid moiety at the hydrophobic terminal was successfully synthesized with 56,97% yields. They were characterized by IR, NMR spectroscopic and MALDI-TOF MS analyses. It is suggested by DLS measurement that the collapse of the micelle-like aggregation occurred under basic condition. This synthetic procedure would be applicable to surfactants with sufficient hydrophilic and lipophilic balances, allowing precise control of pH-responsive micellar systems. [source]

Synthesis and characterization of pH sensitive poly(glycidol)- b -poly(4-vinylpyridine) block copolymers

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 7 2009
Sebastian Mendrek
Abstract Block copolymers of poly(glycidol)- b -poly(4 -vinylpyridine) were obtained by ATRP of 4-vinylpyridine initiated by ,-(2-chloropropionyl) poly(glycidol) macroinitiators. By changing the monomer/macroinitiator ratio in the synthesis polymers with varied P4VP/PGl molar ratio were obtained. The obtained block copolymers showed pH sensitive solubility. It was found that the linkage of a hydrophilic poly(glycidol) block to a P4VP influenced the pKa value of P4VP. DLS measurements showed the formation of fully collapsed aggregates exceeding pH 4.7. Above this pH values the collapsed P4VP core of the aggregates was stabilized by a surrounding hydrophilic poly(glycidol) corona. The size of the aggregates depended significantly upon the composition of the block copolymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1782,1794, 2009 [source]

Synthesis and supramolecular self-assembly of thermosensitive amphiphilic star copolymers based on a hyperbranched polyether core

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2008
Haiyan Hong
Abstract A novel amphiphilic thermosensitive star copolymer with a hydrophobic hyperbranched poly (3-ethyl-3-(hydroxymethyl)oxetane) (HBPO) core and many hydrophilic poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA) arms was synthesized and used as the precursor for the aqueous solution self-assembly. All the copolymers directly aggregated into core,shell unimolecular micelles (around 10 nm) and size-controllable large multimolecular micelles (around 100 nm) in water at room temperature, according to pyrene probe fluorescence spectrometry and 1H NMR, TEM, and DLS measurements. The star copolymers also underwent sharp, thermosensitive phase transitions at a lower critical solution temperature (LCST), which were proved to be originated from the secondary aggregation of the large micelles driven by increasing hydrophobic interaction due to the dehydration of PDMAEMA shells on heating. A quantitative variable temperature NMR analysis method was designed by using potassium hydrogen phthalate as an external standard and displayed great potential to evaluate the LCST transition at the molecular level. The drug loading and temperature-dependent release properties of HBPO- star -PDMAEMA micelles were also investigated by using indomethacin as a model drug. The indomethacin-loaded micelles displayed a rapid drug release at a temperature around LCST. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 668,681, 2008 [source]

Gold Nanoparticles Functionalized by a Dextran-Based pH- and Temperature-Sensitive Polymer

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 5 2010
Weipeng Lv
Abstract A dextran-based dual-sensitive polymer is employed to endow gold nanoparticles with stability and pH- and temperature-sensitivity. The dual-sensitive polymer is prepared by RAFT polymerization of N -isopropylacrylamide from trithiocarbonate groups linked to dextran and succinoylation of dextran after polymerization. The functionalized nanoparticles show excellent stability under various conditions and can be stored in powder-form. UV and DLS measurements confirm that the temperature-induced optical changes and aggregation behaviors of the particles are strongly dependent on pH. [source]

Preparation of Polystyrene-Poly(N -isopropylacrylamide) (PS-PNIPA) Core-Shell Particles by Photoemulsion Polymerization

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 14 2006
Yan Lu
Abstract Summary: Monodisperse thermosensitive PS-NIPA core-shell particles composed of a PS core and a cross-linked PNIPA shell can be successfully synthesized by a novel method: photoemulsion polymerization. Cryo-TEM images indicate clearly the core-shell morphology of the PS-NIPA particles: A homogeneous regular PNIPA shell has been affixed on the spherical PS core. DLS measurements indicate that the obtained PS-NIPA latex particles are thermosensitive. The shell of PNIPA networks with different cross-linking densities can shrink and re-swell with temperature and the volume transition temperature is around 32,°C in all cases. Cryo-TEM image of PS-NIPA core-shell particles. [source]