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Poly(ethylene oxide)‐ and Poly(perfluorohexylethyl methacrylate)‐Containing Amphiphilic Block Copolymers: Association Properties in Aqueous Solution
Author(s) -
Hussain Hazrat,
Busse Karsten,
Kressler Jörg
Publication year - 2003
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.200390070
Subject(s) - copolymer , micelle , dynamic light scattering , hydrodynamic radius , polymer chemistry , ethylene oxide , critical micelle concentration , aqueous solution , amphiphile , polymerization , atom transfer radical polymerization , materials science , methacrylate , chemical engineering , chemistry , polymer , organic chemistry , nanoparticle , nanotechnology , engineering
Abstract Amphiphilic di‐ and triblock copolymers containing poly(ethylene oxide) (PEO) as the hydrophilic block and poly(perfluorohexylethyl methacrylate) (PFMA) as the hydrophobic block were synthesized by atom‐transfer radical polymerization using hydroxy‐terminated PEO as the macroinitiator. The copolymers were characterized by size exclusion chromatography and 1 H NMR spectroscopy. Self‐association in aqueous solution has been investigated using surface tension measurements, dynamic light scattering (DLS), and transmission electron microscopy (TEM). From surface tension measurements in water, a characteristic concentration ( c *) can be detected, which is interpreted as the critical micelle concentration (cmc). The cmc decreases with an increase in fluoro content in the triblock copolymer up to 11 wt.‐% PFMA (solubility limit). DLS studies have been carried out for different samples above the cmc, showing small aggregates (micelles) and single chains for diblock copolymer solutions. In the case of triblock copolymers large clusters were the dominant aggregates in addition to the micelles and single chains. The effect of temperature and concentration on the micelle and cluster formation has been investigated by DLS. Micelle size was found to be resistant to any change by temperature, however, a slight but significant increase in apparent hydrodynamic radius was observed with an increase in concentration, while both temperature and concentration affected the formation of large clusters, especially in concentrated solutions. TEM has been carried out to visualize the morphology of the aggregates after transferring the solution to carbon film. The initial concentration for the preparation of TEM samples was found to have a strong influence on the morphology of the aggregates. By adding colloidal gold particles to the solutions, the typical covering by the polymer was observed by TEM.Decay‐rate distributions for PEO 10 F5 (4.0 g · L −1 ); obtained from the time correlation functions.