ISSN:
1435-1536
Keywords:
Key words Block copolymers
;
micelle
;
temperature
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The association behaviour of triblock copoly(ethylene oxide/tetrahydrofuran/ethylene oxide), in particular E100T27E100, in aqueous solutions has been investigated by means of static and dynamic light scattering, nuclear magnetic reso-nance (NMR) and surface tension techniques. On raising the polymer concentration at room temperature, the copolymer aggregates to form micelles with an aggregation number of about 105 (R G, mic≈15 nm and R H, mic≈13 nm, as revealed by light scattering and FT-PGSE NMR measurements, respectively). The micelles are kinetically quite stable, the micellar lifetime is shown to be more than 1 h. The residence time of a single unimer in a micelle is more than 140 ms. The apparent radius of gyration R G, mic is fairly independent of concentration, but large effects are observed on varying the temperature. Raising the temperature initially results in an increase of the apparent micellar size, followed by a maximum at an intermediate temperature (≈45 °C). At higher temperatures a contraction of the micelles is observed. The shape of the micelles also appear to vary in this temperature interval. The interactions responsible for these phenomena are discussed in terms of, e.g., the temperature-dependent solubility of the alkylene oxide segments in water and polydispersity effects.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s003960050105
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