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PO: Polymerphysik
PO 8: Poster: Polymermischungen und Copolymere
PO 8.10: Poster
Tuesday, March 2, 1999, 14:00–16:00, Foyer
Structure Formation in Aqueous Solutions of Triblock Copolymers. H2O/D2O Isotope Effects — •H. Knoll1, K. Gille1, F. Rittig2, G. Fleischer2, and J. Kärger2 — 1Universität Leipzig, Wilhelm-Ostwald-Institut f. Physikalische und Theoretische Chemie, Fakultät f. Chemie u. Mineralogie, 04103 Leipzig, Linnéstr. 2 — 2Universität Leipzig,Institut f. Experimentelle Physik I
The PEO-PPO-PEO triblock copolymers (Pluronics) have been widely studied in the past because they are an amphiphile polymer of large industrial interest. By us structure formation (micellization) in aqueous solutions of PEO-PPO-PEO triblock copolymers on increasing temperature was followed by determination of a) chemical reaction rate constants kiso of the thermal cis-trans isomerization of an azo dye by means of flash photolysis, and b) self-diffusion coefficients D of the copolymer molecules by means of PFG NMR, in H2O and D2O. The S-shape of the ln (kiso or D) vs. 1/T curves is due to changes of the microenvironment of the dye molecules and media effects on reaction rate, and changes of the chain mobility of copolymer molecules, respectively, on micellization. Cmt-values derived by both methods are in satisfactory agreement with each other and with the literature. Rate constants kiso, diffusion coefficients D, and the hydrodynamic radii of the diffusing species are larger in H2O than in D2O. The reason for the considerable H2O/D2O isotope effects observed is seen in the stronger hydrogen bonds between EO units and D2O compared to EO units and H2O.