American Chemical Society
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Dendronized Polymers with Peripheral Oligo(ethylene oxide) Chains: Thermoresponsive Behavior and Shape Anisotropy in Solution

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journal contribution
posted on 2011-11-22, 00:00 authored by Jérôme Roeser, Firmin Moingeon, Benoît Heinrich, Patrick Masson, Françoise Arnaud-Neu, Michel Rawiso, Stéphane Méry
A series of dendronized polymers carrying oligo(ethyleneoxy) peripheral branches have been prepared by postpolymerization functionalization of multiallylic dendronized polymers using a radical addition of mercaptans, namely 2-methoxy(ethoxy)ethanethiol (EO2) and {2-(2-methoxyethoxy)ethoxy)}ethanethiol (EO3). The functionalization proved to be quite efficient, leading to up to 6 or 9 EO chains per monomer repeating unit. A constant Tg value was observed independently of the material characteristics, indicating that Tg is ruled by the sole presence of EO chains. According to the hydrophilic and hydrophobic balance, some polymers exhibited a thermoresponsive behavior in water solution, characterized by a sharp lower critical solution temperature (LCST) transition and a small hysteresis. These LCST showed an unusual increase with DP, which might be correlated to a dilution effect and an increase of polymer hydrophilicity by densification of the dendritic coverage. By SAXS investigations and using a spherocylinder shape model, the polymers in solution (below the LCST) could be satisfactorily described. By increasing the DP, the shape of the macromolecule was found to evolve from a spherical to a spherocylinder shape with a constant cross section of ca. 40 Å.