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Rueda, J.C. ; Zschoche, St. ; Komber, H. ; Schmaljohann, D. ; Voit, B.
Synthesis and Characterization of Thermoresponsive Graft Copolymers of NIPAAm and 2-Alkyl-2-oxazolines by the "Grafting from" Method

New thermoresponsive graft copolymers were synthesized by the cationic ring-openingpolymerization of 2-methyl-2-oxazoline (MeOxa) or 2-ethyl-2-oxazoline (EtOxa), initiated by the randomcopolymers of chloromethylstyrene (CMS) and N-isopropylacrylamide (NIPAAm) using the "grafting from"method with a yield of 66-94%. The polymers were characterized by NMR, GPC, and DSC, and theconformational transition (lower critical solution temperature, LCST) of macroinitiators and graftcopolymers was determined by the turbidity and DSC measurements. The transition temperature of thegraft copolymers could be fine-tuned through the composition of the macroinitiator and the graft copolymer.An increasing quantity of the hydrophobic comonomer chloromethylstyrene in the macroinitiator loweredits LCST, while in the graft copolymer an increasing content of the hydrophilic segment of poly(2-methyl-2-oxazoline) or poly(2-ethyl-2-oxazoline) raised the transition temperature. For graft copolymers with ahigh content of long poly(2-alkyl-2-oxazoline) grafts, stabilized aggregates with a thermoresponsive corecan be formed at the LCST instead of precipitation of the material.

Macromolecules 38



Erschienen am
September 2005

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