NMR study of thermoresponsive block copolymer in aqueous solution

0460278 - ÚMCH 2017 RIV DE eng J - Journal Article
Spěváček, Jiří - Konefal, Rafal - Čadová, Eva
NMR study of thermoresponsive block copolymer in aqueous solution.
Macromolecular Chemistry and Physics. Roč. 217, č. 12 (2016), s. 1370-1375. ISSN 1022-1352. E-ISSN 1521-3935
R&D Projects: GA ČR(CZ) GA15-13853S
Institutional support: RVO:61389013
Keywords : aqueous solutions * NMR * NOESY
Subject RIV: CD - Macromolecular Chemistry
Impact factor: 2.500, year: 2016

Temperature behavior of D2O solutions of poly(ethylene oxide) (PEO)114-block-poly(N-isopropylacrylamide) (PNIPAm)109 is characterized by NMR methods. At temperatures above the lower critical solution temperature (LCST) transition of PNIPAm component, 1H NMR spectra are consistent with existence of micelles where immobilized PNIPAm blocks form rather compact core and mobile PEO blocks form a shell of micelles. The transition of PNIPAm component shifts toward lower temperatures with increasing polymer concentration. 2D nuclear Overhauser effect spectroscopy spectra which can provide information on proton groups in close spatial contact (<0.5 nm) show an increase in intensity of cross-peaks between PEO protons and main chain CH and CH2 protons, and isopropyl CH protons of PNIPAm units after increasing the temperature from 292.7 to 301.6 K. The fact that this change occurs at temperature, which is still below the LCST transition of PNIPAm component evidences certain conformation changes in the PEO-b-PNIPAm block copolymer already in the pretransition region.
Permanent Link: http://hdl.handle.net/11104/0260410