Temperature behavior of aqueous solutions of poly(2-oxazoline) homopolymer and block copolymers investigated by NMR spectroscopy and dynamic light scattering

0531870 - ÚMCH 2021 RIV CH eng J - Journal Article
Konefal, Rafal - Černoch, Peter - Konefal, Magdalena - Spěváček, Jiří
Temperature behavior of aqueous solutions of poly(2-oxazoline) homopolymer and block copolymers investigated by NMR spectroscopy and dynamic light scattering.
Polymers. Roč. 12, č. 9 (2020), s. 1-16, č. článku 1879. E-ISSN 2073-4360
R&D Projects: GA ČR(CZ) GA15-13853S; GA ČR(CZ) GA18-12925S
Institutional support: RVO:61389013
Keywords : thermoresponsive polymer * poly(2-ethyl-2-oxazoline) * poly(2-isopropyl-2-oxazoline)
OECD category: Polymer science
Impact factor: 4.329, year: 2020
Method of publishing: Open access
https://www.mdpi.com/2073-4360/12/9/1879

1H NMR methods in combination with dynamic light scattering were applied to study temperature behavior of poly(2-isopropyl-2-oxazoline) (PIPOx) homopolymer as well as PIPOx-b-poly(2-methyl-2-oxazoline) (PMeOx) and poly(2-ethyl-2-oxazoline) (PEtOx)-b-PMeOx diblock copolymers in aqueous solutions. 1H NMR spectra showed a different way of phase transition for the main and side chains in PIPOx-based solutions. Additionally, the phase transition is irreversible for PIPOx homopolymer and partially reversible for PIPOx-b-PMeOx copolymer. As revealed by NMR, the phase transition in PEtOx-based copolymers solutions exists despite the absence of solution turbidity. It is very broad, virtually independent of the copolymer composition and reversible with some hysteresis. Two types of water molecules were detected in solutions of the diblock copolymers above the phase transition—“free” with long and “bound” with short spin–spin relaxation times T2. NOESY spectra revealed information about conformational changes observed already in the pre-transition region of PIPOx-b-PMeOx copolymer solution.
Permanent Link: http://hdl.handle.net/11104/0310873