Issue 41, 2019

Enrichment of methanol inside pNIPAM gels in the cononsolvency-induced collapse

Abstract

Crosslinked poly-N-isopropylacrylamide (pNIPAM) gels adapt to their environment by a unique transition from a flexible, swollen macromolecular network to a collapsed particle. pNIPAM gels are swollen in both, pure water and pure methanol (MeOH). However, a drastic volume loss is observed in mixtures of water and methanol over a wide composition range. This effect is referred to as cononsolvency. Cononsolvency couples the volume phase transition to the transport of the cosolvent into the polymeric network. So far, the mechanisms underlying cononsolvency have not been fully elucidated. To obtain insights on cononsolvency, Raman microspectroscopy was applied to capture spatially resolved spectra distinguishing between the surroundings and the inside of the gel. Here, we used Indirect Hard Modelling (IHM) for the spectral analysis. Mass balancing allowed the calculation of the solvent composition inside the pNIPAM gel. The results show an increased methanol fraction inside the collapsed gel as compared to its surroundings. Furthermore, the sensitivity of the vibrational bands of methanol to its local hydrogen bonding environment allow to derive information about the molecular interactions. The methanol peak shifts measured inside the gel point towards donor-type hydrogen bonds between methanol and the peptide group of pNIPAM in the cononsolvency-induced collapse. The presented data should enhance our understanding of cononsolvency.

Graphical abstract: Enrichment of methanol inside pNIPAM gels in the cononsolvency-induced collapse

Supplementary files

Article information

Article type
Paper
Submitted
07 ኦገስ 2019
Accepted
29 ሴፕቴ 2019
First published
30 ሴፕቴ 2019

Phys. Chem. Chem. Phys., 2019,21, 22811-22818

Enrichment of methanol inside pNIPAM gels in the cononsolvency-induced collapse

K. Nothdurft, D. H. Müller, T. Brands, A. Bardow and W. Richtering, Phys. Chem. Chem. Phys., 2019, 21, 22811 DOI: 10.1039/C9CP04383G

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements