Re-entrance of Poly(N,N-diethylacrylamide) in D2O/d-Ethanol Mixture at 27°C

Published

July 26, 2016

Author(s)

Di Jia, Taisen Zuo, Sararh Rogers, He Cheng, Boualem Hammouda, Charles C. Han

Abstract

The re-entrance of poly(N,N-diethyl acrylamide) (PDEA)in D₂O/d-ethanol mixtures (i.e., the coil-to-globule-to-coil transition) has been observed at 27 °C by small-angle neutron scattering (SANS). PDEA has a lower critical solution temperature (LCST) phase diagram in the D₂O-rich region, and is soluble in the D₂O-poor region for all of the observed temperature ranges. Its spinodal temperature decreases first from 33.5°C in pure D₂O to 26.7°C in 80 w% D₂O/20 w% d-ethanol, then increases to 283.1 °C in 50 w% D₂O/50 w% d-ethanol. With the further decrease of D₂O content, PDEA dissolves well and its phase boundary can no longer be observed by SANS. Therefore, at 27 °C, PDEA dissolves as random coils when the D₂O content is higher than 90 w%, and then collapses and aggregates to form the globule phase in 20 w% D₂O/80 w% d-ethanol, finally, it re-swells and behaves as random coils again with excluded volume in The D₂O-poor region. The ternary random phase approximation model (RPA) is used to analyze the SANS profiles, and three Flory-Huggins interaction parameters (χ_{PDEA-d-ethanol},χ_PDEA-Dd2^O^ and χ_PDEA-Dd2^O). With the addition of more d-ethanol, its interaction with water becomes weaker, but still stronger than those between PDEA-D₂O and PDEA-d-ethanol. Neither d-ethanol nore D₂O want to help the dissolution of PDEA in the first place, until the structure of mixed solvents tends to be pure d-ethanol in D₂O-poor region.

Citation

Macromolecules

Volume

49

Pub Type

Journals

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Keywords

PNIPAM, SANS, RPA, random phase approximation, ternary mixtures, mixed solvents

Citation

Jia, D. , Zuo, T. , Rogers, S. , Cheng, H. , Hammouda, B. and Han, C. (2016), Re-entrance of Poly(N,N-diethylacrylamide) in D₂O/d-Ethanol Mixture at 27°C, Macromolecules, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=920301 (Accessed April 24, 2024)