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



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


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 (χPDEA-d-ethanolPDEA-Dd2^O^ and χPDEA-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.


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


Jia, D. , Zuo, T. , Rogers, S. , Cheng, H. , Hammouda, B. and Han, C. (2016), Re-entrance of Poly(N,N-diethylacrylamide) in D<sub>2</sub>O/d-Ethanol Mixture at 27&#176;C, Macromolecules, [online], (Accessed July 13, 2024)


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Created July 25, 2016, Updated October 12, 2021