TY - JOUR
T1 - Fourier transform infrared spectroscopy investigation of water microenvironments in polyelectrolyte multilayers at varying temperatures
AU - Eneh, Chikaodinaka I.
AU - Bolen, Matthew J.
AU - Suarez-Martinez, Pilar C.
AU - Bachmann, Adam L.
AU - Zimudzi, Tawanda J.
AU - Hickner, Michael A.
AU - Batys, Piotr
AU - Sammalkorpi, Maria
AU - Lutkenhaus, Jodie L.
N1 - Funding Information:
This work is supported by the National Science Foundation under Grant No. 1609696 (J. L. L.), Academy of Finland Grant No. 309324 (M. S.), and National Science Centre (Poland) Research Grant Sonata, UMO 2018/31/D/ST5/01866 (P. B.).
Publisher Copyright:
This journal is © 2020 The Royal Society of Chemistry.
PY - 2020/3/7
Y1 - 2020/3/7
N2 - Polyelectrolyte multilayers (PEMs) are thin films formed by the alternating deposition of oppositely charged polyelectrolytes. Water plays an important role in influencing the physical properties of PEMs, as it can act both as a plasticizer and swelling agent. However, the way in which water molecules distribute around and hydrate ion pairs has not been fully quantified with respect to both temperature and ionic strength. Here, we examine the effects of temperature and ionic strength on the hydration microenvironments of fully immersed poly(diallyldimethylammonium)/polystyrene sulfonate (PDADMA/PSS) PEMs. This is accomplished by tracking the OD stretch peak using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy at 0.25-1.5 M NaCl and 35-70 °C. The OD stretch peak is deconvoluted into three peaks: (1) high frequency water, which represents a tightly bound microenvironment, (2) low frequency water, which represents a loosely bound microenvironment, and (3) bulk water. In general, the majority of water absorbed into the PEM exists in a bound state, with little-to-no bulk water observed. Increasing temperature slightly reduces the amount of absorbed water, while addition of salt increases the amount of absorbed water. Finally, a van't Hoff analysis is applied to estimate the enthalpy (11-22 kJ mol-1) and entropy (48-79 kJ mol-1 K-1) of water exchanging from low to high frequency states.
AB - Polyelectrolyte multilayers (PEMs) are thin films formed by the alternating deposition of oppositely charged polyelectrolytes. Water plays an important role in influencing the physical properties of PEMs, as it can act both as a plasticizer and swelling agent. However, the way in which water molecules distribute around and hydrate ion pairs has not been fully quantified with respect to both temperature and ionic strength. Here, we examine the effects of temperature and ionic strength on the hydration microenvironments of fully immersed poly(diallyldimethylammonium)/polystyrene sulfonate (PDADMA/PSS) PEMs. This is accomplished by tracking the OD stretch peak using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy at 0.25-1.5 M NaCl and 35-70 °C. The OD stretch peak is deconvoluted into three peaks: (1) high frequency water, which represents a tightly bound microenvironment, (2) low frequency water, which represents a loosely bound microenvironment, and (3) bulk water. In general, the majority of water absorbed into the PEM exists in a bound state, with little-to-no bulk water observed. Increasing temperature slightly reduces the amount of absorbed water, while addition of salt increases the amount of absorbed water. Finally, a van't Hoff analysis is applied to estimate the enthalpy (11-22 kJ mol-1) and entropy (48-79 kJ mol-1 K-1) of water exchanging from low to high frequency states.
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U2 - 10.1039/c9sm02478f
DO - 10.1039/c9sm02478f
M3 - Article
C2 - 32043105
AN - SCOPUS:85081146189
SN - 1744-683X
VL - 16
SP - 2291
EP - 2300
JO - Soft matter
JF - Soft matter
IS - 9
ER -