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Ionically Paired Layer-by-Layer Hydrogels: Water and Polyelectrolyte Uptake Controlled by Deposition Time

Department of Materials Science & Engineering, Texas A&M University, College Station, TX 77843, USA
Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
Author to whom correspondence should be addressed.
Received: 18 November 2017 / Revised: 28 December 2017 / Accepted: 8 January 2018 / Published: 11 January 2018
(This article belongs to the Special Issue Polyelectrolyte Gels)
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Despite intense recent interest in weakly bound nonlinear (“exponential”) multilayers, the underlying structure-property relationships of these films are still poorly understood. This study explores the effect of time used for deposition of individual layers of nonlinearly growing layer-by-layer (LbL) films composed of poly(methacrylic acid) (PMAA) and quaternized poly-2-(dimethylamino)ethyl methacrylate (QPC) on film internal structure, swelling, and stability in salt solution, as well as the rate of penetration of invading polyelectrolyte chains. Thicknesses of dry and swollen films were measured by spectroscopic ellipsometry, film internal structure—by neutron reflectometry (NR), and degree of PMAA ionization—by Fourier-transform infrared spectroscopy (FTIR). The results suggest that longer deposition times resulted in thicker films with higher degrees of swelling (up to swelling ratio as high as 4 compared to dry film thickness) and stronger film intermixing. The stronger intermixed films were more swollen in water, exhibited lower stability in salt solutions, and supported a faster penetration rate of invading polyelectrolyte chains. These results can be useful in designing polyelectrolyte nanoassemblies for biomedical applications, such as drug delivery coatings for medical implants or tissue engineering matrices. View Full-Text
Keywords: polyelectrolytes; layer-by-layer; multilayers; neutron reflectometry; exponential growth polyelectrolytes; layer-by-layer; multilayers; neutron reflectometry; exponential growth

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Selin, V.; Ankner, J.F.; Sukhishvili, S.A. Ionically Paired Layer-by-Layer Hydrogels: Water and Polyelectrolyte Uptake Controlled by Deposition Time. Gels 2018, 4, 7.

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