Unique thermo-responsivity and tunable optical performance of poly(N-isopropylacrylamide)-cellulose nanocrystal hydrogel films

Xiaohang Sun; Preeti Tyagi; Sachin Agate; Lucian Lucia; Marian McCord; Lokendra Pal

doi:10.1016/j.carbpol.2018.12.067

Unique thermo-responsivity and tunable optical performance of poly(N-isopropylacrylamide)-cellulose nanocrystal hydrogel films

Carbohydr Polym. 2019 Mar 15:208:495-503. doi: 10.1016/j.carbpol.2018.12.067. Epub 2018 Dec 21.

Authors

Xiaohang Sun¹, Preeti Tyagi¹, Sachin Agate¹, Lucian Lucia¹, Marian McCord¹, Lokendra Pal²

Affiliations

¹ Department of Forest Biomaterials, North Carolina State University, Campus Box 8005, Raleigh, NC 27695-8005, USA.
² Department of Forest Biomaterials, North Carolina State University, Campus Box 8005, Raleigh, NC 27695-8005, USA. Electronic address: lokendra_pal@ncsu.edu.

PMID: 30658828
DOI: 10.1016/j.carbpol.2018.12.067

Abstract

A hybrid materials system to modulate lower critical solution temperature (LCST) and moisture content for thermo-responsivity and optical tunability was strategically developed by incorporating cellulose nanocrystals (CNCs) into a poly(N-isopropylacrylamide) (PNIPAm) hydrogel matrix. The PNIPAm/CNC hydrogel films exhibit tunable optical properties and wavelength bandpass selectivity as characterized by PROBE Spectroscopy and Dynamic Light Scattering (DLS). Importantly, the micro/nano structures of the PNIPAm/CNC hydrogel films were completely different when dried below and above the LCST. Below the LCST, PNIPAm/CNC hydrogel films exhibit transparency or semi-transparency due to the uniform bonding of hydrophilic PNIPAm and CNC through hydrogen bonds. Above the LCST, the hydrogel films engage in both hydrophobic PNIPAm and hydrophilic CNC interactions due to changes in PNIPAm conformation which lead to light scattering effects and hence opacity. Furthermore, the incorporation of CNC induces a ∼ 15 °C reduction of the LCST relative to pure PNIPAm hydrogel films.

Keywords: Cellulose nanocrystals; Hydrogels; Poly(N-isopropylacrylamide); Thermal responsive; Transparency.