Organic Acid-Doped Cellulose Nanocrystals in Biocomposite Laminates as Chiral Nematic Photonic Films: Implications for Intelligent Packaging

Abstract

The organic photonic film is one of the important materials in optical, bioengineering, and sensing applications. It is a task to achieve excellent mechanical properties and foldability of the biopolymer composites having chiral nematic structures without sacrificing their iridescence. Herein, we have proposed an approach to preserve and lock the self-assembled cellulose nanocrystal (CNC) films based on agro-waste between the layers of a poly(lactic acid) (PLA)/polycaprolactone (PCL) biocomposite. The photonic properties of the composites were tweaked by doping with different organic acids (OAs). The addition of OAs into CNCs has resulted in the generation of flexible films. The multilayer films were studied for interfacial interactions in the form of spherulite interlocking between CNCs and polymer blends through polarized optical microscopy and differential scanning calorimetry analysis. Composite films exhibited high mechanical strength and also showed reflection from the UV region to the near-IR region. The composite films displayed good visual color-sensing properties with moderate antibacterial activity for Escherichia coli bacteria. Such ordered nanocellulose–polymer biocomposites fabricated by a facile layer-by-layer approach may assist the growth of obtained photonic films as candidate materials having implications in bio-optical engineering and packaging.