Tailoring of hydroxypropyl cellulose for high performance biodegradable liquid crystal and mechanical films

Biodegradable polymers with functional properties are vital for reducing environmental impact. This study explores the upcycling of Giant Reed waste to enhance the optical and mechanical performance of hydroxypropyl cellulose (HPC) films. Modified cellulose nanoparticles were incorporated into the HPC matrix and compared with carbon-based nanoparticles. The liquid crystalline behavior was examined in both lyotropic suspensions—through rheological and optical analysis and in solid nanocomposite films using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), thermogravimetric analysis (TGA), water contact angle measurements, mechanical testing, scanning electron microscopy (SEM), and optical microscopy. The results revealed that the addition of esterified nanoparticles, especially esterified nanocellulose, significantly reduced the critical concentration for anisotropic phase formation in HPC lyotropic solutions from 38 wt% to 32 wt%. The smallest reduction was observed with cellulose nanoparticles alone. In solid films, the incorporation of esterified nanoparticles, particularly esterified graphite oxide in combination with cellulose acetate, notably enhanced hydrophobicity (contact angle increased from 55.2° to 74°), mechanical strength, thermal stability, and crystallinity. Morphological analysis confirmed the presence of well-defined fingerprint textures, especially in films containing esterified cellulose nanoparticles and graphite oxide. These findings demonstrate the potential of esterified biobased nanomaterials to advance the development of functional, sustainable liquid crystal nanocomposites. The developed HPC-based nanocomposites show strong potential for use in biodegradable optical films, sustainable packaging, and smart environmental sensors, owing to their enhanced optical anisotropy, mechanical strength, hydrophobicity, and thermal stability.