Nanocellulose dissolution in deep eutectic solvent for carrageenan biocomposite reinforcement / Okwuwa Chigozie Charity

Faculty of Chemical and Process Engineering Technology

Thesis (Master of Science) -- Universiti Malaysia Pahang – 2025

Includes bibliographical references

Carrageenan, a widely used edible biopolymer, holds promise for hard capsule production in the pharmaceutical industry due to its gelling properties. However, its rough surface qualities, low thermal stability, and weak mechanical strength limit its industrial applicability. While incorporating cellulose nanocrystals (CNCs) can enhance structural integrity, their strong hydrogen bonding network renders them insoluble in water, leading to poor dispersion and reduced mechanical performance. Conventional solvents for CNC dissolution pose environmental and economic concerns, necessitating the search for sustainable alternatives. This study aims to evaluate the dissolution of CNCs in deep eutectic solvents (DES) by varying the hydrogen bond donor (HBD), which was used to improve the mechanical and thermal properties of carrageenan-based biocomposites for pharmaceutical applications, particularly in hard capsule production. 0.2 g of CNCs were dissolved in 10 g of choline chloride-glycerol DES with varied hydrogen bond donor (HBD) ratios (1:1 to 1:4). The intermolecular interactions between CNC and DES were investigated using Gaussian 09W simulations and nuclear magnetic resonance (NMR) spectroscopy. At the same time, the biocomposites mechanical and thermal properties were assessed through tensile strength, loop strength, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The findings reveal that a 1:3 HBD ratio optimally dissolved CNCs, significantly improving biocomposite properties. At this ratio, tensile strength increased to 102.04 MPa, and hard capsule loop strength reached 75.83 MPa, indicating enhanced mechanical performance. ¹H NMR analysis showed hydrogen bond disruption at H2 and H4, while XRD results confirmed a reduction in CNC crystallinity size to 1.26 nm, improving dispersion. FTIR spectra indicated intensified hydrogen bonding and TGA analysis demonstrated superior thermal stability, with biocomposites exhibiting a melting temperature of 245°C. These findings establish DES as a viable green solvent for CNC dissolution and highlight its potential to enhance carrageenan biocomposites for pharmaceutical applications, drug delivery systems, and sustainable material innovations. This research advances the development of eco-friendly, high-performance biomaterials, contributing to sustainability in the pharmaceutical and materials industries.