The effects of aspect ratio of cellulose nanocrystals on the properties of all CNC films: Tunicate and wood CNCs

In this study, the physicochemical, mechanical, and thermal properties of films made from cellulose nanocrystals (CNCs) obtained from two sources - wood and tunicate - and their hybrids were investigated. It was found that different morphologies affect the properties of CNC films. Specifically, the surface morphology of tunicate CNC (TCNC) films differed significantly from wood CNC (WCNC) films, and the structure of hybrid CNC (HCNC) films was also different. Compared to wood CNC-containing films, tunicate CNC films exhibited significantly higher BET surface areas, superior thermal properties, greater surface roughness, and very low (approximate to 1 wt.%) dispersibility in water due to their ability to form long-range connectivity. The average BET surface area of TCNC films was measured at 91.9 +/- 2.1 m2/g, and this value decreased with the addition of WCNCs to the film structure. The pore diameter also decreased from 11.362 nm for TCNC films to 0.437 nm for WCNC films, indicating the filler effect of WCNCs on the TCNC films. The chiral nematic phase exhibited by WCNC films was confirmed by their iridescent appearance, as observed through cross-sectional SEM images. The TS for TCNC and HCNC3 was measured at 185.2 +/- 10.5 MPa and 182.9 +/- 13.7 MPa, respectively, which were the highest values among the samples. The lowest TS value of 113.1 +/- 9.5 MPa was observed in the WCNC films. A similar decline was observed in the EB values, from 1.76 +/- 0.37% for TCNC to 0.9 +/- 0.22% for WCNC. This study provides information and knowledge useful for understanding the impact of biomass source on the properties of CNC films for a variety of purposes, including packaging materials, biodegradable coatings, flexible electronics, and membrane applications.