Nano-Brushes of Alcohols Grafted onto Cellulose Nanocrystals for Reinforcing Poly(Butylene Succinate): Impact of Alcohol Chain Length on Interfacial Adhesion

Abstract

Despite the many interesting properties of cellulose nanocrystals (CNCs), their hydrophilicity is one of the main challenges for their processing with hydrophobic polymers and matrices. To overcome this challenge, this paper describes the preparation of brush-like CNCs with tailored surface properties by grafting alcohols of different chain lengths onto their surfaces. Ethanol, 1-butanol, 1-hexanol, and 1-octanol were grafted on the CNC surface using 2,4-toluene diisocyanate (TDI) as a linker. The CNCs were characterized for their structural, morphological, surface, and thermal properties. Because of the grafting, the water contact angle of the CNCs significantly increased from 32° to up to 120°, which was dependent on the chain length of the grafted alcohol. The thermal stability of the CNCs was also improved, mainly as a result of the reaction of TDI with the CNC hydroxyl groups. Later, the CNCs were used to reinforce films of poly(butylene succinate) (PBS), which were then characterized using dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). An increase of up to two-fold in the storage modulus was observed using DMA, which was dependent on the chain length of the grafted alcohol. However, no change in the glass transition temperature or degradation temperature of PBS was detected. This approach is proved efficient for tailoring the surface properties of CNCs towards excellent interfacial adhesion in their composites.

Impact of the Surface Properties of Cellulose Nanocrystals on the Crystallization Kinetics of Poly(Butylene Succinate)

“…Following this procedure, almost every CNC surface hydroxyl had an alcohol chain attached to it. This has been confirmed in a previous paper by the authors [19].…”

“…In a previous report by the authors, the surface properties of CNCs were tailored by grafting alcohols of different chain lengths onto their whole surface (almost all available surface hydroxyls, i.e., a degree of surface modification of ca. 100%) using 2,4-toluene diisocyanate (TDI) as a linker (Figure 1) [19]. Four alcohols were explored: ethanol, 1-butanol, 1-hexanol, and 1-octanol.…”

Recent Advances on Cellulose Nanocrystals and Their Derivatives

“…Despite the above benefits, there are relatively few coupling agents, which can connect functional molecules to CNC because of the lack of convenient coupling agents and a suitable solvation system. Another example of reacting isocyanate and CNCs was reported by H. Abushammala et al who highlighted a successful attachment of different alcohols (ethanol, 1-butanol, 1-hexanol, and 1-octanol) on CNCs [68]. Grafting the alcohols with different chain lengths changes CNC's hydrophilicity dramatically.…”

“…Another example of reacting isocyanate and CNCs was reported by H. Abushammala et al who highlighted a successful attachment of different alcohols (ethanol, 1-butanol, 1-hexanol, and 1-octanol) on CNCs [ 68 ]. Grafting the alcohols with different chain lengths changes CNC’s hydrophilicity dramatically.…”

“…( b ) The relationship between the contact angle of the alcohol-grafted CNCs and their capabilities to reinforce PBS. ( c ) The dependence of the contact angle of the modified CNCs on the chain length of the alcohols grafted onto their surfaces [ 68 ]. Open access.…”