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

Hatem Abushammala

doi:10.3390/polym12010095

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.

Highlights

Cellulose nanocrystals (CNCs), a form of nanocellulose, are rod-like nanoparticles with a thickness of 3–10 nm and a length of a few hundred nanometers [1]
Small degrees of chemical modifications have been shown to have a major impact on the surface properties of cellulose [44]
A maximum para/ortho selectivity was obtained using 35 ◦ C and a molar ratio of 3. Under these reaction conditions, all of the surface hydroxyls of the CNCs are reacted with toluene diisocyanate (TDI) and 93% of the ortho-isocyanates are available for the following reaction such as the grafting of alcohols in this paper [23]

Summary

Introduction

Cellulose nanocrystals (CNCs), a form of nanocellulose, are rod-like nanoparticles with a thickness of 3–10 nm and a length of a few hundred nanometers [1]. They can be extracted from cellulose and wood using a variety of chemicals and techniques [2,3,4]. CNCs have inherited many of the properties of cellulose such as mechanical strength, biocompatibility, and hydrophilicity [5]. Due to their nanosize and shape, CNCs have a high surface area of up to 500 m2 /g and can form liquid crystalline structures [6,7]. These chemical modifications included relatively simple procedures such as acetylation, silylation, and carbanilation, or grafting bulky hydrophobic moieties onto the CNC surface [12,13,14,15]

Methods

Results

Conclusion