Low-Birefringent and Highly Tough Nanocellulose-Reinforced Cellulose Triacetate

Abstract

Improvement of the mechanical and thermal properties of cellulose triacetate (CTA) films is required without sacrificing their optical properties. Here, poly(ethylene glycol) (PEG)-grafted cellulose nanofibril/CTA nanocomposite films were fabricated by casting and drying methods. The cellulose nanofibrils were prepared by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation, and amine-terminated PEG chains were grafted onto the surfaces of the TEMPO-oxidized cellulose nanofibrils (TOCNs) by ionic bonds. Because of the nanosize effect of TOCNs with a uniform width of ∼3 nm, the PEG-TOCN/CTA nanocomposite films had high transparency and low birefringence. The grafted PEG chains enhanced the filler-matrix interactions and crystallization of matrix CTA molecules, resulting in the Young's modulus and toughness of CTA film being significantly improved by PEG-grafted TOCN addition. The coefficient of thermal expansion of the original CTA film was mostly preserved even with the addition of PEG-grafted TOCNs. These results suggest that PEG-TOCNs are applicable to the reinforcement for transparent optical films.

Improvement of the Thermal Stability of TEMPO‐Oxidized Cellulose Nanofibrils by Heat‐Induced Conversion of Ionic Bonds to Amide Bonds

“…Moreover, no PEG‐NH 2 chains can adsorb on the TOCN surface because of the high grafting density. Almost all the TOCN carboxyl groups formed ionic bonds with amine groups of PEG‐NH 2 , and therefore the PEG‐NH 2 chains behave like polymer brushes …”

“…Almost all the TOCN carboxyl groups formed ionic bonds with amine groups of PEG-NH 2 , and therefore the PEG-NH 2 chains behave like polymer brushes. [ 2,18,19 ] This study aims, therefore, to show that the underlying mechanism is based on the heat-induced conversion of ionic bonds to amide bonds. This chemical modifi cation enables the grafting of polymers on TOCN surfaces without using any catalyst or organic solvent, which should be removed after reaction during the isolation and purifi cation process.…”

“…Coupling of polyoxyethylene (PEO) or polyethylene glycol (PEG) with CNCs or TOCNs is often performed. Depending on the molecular weight (MW), coupling protocol, or interactions between the polymer and nanocellulose (e.g., hydrogen, ionic, or covalent bonds), various conclusions have been made concerning the thermal properties.…”

“…Different strategies have been investigated, such as adsorption, [ 13 ] grafting of highly thermally stable polymers to oxidized nanocellulose, [ 14,15 ] and simply mixing nanocellulose with a polymeric matrix. [ 14 ] Coupling of polyoxyethylene (PEO) [ 16,17 ] or poly ethylene glycol (PEG) [ 13,[18][19][20][21] with CNCs or TOCNs is often performed. Depending on the molecular weight (MW), coupling protocol, or interactions between the polymer and nanocellulose (e.g., hydrogen, ionic, or covalent bonds), various conclusions have been made concerning the thermal properties.…”

Cellulose triacetate synthesis via one-pot organocatalytic transesterification and delignification of pretreated bagasse

“…cellulose acetate) have been widely utilised for diverse applications [1][2][3] such as membrane matrices, 4 optical lms, 5 cigarette lters, 6 etc. [7][8][9][10][11] Their importance can also be acknowledged from the viewpoint of green and sustainable chemistry. 12 Cellulose is a major component of lignocellulosic biomass, so-called lignocellulose, that is independent from the instinctive competition with human food supplies.…”