Abstract
Cellulose nanocrystals (CNCs) are the most commonly used natural polymers for biomaterial synthesis. However, their low dispersibility, conductivity, and poor compatibility with the hydrophobic matrix hinder their potential applications. Therefore, we grafted sulfate half-ester and carboxylic functional groups onto CNC surfaces (S-CNC and C-CNC) to overcome these shortcomings. The effect of the dopants, surfactant ratios, and properties of CNCs on the thermal stability, conductivity, and surface morphology of polyaniline (PANI)-doped CNC nanocomposites were investigated through emulsion and in situ polymerization. The higher electrical conductivity and well-dispersed morphology of SCNC–PANI30 (1.1 × 10−2 S cm−1) but lower thermal stability than that of CCNC–PANI30 (T0: 189 °C) nanocomposites are highly related to dispersibility of S-CNCs. However, after 4-dodecylbenzenesulfonic acid (DBSA) was added, the conductivity and thermal stability of SCNC/PANI increased up to 2.5 × 10−1 S cm−1 and 192 °C with almost no particle aggregation because of the increase in charge dispersion. The proposed biodegradable, renewable, and surface-modified S-CNC and C-CNC can be used in high-thermal-stability applications such as food packaging, optical films, reinforcement fillers, flexible semiconductors, and electromagnetic materials.
Highlights
Cellulose nanocrystals (CNCs) have attracted considerable attention worldwide because of their high surface area, hydroxyl group-rich structure, nontoxicity, and high mechanical strength.[1,2] Owing to their unique characteristics, CNCs are highly coveted for processes such as surface modi cation, drug delivery, lm packaging, and pH detection.[3,4,5,6] The dispersibility, thermal stability, and electrical conductivity of CNCs depend on surface charges, which prevent CNC aggregation in aqueous mediums due to electrostatic interaction.[7]
An additional peak at 1719 cmÀ1 occurred in the spectra of carboxylic group on cellulose nanocrystals (C-CNC) and CP30, which indicated that the hydroxyl groups of cellulose were converted into carboxyl groups on C-CNC surfaces during ammonium persulfate (APS) oxidation.[42]
CNCs dispersibility were successfully increased by gra ing sulfate half-ester and carboxylic groups
Summary
Lower thermal stability, dispersibility, and conductivity than CCNC. Intrinsically conductive polymers (ICPs) have been investigated for the development of supercapacitors. Carboxylic groups onto cellulose nanocrystal (C-CNC) were prepared by the APS oxidation method.[38] Firstly, 10 g of MCC was added in the reactor with the 1 L 1 M ammonium persulfate solution. The DBSA–SCNC–PANI (DSP) nanocomposites were prepared by adding DBSA via emulsion polymerization as shown in Fig. S6.† 39 The mixture of S-CNC 0.94 g and water 74.6 mL was sonicated for 10 min in an ice bath to obtain the semi-transparent suspended liquid of nanocrystal cellulose. The centrifugation of suspension was done by centrifuging (Hermle Z383K, Tomy GRX-220) at 8000 rpm for 30 min to remove the by-product followed by the dialysis against deionized water, and the suspension was sonicated in an ice bath for 5 min to produce a well dispersed and homogenous of DSP. The imaging of S-CNC and C-CNC were monitored by FieldEmission Scanning Electron Microscope (JEOL JSM-6330F), which provides higher magni cation, higher resolution imaging, and lower potential risk of sample damage due to the fact of narrow electron beam with high electron energy
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