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Abstract
This study attempts to clarify thermodynamic quantification on interaction between poly(vinyl alcohol) (PVA) and wood-derived cellulose nanofibrils (CNFs) obtained by aqueous counter collision (ACC) method. Aqueous mixtures of PVA/ACC-CNFs with various fiber widths were cast as the target materials. The interfacial interactions between the two components were characterized through thermodynamic evaluation of the crystalline PVA component as a probe in the cast mixture. As the result, surface properties of the ACC-CNFs found to reflect on the crystallization behavior of the interacted PVA component, resulting in dual nano-size effects of either diluent or nucleating agent. Melting point depression behaviors of the PVA component indicated that ACC-CNFs with thinner widths induced nucleation effects on PVA crystallization, whereas ACC-CNFs with ca. 100 nm in width encouraged diluent effects on PVA components. It is noted that this trend found to be reverse to the case for PVA/ACC-CNFs of bacterial nanocellulose previously reported.
Highlights
The present results have shown that the aqueous counter collision (ACC)-cellulose nanofibrils (CNFs) surface has a dual nano-size effect on poly(vinyl alcohol) (PVA) crystallization, but the reversal trend to ACC-bacterial CNFs reported previously [37]
ACC‐CNFs with different nanoscale widths The starting micro-sized wood-derived microcrystalline cellulose (MCC) samples were fractured into various nano-objects, depending on the ACC ejection pressure, which regulates collision energy to selectively cleave non-covalent bond in the microfibril under the purpose to control the width-size at the nanoscale
Three types of CNFs with different widths were successfully prepared from microcrystalline cellulose by ACC treatments and subsequent centrifugation, without any chemical reaction
Summary
In the last two decades, nanocellulose, which is in general categorized into cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs), of width less than 50 nm and with an aspect ratio greater than 100, have attracted increasing attention in both basic and applied fields, e.g., in composites [1,2,3,4,5,6], paper and board [7], medicine [8], coatings [9,10,11], aerogels [12, 13], filtration [14], electronics [15], and rheological modifiers [16]. Macrofibers are fabricated by van der Waals interactions between the water-hating faces [= (200) crystalline plane] of the glucan sheets. Destruction and disruption of the weaker van der Waals forces in microfibers produced by ACC expose the inherent water-hating faces on the resulting nanosized cellulose surfaces (see Fig. 1). In this way, the ACC process creates “amphiphilic CNFs with a Janus-type surface” having both hydrophobic and hydrophilic planes in a single nanofiber (ACC-CNF: see Fig. 1), and this enables their use to further extend towards surface modifiers, surfactants, emulsifiers, and dispersers [25, 30, 31]
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