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Study of the Effect of Grafting Method on Surface Polarity of Tempo-Oxidized Nanocellulose Using Polycaprolactone as the Modifying Compound: Esterification versus Click-Chemistry

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ABSTRACT

Esterification and click-chemistry were evaluated as surface modification treatments for TEMPO-oxidized nanocelluloses (TONC) using Polycaprolactone-diol (PCL) as modifying compound in order to improve the dispersion of nanofibers in organic media. These two grafting strategies were analyzed and compared. The first consists of grafting directly the PCL onto TONC, and was carried out by esterification between hydroxyl groups of PCL and carboxyl groups of TONC. The second strategy known as click-chemistry is based on the 1,3-dipolar cycloaddition reaction between azides and alkyne terminated moieties to form the triazole ring between PCL and TONC. The grafted samples were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Thermogravimetry analysis (TGA). Further, the effects of the two treatments on the surface hydrophobization of TONC were investigated by contact angle measurements. The results show that both methods confirm the success of such a modification and the click reaction was significantly more effective than esterification.

No MeSH data available.


Profiles of water contact angles on TONC-g-PCL via esterification and TONC-g-PCL via click-chemistry 25 s after drop deposition.
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nanomaterials-03-00638-f011: Profiles of water contact angles on TONC-g-PCL via esterification and TONC-g-PCL via click-chemistry 25 s after drop deposition.

Mentions: To verify the polarity of TONC-g-PCL, we further characterized our samples using contact angle (CA) measurements which allow the estimation of the change in the hydrophobicity of the TONC-g-PCL compared to unmodified TONC. While the water droplet was rapidly adsorbed on the surface of (TONC-g-PCL)ester, the initial shape of the water droplet remained unchanged for a much longer period of time in the case of the (TONC-g-PCL)click (Figure 10). In addition, a significant increase in contact angle values was observed for (TONC-g-PCL)click (CA~75°) compared to (TONC-g-PCL)ester (CA~43°) (Figure 11), which show clearly the more hydrophobic nature of the grafted substrate produced by click chemistry compared to that produced by esterification. The contact angle values obtained for (TONC-g-PCL)click is in agreement with those found in the literature [40,41]. The highest contact angle value observed for (TONC-g-PCL)click is ascribed to the highest grafting efficiency, thanks to the intercalation of a spacer molecule, that moves away the reactive functions from the surface of TONC and, consequently, makes them more accessible for further grafting with high molecular weight grafts.


Study of the Effect of Grafting Method on Surface Polarity of Tempo-Oxidized Nanocellulose Using Polycaprolactone as the Modifying Compound: Esterification versus Click-Chemistry
Profiles of water contact angles on TONC-g-PCL via esterification and TONC-g-PCL via click-chemistry 25 s after drop deposition.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5304593&req=5

nanomaterials-03-00638-f011: Profiles of water contact angles on TONC-g-PCL via esterification and TONC-g-PCL via click-chemistry 25 s after drop deposition.
Mentions: To verify the polarity of TONC-g-PCL, we further characterized our samples using contact angle (CA) measurements which allow the estimation of the change in the hydrophobicity of the TONC-g-PCL compared to unmodified TONC. While the water droplet was rapidly adsorbed on the surface of (TONC-g-PCL)ester, the initial shape of the water droplet remained unchanged for a much longer period of time in the case of the (TONC-g-PCL)click (Figure 10). In addition, a significant increase in contact angle values was observed for (TONC-g-PCL)click (CA~75°) compared to (TONC-g-PCL)ester (CA~43°) (Figure 11), which show clearly the more hydrophobic nature of the grafted substrate produced by click chemistry compared to that produced by esterification. The contact angle values obtained for (TONC-g-PCL)click is in agreement with those found in the literature [40,41]. The highest contact angle value observed for (TONC-g-PCL)click is ascribed to the highest grafting efficiency, thanks to the intercalation of a spacer molecule, that moves away the reactive functions from the surface of TONC and, consequently, makes them more accessible for further grafting with high molecular weight grafts.

View Article: PubMed Central - PubMed

ABSTRACT

Esterification and click-chemistry were evaluated as surface modification treatments for TEMPO-oxidized nanocelluloses (TONC) using Polycaprolactone-diol (PCL) as modifying compound in order to improve the dispersion of nanofibers in organic media. These two grafting strategies were analyzed and compared. The first consists of grafting directly the PCL onto TONC, and was carried out by esterification between hydroxyl groups of PCL and carboxyl groups of TONC. The second strategy known as click-chemistry is based on the 1,3-dipolar cycloaddition reaction between azides and alkyne terminated moieties to form the triazole ring between PCL and TONC. The grafted samples were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Thermogravimetry analysis (TGA). Further, the effects of the two treatments on the surface hydrophobization of TONC were investigated by contact angle measurements. The results show that both methods confirm the success of such a modification and the click reaction was significantly more effective than esterification.

No MeSH data available.