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Orienting Cellulose Nanocrystal Functionalities Tunes the Wettability of Water-Cast Films
Charles Bruel1, Salomé Queffeulou1, Pierre J Carreau1
1Research Center for High Performance Polymer and Composite Systems (CREPEC), Department of Chemical Engineering, Polytechnique Montréal, P.O. Box 6079, Stn Centre-Ville, Montreal, Quebec H3C 3A7, Canada.
Langmuir : the ACS Journal of Surfaces and Colloids
|September 28, 2020
Summary
Cellulose nanocrystal (CNC) wetting varies due to surface functional group orientation. This study reveals how CNC dispersion affects wettability, enabling tailored material properties for diverse applications.
Area of Science:
- Materials Science
- Surface Chemistry
- Nanotechnology
Background:
- Cellulose nanocrystals (CNCs) exhibit unpredictable wetting behavior, with contact angle variations up to 30°.
- The amphiphilic nature of CNCs suggests their orientation at interfaces influences macroscopic properties.
Purpose of the Study:
- To investigate the hypothesis that CNC orientation at the air interface causes variable wetting.
- To develop a method for predicting CNC wettability based on surface chemistry.
Main Methods:
- Application of Hansen solubility parameter theory to define surface tension parameters for CNCs.
- Advancing/receding contact angle measurements on CNC films prepared by spin-coating and oven-casting.
- Analysis of CNC dispersion states (individual vs. agglomerated) at interfaces.
Main Results:
- Proposed surface tension parameters correlate CNC wettability with non-polar surface moieties.
- Spin-coating yields purely polar CNC films, while oven-casting produces amphiphilic surfaces.
- CNC orientation at interfaces is determined by dispersion state: individual CNCs orient non-polar surfaces, while agglomerates orient polar surfaces.
Conclusions:
- Demonstrated the first compelling evidence of CNC orientation at interfaces, explaining wetting variability.
- The findings enable the tuning of CNC material wettability for applications in Pickering emulsions and nanocomposites.
