The influence of versatile thiol-norbornene modifications to cellulose nanofibers on rheology and film properties

Kendra Fein; Douglas W Bousfield; William M Gramlich

doi:10.1016/j.carbpol.2019.115672

The influence of versatile thiol-norbornene modifications to cellulose nanofibers on rheology and film properties

Carbohydr Polym. 2020 Feb 15:230:115672. doi: 10.1016/j.carbpol.2019.115672. Epub 2019 Nov 30.

Authors

Kendra Fein¹, Douglas W Bousfield¹, William M Gramlich²

Affiliations

¹ Paper Surface Science Program, University of Maine, Orono, ME 04469, United States; Department of Chemical and Biomedical Engineering, University of Maine, Orono, ME 04469, United States.
² Paper Surface Science Program, University of Maine, Orono, ME 04469, United States; Department of Chemistry, University of Maine, Orono, ME 04469, United States. Electronic address: william.gramlich@maine.edu.

PMID: 31887920
DOI: 10.1016/j.carbpol.2019.115672

Abstract

Cellulose nanofibrils (CNF) can form impressive barrier layers but difficult rheological properties, brittleness, and sensitivity to moisture limit their use. To overcome these challenges, esterification reactions were performed in water without volatile organic solvents to create carbic-functionalized CNFs (cCNFs) that enabled versatile, thiol-norbornene secondary modifications. Chemical analysis determined that on average 5% anhydroglucose repeat units were functionalized with norbornene groups. Thiol-norbornene reactions added molecules with varying polar surface areas to the CNFs. Modifications did not change the film properties to a large extent. All CNF films were excellent grease barriers. The modifications significantly changed the rheology of CNF suspensions as the complex viscosity of the modified CNF was 27 times lower than unmodified CNFs. Modification also reduced the filtration rate by a factor of four. Surface modifications appeared to alter the colloidal forces between fibers in suspension that influence the flow and drainage properties.

Keywords: CNF films; Cellulose nanofibrils; Suspension rheology; Thiol-norbornene reactions; Water-based chemistry.