TEMPO-oxidized cellulose nanofibrils (TOCNs) are expected to be new and bio-based nanomaterials because of their unique properties such as high elastic moduli and high aspect ratios. It is sometimes necessary to improve nano-dispersibility of hydrophilic TOCNs directly in melted polymers or organic solvents dissolving polymers used as matrices of nano-composites. This study aims to provide nano-dispersibility of TOCNs in organic solvents by modifications of sodium carboxylate groups abundantly present on the TOCN surfaces. Sodium carboxylate groups of TOCNs were converted to free carboxyls (TOCN-COOH), N-acylureas (TOCN-N-acylureas) and carboxyl/amine salts (TOCN-COOH/amine salts). Conversion ratios of carboxyl groups to N-acylureas are approximately 80 and 60%, when N,N'-diisopropylcarbodiimide and N,N'-dicyclohexylcarbodiimide, respectively, of 5 mol per mole of carboxyl groups were used as the reagents. TOCN/amine-salts were prepared by introducing primary aliphatic amines to most of (>95%) carboxyl groups densely present on the TOCN surfaces via carboxyl/amine salt formation. The TOCN-COOH and TOCN-N-acylureas became nano-dispersible in DMF or other polar aprotic solvents with high boiling points. On the other hand, the TOCN-COOH/amine salts were nano-dispersible in isopropyl alcohol (IPA).

Modification of sodium carboxylate groups on TEMPO-oxidized cellulose nanofibril surfaces

243rd National Meeting (2012)

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