Synthesis, characterization and hydrophobicity of silylated starch nanocrystal.

Starch nanocrystal (SNC) was silylated by hexadecyltrimethoxysilane (HDS) aiming to improve its hydrophobicity. HDS was firstly hydrolyzed in ethanol/water and then adsorbed onto SNC through hydrogen bonds, finally the long chain hydrocarbon was covalently linked to the surface of SNC through SiOC bonds which formed via the condensation reaction between hydroxyl and silanol groups. Due to the multilayer coverage of the hydrolyzed HDS, the long chain hydrocarbon crystalized on the surface of SNC and superimposed over the original A-type starch diffraction pattern. Both the hydrophobicity and hydrophobic stability were increased with the increase of the applied HDS. The contact angle of modified SNC increased from 43° to 119° as the applied HDS increased from 0% to 0.3% (v/v). The modification significantly improved its dispersibility in non-polar solvents and a homogenous suspension could be formed in acetone and n-hexane.