Model films of cellulose: I. Method development and initial results

This report presents a new method for the preparation of thin cellulosefilms. NMMO (N-methylmorpholine-N-oxide) was used to dissolve cellulose andaddition of DMSO (dimethyl sulfoxide) was used to control viscosity of thecellulose solution. A thin layer of the cellulose solution is spin-coated ontoasilicon oxide wafer and the cellulose is precipitated in deionised water. Thecellulose film is anchored onto the silicon oxide wafer by a saturated polymerlayer. Among many different polymers tested, PVAm (polyvinylamine) and G-PAM(glyoxalated-polyacrylamide) worked well. The preparation of cellulose modelfilms described in this paper resulted in films with thicknesses in the range20–270 nm and the thickness can be controlled by alteringtheconcentration of cellulose solution by addition of different amounts of DMSO.The films were cleaned in deionised water and were found to be free fromsolvents by ESCA analysis and contact angle measurements. The molecular weightdistribution of the cellulose surface material shows that there is only minorbreakdown of the cellulose chains, mainly by cleavage of the longest molecularmass fraction and without creation of low molecular mass oligomers of glucose.