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Probing cellulose wettability by electron paramagnetic resonance

Ionita G., Ghica C., Ionita P.

Materials Science Poland

2007

Vol. 25, No. 4

1011--1017

Carboxymethyl-cellulose has been labelled with a stable free radical by reaction with 4-aminotempo in the presence of a coupling agent (EEDQ). The spin-labelled cellulose is highly stable, no leaking being noticed after months at room temperature. EPR spectroscopy was used as a main tool to study the wettability of such a material. The EPR spectrum of the dry spin-labelled cellulose shows the expected anisotropy, while addition of several solvents (acetone, ethyl acetate, DCM, methanol, toluene, PEG 200) induces the splitting of the spectrum into a two component system. Thus, the EPR spectrum is composed of a mobile component superimposed onto an immobilized one. Addition of water leads to a monocomponent isotropic spectrum. These data clearly indicate the presence of two types of sites to which the spin-label is attached. Variable temperature EPR spectra showed that an increase of temperature results in an increase in the mobility of the spin-label. Deposition of plain or spin-labelled gold nanoparticles on the cellulose fibres also affects the structure of the polymeric chain, as seen by changes in the EPR spectra.

Synthesis Based on 9-Amino-N-picrylcarbazyl

Ionita G., Caproiu M., Meghea A., Maior O., Rovinaru M., Ionita P.

Polish Journal of Chemistry

1999

vol. 73 nr 7

1177-1183

Starting from 9-amino-N-picrylcarbazole, the nitro-, cyano-, bromo- and dibromo-derivatives of the title compound, and the corresponding free radicals, were synthesized. The pK values and the redox properties of the compounds synthesized were reported.