Cellulosic blends with poly(acrylonitrile): Characterization of hydrogen bonds using regioselectively methylated cellulose derivatives

Hydrogen bonds in cellulosic blends with poly(acrylonitrile) (PAN) were characterized in terms of hydroxyl regiochemistry in the cellulosics using Fourier transform infra-red (FTi.r.) spectroscopy. Regioselectively substituted O-methylcelluloses (MC), 2,3-di-O-methylcellulose (23MC) and 6-O-methylcellulose (6MC), were used as cellulosic model components. Wide-angle X-ray diffraction studies of the cast films of blends having more than 50 wt% cellulosic content showed them to be highly amorphous, indicating the presence of a certain interaction between the cellulosics and PAN. FTi.r. analysis revealed that the hydrogen bonds in cast films washed with solvents were only engaged between the primary hydroxyl groups (OH) at the C-6 position of cellulose and the nitrile group (CN) of the PAN molecule, while there was no evidence for polymer-polymer interactions in the secondary hydroxyl groups at the C-2 and C-3 positions in cellulosics or in the ether oxygens such as ring oxygen (O-5) and glucosidic linkage oxygen. In contrast, the remaining DMAc after film cast seems to have an additional interaction to connect the two polymer components, which makes the blends more miscible. Quantitative analysis was also carried out to ascertain the amounts of OH at the C-6 position engaged in the intermolecular hydrogen bonds.