Preparation of different polymorphs of cellulose from different acid hydrolysis medium.

In this study, medical cotton was subjected to acid hydrolysis in sulfuric, hydrochloric and phosphoric acid medium to prepare cellulose nanocrystals (CNC) with different morphologies and polymorphism. Morphology of the prepared CNC samples revealed fiber shaped morphology for sulfuric and hydrochloric acid hydrolyzed samples, whereas, spherical shaped for phosphoric acid hydrolyzed samples. The size of the spherical shaped CNC decreased with the increase of hydrolysis time, from 853 nm for 12 h to 187 nm for 48 h. X-ray Diffraction analysis showed that hydrochloric acid hydrolyzed CNC is cellulose I (CI), phosphoric acid hydrolyzed CNC is cellulose II (CII) and sulfuric acid hydrolyzed CNC contain both CI and CII. The crystallinity of sulfuric and hydrochloric acid hydrolysis samples was 91%, whereas, the crystallinity of phosphoric acid hydrolysis samples was between 43 and 60% depending on hydrolysis time. Thermal properties were also affected by the hydrolysis medium. Thus cellulose nanocrystals were prepared with different morphologies and physical characteristics through a facile method.

Activation energy of aggregation-disaggregation self-oscillation of polymer chain.

In this paper, we investigated the activation energies of the aggregation−disaggregation self-oscillation induced by the Belousov-Zhabotinsky (BZ) reaction by utilizing the nonthermoresponsive polymer chain in a wide temperature range. This is because the conventional type self-oscillating polymer chain, with thermoresponsive poly(Nisopropylacrylamide) (poly(NIPAAm) main-chain covalently bonded to the ruthenium catalyst (Ru(bpy)(3)) of the BZ reaction, cannot evaluate the activation energy over the lower critical solution temperature (LCST). The nonthermoresponsive self-oscillating polymer chain is composed of a poly-vinylpyrrolidone (PVP) main-chain with the ruthenium catalyst (Ru(bpy)(3)). As a result, we clarified that the activation energy of the aggregation−disaggregation self-oscillation of the polymer chain is hardly affected by the concentrations of the BZ substrates. In addition, the activation energy of the nonthermoresponsive self-oscillating polymer chain was found to be almost the same value as normal BZ reaction, i.e., not including the self-oscillating polymer system with Ru moiety.