Glycerol, molecular motions

In later studies, the effectiveness of glycerol in promoting molecular motion was compared with that of dimethylsulfoxide and water. It was found that, although all three promote ordering in cellulose, water was definitely the most effective. 

The Tx -values for the side chains of DPL in deuterochloroform or sonicated DPL in deuterium oxide buffer were found to increase from the central glycerol moiety toward both the ends of the fatty acid chains and the trimethyl quaternary ammonium group of the choline (Metcalfe et al., 1971). This means that molecular motion becomes more restricted in moving from a methylene further from the glycerol skeleton to one that is closer to this backbone. Additionally, the 13C nmr spectrum of human erythrocyte membranes (10% w/w) in D20 buffer at 28° was also obtained (Metcalfe et al., 1.971). 

This is the temperature below which an amorphous rubbery polymer becomes brittle. These changes are completely reversible and depend on the molecular motion within the polymer chain. In the rubbery state of polymer melt, the chains are in rapid rotational motion (many rotations per second), but as the temperature is lowered, this movement is slowed down until it eventually stops and the polymer behaves like a frozen liquid with a completely random structure. Although the value of Tg is useful when considering polymers, any glass-forming liquid will have a similar transition, e.g. TgS for quartz 1200 °C, B2O3 250 °C, sulphur 75 °C, polyphosphoric acid — 10 °C, glycerol — 90 °C, toluene — 170°C. 

The protein/glycerol/water/Cloisite Na (treated) sample also showed a single Tg at 118.0 °C, 5.5 °C higher than observed in the untreated nanocomposite, due to the further restriction in molecular motion of the protein by the predominantly exfoliated dispersion of the nano-clay. The secondary (or (3) relaxation in the neat protein/glycerol/water/Cloisite Na (untreated) sample was situated at... 

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