Condensation Of Hydroxyl Groups Research Articles

States of water associated with electrodeposited manganese dioxide as revealed by pyknometric density measurements

The densities of different states of water associated with an electrodeposited manganese dioxide have been estimated from the original density of the manganese dioxide, the weight of water removed by outgassing and the outgassed density. Outgassing at room temperature removed water which in the associated state had the density of normal water. This water resided in the second and outer physisorbed layers and required two days' outgassing for complete removal. Temperatures of 60–120°C were necessary to remove further water which in the associated state had a density of about 1.25 g cm −3. This water is considered to be ordered or structured and in its amount corresponded to a monolayer. After removal this ordered layer required several days of immersion in water to reform. Outgassing at 170–250°C caused condensation of hydroxyl groups, and products resulting from such treatments reacted slowly with water on immersion.

Investigation of the conversions of polyorganosiloxanes in the process of thermal polycondensation and catalytic polymerization

1. The structural difference of the oligomers produced by the reaction of exchange decomposition and hydrolytic polycondensation was confirmed by the method of IR spectroscopy. In the process of thermal and catalytic transformations, these differences are smoothed out, and the polymers are close in structure, independent of the method of production of the original oligomers. 2. It was hypothesized that thermal polycondensation takes place with the formation of oxygen bridges among the molecular chains on account of condensation of hydroxyl groups and hydrocarbon bridges as a result of the oxidation of the methyl groups of the neighboring molecular chains; the ratio between these two processes is determined by the composition and structure of the oligomers. 3. Catalytic polymerization, in comparison with thermal polycondensation, leads to the formation of polymers with a lower vitrification point and a broader temperature region of the highly elastic state, which is due to the greater flexibility and mobility of their molecular chains on account of the opening of the cyclic units of the oligomer molecules.