The fusion of ethylene oxide polymers |
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Authors: | A Bartolotta G Di Marco M Lanza G Carini |
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Institution: | (1) Contrada Papardo, ITS del CNR, Salita Sperone 31, 98166 S. Agata (Messina), Italy;(2) Dipartimento di Fisica dell’Università Contrada Papardo, Salita Sperone 31, 98166 S. Agata (Messina), Italy |
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Abstract: | Summary Calorimetric measurements by DSC technique have been made in pure polyethylene glycol (PEG) and oxide (PEO) polymers having
a very wide molecular-weight range (from 600 to 4000 000) and in PEO (MW 600 000)-NaSCN complexes. It was found that the melting
temperature increases with increasing molecular weight, ranging from 293 K in the polymer with MW=600 to 340 K in that with
MW=4000 000. The behaviour of the heats of fusion with increasing molecular weight reflects the trend expected in systems,
in which the increase of the main chain length produces a relevant growth of the degree of crystallinity. A distinct maximum
of the heat of fusion has been found at about MW=10000, this result being an evidence of the high amount of crystalline regions
building up the structure of that system. The dependence of the melting temperature on molecular weight has been nicely accounted
for by using the expression of Flory, deduced from the statistical theory of polymers having the most probable molecular-weight
distribution. The addition of sodium thiocyanate to PEO modifies the morphology of the host polymer and, for salt concentrations
higher than 0.03 molar fraction, gives rise to the formation of a PEO-salt crystalline complex characterized by a high melting
temperature.
Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994. |
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Keywords: | Polymers elastomers and plastics |
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