NMR study of liquid crystalline polymer curing in magnetic field

Gur’eva, L. L.; Tarasov, V. P.; Ermolaev, K. V.; Erofeev, L. N.; Розенберг, Б. А.

doi:10.1007/bf03164137

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“…When a DGET sample is placed into a magnetic field at a temperature of the LC range (169°C in our particular case), its quick melting occurs and a transition from the wide line corresponding to the solid phase into the narrow one, which is characteristic of liquids, is observed in the NMR spectrum (15). Due to orientation of the DGET molecules in the magnetic field the spectrum line is splitted and progressive narrowing of the doublet line occurs within one minute (Figure la).…”

Section: Formation Of Aligned Structures During Dget Cure In the Magnmentioning

confidence: 99%

Ordered Liquid-Crystalline Thermosets

Розенберг

Gur’eva

1996

ACS Symposium Series

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The paper is an overview of the authors' works on the regularities of formation of ordered networks via the epoxy liquid crystalline thermoset (ELCT) curing in the magnetic field. The changes of order parameter during ELCT cure in the magnetic field are the focus of this work. The result of the preliminary study of the influence of a magnetic field on ELCT cure kinetics is reported. The effect of the magnetic field on the properties of cured ELCT is discussed.Liquid crystalline thermosets (LCT) with a rigid rod-like mesogenic group capped from both ends by reactive functional groups can be used as matrices for production of advanced composites, coatings or adhesives (1, 2). In this case ordering of the chains of the final network polymer is the only way to improve its physical and mechanical properties.Using LCT as a starting material gives an advantage in comparison to the high molar mass linear LC polymers because high degree of orientation can be easily achieved even in comparatively weak magnetic fields (3).One could expect that the process of LCT cure in the LC temperature range under the action of a magnetic field can proceed both with preservation of high initial degree of orientation of LCT and with disordering of the interknot chains of forming network polymer. The understanding of the character of changes of the order parameter for a curing LCT is the key problem of the study.One of the major questions arising in this case was how the evolution of the degree of orientation during cure depended on the method of the network formation (polymerization or poly condensation) and structure of polymer formed.The second problem was that our interests in this study consisted of clearing up the influence of macroscopic ordering under the action of magnetic field of the thermoset molecules on cure kinetics. Only few publications were known, in which the influence of magnetic field on the rate of the LC molecules' reactions were described (4-6). Contradictory results on the influence of magnetic field on the rate of

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Section: Formation Of Aligned Structures During Dget Cure In the Magnmentioning

confidence: 99%