Liquid Crystalline Poly(ester amide)s Based on N,N‘-Dimethyldiamines and an Aromatic Ester Triad
| Autor: | S. Curran, T. F. Mccarthy, Simon W. Kantor, R. W. Lenz |
|---|---|
| Rok vydání: | 1997 |
| Předmět: |
chemistry.chemical_classification
Materials science Polymers and Plastics Organic Chemistry Nuclear magnetic resonance spectroscopy Polymer Thermotropic crystal Inorganic Chemistry chemistry.chemical_compound Crystallography Differential scanning calorimetry chemistry Liquid crystal Amide Materials Chemistry Magic angle spinning Melting point Organic chemistry sense organs |
| Zdroj: | Macromolecules. 30:2825-2838 |
| ISSN: | 1520-5835 0024-9297 |
| DOI: | 10.1021/ma960421u |
| Popis: | A series of thermotropic liquid crystalline poly(ester amide)s was synthesized based on various N,N'-dimethylalkylenediamines and terephthaloyl bis(4-oxybenzoyl chloride), TBOC. Several different synthetic procedures were investigated to synthesize liquid crystalline (LC) polymers having a broad range of molecular weights. The highest molecular weight polymers were obtained by the low-temperature solution condensation of N,N'-bis(trimethylsilyl)diamines and TBOC. Analyses of the polymers by wide angle X-ray diffraction, differential scanning calorimetry, and polarizing optical microscopy showed that the as-prepared crystalline polymers melted to form a nematic,liquid crystalline phase, which showed no evidence of recrystallization upon cooling. The LC polyesteramides with a 6-methylene spacer unit exhibited a monotropic behavior in contrast to the polymers or copolymers with a 12-methylene spacer unit which are enantiotropic. Changes in polymer conformation which occurred on heating in the solid state and in the liquid crystalline state were evaluated by solid state 13 C cross polarization magic angle spinning NMR spectroscopy which showed that the polymers had considerable mobility at temperatures well below the crystalline melting point. The polymers, when precipitated from solution, contained mixtures of syn and anti amide units, but after melting, the syn amide unit was exclusively obtained indicating that it is likely the most thermodynamically stable conformation. |
| Databáze: | OpenAIRE |
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