ISSN:
0098-1273
Keywords:
Physics
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Cellulose triacetate (CTA) forms cholesteric mesophases in trifluoroacetic acetic acid (TFA) and mixtures of TFA and CH2Cl2, 1,2-dichloroethane (1,2-DCE), and CHCl3. Cholesteric pitches and solution flow times indicate that the order of solvent powers is TFA-CH2Cl2 〉 TFA-1,2-DCE 〉 TFA 〉 TFA-CHCl3, which is the order of decreasing acidity of the solvent systems. With TFA-CH2Cl2 as solvent, the one-fourth power of the pitch varies inversely with the CTA concentration, and increases linearly with temperature. The pitch increases exponentially with time and increases faster the more acidic the solvent. In a magnetic field a cholesteric to nematic transition occurs. A minimum in solution viscosity occurs at 34% w/v of CH2Cl2 for solutions in TFA-CH2Cl2. The miscibility gap as a function of molecular weight depends on the solvent composition and is smaller the higher the acidity of the solvent. Agreement between the experimentally observed A and B points and the theoretical points is better for the Khokhlov and Semenov theory for semiflexible chains than for the original Flory theory or the Flory-Ronca modification.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1983.180210708
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