ISSN:
0360-6376
Keywords:
Physics
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Spin-lattice relaxation times and nuclear Overhauser enhancements (NOE) for 13C nuclei in copolymers of acrylonitrile and vinylidene chloride were measured at 20.1 and 67.9 MHz. In the —CCl2— region of the spectrum T1 and NOE values of the various resonances are equal within experimental error and are invariant to changes in composition. The T1 and NOE values of the —CCl2— region, however, are not equal to those of the —CH— or —CN region. As a result compositions cannot be calculated by direct comparison of the areas in the —CCl2— region and either the —CH— or the —CN region. Discrepancies can be corrected for the —CH— resonances by multiplication of the area by an empirical constant. A similar constant for the —CN region is composition-dependent at 20.1 and 67.9 MHz. A chemical shift anisotropy mechanism is postulated as important for relaxation of the —CN resonances. The overall influence of variable T1 and NOE values on quantitative determination of polymer composition is considered.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1982.170200315
