ISSN:
0025-116X
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Isotactic and syndiotactic poly(alkyl methacrylate)s (R = CH3, C2H5, isoC3H7, n-C4H9 and t-C4H9) were prepared by anionic mechanism and the spin-lattice relaxation times T1 of individual carbons and protons were measured mainly in toluene-d8 by the inversion-recovery Fourier transform (IRFT) method. The T1's of the carbons in the isotactic polymers were consistently longer than those of the comparable carbons in the syndiotactic polymers. The ratios of 13C-T1's for syndiotactic and isotactic polymers were always in the range of ca. 0,4-0,6 for all types of carbons. The 13C-T1's decreased with an increase in the bulkiness of the ester group in both polymers. From the measurements of the nuclear Overhauser enhancement (NOE) it was found that the spin-lattice relaxations of carbons in polymethacrylates are dominated by 13C-1H dipolar interactions and that the extreme narrowing condition is satisfied at least above 70°C. The effect of solvent on 13C-T1 was also studied. The results of the measurements of 1H-T1's were parallel to those in the carbons' case. It was concluded that the dependence of T1 upon the configuration of the polymer is mainly caused by the configurational dependence of the segmental mobility of the polymer.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/macp.1978.021790223
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