Pulsed NMR in Linear Aliphatic Polyesters

Abstract

Solid echo NMR measurements were carried out for poly(ethylene sebacate) (2-8), poly(decamethylene 1,16-hexadecanedicarboxylate) (10-16), and chemically degraded 2-8 polyesters. The following results were found: (1) all the samples are composed of three phases: i.e., crystalline, intermediate, and amorphous components; (2) the rand {3relaxations are found in the amorphous component of the 2-8 and 10-16 polyesters, in agreement with earlier conclusions from dielectric measurements; (3) in the {3-relaxation, the chain mobility in the amorphous region and the value of the activation energy increase with increasing ester group concentration in the polyester; but the degree of restriction imposed upon the local mode motion in the amorphous region is greatly influenced not only by the ester group concentration but also by the morphology of the sample; (4) in the chemically degraded 2-8 polyester, the content of the intermediate phase decreases with increasing crystallinity, however, the mobility of this phase is less sensitive to both crystallinity and temperature. KEY WORDS Pulsed NMR I Linear Aliphatic Polyesters I Solid Echo I Poly(ethylene sebacate) I Poly(decamethylene 1,16-hexadecanedicarboxylate) I Chemically Degraded Polyester I Intermediate Component I Chain Mobility I Ester Group Concentration I Morphology I Recently, much attention has been focused on the effects of chemical structure on the morphology of semicrystalline polymers such as polyamides 1 and polyesters. 2 ' 3 It is of interest to investigate the relation between the chemical structure and the relaxation behavior of these crystalline polymers. motion may also be found in the other relaxation mechanisms of the polyesters.