Molecular Motion in the Biocopolymer Sequence of Glycolide and Lactide Studied by Solid-State NMR

This paper reports a nuclear magnetic resonance study of the molecular motion in copolymers derived from glycolide and L-lactide in the solid state. Variation of T1 relaxation times with temperature reflects a local disorder and the fast segment conformational motions which can be quantified in terms of correlation times predicted by the Bloembergen–Purcell–Pound and Davidson–Cole models. At low temperatures, spin relaxation is dominated by the axial methyl rotation in lactide units described by an asymmetry parameter of the correlation time δ which takes a value of about 0.45 for all systems. Above the devitrification points the trans and gauche isomerization in glycolide segments occurs. In addition to the chemical structure characterization, solid-state magic-angle spinning spectroscopy gives an insight into the role of glycol segments in the chain mobility.