Abstract: The relaxation character and glass transition temperature of crystalline poly (methyl methacrylate)(PMMA) have been studied by means of NMR and DSC techniques. Compared with amorphous PMMA, the ¹³C CP/MAS spectra of the crystalline one has similar band shape, band width and chemical shifts. α-CH₃ carbon resonance exhibits two bands with a very asymmetrical shape, which may be related to conformational structure in sequence of the so-called γ-gauche effect. The two values of the proton spin-lattice relaxation time in rotating frame T_1ρ (H) observed correspond to amorphous and crystaline structure respectively dectected by inverse gated decoupling. Aggregated structure wasn't detected by NMR means.

Key words: NMR relaxation time, DSC, Glass transition temperature, Crystalline PMMA