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Real-Time Monitoring of Molecular Dynamics of Ethylene Glycol Dimethacrylate Glass Former

2009; American Chemical Society; Volume: 113; Issue: 43 Linguagem: Inglês

10.1021/jp903212g

1520-6106

María Teresa Viciosa, Natália T. Correia, Manuel Salmerón‐Sánchez, Ana Luı́sa Carvalho, Maria João Romão, José Luís Gómez Ribelles, Madalena Dionı́sio,

Liquid Crystal Research Advancements

The isothermal cold-crystallization of the glass-former low-molecular-weight compound, ethylene glycol dimethacrylate (EGDMA), was monitored by real-time dielectric relaxation spectroscopy (DRS) and differential scanning calorimetry (DSC). The α-relaxation associated with the dynamic glass transition as detected by DRS was followed at different crystallization temperatures, Tcr, nearly above the glass transition temperature, 176 K (1.06 ≤ Tcr/Tg ≤ 1.12). It was found that the α-process depletes upon cold-crystallization with no significant changes in either shape or location. At advanced crystallization states, a new relaxation, α′-process, evolves that was assigned to the mobility of molecules lying adjacent to crystalline surfaces. From the time evolution of the normalized permittivity, it was possible to get kinetic information that was complemented with the calorimetric data. From DSC measurements that were also carried out under melt-crystallization, an enlarged temperature range was covered (up to Tcr/Tg = 1.24), allowing us to draw a diagram of time−temperature crystallization for this system. Dielectric relaxation spectroscopy proved to be a sensitive tool to probe the mobility in the remaining amorphous regions even at high crystallinities.