CONICET | Buscador de Institutos y Recursos Humanos

Grafted block copolymers based on ε-caprolactone were obtained through a combination of simultaneous ?grafting through? and ?grafting from? methods in a one-pot radical addition fragmentation transfer (RAFT) and ring opening polymerization (ROP) reaction afforded P(HEMA-co-HEMA-g-PCL)-b-PCL comb-like copolymers. Synthesized copolymers were characterized by Size exclusion chromatography, Fourier transform infrared spectroscopy and Thermogravimetric analysis. The isothermal crystallization kinetics of grafted block copolymers was performed by differential scanning calorimetry (DSC) at different crystallization temperatures. Thus, samples were heated from15 to 90 °C at 10 °C min-1 and was rapidly cooled (60 °C min-1) to the selected crystallization temperatures for the PCL block. Isothermal crystallization experiments were carried out for temperatures between 16 and 24 °C, by using steps of 2 °C, Figure 1. The analysis based on the Avrami theory, was applied to describe the process of isothermal crystallization, in order to obtain kinetics parameters of interest, such as the half-life for the crystallization process (t1/2), the bulk crystallization constant (k), and the Avrami?s exponent (n). The chemical nature of the grafted copolymers affected the kinetics parameters of Avrami?s equation, as can be deduced by comparing the values obtained for a linear poly(ε-caprolactone),PCL. Avrami?s exponent values obtained were in the range of 1.7?2.8, indicating that PCL block in the copolymers crystallizes in two dimensions (disk and cylindrical). Besides, the Avrami theory, indicated that the spherulite growth rate, overall crystallization rate, and activation energy (Ea) of copolymers were affected by the length of PCL branches. On the other hand, the obtained copolymers showed the thermal degradation events associated to PCL and PHEMA homopolymers. However, for copolymers, a reduction in the maximum degradation temperature was observed.

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