Crystallization of star-shaped and linear poly (l-lactide)s

Bojda, J., Piorkowska, E., Lapienis, G., & Michalski, A.

European Polymer Journal 105 (2018): 126-134.

Three star-shaped poly(ʟ-lactide)s (PLLAs) were synthesized, two 6-arm with Mw of 120 and 245 kg/mol and one 4-arm with Mw of 123 kg/mol. Linear PLLAs with Mw of 121 and 339 kg/mol were also prepared. Crystallization, both isothermal and nonisothermal, of all PLLAs was studied by means of DSC. The growth rate of spherulites was measured in a broad range of crystallization temperature using PLM. At Mw close to 120 kg/mol the star architecture slowed down the spherulite growth above 120 °C, up to 145 °C. The spherulite growth in PLLAs with Mw> 200 kg/mol was slower than that in the other polymers and unaffected by the macromolecule architecture. The differences in the spherulite growth rate were reflected in overall crystallization kinetics in isothermal conditions and also in crystallization peak temperature and crystallinity developed during cooling. The highest crystallinity developed during isothermal crystallization in linear and 6-arm PLLAs with Mw close to 120 kg/mol, whereas the lowest in PLLAs with Mw > 200 kg/mol. For Mw > 200 kg/mol the star architecture decreased the melting temperature. The glass transition temperature of all PLLAs was the same, at 61–62 °C, regardless of Mw and macromolecule architecture.gtrcfrvvvg


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