A synchrotron SAXS study of PLLA crystallized at different temperatures: One-dimensional correlation functions

Time-resolved variable-temperature synchrotron techniques have been employed for learning about semicrystalline structure and morphology of an L-rich (4.2 mol% in D-isomer) poly(lactic acid), PLLA. An amorphous specimen has been isothermally crystallized from the glassy state at different temperatures, aiming to gain knowledge about development of the two polymorphs, α′ and α. Subsequent melting of these cold crystallized samples has been analyzed by DSC and synchrotron techniques. Besides studying Lorentz-corrected SAXS profiles, one-dimensional correlation functions have been determined for two crystallization temperatures, selected for yielding neat α′ and α polymorphs respectively. Long spacing, crystal thickness and local crystallinity have been determined. Results show a clear discontinuity with temperature of some of these parameters when transition from disordered α′ to more ordered α modification occurs. Additionally, a SAXS-determined glass transition has been obtained and compared with that derived from the corresponding DSC results.Grant PID2020-114930GB-I00 was funded by MCIN/AEI/10.13039/ 501100011033. Authors acknowledge this support together with that received from ALBA Synchrotron Light Facility. Grant BES-2017-082284 was also funded by MCIN/AEI/10.13039/501100011033 and, thus, TMDR is also thankful for her pre-doctoral funding. The synchrotron experiments were carried out in the beamline BL11-NCD-SWEET at ALBA Synchrotron Light Facility with the collaboration of ALBA staf