Poly(L-lactic acid)Montmorillonite (MMT)CrystallizationFTIRTwo-dimensional correlation spectroscopyPerturbation-correlation moving windowDifference spectraVariable temperaturePOLY(L-LACTIC ACID)COLD CRYSTALLIZATIONSILICATE NANOCOMPOSITESPOLY(LACTIC ACID)THERMAL-BEHAVIORPOLYMORPHISMMORPHOLOGYKINETICSNANOCLAYBARRIER