Polymorphism, L-Polylactide - METTLER TOLEDO

Polymorphism, L-Polylactide

SampleL-Polylactide

L-Polylactide

 

Application

Inactive ingredient

 

Conditions

Measuring cellDSC820

Pan: Aluminum 40 µl, hermetically sealed

Sample preparation: As received

DSC measurement: Heating from 30 °C to 300 °C at 10 K/min

Atmosphere: Nitrogen, 50 cm3/min

 

 

 

Interpretation

The form of the DSC curve is typical for substances that undergo transformations in the melt. A separation of the two peaks depends on the crystallization rates of the modifications. In spite of the good peak separation, the measured heat of fusion of the first modification is too low: firstly, because an unknown quantity of the high-melting modification is already present, secondly, because the exothermic crystallization of the high-melting form takes place at the same time as the melting of the first form, and thirdly, because a solid-solid transition can occur. The second peak is usually too small, because the transformation or crystallization is incomplete when heating dynamically. For this reason both heats of fusion are displayed in brackets.

In order to produce the high temperature form, the sample could be annealed at 160 °C in a similar way to that described in application example 33.

 

Evaluation

Several different baseline options have to be applied in order to evaluate the melting peak correctly. For the first peak the type ‘horizontal left’ is used and for the second peak the type ‘horizontal right’.

 Onset, °CΔH, J/g
First peak151.0(24.4)
Second peak168.4(58.9)

 

Conclusion

The example demonstrates that polymers can also exhibit polymorphism.

 

Polymorphism, L-Polylactide | Thermal Analysis Application No. HB830 | Application published in METTLER TOLEDO TA Application Handbook Pharmaceuticals