Miscibility in poly(L-lactide)-b-poly(epsilon-caprolactone) double crystalline diblock copolymers

Area of Science:

• Polymer Science
• Materials Science
• Physical Chemistry

Background:

• Poly(L-lactide)-b-poly(epsilon-caprolactone) diblock copolymers are semicrystalline materials with complex phase behavior.
• Understanding their miscibility and segmental dynamics is crucial for tailoring material properties.

Purpose of the Study:

• To investigate the miscibility and segmental dynamics of poly(L-lactide)-b-poly(epsilon-caprolactone) diblock copolymers across a wide composition range.
• To correlate thermal properties, morphology, and molecular mobility.

Main Methods:

• Thermally stimulated depolarization currents (TSDC) for dielectric relaxations.
• Wide-angle X-ray scattering (WAXS) for structural analysis.
• Differential scanning calorimetry (DSC) for thermal transitions.
• Polarized light optical microscopy (PLOM) for morphology visualization.

Main Results:

• Miscibility in the amorphous phase was determined through primary relaxations (glass transitions) and morphology.
• Distinct segmental mobilities were observed, with the alpha relaxation of poly(L-lactide) shifting to lower temperatures as poly(epsilon-caprolactone) content increased.
• A bimodal distribution of relaxation times was evident in poly(epsilon-caprolactone)-rich copolymers.

Conclusions:

• The self-concentration model accurately predicts the composition dependence of multiple glass transitions in these weakly segregated copolymers.
• The study provides insights into the relationship between composition, morphology, and molecular dynamics in block copolymers.