Polymer crystallization dynamics investigated by synchronous scanning spectrum.

Area of Science:

• Materials Science
• Polymer Science
• Spectroscopy

Background:

• Reflected light intensity correlates with a solid surface's refractive index, which is linked to density and concentration fluctuations.
• Changes in internal material structures can be detected through variations in reflected light.
• The Synchronous Scanning Spectrum (SSS) technique leverages these optical principles.

Purpose of the Study:

• To apply the SSS technique for monitoring the melting and nonisothermal melt-crystallization processes of poly(ε-caprolactone) (PCL) films.
• To characterize macromolecular structure evolution during these phase transitions.
• To validate SSS as an effective in situ method for polymer analysis.

Main Methods:

• Utilized a spectrofluorimeter to perform SSS by simultaneously scanning excitation and emission monochromators (Δλ = 0 nm).
• Focused on two dominant peaks (467 and 473 nm) in PCL films to analyze structural changes.
• Obtained thermodynamic and crystallization kinetics parameters, including the Avrami exponent and crystallization activation energy.

Main Results:

• The SSS method successfully monitored melting and nonisothermal melt-crystallization of PCL films.
• The Avrami exponent (n) averaged 3.13, indicating heterogeneous nucleation and 3D spherulitic growth.
• Crystallization activation energy was determined to be -158.2 kJ·mol⁻¹, consistent with Differential Scanning Calorimetry (DSC) results.

Conclusions:

• The SSS technique is a simple, effective, and universal in situ method for studying polymer dynamic melting and crystallization.
• SSS can monitor both luminescent and non-luminous solid polymers.
• This spectroscopic approach provides valuable thermodynamic and kinetic data for polymer characterization.