Circular dichroism of optically active poly(dialkylsilane) aggregates in microcapsules

Area of Science:

• Polymer Science
• Materials Science
• Spectroscopy

Background:

• Polysilanes are known for their unique optical and electronic properties.
• Controlling polymer aggregation within confined environments is crucial for material design.
• Circular dichroism (CD) is a sensitive technique for probing chiral structures and aggregation states.

Purpose of the Study:

• To investigate the aggregation behavior and optical properties of poly[n-hexyl-(S)-3-methylpentylsilane] confined in microcapsules.
• To understand how polymer mass and preparation conditions influence the aggregation structure and optical activity.
• To explore the solvent and temperature effects on polysilane aggregates using circular dichroism.

Main Methods:

• Synthesis of poly[n-hexyl-(S)-3-methylpentylsilane] with controlled molecular weight.
• Encapsulation of polysilane aggregates within microcapsules.
• Circular dichroism (CD) spectroscopy measurements in ethanol and tetrahydrofuran at various temperatures.

Main Results:

• Optical activity, measured by CD, was found to be directly proportional to the polymer mass (m(p)) within the microcapsules.
• The size of the polysilane aggregates did not influence the observed optical activity.
• Significant thermal hysteresis in CD peak height was observed in tetrahydrofuran between 0 and 25°C, indicating structural memory.

Conclusions:

• The stacking structure of polysilane aggregates is sensitive to preparation methods, including solvent and temperature.
• Polysilane aggregates within microcapsules retain a 'memory' of their initial formation conditions.
• Circular dichroism is a valuable tool for characterizing the supramolecular structure and thermal behavior of confined polymers.