σ-σ^* conjugation Across Si─O─Si Bonds.

Area of Science:

• Materials Science
• Polymer Chemistry
• Organic Electronics

Background:

• Polysiloxanes and silsesquioxanes are typically insulating materials.
• Conjugation in polymers usually involves carbon-based backbones.
• Si-O-Si linkages are widely considered insulating.

Purpose of the Study:

• To investigate conjugation in polysiloxane copolymers.
• To characterize the photophysical properties of these novel copolymers.
• To explore the role of Si-O-Si bonds in electronic conjugation.

Main Methods:

• Synthesis and characterization of polysiloxane-chromophore copolymers.
• Photophysical measurements (emission spectra, absorption spectra).
• Theoretical calculations (electronic structure, orbital interactions).

Main Results:

• Copolymers exhibit redshifted emission compared to model compounds, indicating conjugation.
• Evidence of electron transfer and bandgap narrowing with increasing molecular weight.
• Si-O-Si bond angles change significantly due to conjugation, approaching planarity.

Conclusions:

• Si-O-Si bonds can facilitate electronic conjugation in polysiloxane copolymers.
• These materials exhibit properties like intersystem charge transfer (ICT) and large Stokes shifts.
• Findings challenge traditional views of polysiloxanes as purely insulating materials.