Ordering minimalist bridged polysilsesquioxane films under visible LED light irradiation

ABSTRACT

A visible light-mediated sol–gel process can promote the ordering of hexylene, octylene, and decylene-bridged polysilsesquioxane (SQ) with very simple organosilane building blocks having only a short alkylene bridging group: (CH₃O)₃SiC_nH_2nSi(OCH₃)₃ (n = 6, 8, 10). Photocondensation and self-assembly of films are promoted through exposure to a light-emitting diode (LED; 405 nm). The solvent-free synthesis involves very low light intensity (0.1 mW/cm²) and a minimum amount of photoacid generator (PAG; 0.5 wt%) acting as a photocatalyst. X-ray diffraction (XRD) and scanning electron microscopy (SEM) prove the high level of organization, while real-time Fourier transform infrared spectroscopy shows conformational ordering of alkylene chains throughout irradiation. Molecular modeling reveals a multilayer structure based on the stacking of a single polysiloxane chain, with organic groups attached to adjacent Si atoms showing up and down orientation.

KEYWORDS:

• Bridged polysilsesquioxane
• lamellar structure
• self-assembly
• sol–gel photopolymerization

Funding

Dr. Lingli Ni would like to thank the financial support from the National Natural Science Foundation of China (No. 51503072, 21606098), and Natural Science Foundation of Jiangsu Province (No. BK20150419).

Supplemental data

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Additional information

Funding

Dr. Lingli Ni would like to thank the financial support from the National Natural Science Foundation of China (No. 51503072, 21606098), and Natural Science Foundation of Jiangsu Province (No. BK20150419).