Microstructure and surface property of macroscopic gradient polymer initiated by polysiloxane benzophenone photoinitiators with different silicone chain lengths

This paper reported three kinds of polysiloxane benzophenone photoinitiators (HBP-Si-A/B/C) with different silicon contents, which were synthesized based on traditional photoinitiator 4-hydroxy benzophenone (HBP) and epoxy polysiloxane. The effect of silicon content in the photoinitiator molecule on its photopolymerization property, the ability to float up and surface morphology and the property of the gradient polymer film initiated by it was investigated. It is proved by UV absorption and gel permeation chromatography (GPC) measurements that HBP-Si-A/B/C with different silicon content had different abilities to float up. As a result, the gradient polymer with more significant molecular weight gradients could be obtained by using the polysiloxane benzophenone photoinitiator with higher silicon content, which had a better ability to float up caused by lower surface tension and energy, and the surface property was connected with the surface microstructure. The increase of silicon content in the polysiloxane-based photoinitiator could decrease the dispersion surface energy of gradient polymer film initiated by it and generate a more hydrophobic surface by a change of microstructure. In addition, the polysiloxane-based photoinitiator could also restrain the forming of wrinkling on the surface of the UV-curable film due to mitigation of oxygen inhibition in radical photopolymerization, and it may have potential in controlling patterned microstructures and surface property.