Cyclomatrix-type polyphosphazene optical film coating: Preparation, characterization and properties

The cyclomatrix-type polyphosphazene is hypothesized to have potential as optical material due to the existing of transparent P=N ring skeleton. However, as an insoluble and infusible cross-linked polymer, cyclomatrix-type polyphosphazene is very difficult to be processed into film coatings. Herein, we reported a facile in situ template method to prepare cyclomatrix-type polyphosphazene optical film coating based on in situ polymerization between chlorocyclophosphazene and 4,4’-oxydianiline. A transparent coating with smooth surface and a translucent coating with uneven surface were successfully obtained by controlling reaction time. Their molecular structures, surface morphologies and topographies, cross-section morphologies, optical properties and preparation mechanisms were studied, respectively. As expected, the novel film coatings had good transmission in the visible region, especially the smooth transparent coating, which exhibited high transmittance (80 ∼ 90%). Moreover, the coatings unexpectedly exhibited UV-shielding capacity, especially the uneven translucent coating, which blocked the vast majority of UVA radiation (78.6%) and almost all of UVB radiation (99.8%). In addition, the possible preparation mechanisms of two coatings were also discussed. The primary stage of polymerization was dominated by a film-forming process based on template self-assembly, leading to smooth transparent film coating. As polymerization progress, many cyclomatrix-type polyphosphazene microspheres were produced by a forming-microsphere process and then deposited on the film surface, forming uneven translucent coating.