Fluorescent Spherical Particle Formation from Solid Polysilanes by the Aid of Laser Ablation and Photochemical Reaction

Abstract

With the aid of laser ablation using the third harmonic of Nd:YAG laser light, spherical fine particles were produced from poly(dimethylsilane) (PDMS) powder and poly(methylphenylsilane-co-diphenylsilane) (P(MPS-co-DPS)) powder in the atmosphere of allyltrimethylsilane (ATMeSi). The particle size and the product yield of laser-ablated PDMS/ ATMeSi particles increased with increasing vapor pressure of ATMeSi, suggest- ing that ATMeSi reacted with silyl radical end of polysilane chain and during the poly- merization reaction of ATMeSi, it reacted with silyl radical end of another polymer chain to extend the particle size. Laser-ablated PDMS/ATMeSi particles emitted fluorescence at shorter wavelengths than PDMS powder without laser ablation. With increasing vapor pressure of ATMeSi, fluorescence peak shifted to shorter wavelengths, indicating that recombination of polymer silyl radicals was inhibited by the reaction with ATMeSi, and hence the average length of polysilane chains became shorter. Laser-ablated P(MPS-co- DPS)/ATMeSi particles also emitted fluorescence. In addition to a narrow band observed at 368 nm, a broad band was observed at ∼485 nm due to branching of polysilane chain. Chemical processes to form branched polymer chain were discussed briefly.