Synthesis of the end-functionalized polymethyl methacrylate incorporated with an asymmetrical porphyrin group via atom transfer radical polymerization and investigation on the third-order nonlinear optical properties

摘要

A novel asymmetrical zinc(II) porphyrin (ZnPor-Br) was synthesized as the initiator for the atom transfer radical polymerization (ATRP). Using CuBr/2,2'-dipyridyl as the catalyst system, the ATRP of polymethyl methacrylate (PMMA) was carried out to afford a new linear PMMA with the end group of the asymmetrical porphyrin (ZnPor-PMMA). The structures of the porphyrin, ZnPor-Br and as-prepared polymer were determined by FT-IR, ~1H NMR spectra and further confirmed by element analysis. Polydisper-sity index (PDI) obtaining from the gel permeation chromatograph (GPC) indicated that the molecular weight distribution was narrow, and the whole process of polymerization was well controlled. The third-order nonlinear optical properties of polymers were investigated by using Z-scan technique in the pico-second time scale. The nonlinear refracting index (n2) and the third-order nonlinear polariz-ability [χ~((3))] were 4.1 x 10~(-10) esu and 1.64 x 10~(-10) esu respectively, while the molecular polarizability (γ' ) was 1.01 x 10~(-28) esu (M_n = 2000). The obtained results implied that the prepared compound featured the large nonlinear optical limiting properties and could serve as a potential candidate for the reverse saturable absorption (RSA) and the refractive-based optical limiting applications in the laser protection field.