Synthesis and Nonlinear Optical Performance of Triphenylamine-Fluorene Copolymer Covalently Bridged 60Fullerene Triad

As one of the quasi-zero-dimensional materials, 60fullerene (C₆₀) and its organic/polymeric derivatives exhibit great application potential in many high-technology fields due to their outstanding optical, electronic, optoelectronic and magnetic properties. A new triphenylamine-fluorene copolymer-60fullerene covalently bridged triad (C₆₀-PTF-C₆₀) was synthesized by the 1,3-dipole addition reaction of C₆₀, sarcosine and PTF terminated with two aldehyde groups (CHO-PTF-CHO). This material, which was highly soluble in some common organic solvents, was embedded into an optically nonactive transparent poly(methylmethlacrylate) (PMMA) matrix to produce the PMMA-based C₆₀-PTF-C₆₀ film for nonlinear optics. The nonlinear optical (NLO) and optical limiting (OL) properties of C₆₀-PTF-C₆₀ were investigated through an open-aperture Z-scan setup at 532 nm.The C₆₀-PTF-C₆₀/PMMA film exhibited more excellent NLO and OL responses when compared to the C₆₀/PMMA film under the same experimental conditions due to photo-induced electron transfer between C₆₀ and PTF in the copolymer structure. The achieved nonlinear coefficient (β_eff), imaginary third-order susceptibility (Imχ⁽³⁾), and OL threshold were 437.75 cm/GW, 1.87×10⁻¹⁰ esu, and 0.34 GW/cm², respectively. For comparison purpose, the corresponding β_eff, Imχ⁽³⁾, and limiting threshold of the C₆₀/PMMA film were 188.87 cm/GW, 0.81×10⁻¹⁰ esu, and 0.53 GW/cm², respectively.