C60 end-functionalized four-armed polymers:: synthesis and optical limiting properties

A series of bromo-terminated four-armed homopolymers [polystyrene (PSt) and poly(methyl methacrylate) (PMMA)], prepared by atom transfer radical polymerization (ATRP), were subsequently functionalized with fullerene C-60 by atom transfer radical addition (ATRA) reaction using CuBr/2,2'-bipyridine (bipy) as the catalyst system. The C-60 end-capped four-armed polymer derivatives were then characterized by gel permeation chromatography (GPC), UV-vis, FT-IR, thermal gravimetric analyses (TGA) and differential scanning calorimeter (DSC). Another technique of synthesizing C-60-functionalized four-armed polymers from azide functional polymers was also applied for comparison. The optical limiting behavior of C-60 end-capped four-armed polymers prepared via ATRA reaction were measured in THF solution at 532 nm. Both groups of fullerene-functionalized polymers (C-60-PSts and C-60-PMMAs) are provided with optical limiting properties.