Efficient Synthesis of Block Copolymers Bearing Donor-Acceptor Chromophores for Second-Order Nonlinear Optical Applications

Abstract

Block copolymers composed of unsubstituted polystyrene and electron-rich alkyne functionalized polystyrene segments were prepared by atom transfer radical polymerization (ATRP) of N,N-didodecyl-4-[(4-vinylphenyl)ethynyl]aniline (2) with bromine-terminated polystyrene (1). Subsequently, the atom-economic addition reaction between electron-rich alkynes and tetracyanoethylene (TCNE) was applied as an efficient post-functionalization method to introduce donor-acceptor chromophores. All polymers were comprehensively characterized by GPC, ¹H NMR, IR and UV-Vis spectroscopies, and electrochemistry. The TCNE-adducted polymers showed intense charge-transfer (CT) bands, well-defined redox activities, and good thermal stability. Furthermore, the second harmonic generation (SHG) of the spin-coated polymer thin films on a glass slide was measured before and after electric poling, and the SHG coefficient (d₃₃) of the poled thin film reached 3.0 pm V^-1.