Promotion of the second-order nonlinear optical effect by introducing ether linkage into polymer main chains

Second-order nonlinear optical (NLO) linear–dendritic (L–D) copolymers were designed and successfully prepared by the combination of a dendritic chromophore and an alkyl chain (P1) or alkoxy chains (P2–P5). Thanks to the lower rotational barrier of the ether bond than that of the single carbon–carbon one, much enhanced macroscopic NLO performance, as characterized by d₃₃ values, was achieved with the highest value of 166 pm V⁻¹, approximately 1.8 times that of P1 (94 pm V⁻¹). This finding opens up a new approach to the efficient control of the poling efficiency of chromophore moieties by subtle modifications to boost the NLO performance of polymeric materials as high as possible.