Photo-crosslinked Second-order Nonlinear Optical Polymer Films with Large Nonlinear Optical Effect and High Thermostability

One of the most significant challenges in commercializing organic second-order nonlinear optical (NLO) materials lies in the inherent trade-off between nonlinearity and stability. A key factor in mitigating this compromise is achieving precise temporal synchronization between the formation of the cross-linked network and the establishment of an optimal non-centrosymmetric alignment of the chromophores. Guided by this principle, we developed a series of NLO polymers incorporating multiple ether chains with low rotational energy barriers, which facilitate molecular reorientation during electric field poling, thereby enhancing the NLO response effectively. Combined with an optimized photo-crosslinking strategy, the resulting PX4o/PETMP doped film achieved large macroscopic NLO coefficient of 190 pm·V⁻¹ and thermal degradation temperature as high as 120 °C. This work offers a universal approach to alleviating the “nonlinearity-stability” trade-off in a wide range of polymeric systems.