The Nonlinear Optical Behavior of Linear Diamantane Polyamides

We report the synthesis and characterization of a new family of single‐component polyamides incorporating rigid diamantane monomers, and investigate their structural, thermal, and nonlinear optical properties. These polymers are largely amorphous and exhibit exceptional thermal stability, with decomposition events in the 400–600 °C range, significantly exceeding those of conventional nylons such as nylon‐6 and nylon‐66. Thermal analysis further shows that polyamides containing aromatic units retain higher residual yields than purely aliphatic analogues. Powder X‐Ray diffraction, dynamic light scattering, and scanning electron microscopy reveal pronounced morphological differences, ranging from irregular nanoscale particulates to smooth, rubbery domains. A direct correlation between morphology and optical behavior is observed: polyamides with disordered or finely particulate structures display intrinsic white‐light emission (WLE, 490–700 nm, λ max ≈ 610 nm) under continuous near‐infrared (980 nm) laser irradiation, whereas the smooth morphology suppresses this response. Importantly, this dopant‐free WLE is unprecedented for polyamides, identifying diamantane‐based polymers as an attractive platform for efficient, thermally robust, and cost‐effective organic light‐emitting materials.