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Here, we report the synthesis of DD SQ terpolymers with alternating biphenyl/terphenyl/stilbene and thiophene/hexylthiophene/bithiophene/thieno- thiophene linkers. These terpolymers were characterized using 1H and 13C nuclear magnetic resonance, gel permeation chromatography, matrix-assisted laser desorption/time-of-flight spectrometry, thermogravimetric analysis, and Fourier- transform infrared with the goal of combining long-wavelength emissions with high quantum yields. Density functional theory modeling studies using the Vienna ab initio simulation package and Gaussian 16 methods were also explored in attempts to determine HOMO-LUMO electronic configurations. Terpolymers’ UV−vis properties demonstrate an emission intermediate between the respective copolymers rather than emission from both units as would be expected from physical mixtures, supporting electronic communication along polymer chains and through cages linked via disiloxane units as seen in previous reports on copolymers of the same systems. In addition, terpolymers of DD, thiophene, and terphenyl/ stilbene offer ΦF that improved from 0.09 for DD/thiophene to 0.20 and 0.24, respectively. Compared to the corresponding terphenyl and stilbene copolymers, terpolymers display 35 nm red-shifted emissions, suggesting that it is possible to combine features of both copolymers in a single terpolymer, suggesting new opportunities to tailor photophysical properties by modifying structures, especially in systems with disiloxane linkers. 

Abstract Band edges at the high symmetry points in reciprocal space of periodic structures hold special interest in materials engineering for their high density of states. In optical metamaterials, standing waves found at these points have facilitated lasing, bound‐states‐in‐the‐continuum, and Bose–Einstein condensation. However, because high symmetry points by definition are localized, properties associated with them are limited to specific energies and wavevectors. Conversely, quasi‐propagating modes along the high symmetry directions are predicted to enable similar phenomena over a continuum of energies and wavevectors. Here, quasi‐propagating modes in 2D nanoparticle lattices are shown to support lasing action over a continuous range of wavelengths and symmetry‐determined directions from a single device. Using lead halide perovskite nanocrystal films as gain materials, lasing is achieved from waveguide‐surface lattice resonance (W‐SLR) modes that can be decomposed into propagating waves along high symmetry directions, and standing waves in the orthogonal direction that provide optical feedback. The characteristics of the lasing beams are analyzed using an analytical 3D model that describes diffracted light in 2D lattices. Demonstrations of lasing across different wavelengths and lattice designs highlight how quasi‐propagating modes offer possibilities to engineer chromatic multibeam emission important in hyperspectral 3D sensing, high‐bandwidth Li‐Fi communication, and laser projection displays.