Modulating The Hierarchical Structures And Optoelectronic Properties Of One-Dimensional Organic Nanopolymers Via Polygridization

Organic wide-bandgap semiconductors with high fluorescence quantum yields,carrier mobilities,dielectric constants and quality factors are fascinating for electrically pumping lasers and new-generation plastic/flexible electronics,which require the elimination of structural defects and the breakthrough of molecular limitations for excitonic emission,charge carrier transport and photonic propagation/oscillation.Herein,we establish the nanomolecular design platform of one-dimensionalπ-nanopolymers（also called polygrids）that consist of nanogrid repeat units,based on the covalent extension of nanogridarene units with wide-bandgap optoelectronic properties and multiple hindrance-functionalization features.The main-chain feature of polygrids hybridizes one-dimensional conjugated polymer backbones with two-dimensional covalent organic frameworks,allowing the integrated advantages of inorganics-like optoelectronic properties with polymer-like solution-processability.The one-dimensional single-chain configuration（as the primary structure）of polygrids is precisely controlled using Friedel-Crafts polygridizations from A₂B₂-type nanosynthons or Yamamoto coupling polymerizations from brominated nanogrid monomers.On this basis,through the specific covalent linkage between nanogrid repeat units,we extensively tailor the single-chain conformation（as the secondary structure）of polygrids with various persistence lengths,and further modulate special interchain intanglement and self-assembled morphologies（as the tertiary structure）via tunable supersteric hindrance effect.As a result,the polygrid nanochains provide polymer semiconductors with unique nanoscale ordering and the mesoscale ordering in the hierarchical structures,as the fundamental support for special optoelectronic properties and high-performance devices.The significant findings are as follows:Initially,we create the superelectrophilic polygridization with a high meso-selectivity of～80%de through the anti-parallel and centrosymmetric molecular packing of A₂B₂-type monomers,using synergistically stacking interactions on diazafluorene-carbazole backbones with multi-cationic repulsion on protonated diazafluorenes.Such superelectrophilic polygridization affords a series of meso-isotactic polygrids with linear rod-like configurations composed of drawing-hand nanogrid units,which have been characterized by ¹H NMR,¹H-¹H COSY,FT-IR,GPC,DLS and AFM methods.Molecular dynamic simulation reveals that the fully meso-isotactic polygrid can form a rod-like collapsed conformation with high structural anisotropy,distinguished from the fully rac-isotactic polygrid with toroid patterns.Then,inspired by double-stranded DNA structures,we construct an ultrarigid nanopolyspirogrid to suppress conformational entropy and increase the order of secondary structures,through the four-armed covalent extension of spirofluorene building blocks.The fully double-bond-linked polygrid induces covalent lock effect on enhancing the persistence length up to 41 nm,drastically longer than general conjugated polymers with average persistence length of 3～20 nm.On this basis,although withπ-interrupted mainchain in the amorphous film state,such nanospiropolygrid achieves an ultralow energy disorder（46.6 me V）for the high carrier mobility of 3.93×10^-3 cm² V^-1 s^-1,reaching the highest level among generally amorphous conjugated polymers.Moreover,the covalent nanoscale ordering enables to strengthen dipole polarization and induce high dielectric constant（k=8.43）,which allows the improvement of carrier mobility in OFET devices(from 0.2 to 0.9 cm² V^-1 s^-1,pentacene as the semiconductor layer).Based on the covalent nanoscale ordering,we discover the mesoscale ordering ofπ-conjugated polygrid,which enables the thermodynamics-controlled self-assembly into one-dimensional single-component photonic crystals like butterflies’wings.The Bragg-Snell diffraction law in angle-dependent reflectance spectra verifies the feature of photonic crystals with mesocale periodicity.Such photonic crystals possess a high optical transmittance up to 85～90%,an angle-dependent luminescence anisotropy switching between blue and green emission,an electroluminescence efficiency enhancement（by 3～5 times）as well as an ultralow waveguide loss coefficient(2.6 cm^-1)in amplified spontaneous emission.Moreover,such photonic crystal possesses a tensile strain of 15%and a high toughness of 30～40 J m^-3,showing good mechanical flexibility for next-generation multifunctional optical plastics.Further,we utilizeπ-interrupted polygrid to endow self-assembled photonic crystals with micrometer-scale material/air interfaces containing large refractive index contrast（?n≥0.8）.Theπ-interrupted polygrid with stronger supersteric hindrance effect is capable of showing two times higher quantum yields（40～50%）on micrometer-thick photonic crystals than those on spin-coating thin films（18～22%）,which reveals an intriguingly anti-aggregation-caused quenching（anti-ACQ）feature.By synergizing photonic-crystal-driven waveguide effect with interface-induced light reflection,the deep-blue randome lasers are achieved with low threshold 22.3μJ cm^-2 and high quality factor up to5500～6200,probably as the highest level among organic and inorganic wide-bandgap semiconductor lasers.In conclusion,we deeply tailored the hierarchical multi-scale ordering of gridarene-based organic nanopolymers through the modulation of backbone tacticity,ultrlong persistence and photonic-crystal-directed mesoscale self-assembly,based on the polygridization strategy.These works provide potential molecular toolbox with high carrier mobility,high dielectric constant,high quantum yields and high quality factors for electronically pumping lasers.Further,gridarene-based nanopolymers are demonstrated as the protential candidate for new-generation optical plastic membranes and plastic/flexible electronic intelligence.