Hereditary Character of Alkyl-Chain Length Effect on β-Phase Conformation from Polydialkylfluorenes to Bulky Polydiarylfluorenes

Abstract

Although alkyl chain engineering provides an effective tool for regulation of polymorphic behaviors of conjugated polymers, there is no report on extracting universal rule from complicated structure−property relationships among various molecule systems. Here, a series of bulky polydiarylfluorenes with incremental length of n-alkyl chains (PnDPF, n = 6, 7, 8, 9) was investigated, examining conformation, gelation and crystallinity behavior. By analyzing the UV−vis absorbance and photoluminescence (PL) spectra of PnDPF from single chains to the aggregate state, β-phase was found in P7DPF and P8DPF. P8DPF adopted the largest torsional angle inferring from the degree of red-shift in PL and Raman spectra. By thermal annealing at 220 °C, crystallization process was observed in these four polymers, but β-phase only appeared in P7DPF and P8DPF. Finally, both thermodynamic and kinetic paths were used to illustrate the mechanism of βphase formation for PnDPF. Our results suggested that the alkyl-chain length effect on PnDPF exhibited the characters inheriting from the corresponding polydialkylfluorenes (PFn, n = 6,7,8,9). By comparative study between PnDPF and PFn, an explicit relationship between the side-chain length and polymorphic behaviors is established for the first time in bulky polymer semiconductors.

Ultrastable Supramolecular Self‐Encapsulated Wide‐Bandgap Conjugated Polymers for Large‐Area and Flexible Electroluminescent Devices

“…In addition, instead of larger aggregates or domains, we found a slightly smoother morphology in all annealed films, which indicates excellent thermal morphological stability (Figure A). However, the thermally annealed PHDPF films showed some obvious aggregate formation and crystalline superstructure, consistent with our previous work . However, evaluating the stability via thermal annealing is extremely not enough.…”

“…For all the effort put into the design of polyfluorenes over the last few decades, the utilization of the fluorene 4,5 position has been completely ignored. Recently, the second planar (β) conformational stable polydiarylfluorenes was designed with a balance between the steric interaction of bulky diphenyl (9‐position) and the entangled attraction of octyl side chain at 4‐position (van der Waals force, vDW) . Herein, we demonstrate a supramolecular approach in plastic electronic (also called supramolecular plastic electronic, SPE) to subtly avoid various pathways for defect generation based on ketone and aggregate formation to construct supramolecular self‐encapsulated polyfluorenes.…”

Hierarchical Uniform Supramolecular Conjugated Spherulites with Suppression of Defect Emission

“…Fundamentally, the dynamic and reversible nature of orthogonal hydrogen-bonding interactions is an intrinsic, original, and basic factor enabling these organized macromolecules to self-assemble into advanced supramolecular functional systems (Aida et al., 2012, Hoeben et al., 2005, Lehn, 2010, Sengupta and Würthner, 2013). Compared with the conventional superstructure with a range of common smart and mechanical properties, supramolecular conjugated solid states display a wide variety of complicated, photophysical mechanisms for electron delocalization, hybridization, and coupling (Heeger, 2010, Huang et al., 2019, Liu et al., 2017a, Liu et al., 2017b; Mikhnenko et al., 2015, Xie et al., 2012, Yang et al., 2018, Ye et al., 2018). Similar to the ordered, natural systems, the highly uniform and well-defined conjugated nanostructures that are receptive to processing can provide an effective and favorable electronic micro-environment that promotes exciton diffusion (Jin et al., 2018, Lin et al., 2010, Mikhnenko et al., 2015) and energy transport (Haedler et al., 2015, Kim et al., 2013, Vogelsang et al., 2011).…”

The Importance of Microstructure in Determining Polaron Generation Yield in Poly(9,9-dioctylfluorene)

“…[28][29][30][31][32][33][34] In recent years, a growing number of PFO derivatives and related polyfluorenes have also shown a similar β-phase conformation. [35][36][37][38][39][40][41][42][43][44] Polymer chain segments adopting a β-phase conformation exhibit a planarised interunit torsion angle of ≈ 180°, in comparison to the majority in-plane isotropic 'glassy-phase' segments which adopt a much wider range of more twisted torsion angles of ≈ 120-140°. 30,45 While for β-phase the alternation of side chains leads to formation of a 21 helix, the direction of side chain extension does not necessarily alternate for the glassy-phase.…”