A Rational Molecular Design of β-Phase Polydiarylfluorenes: Synthesis, Morphology, and Organic Lasers

Abstract

Rational molecular design allows for manipulating the chain conformations of polymer semiconductors by cooperative arrangement of bulky groups with steric hindrance effect and supramolecular groups with noncovalent attractions. Herein, a model polyfluorene with β-phase, poly[4-(octyloxy)-9,9-diphenylfluoren-2,7-diyl]-co-[5-(octyloxy)-9,9-diphenylfluoren-2,7-diyl] (PODPF), has been synthesized successfully via key Baeyer–Villiger rearrangement reaction. Its thin film exhibited excellent spectral stability without green band emission after thermal annealing at 200 °C under air and nitrogen ambients. The β-phases of PODPF in the concentrated toluene solution, organogels, and films have been characterized and confirmed by UV absorption and PL spectra as well as grazing-incidence X-ray scattering. The results suggest that the octyloxy substituents enable backbone planarization via van der Waals forces of the in-plane alkyl chains to overcome intrachain repulsion between fluorene monomers. Organic lasers using β-phase PODPF exhibit lower threshold than those of poly(9,9-dioctylfluorene), suggesting promising optical gain media. This observation suggested that supramolecular steric hindrance (SSH) is a promising molecular design of polymer semiconductors, and supramolecular steric polymers are one kind of model to get insight into the structure–function relationships for electrically pumped organic lasers in organic electronic and photonics.

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

“…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.…”

“…In this work, we introduced a π‐stacked carbazole (Cz) group into polyfluorene as a pendent steric synthon to fabricate a novel supramolecular bulky wide‐bandgap LCPs, PHDPF‐Cz (Scheme B; Figure S1, Supporting Information) . PHDPF‐Cz together with the controlled polymers PHDPF, PODPF, PNDPF, and PFO was synthesized following our previous works (Scheme S1, Supporting Information) . GPC measurements revealed the number‐average molecular weight ( M n ) of 4.96 × 10 4 with a polydispersity index (PDI) of 1.65 for PHDPF‐Cz, 4.37 × 10 4 (PDI = 1.68) for PHDPF, 4.74 × 10 4 (PDI = 1.56) for PNDPF, and 5.80 × 10 4 (PDI = 1.42) for PFO (Figure S2, Supporting Information).…”

Steric Poly(diarylfluorene‐co‐benzothiadiazole) for Efficient Amplified Spontaneous Emission and Polymer Light‐Emitting Diodes: Benefit from Preventing Interchain Aggregation and Polaron Formation

“…Novel diarylfluorene monomers with aryl substituents at 9‐position and pendant solubilizing alkoxy chains at 4‐position are synthesized according to procedures reported elsewhere . All copolymers were prepared via Suzuki polymerization (Scheme S1, Supporting Information) following a procedure which is described in the Supporting Information.…”

Supramolecular Steric Hindrance at Bulky Organic/Polymer Semiconductors and Devices

“…We proposed a monomer with SSH that has the bulky diaryl moieties at 9,9- fluorene [71]. In order to obtain the beta phase of polydiarylfluorenes, we introduced alkyl side chain at the crossing 4-position of fluorene.…”