Preparation and Characterization of Polyfluorene-Based Supramolecular π-Conjugated Polymer Gels

Abstract

During the past decades, π-conjugated polymers have been studied intensively owing to their potential applications in organic optoelectronic devices, such as polymeric light-emitting diodes, bulk heterojunction solar cells, organic field-effect transistors (OFETs), organic memories, biosensors, and actuators. 1,2 The performance of organic devices is determined not only by the inherent electronic structures of individual polymer chain 3,4 but also by multiscale morphologies that were constructed by the drive of supramolecular interactions or van der Waals' forces. Many efforts have been made to design the controllable welldefined nanostructures or hierarchically ordered assemblies in the field of supramolecular semiconductors and electronics for the high-performance or new functional devices. 5,6 One typical example is that ordered self-organization of polythiophenes dramatically influences the performance of bulk heterojunction photovoltaic cells as well as the mobility of OFETs. 7,8 Lightemitting polyfluorenes (PFs) is another impressive example of polymorphisms, including amorphous phase, semicrystalline (R-) phase and R 0 -phase, β-phase, and nematic liquid crystalline (N-) phase. These abundant phases provide a unique opportunity to study the relationship between phase morphology and device performances. 9-13 For example, PFO thin film containing the β-phase exhibits the excellent spectral stability in PLEDs and the pumped lasers with low threshold. 14-16 In this context, it is of the utmost importance to explore further the unique morphology and phase of π-conjugated polymers, which are based on its unique self-assembly mode and supramolecular interactions. Supramolecular gel is a fascinating state that appears solid-like and yet is composed predominantly of a liquid and a small amount of gelators stabilized by supramolecular interactions with 3D networks. 17-20 Until now, low-molecular-mass organogels (LMOGs) have been applied in a wide range of fields, such as biomimetics, separations, drug delivery, soft templates, and tissue engineering. 21-24 Steroid or lipid units have served as gelators to generate cross-linking points in the 3D networks. 25 In addition, some electronically inactive comb-shaped polymers (isotactic and syndiotactic polystyrene (PS), 26 poly(methyl methacrylate), 27 and polyesters 28 ) have also been found to form gel networks easily owing to their unique helical conformations. However, little attention has been paid to π-conjugated polymers. 29-32 Supramolecular π-conjugated polymer gels (SCPGs) can be served as one kind of semiconducting soft materials with distinguished porous structures that may find applications in nanosensors, 33 mimic-artificial muscle, 34 super capacitor, 35 and lithium battery material. 36 Poly(3-alkylthiophene)-based gels were prepared by quenching xylene solution at 150°C, and its conductivity was improved. 37,38 ABSTRACT: Supramolecular π-conjugated polymer-based gels (SCPGs) are one important kind of semiconducting soft materials. Herein we demonstrate a p...

Intermetallic compounds in heterogeneous catalysis—a quickly developing field

“…[86, 87] as well as [85] for a recent review). The complexity of the ZnPd–ZnO interface as well as the presence of methanol, water and the different reaction products has so far hindered a quantum chemical calculation taking possible beneficial effects of the interface into account.…”

Solvent and Steric Hindrance Effects of Bulky Poly(9,9-diarylfluorene)s on Conformation, Gelation, Morphology, and Electroluminescence

“…Therefore, the unexpected wavelength absorption peak in 434 nm we observed here can be easily ascribed to the β‐phase of PFs, even existing 3 nm blue‐shift compared with PFO. The maximum emission peak of the three PFs gels is red‐shift to 470 nm, which is close to the second emission peak of β‐phase, the same as the previous work of PFO β‐phase‐based gel emission, and the mechanism of the characteristic emission was proposed as well . The 3D networks with shorter π–π stacking distance in gel state lead to intense aggregation in the gel that results in complete energy transfer from 0–0 vibration to 0–1 of β‐phase.…”

Supramolecular Steric Hindrance at Bulky Organic/Polymer Semiconductors and Devices

“…Among them, polyfluorenes [68] have several metaphases, including beta phase, gamma phase, and gel phase as well as green band-related phase that is still waiting for the clarification of origin. Conformational changes are the origin of phase transition and polymorphism in printing electronics or solution-processable devices.…”