Charge-modulated self-assembly and growth of conjugated polyelectrolyte–polyoxometalate hybrid networks

Abstract

abSelf-assembly of an anionic polyoxometalate with cationic conjugated polyelectrolytes leads to hybrid supramolecular networks whose dimensionality is controlled by the chain length and steric charge distribution.Conjugated polyelectrolytes (CPEs) have attracted significant interest due to their potential applications in optical sensing and imaging, light-emitting diodes and photovoltaic devices.1 They comprise of an extended p-conjugated backbone decorated with side-chains containing ionic terminal groups, thus coupling the optoelectronic properties of organic semiconductors and the charge-mediated behaviour typical of polyelectrolytes. Since the optoelectronic properties of CPEs are intrinsically linked to the conformation of the polymer backbone, 2 understanding and obtaining control of the CPE conformation is a key requirement for the development of efficient organic electronic devices. Self-assembly is an elegant method for the fabrication of conjugated polymer (CP) nanostructures.3 CPEs are inherently amphiphilic, which facilitates their self-assembly into ordered aggregates with diverse morphologies in different solvents. water result in their co-assembly into hybrid networks, that can subsequently be transferred to thin films. We show that the direction of self-assembly and thus, the dimensionality of the resulting supramolecular networks is controlled by the steric distribution of the charged side-chains on the CPE. To the best of our knowledge this is the first report of a self-assembled CPE-POM organicinorganic hybrid exhibiting transferrable supramolecular organisation from solution to the solid-state. Two cationic CPEs, differing significantly in their chain length, number of repeat units (r.u.) and distribution of side chains were chosen: (i) poly [(2,5-bis(2-(N,N-diethylammoniumbromide)) and (ii) poly [(9,9-di(3,3 0 -N,N 0 -trimethylammonium)propylfluorenyl-2,7-diyl)-alt-(1,4-phenylene)] (PFP, M w E 10 000-15 000 g mol À1 )( Fig. 1). While NET is marketed as a polymer, it is in fact an oligomer, containing on average just 2 r.u. per chain; in contrast PFP has B14-22 r.u. per chain. Both CPEs contain two ammonium groups per r.u.; however, since the side-chains are located at adjacent and opposite positions in PFP and NET, respectively, the steric charge distribution differs substantially. Electrostatic association between cationic CPEs and the anionic POM in solution is expected to affect the optical properties. On addition of POM to aqueous solutions of NET and PFP, three distinct spectral changes are observed in the UV/Vis

Flexible and conductive multilayer films based on the assembly of PEDOT:PSS and water soluble polythiophenes

“…In the case of CPEs, their inherent amphilicity enables their self-assembly into ordered aggregates in both solution and solid phases [12][13][14]. Their self-assembly may also be manipulated by combining them with oppositely charged substances such as metal ions and complexes [15][16][17][18], DNA [19,20], surfactants [21][22][23] and polymers [24] for building complex supramolecular structures. In this respect, electrostatic layer-by-layer (LbL) deposition process based on the sequential adsorption of oppositely charged species represents an easy and convenient strategy for obtaining CPE films with controlled composition, architecture and properties at the nanometer scale [25,26].…”

From Simplicity to Complexity in Grafting Dawson-Type Polyoxometalates on Porphyrin, Leading to the Formation of New Organic–Inorganic Hybrids for the Investigation of Third-Order Optical Nonlinearities

“…Polyoxometalates (POMs) are inorganic nanoclusters of early-transition-metal ions with the general formula [MO x ] n , where x = 4–7 and M is V, W, Mo, Nb, and Ta with a marvelous range of physical and chemical properties. − POMs are used in biology, analytical chemistry, materials science, medicine, and so on. POMs, due to the higher oxidation state of metal atoms, are unambiguously strong electronic acceptors. − Therefore, POMs can be used as inorganic sorts for the fabrication of organic–inorganic hybrid materials.…”

Hybrid Gel Electrolytes Derived from Keggin-Type Polyoxometalates and Imidazolium-Based Ionic Liquid with Enhanced Electrochemical Stability and Fast Ionic Conductivity

“…Due to the rich and versatile physical and chemical properties of POMs, they have attracted great attention in the field of analytical chemistry, 5 catalysis, 6,7 biology, 8 medicine, 9 and materials science. 10 POMs-based materials show interesting electronic, 11,12 magnetic, 13 redox, 14 medicinal 15 and photonic properties. 16 Hence, a lot of effort has been taken to incorporate them into organic matrices through chemical and physical approaches to yield hybrid inorganic−organic materials.…”

“…Polyoxometalates (POMs) are metal–oxygen anionic clusters, and complexation of POMs with appropriate counterions form novel compounds. Due to the rich and versatile physical and chemical properties of POMs, they have attracted great attention in the field of analytical chemistry, catalysis, , biology, medicine, and materials science . POMs-based materials show interesting electronic, , magnetic, redox, medicinal and photonic properties .…”