Tuning the Electrical Conductivity and Self-Assembly of Regioregular Polythiophene by Block Copolymerization: Nanowire Morphologies in New Di- and Triblock Copolymers We gratefully acknowledge support from the NSF (CHE-9807707).

Abstract

Over two decades ago the discovery of electrical conductivity in conjugated polymers spurred a tremendous amount of effort aimed at the development of practical conducting plastics. [1] One of the primary motivations was the hope of fabricating inexpensive, lightweight conducting materials. Those efforts have been coming to fruition in recent years with the development of polymer-based light-emitting diodes, [2] field-effect transistors, [3] elements for active matrix displays, [4] and all-polymer integrated circuits. [5] The synthesis and study of regioregular polythiophenes has produced conjugated polymers that self-assemble into well-defined superstructures and has furthered the use of these materials in the aforementioned applications. [6] Formation of ordered supermolecular structures in these regioregular materials correlates strongly with their excellent electrical conductivities (thousands or hundreds of S cm À1 in comparison with a few S cm À1 for regiorandom polymers). Nevertheless, regioregular polythiophenes still have poor mechanical and processing properties relative to typical flexible polymers.One approach to solving this problem is to synthesize block copolymers that contain conducting polymer or oligomer units. [7] Such a block copolymer [8] could self-assemble into a number of nanoscale morphologies, such as lamellar, spherical, cylindrical, and vesicular structures, which would lead to the possibility that new electronic/structural copolymers could be designed, synthesized, and assembled as components in new nano-[*]

Dependence of Regioregular Poly(3-hexylthiophene) Film Morphology and Field-Effect Mobility on Molecular Weight

“…The polymers and electrodes used were fabricated as described previously. 19 All polymers reported in this study are synthesized by the modified McCullough route using 2-methylthiophene as an end-capping agent 28 and have regioregularities greater than 98% as measured by 1 H NMR. MW was adjusted by controlling the ratio of 2-methylthiophene to the monomer.…”

A New Supramolecular Route for Using Rod‐Coil Block Copolymers in Photovoltaic Applications

“…[14][15][16][17][18][19] Block copolymers composed of an electron-donating and an electronaccepting block are therefore particularly interesting for PV applications and are presently studied worldwide by several research groups. [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] Particularly, rod-coil block copolymers using poly[(2,5-di(2-ethyl)hexyloxy)-1,4-phenylenevinylene] (DEH-PPV) as electron donor and various coil blocks (such as polystyrene or polybutylacrylate) with covalently linked fullerene moieties as electron acceptor have been investigated intensively. [23][24][25][26][27][28] Although these studies have given considerable insight into the physics of copolymer self-assembly, their efficient utilization as the active layer in PV devices has not yet been fully demonstrated.…”

Chain Growth Mechanism for Regioregular Nickel-Initiated Cross-Coupling Polymerizations

“…[4][5][6][7] Very recently, we have developed an endgroup functionalization methodology of HT-PATs that allows for the synthesis of a plethora of well-defined block copolymers that form nanowires with high electrical conductivity. 7 Here, we have discovered that the nickel-initiated regioregular polymerization of alkylthiophenes proceeds by a chain growth mechanism and does not occur by the accepted step growth mechanism. 8 We also observed that the degree of polymerization of the synthesized poly(alkylthiophenes) increases with the conversion and can be predicted by the molar ratio of monomer to nickel initiator.…”

“…2,3 Regioregular polythiophenes have led to a multitude of important and novel nano-and microscale electronic materials and devices. [4][5][6][7] Very recently, we have developed an endgroup functionalization methodology of HT-PATs that allows for the synthesis of a plethora of well-defined block copolymers that form nanowires with high electrical conductivity. 7 Here, we have discovered that the nickel-initiated regioregular polymerization of alkylthiophenes proceeds by a chain growth mechanism and does not occur by the accepted step growth mechanism.…”