Conjugated rod–coil block copolymers and optoelectronic applications

Abstract

This review gives a simple introduction to the electronic, optical and structural behaviour of rod-coil block copolymers in which the rod block is conjugated. The current understanding of the optical properties of conjugated polymers is discussed, as is the self-assembly characteristics of rod-coil block copolymers, along with their behaviour with respect to organic light-emitting diode and photovoltaic devices. Poly(p-phenylene), poly(p-phenylenevinylene) and polythiophenes are then used to give concrete examples and a short history of the developments of this astounding field.can have a strong influence on the type of morphology obtained. The asymmetric nature of the highly rigid conjugated block and the coil block tends to increase the Flory-Huggins parameter (χ ) leading to domain formation even with relatively short polymers and oligomers. 42 Indeed, a wide variation of morphologies has been demonstrated through the preparation of mushroomlike aggregates, 43 honeycomb structures, 44 -47 vesicles 48,49 and cylindrical and lamellar aggregates. 50 -52 And it has been shown that, due to charge confinement within domains, the self-assembly process can be altered by using parameters such as light and temperature. 53 -55 It is apparent that rod-coil copolymers containing conjugated segments can lead to well-defined objects at the nanometric scale and that this in turn leads to the materials having an extraordinary range of applications.This review aims to give an overview of the main applications of π -conjugated systems, highlighting the importance of controlling the ineluctable aggregation phenomena and concentrating on the qualities of rod-coil block copolymers. An initial review of the basic electronic and optoelectronic properties of conjugated polymers along with a brief synopsis of their use and operation in more notable applications is given as this helps to explain the characteristics found and sought for with conjugated rod-coil copolymers. ARCHETYPAL CONJUGATED POLYMERSThe discovery in 1977 that polyacetylene exhibits a conductivity of about 10 3 S cm −1 on doping with Br 2 , I 2 or AsF 5 initiated a true interest in this material. 2 However, polyacetylene exhibits low environmental and thermal stabilities and poor solubilities that limit its technical use. Following these observations, many aromatic conjugated polymers such as poly(p-phenylene) (PPP), 56 polythiophene (PT), 57 polypyrrole 58 and others shown in Fig. 1 were studied. Currently, many other analogues are regularly prepared. Poly(3,4-ethylenedioxythiophene) (PEDOT), marketed by the Bayer company since the 1980s, is one of the most widely exploited. 59 -63 This polymer shows reasonable conductivity (ca 1 S cm −1 ), quasi-transparency in films and high stability in the oxidized state. 62 -64 An important development was the discovery of the green electroluminescence of undoped poly(p-phenylenevinylene) (PPV) by Friend and colleagues in 1990. 65 This breakthrough was followed by the ground-breaking preparation of the first blue PLED based ...

Optical properties of amphiphilic copolymer-based self-assemblies

“…Conjugated polymers have been recognized of great importance since they provide a powerful route toward supramolecular objects with novel architectures, functions and physical properties [24]. As shown in Fig.…”

Self-Assembly of Poly(3-hexylthiophene)-block-poly(γ-benzyl-L-glutamate) within Solution-Cast Films and Nanofibers

“…This dominating molecular/crystalline ordering process within PBLG and P3HT blocks possibly resulted in the weak block copolymer domain segregation we found in the TCB‐based films, evident in the single, soft (broad) peak in the SAXS data in Figure . Another point worth noting is that rod–coil block copolymers (with only one rigid block) have been shown to form self‐assembly structures with only planar interfaces, such as lamellar or zig‐zag, owing to the rigid rod conformation and large persistence length of one of the blocks . For the rod–rod diblock copolymer studied in this work, we expected this effect to be even more pronounced due to the rigidity of both blocks.…”

Facile Synthesis of Well-Defined MDMO-PPV Containing (Tri)Block—Copolymers via Controlled Radical Polymerization and CuAAC Conjugation

“…Finally, end group modification and subsequent conjugation of the PPV-b-PtBuA block copolymers using copper catalyzed azide-alkyne cycloaddition (CuAAC) clickchemistry results in an (comparatively) easy to purify PPV-b-PtBuA-b-PEG triblock copolymer-the first of their kind to the best of our knowledge. By combining the excellent optoelectronic properties of PPVs with the advantages of CRP routes, a new generation of highly specific precision block copolymer materials with advanced architecture and sophisticated physical properties becomes available, opening new avenues for conjugated materials outside the field of organic electronics [42,43].…”