Unsaturated alkoxy‐substituted poly(p‐phenylene 1,3,4‐oxadiazole)s: Synthesis and chemical–physical characterization

A new series of alkoxy‐substituted poly(p‐phenylene 1,3,4‐oxadiazole)s modified by the insertion of small percentages of various comonomers were synthesized through the precursor polyhydrazides. The comonomers used contained trans double bonds or meta‐alkoxy‐substituted aromatic rings to improve the solubility of the final polymers. The synthesized copolymers were chemically characterized by ¹H NMR and Fourier transform infrared spectroscopy. In some cases, the copolymers really showed improved solubility in organic solvents. The ¹⁵N solid‐state NMR technique was applied to examine the degree of conversion from the precursor polyhydrazides to the final polymers, which determined the effective conjugated length in the target polyoxadiazoles. Thermal stability and structural characteristics of all the polymers as well as a preliminary investigation on the optical properties of polyoxadiazoles are also reported. The copolymers retained high absorbance in the UV region and high transmission in the whole telecommunication range. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3916–3928, 2003     

Precision Synthesis of Poly(3‐hexylthiophene) from Catalyst‐Transfer Suzuki−Miyaura Coupling Polymerization

^tBu₃ PPd(Ph)Br ( 1 )‐catalyzed Suzuki‐Miyaura coupling polymerization of 2‐(4‐hexyl‐5‐iodo‐2‐thienyl)‐4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolane ( 2 ) was investigated. Monomer 2 was polymerized with 1 at 0 °C in the presence of CsF and 18‐crown‐6 in THF containing a small amount of water to yield P3HT with a narrow molecular weight distribution and almost perfect head‐to‐tail regioregularity. The values increased up to 11 400 g · mol⁻¹ in proportion to the feed ratio of 2 to 1 . The MALDI‐TOF mass spectra showed that P3HT with moderate molecular weight uniformly had a phenyl group at one end and a hydrogen atom at the other, indicating involvement of a catalyst‐transfer mechanism. Successive 1 ‐catalyzed polymerization of fluorene monomer 3 and then 2 yielded a well‐defined block copolymer of polyfluorene and P3HT.

     

Regioregular poly(3‐alkanoylthiophene): Synthesis and electrochemical,photophysical, charge transport,and photovoltaic properties

Head‐to‐tail regioregular poly(3‐heptanoylthiophene) (PHOT) was synthesized by Ni‐catalyzed polycondensation of the 2,2‐dimethyl‐1,3‐propanediol‐protected Grignard monomer followed by deprotection. Cyclic voltammetric (CV) study demonstrates that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of PHOT are 0.5 eV lower in energy than those of the head‐to‐tail poly(3‐hexylthiophene) (HT‐P3HT). Their optical band gaps are essentially the same. Incomplete photoluminescence (PL) quenching was observed in thin films of the 1:1 blend of PHOT and HT‐P3HT. PHOT displayed a glass transition at ～269 °C and decomposed at ～300 °C according to differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Wide‐angle X‐ray diffraction (WAXD) study showed that PHOT exists in a not highly ordered state in solid films especially in the π‐stacking direction. Only p‐channel activity was observed in field‐effect transistors (FETs) for PHOT. The hole mobility was on the order of 10^?4 cm² V^?1 s^?1. Photovoltaic devices with an active layer of 1:1 blend of PHOT and PC₇₁BM had a power conversion efficiency (PCE) of ～0.5%. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

β‐Cyclodextrin Pseudopolyrotaxanes with π‐Conjugated Polymer Axles

Summary: β‐Cyclodextrin (β‐CD) pseudopolyrotaxanes containing poly(thiophene‐2,5‐diyl), PTh , or poly(3‐methylthiophene‐2,5‐diyl)s, P3MeTh s, as an axle were prepared. Structures of the pseudopolyrotaxanes and their inclusion behavior with β‐CD were investigated. The UV‐vis measurements revealed that inclusion of P3MeTh s by β‐CD depended on the flexibility of the main chain and their molecular weight.

Formation of the inclusion complex of β‐CD and PTh .     

Chiral oxazoline substituted optically active poly(m‐phenylene)s: Synthesis and coupling polymerizations of (S)‐4‐benzyl‐2‐(3,5‐dihalidephenyl) oxazoline using transition metal catalysts

Optically active poly(m‐phenylene)s substituted with chiral oxazoline derivatives have been synthesized by the nickel‐catalyzed Yamamoto coupling reaction of optically active (S)‐4‐benzyl‐2‐(3,5‐dihalidephenyl)oxazoline derivatives (X = Br or I). The structures and chiroptical properties of the polymers were characterized by spectroscopic methods and thermal gravimetric analyses. The polymers showed higher absolute optical specific rotation values than their corresponding monomer, and showed a Cotton effect at transition region of conjugated main chain. The optical activities of the polymers should be attributed to the higher order structure such as helical conformations. Moreover, the helical conformation could be induced by addition of metal salts into polymer solutions. The polymers showed good thermal stabilities, which was attributable to the oxazoline side chains. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis of Poly(3‐hexylthiophene) with a Narrower Polydispersity

Summary: The polymerization of 2‐bromo‐3‐hexyl‐5‐iodothiophene ( 1 ) with isopropylmagnesium chloride and Ni(dppp)Cl₂ was quenched with 5 M hydrochloric acid instead of water to yield head‐to‐tail poly(3‐hexylthiophene) (HT‐P3HT) with a very low polydispersity. The of the polymer was controlled by the feed ratio of 1 to Ni(dppp)Cl₂. Quenching with 5 M hydrochloric acid seemed to promote protonolysis of HT‐P3HT‐Ni complexes before the coupling reaction between HT‐P3HT.

GPC profiles of HT‐P3HT obtained after quenching with water and 5 M hydrochloric acid, respectively.     

Regioregular Poly[3‐(4‐alkoxyphenyl)thiophene]s: Evidence for a Two‐Step Aggregation Process

Summary: A chiral, regioregular poly[3‐(4‐alkoxyphenyl)thiophene] has been prepared and studied. Films prepared by fast evaporation of the solvent, consist of random‐coils, while films prepared by slow evaporation are composed of chirally aggregated, coplanar strands. Heat treatment transforms the random‐coils into aggregated films via an intermediate state, which was characterized as chiral, coplanar, unaggregated polymer strands.

Overview of the possible aggregation processes.     

Synthesis and properties of poly(heteroaryleneethynylene)s consisting of electron‐accepting benzothiadiazole/quinoxaline units and electron‐donating alkyl thiophene units

Low‐band‐gap π‐conjugated polymers composed of π‐excessive thiophene and π‐deficient benzothiadiazole and quinoxaline units were prepared in high yields by a polycondensation method using palladium cross‐coupling reactions of alkylthiophene diacetylenes, 4,7‐dibromo‐2,1,3‐benzothiadiazole, and 5,8‐dibromo‐2,3‐dipyridine‐2‐ylquinoxaline. The copolymers were characterized by NMR, IR, UV, gel permeation chromatography, and elemental analysis. High‐molecular‐weight (weight‐average molecular weight up to 82,600 g/mol), thermostable, soluble, and film‐forming materials were obtained. The polymers were photoluminescent in chloroform and showed metallic luster in the solid state. The absorption and emission in solution and in the solid state of the polymers revealed that the polymers generated a π‐stacked structure in the solid state, and the polymer molecules in the film were ordered. Thin films of poly[3‐dodecylthiophen‐2,5‐diylethynylene‐(benzo[1,2,5]thiadiazole‐4,7‐diyl)ethynylene] ( P‐1 ), poly[3,4‐di dodecylthiophen‐2,5‐diylethynylene‐(benzo[1,2,5]thiadiazole‐4,7‐diyl)ethynylene] ( P‐2 ), poly[3‐dodecylthiophene‐2,5‐diylethynylene‐(2,3‐dipyridine‐2‐ylquinoxaline‐5,8‐diyl)ethynylene] ( P‐3 ), and poly[3,4‐didodecylthiophene‐2,5‐diylethynylene‐(2,3‐dipyridine‐2‐ylquinoxaline‐5,8‐diyl)‐ethynylene] ( P‐4 ) exhibited an optical band gap of ～1.85–2.08 eV. The highest occupied molecular orbital and lowest unoccupied molecular orbital levels of the polymers were determined from electrochemical measurements. In the absorption and emission spectra of these polymers in chloroform/methanol mixtures, all the polymers revealed solvatochromic effects, which were related to the formation of aggregates, as confirmed by temperature‐dependence absorption investigations. The absorption spectra of P‐2 and P‐4 at different temperatures also revealed significant effects of the structure on the molecular interactions. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6445–6454, 2005     

Optimization of direct arylation polymerization conditions for the synthesis of poly(3‐hexylthiophene)

Direct arylation polymerization (DArP) is an emerging alternative to Stille and Suzuki polymerizations. This method is attractive as it allows preparation of high‐molecular‐weight conjugated polymers in good yield without the need to metallate monomers. Despite this promise, for poly(3‐hexylthiophene) (P3HT) and related polymers that have β‐protons on the thiophene ring, DArP is known to produce β‐defects, which make the polymer properties different from polymers produced by traditional methods. Here, we demonstrate that DArP conditions based on simple, inexpensive, and bench‐stable reagents can be tuned to limit the amount of defects and produce P3HT with properties remarkably similar to Stille P3HT. Specifically, lowering the reaction temperature, lowering the amount of catalyst, and using a bulkier carboxylate ligand is critical. Optimized conditions include reacting 2‐bromo‐3‐hexylthiophene with 0.25 mol % of Pd(OAc)₂, 1.5 equivalents of K₂CO₃, and 0.3 equivalents of neodecanoic acid in N,N‐dimethylacetamide at 70 °C and give DArP P3HT with ～60% yield, regioregularity of 93.5%, molecular weight of 20 kDa, polydispersity of 2.8, and melting point of 217 °C, providing a very close match to Stille P3HT, which is obtained with 70–80% yield, 91–94% regioregularity, molecular weight of 15–25 kDa, polydispersity of 2.5–2.8, and melting point of 214–221 °C. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2660–2668     

Alkyne‐Linked Poly(1,8‐carbazole)s: A Novel Class of Conjugated Carbazole Polymers

Novel conjugated carbazole polymers based on the alkyne‐linked 1,8‐carbazole structure are synthesized in high yield by the Sonogashira cross‐coupling reaction and acetylenic oxidative coupling reaction. The polymers are thermally stable and highly soluble in common organic solvents such as CHCl₃, CH₂Cl₂, and THF. As compared to ethynylene‐linked polymer, the butadiynylene‐linked polymer display a bathochromic shift in the absorption maximum and end absorption position. In addition, the fluorescence behaviors in CH₂Cl₂ are almost identical for both polymers. Electrochemical measurements indicate that the ethynylene‐linked polymer possesses a lower first oxidation potential than the butadiynylene‐linked one.

     

Regiospecific design strategies for 3‐arylpolythiophenes with pendant stable radical groups

Carbon—carbon bond‐forming polymerization of 2‐bromo‐3‐(3′,5′‐di‐t‐butyl‐4′‐methoxyphenyl)‐thiophene yields poly[3‐(3′,5′‐di‐t‐butyl‐4′‐methoxyphenyl)‐2,5‐thienylene] with regiospecific connectivity and a degree of polymerization of about six. Lewis‐acid‐moderated‐cleavage of the methoxy groups on the pendant phenyl group yield the corresponding polyphenolic polymer, which is oxidized under solution conditions to yield the title polyradical. Poly[3‐(3′,5′‐di‐t‐butyl‐4′‐oxyphenyl)‐2,5‐thienylene] exhibits a strong, persistent electron spin resonance spectrum and a UV–visible spectrum consistent with formation of the pendant phenoxyl spin‐bearing units. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 779–788, 1999     

Regioregular poly[3‐(4‐alkoxyphenyl)thiophene]s

An easy synthetic procedure for soluble poly[3‐(4‐alcoxyphenyl)thiophene]s is reported. The polymers present a high regioregularity degree as determined by both UV–vis spectra and ¹H and ¹³C NMR analysis. Furthermore, X‐ray powder diffraction analysis performed on films of the polymers suggests a π‐stacked packing structure of the macromolecules. Electrical characterization was performed on one of the synthesized polythiophenes on both undoped and doped (with FeCl₃ or iodine) films. The conductivity and charge‐carrier mobility were assessed by current–voltage and field effect measurements. Well‐structured polymer films were obtained simply via spin coating from chloroform solutions and without the need of further processing, unlike other regioregular polythiophenes reported in the literature. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1758–1770, 2007     

Multi‐Sensitive Microgels Filled with Conducting Poly(3,4‐ethylenedioxythiophene) Nanorods

In this work we describe the synthesis of multi‐sensitive aqueous microgel particles with incorporated conducting poly(3,4‐ethylenedioxythiophene) (PEDOT) nanorods. We demonstrate that the loaded amount of PEDOT nanorods as well as their morphology can be varied by controlling the reaction conditions such as monomer concentration and alcohol concentration in aqueous phase. Obtained microgels can be stimulated by changes in the environment temperature as well as by the repulsion/attraction forces within polymeric network due to the reversible oxidation/reduction of the conjugated polymer. Microgels with unique properties can be operated in colloidal systems or used as building blocks for the preparation of nanostructured films.

     

Effects of Thermal Annealing Upon the Nanomorphology of Poly(3‐hexylselenophene)‐PCBM Blends

Grazing incidence X‐ray diffraction (GI‐XRD) is used to characterize the crystallographic dynamics of low molecular weight (LMW) and high molecular weight (HMW) poly(3‐hexylselenophene) (P3HS) films and blend films of P3HS with [6‐6‐]‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM) as a function of ‘step‐by‐step’ thermal annealing, from room temperature to 250 °C. The temperature‐dependent GIXRD data show how the melting point of P3HS crystallites is decreased by the presence of PCBM. P3HS crystallite domain sizes dramatically increase upon annealing to the P3HS melting temperature. The formation of well‐oriented HMW P3HS crystallites with the (100) plane parallel to the substrate (edge‐on orientation), when cooled from melt, are observed. We compare the behaviour of P3HS pure and blend films with that of poly(3‐hexyl)thiophene (P3HT) pure and PCBM blended films and suggest that the similar temperature dependent behaviour we observe may be a common to polythiophene and related polymers and their blends.

     

Alternating copolymer of thiophene andN‐(phenylethynyl)pyrrole. New π‐conjugated alternating five‐membered ring copolymer and its packing structure

An alternating copolymer, Copoly‐1 , of thiophene and N‐(phenylethynyl)pyrrole was prepared by palladium‐catalyzed polycondensation. Powder X‐ray diffraction (XRD) analysis indicated that Copoly‐1 formed a stacked packing structure with doubly‐running polymer main chains. Optical data support the molecular and packing structures of Copoly‐1 . © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2219–2224, 2005     

Synthesis and Electrooptic Properties of Poly(2,6‐anthracenevinylene)s

High molecular weight poly(9,10‐bis(p‐(2‐ethylhexyloxy)phenyl)‐2,6‐anthracenevinylene) (2,6‐PAV) was synthesized with 2,6‐dimethylanthraquinone as a key intermediate. The as‐synthesized polymer is readily soluble in common organic solvents and can be used for spin‐coating. The as‐synthesized polymer exhibits a broad absorption band ranging from 280 to 520 nm and a bluish green emission band with a peak at 500 nm. The polymer shows good thermal stability, and no distinct glass transition is observed. A simple device with the configuration ITO/PEDOT:PSS/2,6‐PAV/Ba/Al showed a turn‐on voltage of 4.8 V and a maximal brightness of 340 cd · m⁻².

     

Synthesis of End‐capped Regioregular Poly(3‐hexylthiophene)s via Direct Arylation

The synthesis of regioregular head‐to‐tail poly(3‐hexylthiophene)s capped with aryl groups (Ar‐HT‐P3HTs) has been accomplished by palladium‐catalyzed polycondensation of 2‐bromo‐3‐hexylthiophene ( 1 ) via direct arylation. A variety of aryl groups are installed at the initiated end in 86%–98% selectivity using aryl bromides and iodides as capping agents. The polymerization proceeds via a two‐stage process. Before monomer 1 is consumed, the competitive formation of end‐capped and non‐capped HT‐P3HTs is operative, where the molecular weight increases linearly with monomer conversion. After 1 is consumed, the resulting polymers are coupled with each other to afford highly end‐capped HT‐P3HTs.