Synthesis and comparison of the structure–property relationships of symmetric and asymmetric water‐soluble poly(p‐phenylene)s

Sodium salts of water‐soluble polymers poly{[2,5‐bis(3‐sulfonatopropoxy)‐1,4‐phenylene]‐alt‐[2,5‐bis(hexyloxy)‐1,4‐phenylene]} ( P1 ), poly{[2,5‐bis(3‐sulfonatopropoxy)‐1,4‐phenylene]‐alt‐[2,5‐bis(dodecyloxy)‐1,4‐phenylene]} ( P2 ), poly{[2,5‐bis(3‐sulfonatopropoxy)‐1,4‐phenylene]‐alt‐[2,5‐bis(dibenzyloxy)‐1,4‐phenylene]} ( P3 ), poly[2‐hexyloxy‐5‐(3‐sulfonatopropoxy)‐1,4‐phenylene] ( P4 ), and poly[2‐dodecyloxy‐5‐(3‐sulfonatopropoxy)‐1,4‐phenylene] ( P5 )] were synthesized with Suzuki coupling reactions and fully characterized. The first group of polymers ( P1 – P3 ) with symmetric structures gave lower absorption maxima [maximum absorption wavelength (λ_max) = 296–305 nm] and emission maxima [maximum emission wavelength (λ_em) = 361–398 nm] than asymmetric polymers P4 (λ_max = 329 nm, λ_em = 399 nm) and P5 (λ_max = 335 nm, λ_em = 401 nm). The aggregation properties of polymers P1 – P5 in different solvent mixtures were investigated, and their influence on the optical properties was examined in detail. Dynamic light scattering studies of the aggregation behavior of polymer P1 in solvents indicated the presence of aggregated species of various sizes ranging from 80 to 800 nm. The presence of alkoxy groups and 3‐sulfonatopropoxy groups on adjacent phenylene rings along the polymer backbone of the first set hindered the optimization of nonpolar interactions. The alkyl chain crystallization on one side of the polymer chain and the polar interactions on the other side allowed the polymers ( P4 and P5 ) to form a lamellar structure in the polymer lattice. Significant quenching of the polymer fluorescence upon the addition of positively charged viologen derivatives or cytochrome‐C was also observed. The quenching effect on the polymer fluorescence confirmed that the newly synthesized polymers could be used in the fabrication of biological and chemical sensors. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3763–3777, 2006     

Green‐emitting poly[(1,3‐phenylenevinylene)‐alt‐ (1,4‐phenylenevinylene)]s: Effect of the substitution patterns on the optical properties

Green‐emitting substituted poly[(2‐hexyloxy‐5‐methyl‐1,3‐phenylenevinylene)‐alt‐(2,5‐dihexyloxy‐1,4‐phenylenevinylene)]s ( 6 ) were synthesized via the Wittig–Horner reaction. The polymers were yellow resins with molecular weights of 10,600. The ultraviolet–visible (UV–vis) absorption of 6 (λ_max = 332 or 415 nm) was about 30 nm redshifted from that of poly[(2‐hexyloxy‐5‐methyl‐1,3‐phenylenevinylene)‐alt‐(1,4‐phenylenevinylene)] ( 2 ) but was only 5 nm redshifted with respect to that of poly[(1,3‐phenylenevinylene)‐alt‐(2,5‐dihexyloxy‐1,4‐phenylenevinylene)] ( 1 ). A comparison of the optical properties of 1 , 2 , and 6 showed that substitution on m‐ or p‐phenylene could slightly affect their energy gap and luminescence efficiency, thereby fine‐tuning the optical properties of the poly[(m‐phenylene vinylene)‐alt‐(p‐phenylene vinylene)] materials. The vibronic structures were assigned with the aid of low‐temperature UV–vis and fluorescence spectroscopy. Light‐emitting‐diode devices with 6 produced a green electroluminescence output (emission λ_max ～ 533 nm) with an external quantum efficiency of 0.32%. Substitution at m‐phenylene appeared to be effective in perturbing the charge‐injection process in LED devices. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1820–1829, 2004     

New photoluminescent conjugated polymers with 1,4‐dioxo‐3,6‐diphenylpyrrolo[3,4‐c]pyrrole (DPP) and 1,4‐phenylene units in the main chain

A series of π‐conjugated polymers and copolymers containing 1,4‐dioxo‐3,6‐diphenylpyrrolo[3,4‐c]pyrrole (also known as 2,5‐dihydro‐3,6‐diphenylpyrrolo[3,4‐c]pyrrole‐1,4‐dione) (DPP) and 1,4‐phenylene units in the main chain is described. The polymers are synthesised using the palladium‐catalysed aryl‐aryl coupling reaction (Suzuki coupling) of 2,5‐dihexylbenzene‐1,4‐diboronic acid with 1,4‐dioxo‐2,5‐dihexyl‐3,6‐di(4‐bromophenyl)pyrrolo[3,4‐c]pyrrole and 1,4‐dibromo‐2,5‐dihexylbenzene in different molar ratios. Soluble hairy rod‐type polymers with molecular weights up to 21 000 are obtained. Polymer solutions in common organic solvents such as chloroform or xylene are of orange colour (λ_max = 488 nm) and show strong photoluminescence (λ_max = 544 nm). The photochemical stability is found to be higher than for corresponding saturated polymers containing isolated DPP units in the main chain. Good solubility and processability into thin films render the compounds suitable for electronic applications.     

Synthesis and characterization of new π‐conjugated polymers containing 1,8‐naphthyridine in the main chain: Role of the 1,8‐naphthyridine unit in π‐conjugated polymers

Alternating π‐conjugated copolymers of 1,8‐naphthyridine‐2,6‐diyl ( 1,8‐Nap ) with 9,9‐dioctylfluorene‐2,7‐diyl ( P(Flu‐Ph‐1,8‐Nap) ) and 2,5‐didodecyloxy‐1,4‐phenylene ( P(ROPh‐Ph‐1,8‐Nap) ) have been synthesized by Pd‐catalyzed organometallic polycondensation. The copolymers showed UV‐vis absorption peaks at around 390 nm in o‐dichlorobenzene. The polymers were photoluminescent both in o‐dichlorobenzene and in the solid state. In o‐dichlorobenzene, the emission peaks of P(Flu‐Ph‐1,8‐Nap) and P(ROPh‐Ph‐1.,8‐Nap) appeared at λ_EM = 440 and 471 nm, with quantum yields of 87% and 66%, respectively. Electrochemical data revealed that 1,8‐Nap behaved as a typical electron‐accepting unit. When P(Flu‐Ph‐1,8‐Nap) was treated with 10‐camphorsulfonic acid, the emission peak shifted to λ_EM = 598 nm. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Tropone‐containing π‐conjugated polymers: Annulation of tropone onto benzene ring in the conjugated polymer

Tropone‐fused, various π‐conjugated polymers ( P2 – P5 ) were synthesized by the palladium‐catalyzed coupling reaction of 1,4‐dibromo‐6,8‐dimethyl‐7H‐benzocyclohepten‐7‐one with aromatic divinyl, diboronic acid, and diethynyl compounds. The molecular orbital calculation of the model compounds was performed to discuss effective conjugation length of the repeating unit of the polymers. The absorption spectra of phenylenevinylene‐type polymers shifted to longer wavelengths than the model compounds by about 60 nm. They exhibited green fluorescence [λ_max(em) = 544 and 561 nm]. The absorption spectrum of a phenylene‐type polymer blueshifted by 10 nm; however, that of a phenyleneethynylene‐type polymer redshifted by 83 nm as compared with their model compounds. They showed fluorescence with peak maxima at 457 and 489 nm, respectively. As a result, the absorption spectra of phenylene‐ and phenylenevinylene‐type polymers blueshifted, but that of a phenyleneethynylene‐type polymer redshifted by the annulation of tropone onto a benzene ring in the conjugated polymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1208–1215, 2004     

Random poly(fluorenylene‐vinylene)s containing 3,7‐Dibenzothiophene‐5,5‐dioxide units: Synthesis,photophysical, and electroluminescence properties

The synthesis of new random poly(arylene‐vinylene)s containing the electron withdrawing 3,7‐dibenzothiophene‐5,5‐dioxide unit was achieved by the Suzuki–Heck cascade polymerization reaction. The properties of poly[9,9‐bis(2‐ethylhexyl)‐2,7‐fluorenylene‐vinylene‐co‐3,7‐dibenzothiophene‐5,5‐dioxide‐vinylene] (50/50 mol/mol, P1 ) and poly[1,4‐bis(2‐ethylhexyloxy)‐2,5‐phenylene‐vinylene‐co‐3,7‐dibenzothiophene‐5,5‐dioxide‐vinylene] (50/50 mol/mol, P2 ) were compared with those of terpolymers obtained by combining the fluorene, dibenzothiophene, and 1,4‐bis(2‐ethylexyloxy)benzene in 20/40/40 ( P3 ), 50/25/25 ( P4 ), and 80/10/10 ( P5 ) molar ratios. The polymers were characterized by ¹H NMR and IR, whereas their thermal properties were investigated by TGA and DSC. Polymers P1–5 are blue–green emitters in solution (λ_em between 481 and 521 nm) whereas a profound red shift observed in the solid state is emission (λ_em from 578 to 608 nm) that can be attributed both to the charge transfer stabilization exerted by the polar medium and to intermolecular interactions occurring in the solid state. Cyclic voltammetry permitted the evaluation of the ionization potentials and also revealed a quasi‐reversible behavior in the reduction scans for the polymers ( P1–4 ) containing the higher amounts of 3,7‐dibenzothiophene‐5,5‐dioxide units. Electroluminescent devices with both ITO/PEDOT‐PSS/ P1–5 /Ca/Al (Type I) and ITO/PEDOT‐PSS/ P1–5 /Alq₃/Ca/Al (Type II) configuration were fabricated showing a yellow to yellow–green emission. In the case of P4 , a luminance of 1835 cd/m² and an efficiency of 0.25 cd/A at 14 V were obtained for the Type II devices. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2093–2104, 2009     

Thermotropic liquid‐crystalline polymers containing five‐membered heterocyclic groups. X. Relationships between structures of semirigid polyesters based on three disubstituted 2,5‐diphenyl‐1,3,4‐thiadiazoles and thermotropic liquid‐crystalline and optical properties

Thermotropic liquid‐crystalline (LC) semirigid polyesters based on three terphenyl analogues of 1,3,4‐thiadiazole (2,5‐diphenyl‐1,3,4‐thiadiazole)s (DPTD) linking undecamethyleneoxy chain at different substituted positions were synthesized from three disubstituted (4,4′‐, 3,4′‐, and 3,3′‐) dioxydiundecanols of DPTD and four diesters, and the relationships between polymer structures and LC and optical properties were investigated. DSC measurements, texture observations, and wide‐angle X‐ray analyses revealed that the polymers composed of DPTD moiety having a more linear molecular structure and 1,4‐phenylene unit or short aliphatic chain tend to exhibit LC smectic C and/or A phases. The following observations were made: (1) the emergence of smectic C and/or A phases in all the polymers on the basis of 4,4′‐disubstituted DPTD, (2) formation of enantiotropic smectic C and/or A phases in the polymers containing a 1,4‐phenylene unit in the main chain, (3) formation of a more stable smectic C phase in the polymers having a short aliphatic [(CH₂)₄] chain, and (4) a decrease of the mesomorphic property of the polyesters in the order of 4,4′‐DPTD > 3,4′‐DPTD > 3,3′‐DPTD. Solution and solid‐state ultraviolet–visible and photoluminescent spectra indicated that all the polyesters display maximum absorbances and blue emissions arising from the DPTD moiety, whose peak maxima were shifted to lower wavelengths in the order of 4,4′‐DPTD > 3,4′‐DPTD > 3,3′‐DPTD as well as the aforementioned LC property. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2676–2687, 2003     

Synthesis and properties of fluorinated polyimides based on 1,4‐bis(4‐amino‐2‐trifluoromethylphenoxy)‐2,5‐di‐tert‐butylbenzene and various aromatic dianhydrides

A novel fluorinated diamine monomer, 1,4‐bis(4‐amino‐2‐trifluoromethylphenoxy)‐2,5‐di‐tert‐butylbenzene ( 2 ), was prepared through the nucleophilic substitution reaction of 2‐chloro‐5‐nitrobenzotrifluoride and 2,5‐di‐tert‐butylhydroquinone in the presence of potassium carbonate, followed by catalytic reduction with hydrazine and Pd/C. Fluorinated polyimides ( 5a – 5f ) were synthesized from diamine 2 and various aromatic dianhydrides ( 3a – 3f ) via thermal or chemical imidization. These polymers had inherent viscosities of 0.77–1.01 dL/g. The 5 series polyimides were soluble in N‐methyl‐2‐pyrrolidone, N,N‐dimethylacetamide, and N,N‐dimethylformamide and were even soluble in dioxane, tetrahydrofuran, and dichloromethane. 5 (C) showed cutoff wavelengths between 363 and 404 nm and yellowness index (b*) values of 6.5–40.2. The polyimide films had tensile strengths of 93–114 MPa, elongations to break of 9–12%, and initial moduli of 1.7–2.1 GPa. The glass‐transition temperatures were 255–288 °C. The temperatures of 10% weight loss were all above 460 °C in air or nitrogen atmospheres. In comparison with a nonfluorinated polyimide series based on 1,4‐bis(4‐aminophenoxy)‐2,5‐di‐tert‐butylbenzene, the 5 series showed better solubility and lower color intensity, dielectric constants, and moisture absorption. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2272–2284, 2004     

Synthesis and Chemical Properties of Diacetylenes with Pyridinium and 4,4′‐Bipyridinium Groups

Diacetylenes (DAs) having a dipolar D‐π‐A structure (D=donor: amino group; π=π‐conjugation core; A=acceptor: pyridinium (Py) and bipyridinium (BPy) groups), i.e., 4 (APBPyDA) and 5 (APPyPyDA), or an A‐π‐A structure, i.e., 7 (DBPyDA) and 8 (PyDA(Cl)), were obtained by 1 : 1 and 1 : 2 reactions of 4,4′‐(buta‐1,3‐diyne‐1,4‐diyl)bis[benzenamine] (APDA; 3 ) with 1‐(2,4‐dinitrophenyl)‐1′‐hexyl‐4,4′‐bipyridinium bromide chloride (1 : 1 : 1) ( 1 ), 1‐(2,4‐dinitrophenyl)‐4‐(pyridin‐4‐yl)pyridinium chloride ( 2 ), or 1‐(2,4‐dinitrophenyl)pyridinium chloride ( 6 ) (Schemes 1 and 2). The anion‐exchange reactions of 8 with NaI and Li(TCNQ) (TCNQ^?=2,2′‐(cyclohexa‐2,5‐diene‐1,4‐diylidene)bis[propanedinitrile] radical ion (1?)) yielded the corresponding I^? and TCNQ^? salts 9 (PyDA(I)) and 10 (PyDA(TCNQ)). Compounds 10 and 4 exhibited a UV/VIS absorption due to a charge transfer between the TCNQ^? and the pyridinium groups and a strong solute–solvent interaction of a dipolar solute molecule in the polar environment, respectively. Compounds 8 – 10 exhibited photoluminescence in solution, whereas 4 and 7 did not because of the presence of the 4,4′‐bipyridinium quenching groups. Differential‐scanning‐calorimetry (DSC) measurements suggested that the DAs obtained in this study can be converted into poly(diacetylenes) by thermal polymerization.     

Synthesis of three new 1‐(2,6‐diisopropylphenyl)‐2,5‐di(2‐thienyl) pyrrole‐based donor polymers and their bulk heterojunction solar cell applications

A series of three new 1‐(2,6‐diisopropylphenyl)‐2,5‐di(2‐thienyl)pyrrole‐based polymers such as poly[1‐(2,6‐diisopropylphenyl)‐2,5‐di(2‐thienyl)pyrrole] ( PTPT ), poly[1,4‐(2,5‐bis(octyloxy)phenylene)‐alt‐5,5'‐(1‐(2,6‐diisopropylphenyl)‐2,5‐di(2‐thienyl)pyrrole)] ( PPTPT ), and poly[2,5‐(3‐octylthiophene)‐alt‐5,5'‐(1‐(2,6‐diisopropylphenyl)‐2,5‐di(2‐thienyl)pyrrole)] ( PTTPT ) were synthesized and characterized. The new polymers were readily soluble in common organic solvents and the thermogravimetric analysis showed that the three polymers are thermally stable with the 5% degradation temperature >379 °C. The absorption maxima of the polymers were 478, 483, and 485 nm in thin film and the optical band gaps calculated from the onset wavelength of the optical absorption were 2.15, 2.20, and 2.13 eV, respectively. Each of the polymers was investigated as an electron donor blending with PC₇₀BM as an electron acceptor in bulk heterojunction (BHJ) solar cells. BHJ solar cells were fabricated in ITO/PEDOT:PSS/polymer:PC₇₀BM/TiO_x/Al configurations. The BHJ solar cell with PPTPT :PC₇₀BM (1:5 wt %) showed the power conversion efficiency (PCE) of 1.35% (J_sc = 7.41 mA/cm², V_oc = 0.56 V, FF = 33%), measured using AM 1.5G solar simulator at 100 mW/cm² light illumination. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

End‐group modification of poly(2,6‐dimethyl‐1,4‐phenylene ether) and in situ synthesis of poly(2,6‐dimethyl‐1,4‐phenylene ether)‐b‐poly(ethylene terephthalate) block copolymer

The preparation of poly(2,6‐dimethyl‐1,4‐phenylene ether)‐b‐poly(ethylene terephthalate) block copolymer was performed by the reaction of the 2‐hydroxyethyl modified poly(2,6‐dimethyl‐1,4‐phenylene ether) (PPE‐EtOH) with poly(ethylene terephthalate) (PET) by an in situ process, during the synthesis of the polyester. The yield of the reaction of the 2‐hydroxyethyl functionalized PPE‐EtOH with PET was close to 100%. A significant proportion of the PET‐b‐PPE‐EtOH block copolymer was found to have short PET block. Nevertheless, the copolymer structured in the shape of micelles (20 nm diameter) and very small domains with 50–200 nm diameter, whereas unmodified PPE formed much larger domains (1.5 μm) containing copolymer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3985–3991, 2008     

Aromatic poly(1,3,4‐oxadiazole)s and poly(amide‐1,3,4‐oxadiazole)s containing ether sulfone linkages

Polyhydrazides and poly(amide‐hydrazide)s were prepared from two ether‐sulfone‐dicarboxylic acids, 4,4′‐[sulfonylbis(1,4‐phenylene)dioxy]dibenzoic acid and 4,4′‐[sulfonylbis(2,6‐dimethyl‐1,4‐phenylene)dioxy]dibenzoic acid, or their diacyl chlorides with terephthalic dihydrazide, isophthalic dihydrazide, and p‐aminobenzhydrazide via a phosphorylation reaction or a low‐temperature solution polycondensation. All the hydrazide polymers were found to be amorphous according to X‐ray diffraction analysis. They were readily soluble in polar organic solvents such as N‐methyl‐2‐pyrrolidone and N,N‐dimethylacetamide and could afford colorless, flexible, and tough films with good mechanical strengths via solvent casting. These hydrazide polymers exhibited glass‐transition temperatures of 149–207 °C and could be thermally cyclodehydrated into the corresponding oxadiazole polymers in the solid state at elevated temperatures. Although the oxadiazole polymers showed a significantly decreased solubility with respect to their hydrazide prepolymers, some oxadiazole polymers were still organosoluble. The thermally converted oxadiazole polymers had glass‐transition temperatures of 217–255 °C and softening temperatures of 215–268 °C and did not show significant weight loss before 400 °C in nitrogen or air. For a comparative study, related sulfonyl polymers without the ether groups were also synthesized from 4,4′‐sulfonyldibenzoic acid and the hydrazide monomers by the same synthetic routes. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2271–2286, 2001     

New crystalline polymers: poly(2,5‐dialkyl‐1,4‐phenylene oxide)s

New heat‐reversibly crystalline poly‐(alkylated phenylene oxide)s are described. the oxidative polymerization of 2,5‐dimethylphenol catalyzed by (1,4,7‐triisopropyl‐1,4,7‐triazacyclononane) copper dichloride produced poly(2,5‐dimethyl‐1,4‐phenylene oxide), which showed heat‐reversible crystallinity with a high melting point at ca. 300°C, although the isomeric polymer, poly(2,6‐dimethyl‐1,4‐phenylene oxide), never recrystallizes once melted. The polymerization of 2,5‐diethylphenol and 2,5‐dipropylphenol gave the polymers consisting of 1,4‐phenylene oxide units; the latter polymer possessed heat‐reversible crystallinity, however, the former one did not.     

Protein–induced aggregation of fluorescent conjugated polyelectrolytes with sulfonate groups: Synthesis and its sensing application

Anionically charged fluorescent conjugated polyelectrolytes of poly{[4,7‐(2,1,3‐benzothiadiazole)‐alt‐1,4‐phenylene]‐co‐[2,5‐bis(4‐sulfonatobutoxy)‐alt‐1,4‐phenylene]} ( P1 ) and poly{[4,7‐(bis(thiophen‐2‐yl)benzo‐2,1,3‐thiadiazole)‐alt‐1,4‐phenylene]‐co‐[2,5‐bis(4‐sulfonatobutoxy)‐alt‐1,4‐phenylene]} ( P2 ) were synthesized by Suzuki crosscoupling polymerization in the presence of a palladium catalyst. The conjugated polyelectrolytes with sulfonate groups, as efficient signal amplifying reporters, were carefully designed to be soluble in water over the entire pH range examined and interact with proteins through intermolecular forces. The polymers exhibited blue emission in aqueous solutions but green or red emission in solid form depending on the conjugation length due to intermolecular exciton migration. The anionic conjugated polymers exhibited blue‐to‐green or blue‐to‐red changes in fluorescence upon exposure to charged proteins, indicating that the polymers have potential applications in fluorescent array systems for protein. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

The suzuki–heck polymerization as a tool for the straightforward obtainment of poly(fluorenylene‐vinylene) sensitizers for dye‐sensitized solar cells

This article describes the synthesis and properties of the first poly(arylene‐vinylene)‐based sensitizers for application in dye‐sensitized solar cells (DSSC). The polymers were prepared by the Suzuki–Heck copolymerization of potassium vinyltrifluoroborate (PVTB) with a mixture of dibromoaryl comonomers designed to obtain macromolecules able to bind onto the photoelectrode by means of carboxyphenylene units. The copolymerization reactions were carried out in the presence of an excess of PVTB to lower the molecular weights of the polymers, which were obtained as soluble materials. The polymers poly[(9,9‐didodecyl‐2,7‐fluorenylene)‐vinylene‐co‐(carboxy‐2,5‐phenylene)‐vinylene] ( P1 ), poly[(9,9‐didodecyl‐2,7‐fluorenylene)‐vinylene‐co‐(carboxy‐2,5‐phenylene)‐vinylene‐co‐(4,7‐benzothiadiazolylene)‐vinylene] ( P2 ), and poly[(9,9‐didodecyl‐2,7‐fluorenylene)‐vinylene‐co‐(carboxy‐2,5‐phenylene)‐vinylene‐co‐2,5‐thienylene‐vinylene] ( P3 ) were used in DSSC devices, obtaining conversion efficiencies up to 0.88% ( P3 ). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Poly(1,4‐diketo‐3,6‐diphenylpyrrolo[3,4‐c]pyrrole‐alt−3,6‐carbazole/2,7‐fluorene) as high‐performance two‐photon dyes

This article reports the synthesis, one‐ and two‐photon absorption, and excited fluorescence properties of poly(1,4‐diketo‐3,6‐diphenylpyrrolo[3,4‐c]pyrrole‐alt‐N‐octyl‐3,6‐carbazole/2,7‐fluorene) ( PDCZ / PDFL ). PDCZ and PDFL are synthesized by the Suzuki cross‐coupling of 2,5‐dioctyl‐1,4‐diketo‐3,6‐bis(p‐bromophenylpyrrolo[3,4‐c]pyrrole and N‐octyl‐3,6‐bis(3,3‐dimethyl‐1,3,2‐dioxaborolan‐2‐yl)carbazole or 2,7‐bis(3,3‐dimethyl‐1,3,2‐dioxaborolan‐2‐yl)fluorene and have number‐average molecular weights of 8.5 × 10³ and 1.14 × 10⁴ g/mol and polydispersities of 2.06 and 1.83, respectively. They are highly soluble in common organic solvents and emit strong orange one‐ and two‐photon excited fluorescence (2PEF) in THF solution and exhibit high light and heat stability. The maximal two‐photon absorption cross‐sections (δ) measured in THF solution by the 2PEF method using femtosecond laser pulses are 970 and 900 GM per repeating unit for PDCZ and PDFL , respectively. These 1,4‐diketo‐pyrrolo[3,4‐c]pyrrole‐containing polymers with full aromatic structure and large δ will be promising high‐performance 2PA dyes applicable in two‐photon science and technology. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 944–951     

Ethynylene‐containing donor–acceptor alternating conjugated polymers: Synthesis and photovoltaic properties

Four ethynylene‐containing donor‐acceptor alternating conjugated polymers P1 – P4 with 2,5‐bis(dodecyloxy) substituted phenylene or carbazole as the donor unit and benzothiadiazole (BTZ) as the acceptor unit were synthesized and used as donor polymers in bulk heterojunction polymer solar cells. The optical, electrochemical, and photovoltaic properties of these four polymers with the ethylene unit located at different positions of the polymer chains were systematically investigated. Our results demonstrated that absorption spectra and the HOMO and LUMO energy levels of polymers could be tuned by varying the position of the ethynylene unit in the polymer chains. Photovoltaic devices based on polymer/PC₇₁BM blend films spin coated from chloroform and dichlorobenzene solutions were investigated. For all four polymers, open circuit voltages (V_oc) higher than 0.8 V were obtained. P4 , with ethynylene unit between BTZ and thiophene, shows the best performance among these four polymers, with a V_oc of 0.94 V, a J_sc of 4.2 mA/cm², an FF of 0.40, and a PCE of 1.6%. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis and luminescence of yellow/orange‐emitting poly[tris(2,5‐dihexyloxy‐1,4‐phenylenevinylene)‐ alt‐(1,3‐phenylenevinylene)]s

Soluble yellow/orange‐emitting poly[tris(2,5‐dihexyloxy‐1,4‐phenylenevinylene)‐alt‐(1,3‐phenylenevinylene)] derivatives ( 6 ) were synthesized and characterized. These polymers contained oligo(p‐phenylene vinylene) chromophores of equal conjugation length, which were jointed via a common m‐phenylene unit. An optical comparison of 6 and its model compound ( 8 ) at room temperature and low temperatures revealed the similarity in their absorption and fluorescence band structures. The vibronic band structure of 6 was assigned with the aid of the spectroscopic data for 8 at the low temperatures. 6 was electroluminescent and had an emission maximum wavelength at approximately 565 nm. With the device indium tin oxide/PEDOT/ 6 /Ca configuration, the polymer exhibited an external quantum efficiency as high as 0.25%. Simple substitution on m‐phenylene of 6 raised the electroluminescence output by a factor of about 10. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5853–5862, 2004     

Synthesis,characterization, and structure–property investigation of conformationally rigid regioisomers of poly(p‐phenylene ethynylene)s

A series of rigid poly(p‐phenylene ethynylene)s ( PPE1 – PPE4 ) with biphenyl‐ ( M1–M3 ) and phenyl‐ ( M4 ) side groups is prepared from appropriately functionalized monomers. Herein, the solution and solid state absorption studies show the polymers have adopted twisted and rigid conformations, as supported by deep HOMO energy levels (?5.76 to ?5.81 eV). The absorption maxima of PPE1–PPE3 are shifted to shorter wavelength (λ_max = 375–381 nm) as compared to linear poly(p‐phenylene ethynylene)s (446 nm), implying a nonplanar conformation. The self‐assembly of polymers into fibers is examined using scanning electron microscopy. The fibers are not observed in PPE4 with short phenyl side group, suggesting the important role of the interplay between rigidity, position, and size of the side chains toward the formation of fibers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3652–3662     

π‐Conjugated oligomers containing tropone in the main chain: Synthesis,characterization, and optical properties

The synthesis and characterization of tropone‐containing π‐conjugated oligomers were investigated. Two kinds of oligomers [1,4‐phenylene type ( 4a – 4e ) and 2,5‐thienylene type ( 5 )] were successfully obtained by the Wittig polycondensation technique, in which the tropone content could be controlled by the monomer feed ratio for the 1,4‐phenylene‐type oligomers. The absorption maximum blueshifted and the emission intensity decreased with an increase in the tropone content in the oligomers. The emissive color could be tuned by the selection of the aromatic ring; that is, 4a – 4e emitted orange‐yellow light and 5 emitted either orange‐yellow or red light according to the excitation wavelength. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3927–3937, 2002