Synthesis,two‐photon absorption,and optical power limiting of new linear and hyperbranched conjugated polyynes based on bithiazole and triphenylamine

Two new linear and hyperbranched conjugated polymers P1 and P2 have been synthesized by Sonogashira coupling reaction, in which the main chain consists of bithiazole moieties as electron acceptors and triphenylamino groups as donors. The conjugated polymers were characterized by TGA, UV–vis absorption, fluorescence emission, electrochemical cyclic voltammetry, and two‐photon absorption measurements. They exhibited excellent solubility in organic solvents and high thermal stability (5% of weight loss at 299 °C). The two‐photon absorption cross sections (σ) measured by the open aperture Z‐scan technique using 140 femtosecond (fs) pulse were determined to be 1014 and 552 GM per repeating unit for P1 and P2 , respectively. This result shows that the σ of linear conjugated P1 is higher than that of hyperbranched P2 , indicating that the linear polymer offers better intramolecular charge transfer ability. In THF, P1 and P2 exhibit intense frequency up‐converted fluorescence under the excitation of 140 fs pulses at 800 nm with the peaks located at 580 and 548 nm, respectively. Meanwhile, the optical limiting behaviors for the polymers were studied by using a focused 800 nm laser beam of 140 fs duration. It was found that these polymers also exhibit good optical‐limiting properties and make them potential candidates for optical limiters in the photonic fields. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and characterization of a narrow‐bandgap polymer containing alternating cyclopentadithiophene and diketo‐pyrrolo‐pyrrole units for solar cell applications

We have synthesized a narrow‐bandgap conjugated polymer ( PCTDPP ) containing alternating cyclopentadithiophene (CT) and diketo‐pyrrolo‐pyrrole (DPP) units by Suzuki coupling. This PCTDPP exhibits a low band gap of 1.31 eV and a broad absorption band from 350 to 1000 nm, which allows it to absorb more available photons from sunlight. A bulk heterojunction polymer solar cell incorporating PCTDPP and C₇₀ at a blend ratio of 1:3 exhibited a high short‐circuit current of 10.87 mA/cm² and a power conversion efficiency of 2.27%. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1669–1675, 2010     

Synthesis and two‐photon absorption properties of conjugated polymers with N‐arylpyrrole as conjugated bridge and isolation moieties

Three novel conjugated polymers with N‐arylpyrrole as the conjugated bridge were designed and synthesized, which emitted strong one‐ or two‐photon excitation fluorescence in dilute tetrahydrofuran (THF) solution with high quantum yields. The maximal two‐photon absorption (TPA) cross‐sections of the polymers, measured by the two‐photon‐induced fluorescence method using femtosecond laser pulses in THF, were 752, 1114, and 1869 GM, respectively, indicating that the insertion of electron‐donating or electron‐withdrawing moieties into the polymer backbone could benefit to the increase of the TPA cross‐section. Their large TPA cross‐sections, coupled with the relatively high emission quantum yields, made these conjugated polymers attractive for practical applications, especially two‐photon excited fluorescence. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis,characterization, and large two‐photon absorption cross‐sections of solid red‐emitting 1,4‐diketo‐3,6‐diphenylpyrrolo [3,4‐c]pyrrole/3,6‐carbazole/terfluorene copolymers

The synthesis, one‐ and two‐photon absorption (TPA) and emission properties of three novel 1,4‐diketo‐3,6‐diphenylpyrrolo[3,4‐c]pyrrole (DPP)/3,6‐carbazole (Cz)/terfluorene (TF) copolymers are reported. The molar ratios of DPP versus TF are 15:85 ( TCP15 ), 25:75 ( TCP25 ), and 50:50 ( TCP50 ) under Cz:(TF + DPP) = 1. Two distinguished one‐photon absorption and emission bands observed in solutions imply that the electronic states of Cz–DPP–Cz and Cz–TF–Cz are not well mixed and the energy transfer from TF segments to DPP units is incomplete. However, in film states, all three copolymers are monochromatic red emitting with the peak wavelengths at 617, 621, and 631 nm for TCP15 , TCP25 , and TCP50 , respectively, indicating that the interchain interactions also have played an important role in the energy transfer. In two‐photon measurement, the copolymer solutions still exhibit two distinguished emission bands but the relative intensities at short‐wavelength region are obviously decreased, implying that Cz–TF–Cz segment is high one‐photon active but low TPA active, whereas Cz–DPP–Cz unit is low one‐photon active but high TPA active. All the copolymers show large δ over the range of measured wavelengths and the δ values of TCP15 , TCP25 , and TCP50 increase with DPP contents and are up to 530, 770, and 850 GM per repeating unit, respectively. © 2011 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     

Synthesis,electrochemical, and optical properties of low band gap homo‐ and copolymers based on squaraine dyes

A broad series of monomeric and polymeric squaraines was synthesized to investigate the impact of electron‐donating bridges, such as unsaturated triarylamine, carbazole, and saturated piperazine groups, on the spectroscopic and redox properties. These bridges were attached to both standard trans‐indolenine squaraines and dicyanomethylene‐substituted cis‐indolenine squaraines. The conjugates were investigated by absorption, steady‐state, and time‐resolved fluorescence spectroscopy and cyclic voltammetry. While addition of the donors resulted in significant redshift of the absorption of the model compounds, hardly any further shift or broadening was observed for the copolymers. Also the redox properties remained nearly unchanged compared with the model dyes. In contrast, immense broadening and redshift was observed for homopolymers. This behavior is explained by mostly excitonic coupling of localized squaraine transitions. The increasing distance of the chromophores determined by the bridges led to a decrease of the exciton coupling energy. We also performed semiempirical CNDO/S2 calculations on AM1 optimized structures. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 890–911     

A Triphenylamine‐Based Conjugated Polymer with Donor‐π‐Acceptor Architecture as Organic Sensitizer for Dye‐Sensitized Solar Cells

A conjugated polymer containing an electron donating backbone (triphenylamine) and an electron accepting side chain (cyanoacetic acid) with conjugated thiophene units as the linkers has been synthesized. Dye‐sensitized solar cells (DSSCs) are fabricated utilizing this material as the dye sensitizer, resulting a typical power conversion efficiency of 3.39% under AM 1.5 G illumination, which represents the highest efficiency for polymer dye‐sensitized DSSCs reported so far. The results show the good promise of conjugated polymers as sensitizers for DSSC applications.

     

Synthesis,one‐ and two‐photon properties of poly[9,10‐bis(3,4‐bis(2‐ethylhexyl‐oxy)phenyl)‐2,6‐anthracenevinylene‐alt‐N‐octyl‐3,6‐/2,7‐carbazolevinylene]

The synthesis, one‐ and two‐photon absorption (TPA) and emission properties of two novel 2,6‐anthracenevinylene‐based copolymers, poly[9,10‐bis(3,4‐bis(2‐ethylhexyloxy)phenyl)‐2,6‐anthracenevinylene‐alt‐N‐octyl‐3,6‐carbazolevinyl‐ene] ( P1 ) and poly[9,10‐bis(3,4‐bis(2‐ethylhexyloxy)phenyl)‐2,6‐anthracenevinyl‐ene‐alt‐N‐octyl‐2,7‐carbazolevinylene] ( P2 ) were reported. The as‐synthesized polymers have the number‐average molecular weights of 1.56 × 10⁴ for P1 and 1.85 × 10⁴ g mol^?1 for P2 and are readily soluble in common organic solvents. They emit strong bluish‐green one‐ and two‐photon excitation fluorescence in dilute toluene solution (? _P1 = 0.85, ? _P2 = 0.78, λ_em( P1 ) = 491 nm, λ_em( P2 ) = 483 nm). The maximal TPA cross‐sections of P1 and P2 measured by the two‐photon‐induced fluorescence method using femtosecond laser pulses in toluene are 840 and 490 GM per repeating unit, respectively, which are obviously larger than that (210 GM) of poly[9,10‐bis‐(3,4‐bis(2‐ethylhexyloxy) phenyl)‐2,6‐anthracenevinylene], indicating that the poly(2,6‐anthracenevinylene) derivatives with large TPA cross‐sections can be obtained by inserting electron‐donating moieties into the polymer backbone. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 463–470, 2010     

Chiral thiophene derivatives with optimal two‐photon absorption in near‐infrared window I and II

Thiophene derivatives are outstanding organic materials due to their wide spectral response, superior optoelectronic properties, and excellent environmental stability, which have attracted widespread attention in both theory and applications. However, their chiral analogues and corresponding chiroptical behaviors have been rarely investigated. Herein, a series of chiral thiophene derivatives are firstly designed by taking both optical chirality and two‐photon absorption (TPA) response into consideration, and are then investigated by modern analytical response theory. The calculated results demonstrate that these novel chiral thiophene derivatives show optimal TPA in the near‐infrared (NIR) window I and II, indicating that they are promising for biological applications. More importantly, they exhibit reasonable two‐photon circular dichroism (TPCD) signals, which are desirable candidates for chiral recognition regions. Furthermore, the calculations of orbital transitions shed light on that the intramolecular charge transfer plays an important role in their excellent TPA and TPCD behaviors in NIR regions.     

Synthesis and structure‐activity relationship of several aromatic ketone‐based two‐photon initiators

Several novel aromatic ketone‐based two‐photon initiators containing triple bonds and dialkylamino groups were synthesized and the structure‐activity relationships were evaluated. Branched alkyl chains were used at the terminal donor groups to improve the solubility in the multifunctional monomers. Because of the long conjugation length and good coplanarity, the evaluated initiators showed large two‐photon cross section values, while their fluorescence lifetimes and quantum yields strongly depend on the solvent polarity. All novel initiators exhibited high activity in terms of two‐photon‐induced microfabrication. This is especially true for fluorenone‐based derivatives, which displayed much broader processing windows than well‐known highly active initiators from the literature and commercially available initiators. While the new photoinitiators gave high reactivity in two‐photon‐induced photopolymerization at concentration as low as 0.1% wt, these compounds are surprisingly stable under one photon condition and nearly no photo initiation activity was found in classical photo DSC experiment. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and photovoltaic properties of two‐dimensional D‐A copolymers with conjugated side chains

Four novel two‐dimensional (2D) donor–acceptor (D‐A) type copolymers with different conjugated side chains, P1 , P2 , P3 , and P4 (see Fig. 1 ), are designed and synthesized for the application as donor materials in polymer solar cells (PSCs). To the best of our knowledge, there were few reports to systematically study such 2D polymers with D‐A type main chains in this area. The optical energy band gaps are about 2.0 eV for P1 – P3 and 1.67 eV for P4 . PSC devices using P1 – P4 as donor and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester as acceptor in a weight ratio of 1:3 were fabricated and characterized to investigate the photovoltaic properties of the polymers. Under AM 1.5 G, 100 mA/cm² illumination, a high open‐circuit voltage (V_oc) of 0.9 V was recorded for P3 ‐based device due to its low HOMO level, and moderate fill factor was obtained with the best value of 58.6% for P4 ‐based device, which may mainly be the result of the high hole mobility of the polymers (up to 1.82 × 10^?3 cm²/V s). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and characterization of alternating copolymers containing triphenylamine as hole‐transporting units

A series of light‐emitting poly(p‐phenylene vinylene)s with triphenylamine units as hole‐transporting moieties in the main chain were synthesized via Wittig condensation in good yields. The newly formed vinylene double bonds possessed a trans configuration, which was confirmed by Fourier transform infrared and NMR spectroscopy. The high glass‐transition temperature (83–155 °C) and high decomposition temperature (>300 °C) suggested that the resulting copolymers possessed high thermal stability. These copolymers, especially TAAPV1, possessed a high weight‐average molecular weight (47,144) and a low polydispersity index (1.55). All the copolymers could be dissolved in common organic solvents, such as tetrahydrofuran (THF), CHCl₃, CH₂Cl₂, and toluene, and exhibited intense photoluminescence in THF (the emission maxima were located from 478 to 535 nm) and in film (from 478 to 578 nm). The low onsets of the oxidation potential (0.6–0.75 V) suggested that the alternating copolymers possessed a good hole‐transporting property due to the incorporation of triphenylamine moieties. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3278–3286, 2001     

Carbazolevinylene‐based polymers and model compounds with oxadiazole and triphenylamine segments: Synthesis,photophysics, and electroluminescence

Two new soluble alternating carbazolevinylene‐based polymers POXD and PTPA as well as the corresponding model compounds MOXD and MTPA were synthesized by Heck coupling. POXD and MOXD contained 2,5‐diphenyloxadiazole segments, while PTPA and MTPA contained triphenylamine segments. All samples displayed high thermal stability. The polymers had higher glass transition temperature (T_g) than their corresponding model compounds. The samples showed absorption maximum at 364–403 nm with optical band gap of 2.62–2.82 eV. They emitted blue‐green light with photoluminescence (PL) emission maximum at 450–501 nm and PL quantum yields in THF solution of 0.15–0.36. The absorption and the PL emission maxima of PTPA and MTPA were blue‐shifted as compared to those of POXD and MOXD . The electroluminescence (EL) spectra of multilayered devices made using four materials exhibited bluish green emissions, which is well consistent with PL spectra. The EL devices made using poly(vinyl carbazole) doped with MOXD and MTPA as emitting materials showed luminances of 12.1 and 4.8 cd m^?2. POXD and PTPA exhibited 25.4, and 96.3 cd m^?2, respectively. The polymer containing the corresponding molecules in the repeating group showed much higher device performances. Additionally, POXD and MOXD exhibited better stability of external quantum efficiency (EQE) and luminous efficiency with current density resulting from enhancing the electron transporting properties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5592–5603, 2008     

Copolyfluorenes containing bridged triphenylamine or triphenylamine: Synthesis,characterization, and optoelectronic properties

A novel aryl‐bridged triphenylamine derivative, 7‐t‐butyl‐5,5,9,9‐tetraaryl‐13b‐aza‐naphtho[3,2,1‐de]anthracene (ABTPA) was designed and synthesized. The alternating copolymers of ABTPA/dihexylfluorene ( P1 ) and triphenylamine (TPA)/dihexylfluorene ( P2 ) were synthesized by Suzuki coupling reaction. P1 shows excellent thermal stability with a decomposition temperature of 440 °C and a glass‐transition temperature of 326 °C. The HOMO energy levels of the two polymers are very close (?5.15 eV for P1 and ?5.13 eV for P2 ). The maximum absorption peak of P1 is red shifted by 23 nm with respect to P2 , because the incorporation of ABTPA units into the PF backbone enhances the electronic conjugation degree compared with the case of TPA units. The rigidity and the steric hindrance of the ABTPA in P1 result in a small Stokes shift and almost the same emission spectra of P1 between its film and solution. A PLED with simple configurations of ITO/ P1 /TNS (tetranaphthalen‐2‐yl‐silane)/Alq₃ (tris(8‐hydroxyquinolinolato)aluminum)/Al emits a blue light with emission peak at 436 nm, and exhibits a maximum current efficiency of 1.89 cd/A and a maximum luminance of 4183 cd/m², which is superior to the device with P2 as emissive layer under the identical conditions. These results indicate that ABTPA unit could be a very promising candidate to replace TPA unit and find widely application in organic/polymeric optoelectronic materials. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3651–3661, 2009     

Theoretical study on the one‐, two‐, and three‐photon absorption properties of exohedral functionalized derivative of Sc3N@C80

Geometrical structures of three investigated molecules Sc₃N@C₈₀, Sc₃N@C₈₀‐Fc, and C₆₀‐Fc were optimized by density functional theory (DFT) at the B3LYP/6‐31G* level. Then the time‐dependent DFT was employed to investigate the excited states of these molecules. After exohedral functionalization by ferrocene (Fc‐) group as the electron donor or replacing C₆₀ with Sc₃N@C₈₀ as the electron acceptor, the wavelengths of the first one‐photon absorption peak and the strongest two‐photon absorption (2PA) and three‐photon absorption (3PA) peaks shift red. The corresponding cross sections of Sc₃N@C₈₀‐Fc in the 2PA and 3PA processes increase as compared with those of Sc₃N@C₈₀, which originate from the contributions of charge transfers from Fc‐ group to C₈₀ cage and simultaneously the transfers from the C₈₀ cage to the encapsulated Sc₃N cluster. When compared with C₆₀‐Fc, the 2PA and 3PA cross sections of Sc₃N@C₈₀‐Fc decrease, which may result from the more negative charge surface of C₈₀ cage in Sc₃N@C₈₀‐Fc molecule which blocks the charge transfers from Fc‐ moiety to the C₈₀ cage in the excitation processes by compared with C₆₀‐Fc. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

Synthesis and electrochromic properties of triphenylamine containing copolymers: Effect of π‐bridge on electrochemical properties

In this study, a series of benzotriazole (BTz) and triphenylamine (TPA)‐based random copolymers; poly4‐(5‐(2‐dodecyl‐7‐methyl‐2H‐benzo[d][1,2,3]triazol‐4‐yl)thiophen‐2‐yl)‐N‐(4‐(5‐methylthiophen‐2‐yl)phenyl)‐N‐phenylaniline ( P1 ), poly4′‐(2‐dodecyl‐7‐methyl‐2H‐benzo[d][1,2,3]triazol‐4‐yl)‐N‐(4′‐methyl‐[1,1′‐biphenyl]‐4‐yl)‐N‐phenyl‐[1,1′‐biphenyl]‐4‐amine ( P2 ), and poly4‐(5′‐(2‐dodecyl‐7‐(5‐methylthiophen‐2‐yl)?2H‐benzo[d][1,2,3]triazol‐4‐yl)‐[2,2′‐bithiophen]‐5‐yl)‐N‐(4‐(5‐methylthiophen‐2‐yl)phenyl)‐N‐phenylaniline ( P3 ) were synthesized to investigate the effect of TPA unit and π‐bridges on electrochemical and spectroelectrochemical properties of corresponding polymers. The synthesis was carried out via Stille coupling for P1 , P3 , and Suzuki coupling for P2 . Electrochemical and spectral results showed that P1 has an ambipolar character, in other words it is both p‐type and n‐type dopable, whereas P2 and P3 have only p‐doping property. Effect of different π‐bridges and TPA unit on the HOMO and LUMO energy levels, switching time, and optical contrast were discussed. All polymers are promising materials for electrochromic devices. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 537–544     

Synthesis and photovoltaic properties of amorphous polymers based on dithienylbenzothiadiazole‐triphenylamine with hexyl side chains on different positions of thienyl groups

We synthesized and characterized three new amorphous dithienylbenzothiadiazole (TBT)‐triphenylamine (TPA) polymers for application in bulk‐heterojunction (BHJ) organic photovoltaic (OPV) cells. Poly(3HTBT‐TPA) has hexyl side chains on the thienyl groups (pointing toward the benzothiadiazole (BTD) unit), and poly(4HTBT‐TPA) has hexyl side chains on the thienyl groups (pointing outward from the BTD unit). The incident photon to current conversion efficiencies (IPCEs) in the region from 550 to 650 nm for the OPV cells prepared using poly(4HTBT‐TPA) were higher than those for the OPV cells prepared using poly(3HTBT‐TPA) because the absorption spectrum for the poly(4HTBT‐TPA) has a slightly red‐shifted absorption edge. We also demonstrated that the poly(4HTBT‐TPA)‐based OPV performance is independent of the fabrication process, so using an amorphous film to fabricate BHJ OPV cells offers great advantages over using a polycrystalline film in terms of the high reproducibility of the OPV performance. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2536–2544     

Characterization of two‐ and three‐photon absorption of polyfluorene derivatives

Fluorene‐based polymer derivatives are promising materials for organic electronic devices because of their photoluminescence and electroluminescence, good film‐forming ability, and favorable chemical and thermal properties. Although optical properties of polyfluorene have already been reported, most of the studies focused on the linear optical properties, whereas nonlinear optical characteristics have only recently received more detailed attention. Here, we report on two polyfluorene derivatives, poly(9,9′‐n‐dihexyl‐2,7‐fluorenediyl) (LaPPS 10) and poly(9,9′‐n‐dihexyl‐2,7‐fluorene‐diyl‐vinylene) (LaPPS 38), which present intense nonlinear absorption and fluorescence. Two‐photon absorption cross‐section properties of both polymers were characterized in the spectral range from 500 nm up to 900 nm, reaching peak values around 2000 Göppert Mayer units. Optical limiting behavior and two‐photon‐induced fluorescence of both polymers have also been investigated. Furthermore, the first molecular hyperpolarizability of the polymers was also studied using hyper‐Rayleigh scattering. In addition, the three‐photon absorption (3PA) spectra of both materials were also investigated, and 3PA cross‐section values in the order of 1 × 10^?78 cm⁶ s² photon^?2 were observed. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 747–754     

Synthesis and electroluminescent properties of polyfluorene‐based conjugated polymers containing bipolar groups

A bipolar dibromo monomer, bis‐(4‐bromophenyl)[4‐(3,5‐diphenyl‐1,2,4‐ triazole‐4‐yl)‐phenyl]amine ( 9 ), containing electro‐rich triphenylamine and electro‐deficient 1,2,4‐triazole moieties was newly synthesized and characterized. Two fluorescent fluorene‐based conjugated copolymers ( TPAF , TPABTF ) were prepared via facile Suzuki coupling from the dibromo bipolar monomer, 4,7‐dibromo‐2,1,3‐benzothiadiazole ( BTDZ ), and 9,9‐dioctylfluorene. They were characterized by molecular weight determination, IR, NMR, DSC, TGA, solubility, absorption and photoluminescence spectra, and cyclic voltammetry. The polymers showed good solubility in common organic solvents such as dichloromethane, chloroform, tetrahydrofuran, and dichlorobenzene at room temperature. They had glass transition temperatures (T_g) higher than 135 °C and 5% degradation temperatures in nitrogen atmosphere were higher than 428 °C. Single layer polymer light‐emitting diodes (PLED) of ITO/PEDOT:PSS/polymer/metal showed a blue emission at 444 nm and Commission Internationale de I'Eclairage (CIE) 1931 color coordinates of (0.16, 0.13) for TPAF . The device using TPABTF as emissive material showed electroluminescence at 542 nm with CIE1931 of (0.345, 0.625), low turn‐on voltage of 5 V, a maximum electroluminance of 696 cd/m², and a peak efficiency of 2.02 cd/A. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6231–6245, 2009     

Effects of pigments on the volume‐phase‐transition properties of N‐isopropylacrylamide gels as light‐modulation materials

The effects of pigments contained in N‐isopropylacrylamide (NIPAM) gels on their volume‐change properties were investigated. All the NIPAM gel particles, containing various kinds and concentrations of pigments, showed a volume phase transition at 34 °C. No pigment affected the volume‐phase‐transition temperature of the NIPAM gels. As the concentration of the pigment in the NIPAM gels was increased, the amount of the volume change of the NIPAM gels was reduced. The water absorptivity of the NIPAM gels in the swollen state decreased as the pigment concentration increased, whereas the water absorptivity in the shrunken state was almost constant. Reducing the initial monomer concentration of the polymerization of the NIPAM gel increased the water absorptivity in the swollen state. With an increase in the water absorptivity, the volume changes of the NIPAM gels containing pigments were increased. Prototype light modulators in which the NIPAM gel particles containing pigment were dispersed between glass plates were fabricated. The light modulator using the gel particles with improved diameter change (d/d₀ = 2.3, where d and d₀ are the equilibrium diameter and the diameter of the fully shrunken state at 50 °C, respectively) exhibited a larger transmittance change from 8 to 79% than that using the gel particles before the improvement (d/d₀ = 1.7; from 38 to 79%) according to temperature changes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4644–4655, 2006