Synthesis and characterization of a double photochromic initiator for cationic polymerization

A novel cationic photoinitiator namely, 2-benzyl-2-(N,N-dimethyl-2-oxo-2-phenylethyl) ammonium hexafluoroantimonate-1-(4-morpholinophenyl)-butane-1-one (BDMPP⁺ ), carrying two photochromophoric groups was synthesized and characterized. Theoretical absorption characteristics of the salt were studied and compared with those obtained experimentally. Photoinitiation activity of this salt was demonstrated by polymerization of various monomers at λ = 350 nm. Upon irradiation by UV light, cationic species formed from homolytic dissociation followed by electron transfer or directly by heterolytic scission initiate cationic polymerization.     

DYE-SENSITIZED PHOTOPOLYMERIZATION OF METHYL METHACRYLATE INITIATED BY COUMARIN DYE/IODONIUM SALT SYSTEM*

The photosensitive initiating system composed of 7-diethylamino-3-(2'-benzimidazolyl)coumarindye (DEDC) and diphenyliodonium hexafluorophosphate (DIHP) which act as the sensitizer and the initiatorrespectively, can be used to initiate the polymerization of methyl methacrylate (MMA). The results showedthat when exposed to visible light, coumarin dye/iodonium salt undergoes quick electron transfer from DEDCto DIHP and free radicals are produced. The visible light photoinduced reaction between DEDC and DIHP ismainly through the excited singlet state of DEDC and thus it is a little sensitive to O_2. The influence ofconcentration of DEDC, DIHP and MMA on the rate of photopolymerization of MMA was also investigated.     

Photopolymerization of Cyclohexene Oxide Initiated with Iron-arene Complex

Two iron-arene complex photoinitiators with different substituents in arene ligands were synthesized, their activities in initiating photopolymerization of cyclohexene oxide (CHO) were compared with that of IRGACURE 261, a commercialized photoinitiator from Ciba-Geigy. A higher activity was found when the arene ligand was substituted with a stronger electron donating group. For the system initiated by IRGACURE 261 the concentration of active centers in CHO polymerization was determined and it was found that the concentration is maximum at around 35℃. The post (dark) polymerization was significant, the polymerization yield decreased with the increase of irradiation temperature and increased with the increase of post polymerization temperature. The results are interpreted based on the mechanism proposed by Lohse, et al..     

Synthesis and properties of novel hole-transporting materials with triphenylamine units

Two novel organic hole-transporting materials have been synthesized by combination of triphenylamines(TPA) viaπ-conjugated bonds using Wittig reaction.The structures were characterized by NMR,FT-IR and HRMS.The optical,electrochemical and thermal properties of the materials were studied in detail.The results show that these two compounds have blue emission,proper HOMO levels and high thermal stability.Furthermore,a quantum chemical calculation on electron distribution of the two compounds was performed, which suggests the current synthesized materials would be promising candidates for hole-transporting materials.     

Synthesis and electrochromic properties of polyimides with pendent benzimidazole and triphenylamine units

Five novel near-infrared electrochromic aromatic polyimides(PIs) with pendent benzimidazole group were synthesized from 4,4'-diamino-4'-(1-benzylbenzimidazol-2-yl)triphenylamine(named as DBBT) with five different dianhydrides via two-step polymerization process, respectively. The maximum UV-Vis absorption bands of these PIs locate at about 335 nm for solid films due to the π-π* transitions. A reversible pair of distinct redox peaks, that were associated with a noticeable color change from original yellow to blue, was observed in the cyclic voltammetry(CV) test. A new absorption peak emerged at 847 nm in near-infrared(NIR) region with increasing voltage in UV-Vis-NIR spectrum, which indicates that PI can be used as NIR electrochromic material. These novel PIs have good electrochemical stability, appropriate energy levels for the highest occupied molecular orbital(HOMO) and the lowest unoccupied molecular orbital(LUMO), in the range of-5.17 e V to-5.20 e V and-2.14 e V to-2.26 e V(versus the vacuum level) determined by cyclic voltammetry method. These values basically consisted with the results of quantum chemical calculation. These polyimides can be used as novel electrochromic and hole transportation materials.     

PHOTOPOLYMERIZATION INITIATED BY DIMETHYLAMINOCHALCONE/DIPHENYLIODONIUM SALT COMBINATION SYSTEM SENSITIVE TO VISIBLE LIGHT

Several dimethylamino-substituted chalcone (i .e. dimethylaminobenzal acetophenone) (DBA) derivatives with intramolecular charge transfer transition character were used as visible light sensitizers for radical photopolymerization initiated by iodonium salt (DPIO). Initiating radical species is produced from DBA sensitized photolysis of DPIO through the single electron transfer, accompanying the bleaching of DBA, The activity of DBA decreases as a function of substituent attached to phenyl ring in the order: DBA-2 (OCH_3) >DBA-1(H)> DBA-3 (Cl). The kinetic study on photopolymerization of MMA was carried out in CH_3CN solution at 30 ℃by dilatometry. The polymerization rate was determined to be proportional to the concentration with exponents of 0.42, 0.25 and 0.86 for DPIO, DBA-1 and MMA, respectively.     

Synthesis and characterization of novel star-shaped pyridine cored compounds with alternating carbazole and triphenylamine moieties

Amorphous 2,4,6-trissubstituted pyridines containing three peripheral carbazole or two triphenylarnine and one carbazole moieties,respectively,have been synthesized and characterized.The properties of the compounds are investigated by UV-vis absorption,photoluminescence spectroscopy,thermal analysis as well as cyclic voltammetry.The results show that the compounds have high thermal stability,emit blue light.Also,the compounds possess the HOMO and LUMO energy levels comparable to those of NPB.The effects of different substituents on the electronic properties of the materials have been discussed.     

Synthesis and characterization of novel star-shaped pyridine cored compounds with altemating carbazole and triphenylamine moieties

Amorphous 2,4,6-trissubstituted pyridines containing three peripheral carbazole or two triphenylamine and one carbazole moieties, respectively, have been synthesized and characterized. The properties of the compounds are investigated by UV-vis absorption, photoluminescence spectroscopy, thermal analysis as well as cyclic voltammetry. The results show that the compounds have high thermal stability, emit blue light. Also, the compounds possess the HOMO and LUMO energy levels comparable to those of NPB. The effects of different substituents on the electronic properties of the materials have been discussed.     

Synthesis and properties of a star-shaped organic material with triphenylamine and N-vinyl carbazole units

A starburst triphenylamine cored N-vinyl carbazole (V-Cz) branched compound was designed and synthesized via optimized Heck reaction in a yield of 40-60%.Moderate yield came from decomposition of V-Cz and self-coupling of triiodo-triphenylamine. TCz-TPA adopts a highly twisted propeller conformation by molecular mechanical optimization.It is readily soluble for its highly twisted conformation.Transparent and pinhole free films could be easily fabricated by spin-coating for its starburst structure.It emits blue-greenish light in CH_2Cl_2 peaked at 460 nm with a narrow full-width at half-maximum (FWHM) of 65 nm.As compared, the absorption peaks of the spin-coated film blue shifted and emission peak red shifted to 510 nm with a FWHM of 96 nm.     

鎓盐阳离子光敏聚合

本文介绍了硫鎓盐和碘鎓盐引发的阳离子光敏聚合的发展与特点,对其光敏引发机理及影响引发效率的各种因素作了讨论,相应的紫外光固化树脂的组成与应用也作了介绍。还发表了一些新的研究结果。     

Synthesis and photoinitiated cationic polymerization of 1,2,3-tris(1-propenoxy) propane

The synthesis of 1,2,3-tris (1-propenoxy) propane (GTPE) was carried out by the rearrangement of 1,2,3-tris(2-propenoxy) propane (glycerol triallyl ether, GTAE) and the Z: E isomer composition of the GTPE was determined using gas chromatography and ¹HNMR. The photoinitiated cationic polymerization of the GTPE was studied using realtime infrared spectroscopy (RTIR). Employing the data from these studies, rates of polymerization for the respective E and Z propenyl ether double bonds were calculated. The rate of incorporation of Z-double bonds of GTPE into the crosslinked polymer matrix is 1.6 times that of E-double bonds. The effects of oxygen and several other free radical polymerization inhibitors were investigated. An increase in the photogel time and decrease of the gel-content in the presence of these inhibitors implicates the involvement of free radicals in the process of the generation of propagating cationic centers when diaryliodonium salt cationic photoinitiators are used. © 1994 John Wiley & Sons, Inc.     

Synthesis and mesomorphic behaviour of new discotic liquid crystalline compounds containing triphenylamine as a core moiety via Sonogashira coupling

Design and synthesis of cholesterol based disk-like liquid crystalline compounds using triphenylamine as a core moiety have been achieved by Pd-catalyzed cross-coupling reaction. The newly synthesized compounds exhibit a cholesteric phase with fingerprint texture as well as oily texture. In the low temperature region, there is a signature of smectic B with characteristic dendritic and mosaic textures. The mesogenic properties were characterized by polarizing microscopy, differential scanning calorimetry and HRXRD studies.     

Synthesis and characterization of new highly soluble and thermal-stable perylene-PPV copolymers containing triphenylamine moiety

Three new copolymers containing poly(p-phenylenevinylene) (PPV) and triphenylamine (TPA) moieties carrying N-(n-butyl)-N′-ethoxy-1,6,7,12-tetra-(4-tert-butylphenoxy)-3,4,9,10-perylenetetracarboxylic bisimide (PERY) pendant groups were successfully synthesized by Wittig condensation. The molar percentage of perylene pendants in copolymers was controlled by tuning the initial feed ratio of the perylene-bisaldehyde monomer. The structures and properties of three copolymers were characterized and evaluated by FT-IR, NMR, UV, FL, and photovoltaic analyses. The copolymers were highly soluble in conventional solvents such as toluene, CHCl₃, THF, DMF, etc., and they were thermally stable (?396 °C). Three copolymers have emission spectra with characteristic features of the perylene unit, however, and their luminescence are largely quenched with the increasing amount of PERY units in copolymers. The photophysical study in solution has shown that singlet-singlet energy transfers from PPV backbone to perylene in the copolymers. The photovoltaic devices ITO/PEDOT:PSS/copolymers/Ba/Al were fabricated, and the energy conversion efficiency of the device is only about 0.0005%, further indicating that an efficient energy transfer has taken place from PPV to perylene in the copolymers.     

Novel linear and tri-branched copolymers based on triphenylamine for non-doping emitting materials

Novel linear and tri-branched copolymers with triphenylamine and cyano groups in the main chain were synthesized by a concise route and an environment-friendly procedure without metal catalyst. They show strong fluorescence in solid state and can be used as non-doping emitter to fabricate emitting diodes. The single-layer electroluminescence devices with PVK or PEDOT buffer layer have been made with these copolymers as non-doping red-orange emitter, electron-transporting as well as hole-transporting material. The single-layer devices show preliminary results with maximum efficiency of 0.052% and EL wavelengths around 614 nm.     

Sterically hindered active centres in cationic polymerization: Tertiary aromatic amines in the polymerization of 1,3-pentadiene initiated by aluminum trichloride in non-polar solvent

Previous work on the polymerization of 1,3-pentadiene initiated by aluminum trichloride (AlCl₃) in non-polar solvent at 20 °C in the presence of triphenylamine (NPh₃) has highlighted a stabilization of the active centres and a solubilization of AlCl₃ induced by NPh₃ [Delfour M, Bennevault-Celton V, Anh Nguyen H, Cheradame H, Macedo A. Macromol Chem Phys 2004;205:2312-26]. This paper reports the effect of 9-phenylcarbazole, the structure of which is close to that of NPh₃. The results showed a strong decrease of the insoluble fraction (IF), however this electron donor (ED) was a transfer agent alike NPh₃ (alkylation of aromatic rings by the growing polymer chains). To reduce transfer reaction, the influence of two para-substituted triphenylamines—tribromophenylamine (N(PhBr)₃) and tri-p-tolylamine (N(PhCH₃)₃)—on the polymerization of 1,3-pentadiene was studied in the same conditions. Although the presence of Br substituents has no effect on IF, it induced a decrease in the termination reactions with the counter-ion and the transfer reactions. Concerning methyl groups, it has been shown a strong decrease of IF and a negligible amount of alkylation reaction. Moreover the quantity of grafted molecules was reduced and tri-p-tolylamine reduced both the reactions of cyclization and isomerization. Thanks to the stabilization of the active centres by N(PhCH₃)₃ and probably the solubilization of aluminum trichloride, it was possible to obtain a more precisely defined polypentadiene than ever by cationic polymerization in a non-polar medium.     

Synthesis of new bipolar materials based on diphenylphosphine oxide and triphenylamine units: efficient host for deep-blue phosphorescent organic light-emitting diodes

This paper reports the synthesis and physical properties of a series of bipolar host materials, using of a hole-transporting triphenylamine (TPA) monomer as a core incorporated with different numbers of diphenylphosphine oxide (PO) as electron-transporting moieties, 4-(diphenylphosphoryl)-N,N-diphenylaniline (DDPA), 4-(diphenylphosphoryl)-N-(4-(diphenylphosphoryl)phenyl)-N-phenylaniline (DDPP), and tris(4-(diphenylphosphoryl)phenyl)amine (TDPA), for solution-processed deep-blue phosphorescent organic light-emitting devices (PhOLEDs). With the increasing numbers of PO units, the glass-transition temperature of those compounds rise gradually. Moreover, the newly synthesized compounds all possess high triplet energies, which can prevent back energy transfer between the host and dopant molecules, and are expected to serve as appropriate hosts for iridium(III) tris(3,5-difluoro-4-cyanophenyl)pyridinato-N,C′ (FCNIrpic). The solution-processed devices using DDPP and TDPA as the hosts for the phosphorescence emitter FCNIrpic showed the maximum luminance efficiencies of 9.7 and 6.6 cd A⁻¹, respectively. The efficiency of TDPA based device shows nearly three times higher than the value of commonly used host material 1,3-bis(9-carbazolyl)benzene (mCP) with the same structure, which is outstanding with respect to other works related to the solution-processed deep-blue PhOLEDs based on small-molecule hosts.     

Synthesis and cationic polymerization of substituted 2,3-dihydrofurans

Cationic polymerization of substituted 2,3-dihydrofurans has been performed to investigate the substituent effect on the ring-opening polymerization. 2-Phenyl-2,3-dihydrofuran ( III ), 2-methoxy-5-phenyl-2,3-dihydrofuran ( V _a), and 2-ethoxy-5-phenyl-2,3-dihydrofuran ( V _b) were synthesized and polymerized with BF₃ etherate and AlCl₃ as acid catalysts. V _a and V _b ring-opening polymerized well to give the polymers with benzoyl as pendant group which were formed via cationic rearrangement during the ring-opening process, while III polymerized via simple opening of ethylenic double bond to form a polymer with the retention of tetrahydrofuran ring in the main chain. The nature of substituted cyclic vinyl ethers depending on substituents was also discussed.     

A novel hyperbranched copolymer constituted of triphenylamine and divinyl bipyridyl units

A hyperbranched copolymer (HTP) containing triphenylamine and divinyl bipyridyl units has been synthesized via Heck coupling reaction from 5,5′-divinyl-2,2′-bipyridyl and tris(4-bromophenyl)amine. The polymer had a number-average molecular weight of 1895 and a weight-average molecular weight of 2315, and was readily soluble in common organic solvents, such as THF, DMF and chloroform. The chemical structure of HTP was confirmed by FT-IR, ¹H NMR. Its thermal, electrochemical and optical properties have been investigated. The thermal analysis revealed that the polymer had a good thermal stability with the onset decomposition temperature at ca. 267 °C. The Uv-vis absorption and photoluminescence (PL) spectra exhibited that the Stokes shift between the absorption and emission of HTP was relatively large: 103 for HTP solution and 135 nm for HTP film. The electrochemical analysis showed that the electrochemical band gap of HTP was 0.92 eV. The fluorescence of the polymer in solution can be quenched by various transition metal ions and HTP showed different sensitivity in transition metal ions sensing.     

A novel near-infrared chemosensor for mercury ion detection based on D-A structure of triphenylamine and benzothiadiazole

A novel near infrared ratiometric fluorescent chemosensor based on triphenylamine, thiophene and benzothiadiazole has been developed. The emission wavelength of sensor DTPAT-BT-S was in the near infrared region. The wavelength changed from 656 nm to 723 nm, and got a rather long stokes shift about 170 nm. The sensor showed a very high selectivity towards Hg²⁺ ions.