Synthesis and characterization of alternating fluorene-based copolymers containing diaryl- and non-substituted bithiophene units

A series of soluble alternating fluorene-based copolymers containing diaryl- and non-substituted bithiophene units are synthesized by palladium-catalyzed Suzuki coupling reaction. All polymers demonstrate green colors of photoluminescence (PL) in chloroform, good thermal stability (with decomposition temperatures above 436 °C), and high glass transition temperatures (in the range of 120-144 °C). Owing to the large steric hindrance of diaryl substituents on bithiophenes in the polymers (P2-P4), the aggregation of solids is reduced as well as the solubility is improved, so the performance of their PLED devices are superior to that of the non-substituted polymer (P1). Compared with P1, the introduction of substitutents at 3,3′-position of bithiophene in P2-P4 has significant effects on the photophysical properties of resulting polymers in solution and solid states. Though the PL quantum yield of P1 is much higher than those of diaryl-substituted polymers (P2-P4), the PLED device of P1 has the worst electroluminescence (EL) properties due to the poor solubility of P1. Consequently, among these polymers, the device made of P3 as an emitter has the highest luminance of 2590 cd/m² at 9.5 V. For optimum device performance, a device of P3 blended with PVK can be further enhanced to a brighter luminance of 4284 cd/m² at 18 V.     

Synthesis and characterization of amino-functional, blue light-emitting copolymers and their composites with CdTe nanocrystals

Random side-chain functionalized copolymers were synthesized, utilizing a facile Yamamoto protocol by applying 2,7-dibromo-9,9-bis(6-bromohexyl)-9H-fluorene, (E)-1,2-bis(4-bromophenyl)ethene, 2,7-dibromo-9,9-dioctyl-9H-fluorene as comonomers. The precursor copolymers were post-functionalized utilizing di-n-propylamine and the resulting target copolymers were fully characterized. The optical classification parameters have been determined in solutions and in thin films as well. The copolymers revealed blue light emission, wide optical bandgaps Eg_opt of at least 2.84 eV and remarkable quantum yields up to 0.78 in chloroform solutions. The amino-functional copolymers allowed tying semiconductor CdTe nanocrystals.     

Preparation and characterization of photoreactive copolymers containing curable pendants for positive photoresist

tert‐Butyl methacrylate (TBMA) was copolymerized with various comonomers that were selected from methyl methacrylate (MMA), n‐butyl acrylate (NBA), acrylic acid (AA), and 2‐hydroxyethyl methacrylate (HEMA). From film physical properties, poly(TBMA‐co‐HEMA) and poly(TBMA‐co‐AA‐co‐NBA), were selected as resin binders. To introduce unsaturated double bonds onto the side chain of copolymers, they were further functionalized with acryloyl chloride and glycidyl methacrylate. Copolymers synthesized in this investigation were all identified by using FTIR and NMR. The thermal decomposition temperature of functionalized poly(TBMA‐co‐HEMA) showed obvious difference before and after crosslinking. Adding a small amount of EGDMA as the crosslinking agent could increase the degree of crosslinking and obviously improve the physical properties. Functionalized poly(TBMA‐co‐HEMA) was used as a binder resin and composed with a photoacid generator for positive photoresists. From exposure characteristics, the optimal lithographic condition was achieved when exposed for 90 s, PEB at 100°C for 2.5 min, and developed in 10 wt % Na₂CO₃ developer for 30 s. After completing the lithography process, the residual pattern of positive photoresist was further treated at 140°C for 30 min to cure the pendant unsaturated groups. The resolution of the positive photoresist was analyzed by an optical microscope and SEM technique. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 328–333, 2001     

Synthesis and characterization of side-chain liquid crystalline homopolymers and block copolymers containing biphenyl-4-ylthiophene and biphenyl-4-ylfluorene pendants

A series of new liquid crystalline homopolymers (P1 and P2) and block copolymers (P3 and P4) composed of methacrylates containing pendant biphenyl-4-ylthiophene (M1) and biphenyl-4-ylfluorene (M2) units were synthesized by atom transfer radical polymerization (ATRP). The number-average molecular weights (M_n) of the homopolymer (P2) and diblock copolymers (P3 and P4) were in the range of 5153-8713 g mol⁻¹ with polydispersity indices (PDIs) between 1.17 and 1.25. The thermal, mesogenic, and photoluminescence (PL) properties of all polymers were investigated. Except for the absence of mesogenic properties in block copolymer P4, polymers P1 and P3 possessed the smectic A phase and polymer P2 exhibited the nematic phase. Moreover, the mesomorphism and the layer d-spacing values of the smectic A phase in polymers P1 and P3 were confirmed and characterized by X-ray diffraction (XRD) patterns.     

Electroactive Polyimides: Synthesis,Characterization and Photophysics

A series of aromatic electroactive polyimides bearing p-phenoxy pendant at main chain were synthesized as fluorescent materials. The PIs were prepared from electroactive diamine N¹-(4-aminophenyl)-N¹-(4-phenoxyphenyl)benzene-1,4-diamine. The structure of the polyimides was characterized by the fourier transform infrared spectroscopy, Carbon, Hydrogen and Nitrogen analyses, and gel permeation chromatography. The polyimides were analyzed for their photophysical and electrochemical properties by ultraviolet–vis spectral analysis photoluminescence spectroscopy and cyclic voltammetry. Thermal stability of the polyimides was evaluated by thermogravimetric analysis and differential scanning calorimetry. The observed behavior of our synthesized polyimides revealed their shallow highest occupied molecular orbital levels, low E_g, blue light emission and stable redox behavior, and good thermal and mechanical stability making our synthesized polyimides useful for future optoelectronics.     

Synthesis and characterization of styrene–N-butyl maleimide copolymers using iniferters containing thiyl end groups

The radical homopolymerization of styrene or copolymerization of styrene (S) with N-butyl maleimide (I) initiated by tetraethylthiuram disulfide was used to prepare macroinitiators having thiyl end groups. The S–I copolymers from the feeds containing 30–70 mol % I showed approximately alternating composition. The rate of copolymerization and molecular weights decreased with increasing maleimide derivative concentration in the feed; homopolymerization of I alone did not proceed. The macroinitiators served for synthesis of further S–I copolymers. Using polystyrene macroinitiator and the S–I copolymer with thiyl end groups in the polymerization of S–I mixture and styrene, respectively, the copolymers containing blocks of both polystyrene and alternating S–I copolymer were obtained. The copolymerization of S–I mixture initiated with the S–I copolymer bearing thiyl end groups led to the extension of macroinitiator chains by the blocks of alternating copolymer. The presence of the blocks in the polymer products was corroborated using elemental analysis, size exclusion chromatography, and differential scanning calorimetry. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 755–762, 1998     

Synthesis,characterization, swelling-deswelling properties of Novel nanoparticle-hydrogel containing core chitosan and their cyclohexanone-crosslinked counterparts

Novel Chitosan-cyclohexanone Mannich based hydrogel nanoparticles (CCMb1-4) were prepare via the reaction of chitosan with different concentration of 2, 6-bis (piperidin-1-ylmethyl) cyclohexanone. 2HCl (1%, 5%, 10% and 15% wt/wt) at 70–80°C for 7 h. These hydrogels were subjected to equilibrium swelling studies at room temperature in solutions of pH 2, 4, 6 and 8. The (CCMb1-4) showed maximum percent swellability at pH = 2.0. Furthermore, the swelling of the (CCMb1-4) followed Fickian diffusion. This preliminary investigation of chitosan-based interpolymeric hydrogels showed that they may be exploited to expand the utilization of these systems in drug delivery applications.     

Synthesis and characterization of new fluorene-acceptor alternating and random copolymers for light-emitting applications

A series of novel light-emitting copolymers consisted of 9,9-dihexylfluorene (F) and different acceptor segments, including quinoxaline (Q), 2,1,3-benzothiadiazole (BT) and thieno[3,4-b]-pyrazine (TP), were synthesized by the palladium-catalyzed Suzuki coupling reaction. Three fluorene-acceptor alternating copolymers (PFQ, PFBT, PFTP) and six F-TP (PFTP0.5-PFTP35) random copolymers were investigated and compared with the parent polyfluorene (PF). The experimental results suggest that the acceptor strength or content significantly affect the electronic and optoelectronic properties. The optical absorption maxima of the PF, PFQ, PFBT, and PFTP are 368, 416, 470, and 578 nm, respectively, which indicates the significance of intramolecular charge transfer. The electrochemical band gap also shows a similar trend. The incorporation of the acceptor into the PF lowers the LUMO level and thus could improve the electron-accepting ability of the PF. The emission maxima on the photoluminescence (PL) spectra of the PF, PFQ, PFBT, and PFTP films are 424, 493, 540, and 674 nm, which correspond to the color of blue, green, yellow, and red, respectively. It suggests that the full color of emission can be achieved by different acceptors. The significant positive solvatochromism on the PL spectra in different polar solvents suggests the efficient intramolecular charge transfer in PFTP. However, such charge transfer or heavy-atom effect results in fluorescence quenching and thus reduces the PL efficiencies. By random copolymerizing the TP into the PF, the PL efficiency could be improved. A significantly reduction on the PF emission peak with increasing the TP content suggests the energy transfer between the PF and TP segments. Besides, the characteristics on the electroluminescence (EL) devices of ITO/PEDOT:PSS/emissive layer/Ca/Ag suggest that such energy transfer results in the complete quenching of the PF emission at only 1% TP content in the PFTP01. The maximum external quantum efficiency (EQE) of the EL device based on the PFTP01 is superior to that of the PF due to the reduced LUMO level in matching with the Ca. The CIE 1931 coordinates of the PFTP01 based EL device under the condition of maximum EQE is (0.66, 0.31), which is close to the standard red of (0.66, 0.34) demanded by the National Television System Committee (NTSC). The luminescence characteristics based on the prepared polymers depend on the Förster energy transfer or the intramolecular charge transfer, or heavy-atom fluorescence quenching. The present study suggests that the tuning of the electronic and optoelectronic properties could be achieved by incorporating various acceptors or content into the polyfluorenes.     

Thermally cross-linkable hyperbranched polymers containing triphenylamine moieties: Synthesis, curing and application in light-emitting diodes

This paper demonstrates synthesis of hyperbranched polymers (HTP and HTPOCH₃), containing triphenylamine moieties in main chain and thermally cross-linkable periphery or terminal vinyl groups, and application as hole-transporting layer (HTL) in multilayer light-emitting diodes. Absorption and photoluminescence (PL) spectroscopy, cyclic voltammetry (CV) and differential scanning calorimetry (DSC) were employed to investigate their photophysical, electrochemical properties and thermal curing behaviors, respectively. The hyperbranched HTP and HTPOCH₃ were readily cross-linked by heating scan, with the exothermic peaks being at 221 and 210 °C respectively. The glass-transition temperatures (T_g) of the hyperbranched polymers were higher than 140 °C after thermal cross-linking at 210 °C for 30 min. Multilayer light-emitting diodes (ITO/PEDOT:PSS/HTL/MEH-PPV/Ca/Al), using HTP and HTPOCH₃ as HTL, were readily fabricated by successive spin-coating. The performance of MEH-PPV device (maximum luminance: 9310 cd/m², luminance efficiency: 0.26 cd/A) was effectively enhanced by inserting the thermally cross-linked HTP or HTPOCH₃ as HTL (HTP: 12610 cd/m², 0.32 cd/A; HTPOCH₃: 14060 cd/m², 0.33 cd/A). This indicates that these thermally cross-linkable hyperbranched HTP and HTPOCH₃ are very suitable for the fabrication of multilayer PLEDs using solution processes.     

Synthesis, characterization and aggregation behavior of block copolymers containing a polyisocyanopeptide segment

Following up on previous preliminary communications the synthesis of a series of block copolymers by applying amine end-capped polymers as initiators for the nickel(II) catalyzed polymerization of isocyanides is reported. Using a polystyrene derivative as the initiator, superamphiphiles containing a hydrophobic polystyrene tail and a charged helical polyisocyanide headgroup were prepared. Under proper conditions these superamphiphiles self-assembled in water to give a variety of aggregate morphologies, among which are superhelical architectures. Initiators derived from carbosilane dendritic wedges gave block copolymers with a unique combination of structural elements, i.e. a flexible dendritic block and a rigid polyisocyanide block. Block copolymers derived from the 3rd generation dendrimers form well-defined micellar aggregates in the presence of Ag⁺ ions. These aggregates have been used to construct nanoarrays of metallic silver.     

Synthesis and characterization of fluorene-carbazole and fluorene-phenothiazine copolymers with carbazole and oxadiazole pendants for organic light emitting diodes

We report the synthesis and characterization of new series of the fluorene based polymers with carbazole and oxadiazole pendants for the generation of the white emission out of the EL device. In the fluorene backbone, hole transporting units such as carbazole or phenothiazine were incorporated to improve the EL brightness and efficiency. The PFCzOxd-co-PCzs and PFCzOxd-co-PPTZs in EL spectra showed maximum peaks at around 430 nm and additional large peaks at around 530 and 500 nm, respectively. In case of PFCzOxd-alt-PCz and PFCzCzPCz-co-PFOxdOxdPCz, the EL spectra of the polymers showed two distinct peaks comprising the maximum at 427 nm, which corresponds to the EL spectra of the conjugated backbone, and additional broad peaks at around 540 and 530 nm, respectively. The CIE coordinates of the devices from PFCzOxd-alt-PCz and PFCzCzPCz-co-PFOxdOxdPCz were (0.28, 0.33) and (0.25, 0.32), respectively, approaching the value of the standard white of National Television System Committee (NTSC) (0.33, 0.33).     

Synthesis, characterization, and reactivity ratio studies on new sulfide copolymers containing ethylbenzene units

Soluble new sulfide copolymers were synthesized readily by the polycondensation of ethylene dibromide (EDB) (or methylene dibromide (MDB)) with styrene dibromide (SDB) and sodium sulfide (Na₂S) in the presence of phase transfer catalyst. The copolymers were characterized by using Fourier transform-infrared, ¹H NMR, ¹³C NMR, gel permeation chromatography, and thermogravimetric analysis (TGA) techniques. The copolymer composition obtained from the ¹H NMR spectra led to the determination of reactivity ratios. The analysis of reactivity ratios revealed that both EDB and MDB are more reactive than SDB towards Na₂S, and copolymers formed are random in nature. Furthermore, it also gave an insight on the microstructure of the copolymers that both poly (ethylene sulfide-co-styrene sulfide) (p(ES-co-SS)), and poly(methylene sulfide-co-styrene sulfide) (p(MS-co-SS)) copolymers have more of blocky structure with increase in the concentration of ethylene sulfide (ES) or methylene sulfide (MS) units in the respective copolymers. The TGA was used to find out the thermal stability of these polymers. The XRD data indicated an increase in the amorphous content of the copolymers with an increase in the concentration of styrene sulfide (SS) units and thereby resulting in most of these copolymers being soluble in common organic solvents. The solubility and molecular weight of the polymers formed were dependent on the concentration of SDB taken in the feed.     

Synthesis and aqueous solution characterization of amphiphilic diblock copolymers containing carbazole

A series of near-monodisperse diblock copolymers of 2-(N-carbazolyl)ethyl methacrylate and 2-(dimethylamino)ethyl methacrylate (DMAEMA) of relatively low molecular weights (2600-24,000 g mol⁻¹) were synthesized by group transfer polymerization using tetrahydrofuran (THF) as a solvent. The molecular weight distributions and compositions of all the copolymers were obtained using gel permeation chromatography (GPC) in THF and proton nuclear magnetic resonance (¹H NMR) spectroscopy, respectively. Differential scanning calorimetry and thermal gravimetric analysis provided low glass transition temperatures (T_gs) of about 60 °C and decomposition temperatures between 320 and 450 °C for the copolymers, respectively. The three copolymers with the highest DMAEMA content were water-soluble below pH 7. Aqueous GPC at pH 3 showed that the water-soluble block copolymers formed micelles with apparent number average molecular weights above 100,000 g mol⁻¹.     

Novel water‐soluble acryloylmorpholine copolymers: Synthesis,characterization, and metal ion binding properties

Poly(4‐acryloylmorpholine), poly(4‐acryloylmorpholine‐co‐2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid), and poly(2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid) were synthesized by radical polymerization. The water‐soluble polymers obtained, containing tertiary amino, amide, and sulfonic acid groups, were investigated, in view of their metal binding properties, as polychelatogens by using the liquid‐phase polymer‐based retention technique, under different experimental conditions. The metal ions investigated were Ag(I), Cu(II), Co(II), Ni(II), Cd(II), Pb(II), Zn(II), Cr(III), and Al(III). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 180–185, 2006     

Synthesis and characterization studies of homopolymers of N-vinylpyrrolidone,vinyl acetate,and their copolymers

Homopolymers of N-vinylpyrrolidone (VP) and vinyl acetate (VAc) were synthesized by a free-radical solution polymerization technique. Copolymers of VP and VAc in various monomer feed ratios were also synthesized by the same procedure. They were characterized by elemental analysis, FTIR, PNMR, TGA, swelling, and viscosity measurements. The reactivity ratios of the monomers were computed by both Fineman–Ross and Kelen–Tudos methods using data from both PNMR and elemental analysis studies. The activation energy values for various stages of decomposition were calculated from TGA analysis using Broido's method. The viscosity measurements were carried out at four different temperatures: 30, 35, 40, and 45°C. The activation parameters of the viscous flow, voluminosity (V_E), and shape factor (ν) were also computed for all systems. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:91–102, 1998     

Styrene-maleic anhydride copolymers: Synthesis,characterization, and thermal properties

Radical copolymerization of styrene and maleic anhydride have been carried out in N, N-dimethylformamide at 60°C using 2,2′-azobisisobutyronitrile as initiator. The copolymer compositions were determined using an aqueous conductometric direct titration method. Monomer reactivity ratios were calculated by Fineman-Ross, Kelen-Tudos, and conversion-based Kelen-Tudos methods. Gel permeation chromatography was used to determine molecular weights and polydispersity indexes. The thermal degradation and energy of activation of the degradation process were determined by several thermogravimetric analysis and differential scanning calorimetric models. The thermal degradation of the copolymer is a two-stage process, the major degradation being the second stage. The copolymer degrades at a lower temperature than polystyrene. © 1996 John Wiley & Sons, Inc.     

Novel DCPD-modified polyester containing epoxy groups: thermal,viscoelastic, and mechanical properties of their wood flour filled copolymers

In this article, the synthesis of novel DCPD-modified polyesters containing epoxy groups and their possible utilization as polar matrices for wood flour filled copolymers have been studied. The novel DCPD-modified polyester containing epoxy groups was prepared during three-step process. First, the addition reaction of maleic acid to DCPD norbonenyl double bond has been performed. Then, the polyesterification of acidic ester of DCPD, cyclohex-4-ene dicarboxylic anhydride, and ethylene glycol (ethane-1,2-diol, EG) or neopentyl glycol (2,2-dimethyl-1,3-propanediol, NP) in the presence of catalyst was carried out using melt condensation technique. Finally, the oxidation process of prepared DCPD-modified polyesters led to obtain DCPD-modified polyesters containing epoxy groups. The structural characterization of prepared DCPD-modified polyesters containing epoxy functionality has been carried out using FTIR and HNMR spectroscopic methods. The thermal, viscoelastic, and mechanical properties of their unfilled and wood flour filled copolymers have been studied by DSC, DMA, TGA analyses, three-point bending test, and Brinell’s hardness. The performed investigations indicated that novel DCPD-modified polyesters containing epoxy groups can be successfully applied as polar matrices for preparation wood flour filled copolymers due to their “compatibility” with hydrophilic wood flour surface which resulted with stronger interactions between wood and polymer surface and thus producing copolymers which were characterized by improved thermo-mechanical properties compared to unfilled copolymers.     

Novel chalcone-based aromatic polyamides: synthesis,characterization, and properties

Two novel diacid-based monomers have been synthesized by anchoring a benzylideneacetophenone (chalcone) moiety through an amide or ester bridge at the fifth position of the isophthalic acid ring. Two series of new polyamides bearing chalcone side chains were prepared by direct polycondensation reaction of the aforementioned dicarboxylic acids and various aromatic diamines in N-methyl-2-pyrrolidinone, using triphenyl phosphite and pyridine as condensing agents. Their molecular structure and the basic properties were investigated by nuclear magnetic resonance, Fourier-transform IR and UV–vis spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and wide-angle X-ray diffraction. The inherent viscosity, molecular weights measurements (by gel permeation chromatography), water uptake, and solubility tests completed the research study. Introduction of the rigid and bulky chalcone units into the polymer side chains improved remarkably the solubility of the aromatic polyamides, endowed them with an amorphous nature, good thermal stability, and photosensitivity. The resulting polymers were obtained in good yields, inherent viscosities varied between 0.49 and 0.86 dL/g, and their relative high molecular weights conferred them film-forming properties. They were soluble in amide-type polar solvents, such as N,N-dimethylformamide, dimethyl sulfoxide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone. These polyamides had glass transition temperatures between 219 and 264 °C, and 10% weight loss temperatures in the range of 394–436 °C and around 50% residue at 700 °C in nitrogen atmosphere. The polyamides underwent a [2 + 2] photocycloaddition reaction upon UV light irradiation both in solution and film state in the absence of a photoinitiator or photosensitizer. The polymer films became insoluble in solvents as a result of the crosslinking .