Synthesis and light emitting properties of polyacetylenes having pendent fluorene groups

Five novel fluorene‐containing polymers, poly[(9,9‐dimethylfluoren‐2‐yl)acetylene] ( PFA1 ), poly[(1‐pentyl‐2‐(9,9‐dimethylfluoren‐2‐yl)acetylene) ( PFA2 ), poly[1‐decyl‐2‐(9,9‐dimethylfluoren‐2‐yl)acetylene] ( PFA3 ), poly[1‐phenyl‐2‐(9,9‐dimethylfluoren‐2‐yl)acetylene] ( PFA4 ), and poly[1‐(3,4‐difluorophenyl)‐2‐(9,9‐dimethylfluoren‐2‐yl)acetylene] ( PFA5 ) were synthesized by the polymerization of the corresponding fluorene‐substituted acetylenic monomers ( M1–M5), using WCl₆, MoCl_5, and TaCl₅ as catalysts and n‐Bu₄Sn as a cocatalyst. The synthesized polymers were thermally stable and readily soluble in common organic solvents. The degradation temperatures for a 5% weight loss of the polymers were ∼352–503 °C under nitrogen. PFA1–PFA5 show emission peaks from 402 to 590 nm. Besides, their electroluminescent properties were studied in heterostructure light‐emitting diodes (LEDs), using PFA2–PFA5 as an emitting layer. The PFA5 device revealed an orange‐red emission peak at 602 nm with a maximum luminescence of 923 cd/m² at 8 V. A device with the ITO/PEDOT/ a mixture of PFA2 (98 wt %) and PFA5 (2 wt %)/Ca/Al showed near white emission. Its maximum luminance and current efficiency are 450 cd/m² at 15 V and 1.3 cd/A, respectively. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 519–531, 2006     

Synthesis of poly(p‐phenylene sulfide) from bis(4‐bromophenyl) disulfide

Improved reaction conditions for the preparation of poly(p‐phenylene sulfide) (PPS) directly from bis(4‐bromophenyl) disulfide (BBD) have been established. Heating BBD with magnesium metal afforded only a low molecular weight polymer. PPS with a melting temperature around 280 °C was obtained from BBD in the presence of sodium carbonate or zinc metal. The best results were obtained with the addition of a catalytic amount of KI to the zinc–BBD mixture. Polymers prepared by the above methods are semicrystalline and dissolve in 1‐chloronaphthalene and have properties comparable to commercial PPS. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 900–904, 2006     

A copper‐based reverse atom‐transfer radical polymerization process for the living radical polymerization of polyacrylonitrile

The reverse atom‐transfer radical polymerization (RATRP) technique using CuCl₂/2,2′‐bipyridine (bipy) complex as a catalyst was applied to the living radical polymerization of acrylonitrile (AN). A hexasubstituted ethane thermal iniferter, diethyl 2,3‐dicyano‐2,3‐diphenylsuccinate (DCDPS), was firstly used as the initiator in this copper‐based RATRP initiation system. A CuCl₂ to bipy ratio of 0.5 not only gives the best control of molecular weight and its distribution, but also provides rather rapid reaction rate. The rate of polymerization increases with increasing the polymerization temperature, and the apparent activation energy was calculated to be 57.4 kJ mol^?1. Because the polymers obtained were end‐functionalized by chlorine atoms, they were used as macroinitiators to proceed the chain extension polymerization in the presence of CuCl/bipy catalyst system via a conventional ATRP process. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 226–231, 2006     

Synthesis and characterization of poly(arylene ether)s containing 6‐(4‐hydroxyphenyl)pyridazin‐3(2H)‐one or 6‐(4‐hydroxyphenyl)pyridazine moieties

A series of novel soluble pyridazinone‐ or pyridazine‐containing poly(arylene ether)s were prepared by a polycondensation reaction. The pyridazinone monomer, 6‐(4‐hydroxyphenyl)pyridazin‐3(2H)‐one ( 1 ), was synthesized from the corresponding acetophenone and glyoxylic acid in a simple one‐pot reaction. The pyridazinone monomer was successfully copolymerized with bisphenol A (BPA) or 1,2‐dihydro‐4‐(4‐hydroxyphenyl)phthalazin‐1(2H)‐one (DHPZ) and bis(4‐fluorophenyl)sulfone to form high‐molecular‐weight polymers. The copolymers had inherent viscosities of 0.5–0.9 dL/g. The glass‐transition temperatures (T_g's) of the copolymers synthesized with BPA increased with increasing content of the pyridazinone monomer. The T_g's of the copolymers synthesized from DHPZ with different pyridazinone contents were similar to those of the two homopolymers. The homopolymers showed T_g's from 202 to 291 °C by differential scanning calorimetry. The 5% weight loss temperatures in nitrogen measured by thermogravimetric analysis were in the range of 411–500 °C. 4‐(6‐Chloropyridazin‐3‐yl)phenol ( 2 ) was synthesized from 1 via a simple one‐pot reaction. 2 was copolymerized with 4,4′‐isopropylidenediphenol and bis(4‐fluorophenyl)sulfone to form high‐T_g polymers. The copolymers with less than 80 mol % pyridazinone or chloropyridazine monomers were soluble in chlorinated solvents such as chloroform. The copolymers with higher pyridazinone contents and homopolymers were not soluble in chlorinated solvents but were still soluble in dipolar aprotic solvents such as N‐methylpyrrolidinone. The soluble polymers could be cast into flexible films from solution. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3328–3335, 2006     

Synthesis and application as polymer electrolyte of hyperbranched polyether made by cationic ring‐opening polymerization of 3‐{2‐[2‐(2‐hydroxyethoxy)ethoxy]ethoxymethyl}‐3′‐methyl‐oxetane

A novel cyclic ether monomer 3‐{2‐[2‐(2‐hydroxyethoxy)ethoxy]ethoxy‐methyl}‐3′‐methyloxetane (HEMO) was prepared from the reaction of 3‐hydroxymethyl‐3′‐methyloxetane tosylate with triethylene glycol. The corresponding hyperbranched polyether (PHEMO) was synthesized using BF₃·Et₂O as initiator through cationic ring‐opening polymerization. The evidence from ¹H and ¹³C NMR analyses revealed that the hyperbranched structure is constructed by the competition between two chain propagation mechanisms, i.e. active chain end and activated monomer mechanism. The terminal structure of PHEMO with a cyclic fragment was definitely detected by MALDI‐TOF measurement. A DSC test implied that the resulting polyether has excellent segment motion performance potentially beneficial for the ion transport of polymer electrolytes. Moreover, a TGA assay showed that this hyperbranched polymer possesses high thermostability as compared to its liquid counterpart. The ion conductivity was measured to reach 5.6 × 10^?5 S/cm at room temperature and 6.3 × 10^?4 S/cm at 80 °C after doped with LiTFSI at a ratio of Li:O = 0.05, presenting the promise to meet the practical requirement of lithium ion batteries for polymer electrolytes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3650–3665, 2006     

Synthesis and characterization of polyimides derived from (3‐amino‐2,4,6‐trimethylphenyl)‐(3′‐aminophenyl)methanone and aromatic dianhydrides

A series of new polyimides were prepared via the polycondensation of (3‐amino‐2,4,6‐trimethylphenyl)‐(3′‐aminophenyl)methanone and aromatic dianhydrides, that is, 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA), 4,4′‐oxydiphthalic anhydride, 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride, and 2,2′‐bis(3,4‐dicarboxyphenyl) hexafluoropropane dianhydride. The structures of the polyimides were characterized by Fourier transform infrared and NMR measurements. The properties were evaluated by solubility tests, ultraviolet–visible analysis, differential scanning calorimetry, and thermogravimetric analysis. The two different meta‐position‐located amino groups with respect to the carbonyl bridge in the diamine monomer provided it with an unsymmetrical structure. This led to a restriction on the close packing of the resulting polymer chains and reduced interchain interactions, which contributed to the solubility increase. All the polyimides except that derived from BPDA had good solubility in strong aprotic solvents, such as N‐methyl‐2‐pyrrolidinone, N,N′‐dimethylacetamide, N,N‐dimethylformamide, and dimethyl sulfone, and in common organic solvents, such as cyclohexanone and chloroform. In addition, these polyimides exhibited high glass‐transition values and excellent thermal properties, with an initial thermal decomposition temperature above 470 °C and glass‐transition temperatures in the range of 280–320 °C. The polyimide films also exhibited good transparency in the visible‐light region, with transmittance higher than 80% at 450 nm and a cutoff wavelength lower than 370 nm. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1291–1298, 2006     

Atom transfer radical polymerization directly from poly(vinylidene fluoride): Surface and antifouling properties

The direct preparation of grafting polymer brushes from commercial poly (vinylidene fluoride) (PVDF) films with surface‐initiated atom transfer radical polymerization (ATRP) is demonstrated. The direct initiation of the secondary fluorinated site of PVDF facilitated grafting of the hydrophilic monomers from the PVDF surface. Homopolymer brushes of 2‐(N,N‐dimethylamino)ethyl methacrylate (DMAEMA) and poly (ethylene glycol) monomethacrylate (PEGMA) were prepared by ATRP from the PVDF surface. The chemical composition and surface topography of the graft‐functionalized PVDF surfaces were characterized by X‐ray photoelectron spectroscopy, attenuated total reflectance/Fourier transform infrared spectroscopy, and atomic force microscopy. A kinetic study revealed a linear increase in the graft concentration of poly[2‐(N,N‐dimethylamino)ethyl methacrylate] (PDMAEMA) and poly[poly(ethylene glycol) monomethacrylate] (PPEGMA) with the reaction time, indicating that the chain growth from the surface was consistent with a controlled or living process. The living chain ends were used as macroinitiators for the synthesis of diblock copolymer brushes. The water contact angles on PVDF films were reduced by the surface grafting of DMAEMA and PEGMA. Protein adsorption experiments revealed a substantial antifouling property of PPEGMA‐grafted PVDF films and PDMAEMA‐grafted PVDF films in comparison with the pristine PVDF surface. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3434–3443, 2006     

Synthesis of polyacrylonitrile via reverse atom transfer radical polymerization catalyzed by FeCl3/isophthalic acid

FeCl₃ coordinated by isophthalic acid was first used as a catalyst in the azobisisobutyronitrile‐initiated reverse atom transfer radical polymerization of acrylonitrile. N,N‐Dimethylformamide was used as a solvent to improve the solubility of the ligand. An FeCl₃‐to‐isophthalic acid ratio of 0.5 not only gave the best control of the molecular weight and its distribution but also provided rather a rapid reaction rate. The effects of different solvents on the polymerization of acrylonitrile were also investigated. The rate of the polymerization in N,N‐dimethylformamide was faster than that in propylene carbonate and toluene. The molecular weight of polyacrylonitrile agreed reasonably well with the theoretical molecular weight in N,N‐dimethylformamide. The rate of polymerization increased with increasing polymerization temperature, and the apparent activation energy was calculated to be 59.9 kJ mol^?1. Reverse atom transfer radical polymerization was first used to successfully synthesize acrylonitrile polymers with a molecular weight higher than 80,000 and a narrow polydispersity as low as 1.22. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 219–225, 2006     

Highly substituted poly(2,3‐diphenyl‐1,4‐phenylenevinylene) derivatives having bulky phenyl and fluorenyl pendant groups: Synthesis,characterization, and electro‐optical properties

Two series of poly(2,3‐diphenyl‐1,4‐phenylenevinylene) (DP‐PPV) derivatives containing multiple bulky substituents were synthesized. In the first series, two different groups were incorporated on C‐5,6 positions of the phenylene moiety to increase steric hindrance and to obtain blue‐shifted emissions. In the second series, bulky fluorenyl groups with two hexyl chains on the C‐9 position were introduced on two phenyl pendants to increase the solubility as well as steric hindrance to prevent close packing of the main chain. Polymers with high molecular weights and fine‐tuned electro‐optical properties were obtained by controlling the feed ratio of different monomers during polymerization. The maximum photoluminescent emissions of the thin films are located between 384 and 541 nm. Cyclic voltammetric analysis reveals that the band gaps of these light‐emitting materials are in the range from 2.4 to 3.3 eV. A double‐layer EL device with the configuration of ITO/PEDOT/P4/Ca/Al emitted pure green light with CIE′1931 at (0.24, 0.5). Using copolymer P6 as the emissive layer, the maximum luminescence and current efficiency were both improved when compared with the homopolymer P4. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6738–6749, 2006     

Photocrosslinked poly(vinylbenzophenone)‐core micelles via mild Friedel–Crafts benzoylation of polystyrene amphiphiles

Photocrosslinkable poly(vinylbenzophenone)‐containing polymers were synthesized via a one‐step, Friedel–Crafts benzoylation of polystyrene‐containing starting materials [including polystyrene, polystyrene‐block‐poly(tert‐butyl acrylate), polystyrene‐block‐poly(ethylene oxide), polystyrene‐block‐poly(methyl methacrylate), and polystyrene‐block‐poly(n‐butyl acrylate)] with benzoyl trifluoromethanesulfonate as a benzoylation reagent. The use of this mild reagent (which required no added Lewis acid) permitted polymers with well‐defined compositions and narrow molecular weight distributions to be synthesized. Micelles formed from one of these benzoylated polymers, [polystyrene_0.25‐co‐poly(vinylbenzophenone)_0.75]₁₁₅‐block‐poly(acrylic acid)₁₄, were then fixed by the irradiation of the micelle cores with UV light. As the irradiation time was increased, the pendent benzophenone groups crosslinked with other chains in the glassy micelle cores. Dynamic light scattering, spectrofluorimetry, and Fourier transform infrared spectroscopy were all used to verify the progress of the crosslinking reaction. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2604–2614, 2006