Sul-containing fluorinated polyimides for optical waveguide device

Novel sul-containing fluorinated polyimides have been synthesized by the reaction of 2,2′-bis-(trifluoromethyl)-4,4′-diaminodiphenyl sulfide (TFDAS) with 1,4-bis-(3,4-dicarboxyphenoxy)benzene dianhydride (HQDPA), 2,2′-bis-(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), 4,4′-oxydiphthalicanhydride (ODPA) or 3,4,3′,4′-biphenyl-tetracarboxylic acid dianhydride (s-BPDA). The fluorinated polyimides, prepared by a one-step polycondensation procedure, have good solubility in many solvents, such as N-methyl-2-pyrrolidinone (NMP), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), cyclohexanone, tetrahydrofuran (THF) and m-cresol. The molecular weights (M_n's) and polydispersities (M_n/M_w's) of polyimides were in the range of 1.24 × 10⁵ to 3.21 × 10⁵ and 1.59–2.20, respectively. The polymers exhibit excellent thermal stabilities, with glass-transition temperatures (T_g) at 221–275 °C and the 5% weight-loss temperature are above 531 °C. After crosslinking, these polymers show higher thermal stability. The films of polymers have high optical transparency. The novel sul-containing fluorinated polyimides also have low absorption at both 1310 and 1550 nm wavelength windows. Rib-type optical waveguide device was fabricated using the fluorinated polyimides and the near-field mode pattern of the waveguide was demonstrated.     

通过自缩合乙烯基氧阴离子聚合制备超支化聚甲基丙烯酸羟丙酯

由甲基丙烯酸羟丙酯通过自缩合乙烯基氧阴离子聚合(self-condensing vinyl oxyanionic polymerization)制备了端羟基的超支化聚甲基丙烯酸酯. 以氢化钾(KH)和冠醚的复合物为引发剂时, 可以得到高分子量的聚合物. 用¹H NMR和¹³C NMR谱图证实了聚合物的超支化结构. 由于在聚合过程中存在质子转移反应, 引发剂与单体的摩尔比会影响所得聚合物的结构. 超支化聚合物的玻璃化转变温度在58.1～81.4 ℃之间, 且随着引发剂与单体的比例的减小而降低. 当引发剂与单体等摩尔比时, 所得聚合物的支化度为0.49.     

Synthesis and characterization of new thermally stable copoly(ester–amide)s from diester–dicarboxylic acids

Three new aromatic diester–dicarboxylic acids containing furan rings, namely, benzofuro[2,3-b]benzofuran-2,9-dicarboxyl-bis-phenyl ester-4,4^′-dicarboxylic acid, benzofuro[2,3-b]benzofuran-2,9-dicarboxyl-bis-phenyl ester-3,3^′-dicarboxylic acid and benzofuro[2,3-b]benzofuran-2,9-dicarboxyl-bis-naphthyl ester-2,2^′-dicarboxylic acid were synthesized by the reaction of benzofuro[2,3-b]benzofuran-2,9-dicarbonyl chloride with 4-hydroxybenzoic acid, 3-hydroxybenzoic acid and 3-hydroxy-naphthalene-2-carboxylic acid, respectively. Diester–dicarboxylic acids were characterized by FT-IR and NMR spectroscopy and elemental analyses. Then, these monomers were converted to aromatic copoly(ester–amide)s by their reaction with various aromatic diamines via the direct polycondensation. These polymers were characterized by viscosity measurements, solubility tests, FT-IR, Ultraviolet and ¹H-NMR spectroscopy and thermogravimetry. The polymers with inherent viscosities in the range of 0.16–0.37 dl/g in dimethyl sulfoxide at 30 °C were obtained in high yield. Most of them dissolved readily at room temperature in polar solvents. The synthesized copoly(ester–amide)s possessed glass-transition temperatures from 210–255 °C. The copoly(ester–amide)s exhibited excellent thermal stabilities and had 10% weight loss at temperature above 295 °C under nitrogen atmosphere.     

Thermal condensation of imidazole with trifluoroacetaldehyde

The title condensation occurred readily at reflux (100°C) with the methyl hemiacetal of trifluoroacetaldehyde and provided 37.3% of 4(5)-(1′-hydroxy-2′,2′,2′-trifluoroethyl)imidazole as the major product, together with 8.8% of 2-(1′-hydroxy-2′,2′,2′-trifluoroethyl)imidazole, 7.2% of 2,4(5)-bis-(1′-hydroxy-2′,2′,2′-trifluoroethyl)imidazole and 0.4% of the 4,5-bis-product. (Trifluoroacetyl)imidazoles were prepared by oxidation of these condensation products. Nitration and bromination of the condensation products gave the corresponding nitro- and bromoimidazoles, respectively.     

双金属氰化物络合物催化环氧烷烃开环聚合的特征

合成了Co Zn双金属氰化物 (DMC)络合物催化剂 ,以X 射线衍射、元素分析、红外光谱等手段进行了表征 ,考察了该催化体系下环氧丙烷开环聚合的反应特性 ,并初步探讨了聚合反应的机理 .研究发现 ,Co Zn双金属氰化物催化剂具有很高的催化活性 ,适合于中高分子量聚醚的合成 ,但是碱性起始剂起阻聚作用 ;在该催化体系下聚合物分子量可控 ,不饱和度很低 (<0 .0 14meq g) ,分批加料聚合所得到的聚合物分子量分布较窄 (Mn Mw <1.4 ) ,而一步加料聚合所得到的聚合物分子量分布变宽 ;1 3C NMR分析表明聚合物主链具有无规立构分布的特点 ,且链节分布几乎都为头 尾方式 .聚合过程中活性链与非活性链之间可能存在一个交换反应 ;虽然聚合反应有终止 ,但与聚合物链长没有关系 ,聚合物链的终止是可逆的 .     

Chlorine substitution in poly(arylamine)s during synthesis and protonation in hydrochloric acid

The effects of varying the oxidant/monomer ratio in the polymerization of aniline, N-phenyl-p-phenylenediamine and N,N′-diphenylbenzidine in a hydrochloric acid solution of (NH₄)₂S₂O₈ were investigated. With the first two monomers, increasing the oxidant/monomer ratio from 0·3 to 3 results in a substantial increase in polymer yield but the extent of covalent bond formation between chlorine and the polymer is also increased. In addition, differences in the N/C and imine/amine ratios, and in thermal stability, are evident in the polymers synthesized at different oxidant/monomer ratios. The degree of polymerization of N,N′-diphenylbenzidine is low and it exhibits a very high susceptibility to chlorine substitution in the reaction mixture. A comparison of the extent of chlorine substitution is made among polymers synthesized in (NH₄)₂S₂O₈/HCl, and polyaniline base and aromatic amine monomers treated with HCl of the same concentration.     

Sulfonated poly(arylene thioether phosphine oxide)s copolymers for proton exchange membrane fuel cells

High molecular weight sulfonated poly(arylene thioether phosphine oxide)s (sPATPO) with various sulfonation degrees were prepared directly by aromatic nucleophilic polycondensation of 4,4′-thiobisbenzenethiol with sulfonated bis(4-fluorophenyl) phenyl phosphine oxide and bis(4-fluorophenyl) phenyl phosphine oxide. sPATPO in the acid form with sulfonation degrees of 60–100% exhibits a glass transition temperature higher than 230 °C and a 5% weight loss temperature above 400 °C, indicating high thermal stability. sPATPO with a high sulfonation degree shows high proton conductivity and good resistance to swelling as well. For instance, sPATPO-70 displays the conductivity of 0.0783 S/cm and a swelling ratio of 11.6% at 90 °C. TEM micrographs showed that sPATPO membranes with a high sulfonation degree could form continuous ion channels, which are favorable for improving the proton conductivity but harmful to remaining the mechanical property. The membranes are expected to show good performances in fuel cell applications.     

Polymerization of α-Methylstyrene in Cyclohexane with Potassium as Initiator. IV. Thermodynamic Study and Gel-Permeation Chromatographic Analyses of the Polymers

Polymerization of α-methylstyrene in cyclohexane containing traces of tetrahydrofuran (THF) has been carried out at 40°C with potassium as initiator. The conversion of monomer to polymer was very slow, and a solution with [M]₀ of 5.15 mole/ liter, carrying 0.110 mole/liter of the living ends [LE], required two months to reach a stationary state. The gel-permeation chromatographic (GPC) analyses of these polymers showed them to have multimodal distributions which could be split into components D+A, B, and C similar to those found for poly-α-methylstyrene prepared in THF and α-dioxane as solvents. Furthermore, under identical conditions of [M]₀ and [LE], the GPC distributions of poly-α-methylstyrene prepared in cyclohexane, p-dioxane, and THF were the same, in spite of their different dielectric constants. Under identical conditions of [M]₀ but with different [LE], the effect of excessive [LE] on the GPC distributions of the polymers prepared in cyclohexane was not limited to the component D+A as was the case when THF or p-dioxane were the solvents, but also on the component C which increased its contribution [P]_e to the polymer.     

Characterization of hydrophilic networks synthesized by group transfer polymerization

Group transfer polymerization was used to synthesize several series of hydrophilic random and model networks. Cationic random networks were prepared both in bulk and in tetrahydrofuran (THF) using a monofunctional initiator and simultaneous polymerization of monomer and branch units, while a bifanctional initiator was employed in THF for the synthesis of model networks comprising basic or acidic chains. Upon polymerization of the monomer, the latter initiator gives linear polymer chains with two “living” ends, which are subsequently interconnected to a polymer network by the addition of a branch unit. Homopolymer network star polymers were also synthesized in THF by a one‐pot procedure. The synthesis involved the use of a monofunctional initiator and the four‐step addition of the following reagents: (i) monomer, to give linear homopolymers; (ii) branch unit, to form “arm‐first” star polymers; (iii) monomer, to form secondary arms and give “in‐out” star polymers; and, finally (iv) branch unit again, to interconnect the “in‐out” stars to networks. Different networks were prepared for which the degree of polymerization (DP) of the linear chains between junction points was varied systematically. For all networks synthesized, the linear segments, the “arm‐first” and the “in‐out” stars were characterized in terms of their molecular weight (MW) and molecular weight distribution (MWD) using gel permeation chromatography (GPC). The degrees of swelling of both the random and model networks in water were measured and the effects of DP, pH, and monomer type were investigated.     

Use of a MDI-functionalized reactive polymer for the manufacture of modified bitumen with enhanced properties for roofing applications

In this study, the suitability of a reactive polymer, synthesized by reaction of 4,4′-diphenylmethane diisocyanate (MDI) with a low molecular weight polyethylene-glycol (PEG), as a modifying agent for the manufacture of bitumen-based waterproof membranes, was evaluated. With that purpose, rheological and thermal analysis tests, and microstructural observations by AFM were carried out on different samples of modified bitumen having a MDI–PEG content ranging from 0 to 10 wt.%, cured at room temperature for a period of time within 0–30 days. The results obtained demonstrate that the addition of the reactive polymer proposed in this work to bitumen is very suitable at high in-service temperatures, because a noticeable increase in the values of viscosity, at 60 °C, of the resulting modified bitumen samples is observed on a time-scale of days. AFM observations, carried out at 50 °C, evidenced that the reactive polymer MDI–PEG leads to a new microstructure, displaying a higher level of stiffness. Therefore, this polymer should be seriously taken into consideration as a modifier of bituminous coatings for the waterproofing industry.     

Sodium hydride-initiated polymerizations of vinyl monomers in aprotic solvents

Polymerizations of several vinyl monomers at 25°C in aprotic solvents (dimethyl sulfoxide, N,N-dimethylacetamide, and hexamethylphosphoric triamide) using sodium hydride dispersion as initiator yield low to intermediate molecular weight polymers. The molecular weight of the resulting polymer as well as the mode of initiation depends on the monomer and aprotic solvent used. Initiation of polymerization of monomers with available α hydrogens (methyl acrylate, acrylonitrile) involves monomer anion, while initiation of a monomer with no α hydrogen (methyl methacrylate) proceeds by a more complex mechanism. In contrast, initiation of styrene and α-methylstyrene proceeds by dimsyl anion addition to monomer in dimethylsulfoxide. Although the triad tacticities and number-average molecular weights of poly(methyl methacrylate) samples obtained from all three aprotic solvents are nearly the same, poly(methyl methacrylates) prepared in dimethyl sulfoxide and N,N-dimethylacetamide give polymers having polydispersities of ～3, while a very polydisperse polymer is obtained in hexamethylphosphoric triamide.     

Synthesis, water stability and proton conductivity of novel sulfonated polyimides from 4,4′-bis(4-aminophenoxy)biphenyl-3,3′-disulfonic acid

A novel sulfonated diamine monomer, 4,4′-bis(4-aminophenoxy)biphenyl-3,3′-disulfonic acid (BAPBDS) with the high basisity and flexible structure was synthesized by direct sulfonation of 4,4′-bis(4-aminophenoxy)biphenyl (BAPB). Sulfonated polyimides (SPIs) were prepared from 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), BAPBDS and nonsulfonated diamines such as BAPB. The SPI membranes showed much higher water stability at high temperatures than other sulfonated diamine-based SPIs reported so far. Their water vapor sorption isotherm, water uptake (WU), density, dimensional change and proton conductivity σ were investigated. The SPIs showed rather isotropic dimensional changes with WU and the volume increases were slightly smaller than those estimated from the additivity. The SPIs with ion exchange capacities (IECs) of 1.9–2.7 meq/g displayed the similar relationship between σ and WU each other, which was different from those of Nafion 117 and also of the SPIs with the lower IECs. The former SPIs showed reasonably high σ values of 10⁻² S/cm or more even at WU of 25 g/100 g dry polymer under 70% RH at 50 °C, whereas the latter showed the similarly high σ values only in liquid water, but not in the nearly saturated water vapor.     

Synthesis of Reactive-Ended Acrylic Polymers by Group Transfer Polymerization: Initiation with Silyl Ketene Acetals

Living methacrylate polymers are obtained at room temperature and above by initiation with ketene silyl acetals in the presence of a soluble bifluoride catalyst. During the polymerization, a trialkylsilyl group is transferred from the living chain end to incoming monomer. The new procedure has thus been named group transfer polymerization (GTP). Monodisperse polymers with predetermined molecular weights as high as 100,000 can be obtained by adjusting the monomer/initiator ratio. Telechelic poly(methyl methacrylate) with hydroxy or carboxy ends can be obtained by using an initiator containing a protected hydroxy or carboxy group and coupling the resulting living polymer.     

Atom transfer radical polymerization of styrene under pulsed microwave irradiation

A homogeneous solution atom transfer radical polymerization (ATRP) and reverse atom transfer radical polymerization (RATRP) of styrene (St) in N,N-dimethylformamide (DMF) were successfully carried out under pulsed microwave irradiation (PMI), using 1-bromo-1-phenylethane (1-PEBr)/CuCl/N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (PMDETA) as an initiating system at 85°C and 2,2′-azo-bis-isobutyrontrile (AIBN)/CuCl₂/PMDETA as an initiating system at 95°C, respectively. The polymerization rates under PMI were greatly increased in comparison with those under identical conventional heating (CH).     

Hyperbranched polymers generated from oxyanionic vinyl polymerization of commercially available methacrylate inimers

Hyperbranched polymethacrylates were prepared by means of oxyanionic vinyl polymerization of commercially available monomers, including hydroxyethyl methacrylate (HEMA) and poly(ethylene glycol) methacrylate (PEG‐MA). Hyperbranched polymethacrylates with high molecular weight were obtained with the complex of potassium hydride and 18‐crown‐6 as the initiator. The effect of 18‐crown‐6 is very important, and only oligomer can be obtained in the polymerization without 18‐crown‐6. The molecular structure of the hyperbranched polymers was confirmed with ¹H NMR and ¹³C NMR spectra. The ratio of initiator to monomer significantly affects the architecture of the resultant polymers. When the ratio of initiator to monomer equals 1 in the oxyanionic vinyl polymerization of HEMA, the degree of branching of the resulting polymer was calculated to be around 0.49. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3502–3509, 2005     

Homoleptic carbene complexes VI. Bis{1,1′-methylene-3,3′-dialkyl-diimidazolin-2,2′-diylidene}palladium chelate complexes by the free carbene route

1,1′-Methylene-3,3′-dialkyldiimidazolium salts have been deprotonated with n-butylithium in the presence of palladium(II) iodide to give the percarbene complexes 1 (alkyl=Me) and 2 (alkyl=Et), each containing two bidentate 1,1′-methylene-3,3′-dialkyldiimidazolin-2,2′-diylidene chelate ligands. The X-ray structure analysis of 1 reveals a stereochemistry in which the two spiro-linked six-membered metallacycles adopt boat-like conformations strongly bending out of the PdC₄ coordination plane in opposite directions. The carbenoid imidazole rings, which are rotated by +42 and −43°, respectively, relative to this plane, break down into two tightly bound π-systems (N=4C=4N,= C=C) connected by long C---N bonds.     

Synthesis and characterisation of poly[2,2-(m-phenylene)-5,5-bibenzimidazole] as polymer electrolyte membrane for high temperature PEMFCs

Intermediate-high molecular weight poly[2,2-(m-phenylene)-5,5-bibenzimidazole] has been produced by mixing 3,3′,4,4′-tetraminobiphenyl and isophthalic acid in polyphosphoric acid as polycondensing agent and triphenyl phosphite as catalyst. Polymers with intrinsic viscosities close to 1 were measured in 97% sulphuric acid. Membranes were prepared by solution casting and subsequently immersed in phosphoric acid in order to gain ionic conductivity. These membranes were characterised by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analyses, methanol permeation and conductivity measurements. Levels of acid and water absorbed by the membranes were measured and the kinetic of this process was studied. Finally, doped membranes were tested in an actual fuel cell setup, obtaining also information about gases crossover from the open circuit potential. Acceptably reproducible molecular weights between 115,000 and 190,000 were obtained allowing the casting of mechanically stable membranes, which showed a great affinity towards phosphoric acid, high thermal stability, and a conductivity of 0.039 S/cm at 190 °C with the membrane equilibrated in saturated air at 60 °C. Open circuit potential of a PBI membrane was 0.99 V, close to those of commercial perfluorinated membranes. A H₂/O₂ fuel cell with dry gases was able to produce a maximum power output of 0.22 W/cm² at 175 °C.     

Synthesis,crystallization, and morphology of star‐shaped poly(ε‐caprolactone)

Six‐arm star‐shaped poly(ε‐caprolactone) (sPCL) was successfully synthesized via the ring‐opening polymerization of ε‐caprolactone with a commercial dipentaerythritol as the initiator and stannous octoate (SnOct₂) as the catalyst in bulk at 120 °C. The effects of the molar ratios of both the monomer to the initiator and the monomer to the catalyst on the molecular weight of the polymer were investigated in detail. The molecular weight of the polymer linearly increased with the molar ratio of the monomer to the initiator, and the molecular weight distribution was very low (weight‐average molecular weight/number‐average molecular weight = 1.05–1.24). However, the molar ratio of the monomer to the catalyst had no apparent influence on the molecular weight of the polymer. Differential scanning calorimetry analysis indicated that the maximal melting point, cold crystallization temperature, and degree of crystallinity of the sPCL polymers increased with increasing molecular weight, and crystallinities of different sizes and imperfect crystallization possibly did not exist in the sPCL polymers. Furthermore, polarized optical microscopy analysis indicated that the crystallization rate of the polymers was in the order of linear poly(ε‐caprolactone) (LPCL) > sPCL5 > sPCL1 (sPCL5 had a higher molecular weight than both sPCL1 and LPCL, which had similar molecular weights). Both LPCL and sPCL5 exhibited a good spherulitic morphology with apparent Maltese cross patterns, whereas sPCL1 showed a poor spherulitic morphology. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5449–5457, 2005     

Controlled ring‐opening polymerization of propylene oxide catalyzed by double metal‐cyanide complex

A double metal‐cyanide catalyst based on Zn₃[Co(CN)₆]₂ was prepared. This catalyst is very effective for the ring‐opening polymerization of propylene oxide. Polyether polyols of moderate molecular weight having low unsaturation (<0.015 meq/g) can be prepared under mild conditions. The molecular weight of polymer is entirely controlled by a reacted monomer‐to‐initiator ratio. The polymers prepared with stepwise addition of monomer exhibit a narrower molecular weight distribution as compared with those prepared with one‐step addition of monomer. Various compounds containing active hydrogen, except basic compounds and low‐carbon carboxylic acid, may be used as initiators. The reaction rate increases with increasing catalyst amount and decreases with rising initiator concentration. Polymerization involves a rapid exchange reaction between the active species and the dormant species. It was also proven that, to a certain extent, the chain termination of this catalytic system is reversible or temporary. ¹³C NMR analysis showed that the polymer has a random distribution of the configurational sequences and head‐to‐tail regiosequence. It is assumed that the polymerization proceeds via a cationic coordination mechanism. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1142–1150, 2002     

Reactive intermediates in asymmetric cross-coupling catalysed by palladium P-N chelates

The palladium dibromide complexes of (S,R)-(1,1′-bis-diphenylphosphino)-2-ferrocencylthyldimethylamine and (S,R)-(1-diphenylphosphino)-2-ferrocenylethyldimethylamine have been reduced with dilithiocyclooctatetraene to form the corresponding Pd⁰ cyclooctatetraene complexes. Their reactions with E-4-methoxy-2′-bromophenylethene, and then benzylmagnesium chloride at −60 to −30°C, provide information on the structure of intermediates in asymmetric cross-coupling.