Synthesis and properties of various poly(diarylacetylenes) containing siloxy and hydroxy groups

Diarylacetylene monomers ( 1b ? f) containing siloxy and either naphthyl, fluorenyl, or biphenyl groups were polymerized with TaCl₅–n‐Bu₄Sn catalyst, and 1b , 1c , and 1f provided high molecular weight polymers. Free‐standing membranes of polymers 2b , 2c , and 2f were fabricated by casting from toluene solution. Desilylation of these polymer membranes was carried out with trifluoroacetic acid to afford poly (diarylacetylenes) membranes having hydroxy groups ( 3b and 3c ). According to thermogravimetric analysis (TGA), both siloxy‐containing and hydroxy‐containing polymers exhibited high thermal stability, and the onset temperatures of weight loss in air were ～370 °C and ～430 °C, respectively. The CO₂ permeability coefficients of these membranes were in the range of 65–640 barrers. The points of 3b and 3c in the PCO₂ versus PCO₂/PCH₄ plot were located above Robeson's upper bound. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4487–4495, 2007     

Water‐swollen highly oxygen permeable membranes: Analytical technique and syntheses

A generally accepted method for the determination of high oxygen permeabilities (Dk >100 barrers) of water‐immersed membranes is unavailable. We designed and developed a generally applicable method, together with simple equipment, to measure the oxygen permeability up to Dk ～800 barrers of highly oxygen permeable membranes in contact with water. A theory of the methodology is also presented, giving particular attention to the boundary layer effect and the edge effect. The practical applicability of our technique is demonstrated by preparing and using highly oxygen permeable water‐logged membranes, such as polydimethylsiloxane and polysiloxane copolymers important for medicine. According to our measurements, the Dk's of polydimethylsiloxane, poly(dimethylsiloxane_0.80‐co‐diethylsiloxane_0.20), and poly(dimethylsiloxane_0.84‐co‐diphenylsiloxane_0.16) are 792 ± 26, 505 ± 10, and 249 ± 10 barrers, respectively. Evidently, the oxygen permeabilities of polysiloxanes are strongly reduced by substituting the ? OSiMe₂? repeat unit with the structurally similar ? OSiEt₂? and ? OSiPh₂? repeats. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3491–3501, 2005     

Synthesis,properties, and gas permeability of novel poly(diarylacetylene) derivatives

Poly(diphenylacetylene)s having various silyl groups are soluble in common solvents, from whose membranes poly(diphenylacetylene) membranes can be obtained by desilylation. The oxygen permeability coefficients of the desilylated polymers are quite different from one another (120–3300 barrers) irrespective of the same polymer structure. When bulkier silyl groups are removed, the oxygen permeability increases to larger extents. Poly[1-aryl-2-p-(trimethylsilyl)phenylacetylene]s are soluble in common solvents, and afford free-standing membranes. These Si-containing polymer membranes are desilylated to give the membranes of poly[1-aryl-2-phenylacetylene]s. Both of the starting and desilylated polymers show very high thermal stability and high gas permeability. 1-Phenyl-2-p-(t-butyldimethylsiloxy)phenylacetylene polymerizes into a high-molecular-weight polymer. This polymer is soluble in common organic solvents to provide a free-standing membrane. Desilylation of this membrane yields a poly(diphenylacetylene) having free hydroxyl groups, which is the first example of a highly polar group-carrying poly(diphenylacetylene). The P/P and P/P permselectivity ratios of poly(1-phenyl-2-p-hydroxylphenylacetylene) membrane are as large as 47.8 and 45.8, respectively, while keeping relatively high P of 110 barrers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5028–5038, 2006     

Synthesis and properties of poly(phenylacetylenes) having two polar groups or one cyclic polar group on the phenyl ring

Phenylacetylene (PA) derivatives having two polar groups (ester, 2a – d ; amide, 4) or one cyclic polar group (imide, 5a – c ) were polymerized using (nbd)Rh⁺[(η⁶‐C₆H₅)B^?(C₆H₅)₃] catalyst to afford high molecular weight polymers (～1 × 10⁶ – 4 × 10⁶). The hydrolysis of ester‐containing poly(PA), poly( 2a) , provided poly(3,4‐dicarboxyPA) [poly ( 3 )], which could not be obtained directly by the polymerization of the corresponding monomer. The solubility properties of the present polymers were different from those of poly(PA) having no polar group; that is, poly( 2a )–poly( 2d ) dissolved in ethyl acetate and poly( 4 ) dissolved in N,N‐dimethylformamide, while poly(PA) was insoluble in such solvents. Ester‐group‐containing polymers [poly( 2a )–poly( 2d )] afforded free‐standing membranes by casting from THF solutions. The membrane of poly( 2a ) showed high carbon dioxide permselectivity against nitrogen (PCO₂/PN₂ = 62). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5943–5953, 2006     

Synthesis of comb‐type polycarbosilanes via nucleophilic substitution reactions on the main‐chain silicon atoms

A series of comb‐type polycarbosilanes of the type [Si(CH₃)(OR)CH₂]_n {where R = (CH₂)_mR′, R′ = ? O‐p‐biphenyl? X [X = H (m = 3, 6, 8, or 11) or CN (m = 11)], and R′ = (CF₂)₇CF₃ (m = 4)} were prepared from poly(chloromethylsilylenemethylene) by reactions with the respective hydroxy‐terminated side chains in the presence of triethylamine. The product side‐chain polymers were typically greater than 90% substituted and, for R′ = ? O‐p‐biphenyl? X derivatives, they exhibited phase transitions between 27 and 150 °C involving both crystalline and liquid‐crystalline phases. The introduction of the polar p‐CN substituent to the biphenyl mesogen resulted in a substantial increase in both the isotropization temperature and the liquid‐crystalline phase range with respect to the corresponding unsubstituted biphenyl derivative. For R = (CH₂)₁₁? O‐biphenyl side chains, an analogous side‐chain liquid‐crystalline (SCLC) polysiloxane derivative of the type [Si(CH₃)(O(CH₂)₁₁? O‐biphenyl)O]_n was prepared by means of a catalytic dehydrogenation reaction. In contrast to the polycarbosilane bearing the same side chain, this polymer did not exhibit any liquid‐crystalline phases but melted directly from a crystalline phase to an isotropic liquid at 94 °C. Similar behavior was observed for the polycarbosilane with a fluorocarbon chain, for which a single transition from a crystalline phase to an isotropic liquid was observed at ?0.7 °C. The molecular structures of these polymers were characterized by means of gel permeation chromatography and high‐resolution NMR studies, and the crystalline and liquid‐crystalline phases of the SCLC polymers were identified by differential scanning calorimetry, polarized optical microscopy, and X‐ray diffraction. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 984–997, 2003     

Triphenylamine‐based polyimides with trimethyl substituents for gas separation membrane and electrochromic applications

Two series of polyimides I – II with methyl‐substituted triphenylamine units were prepared from the diamines, 4,4′‐diamino‐2″,4″,6″‐trimethyltriphenylamine (Me₃TPA‐diamine; 1 ) and 4,4′‐diamino‐4″‐methyltriphenylamine (MeTPA‐diamine; 2 ), and two commercially available tetracarboxylic dianhydrides via a conventional two‐step chemical imidization. All the polymers were readily soluble in many polar solvents and showed useful levels of thermal stability associated with high glass transition temperatures (266–340 °C) and high char yields (higher than 49% at 800 °C in nitrogen). The polymer films showed reversible electrochemistry/electrochromism accompanied by a color change from neutral pale yellow to green oxidized form with good coloration efficiency, switching time, and stability. The CO₂ permeability coefficients (P_CO2) and permeability selectivity (P_CO2/P_CH4) for these polyimide membranes were in the range of 34.1–229.2 barrer and 21.3–28.9, respectively. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and properties of amino acid esters of hydroxypropyl cellulose

The amino acid esters of hydroxypropyl cellulose (HPC) [R′ = H ( 2a ), CH₃ ( 2b ), CH₂CH(CH₃)₂ ( 2c ), CH₂CONH₂ ( 2d ), CH₂CH₂CONH₂ ( 2e ), CH₂CH₂CH₂CH₂ NHOCOC(CH₃)₃ ( 2f )] were synthesized in good yield by the reaction of t‐butoxycarbonyl (t‐Boc)‐protected amino acids with hydroxy groups of HPC ( 1 ; molar substitution (MS), 4.61). The amino acid functionalities displaying varied chemical nature, shape, and bulk were utilized and the bulk of the substituent on the α‐carbon of amino acids was elucidated to be of vital significance for the observed degree of incorporation (DS_Est). The ¹H NMR spectra and elemental analysis were employed to determine the degree of incorporation of amino acid moiety (DS_Est) and almost complete substitution of the hydroxy protons was revealed for 2a , 2b , and 2f . The presence of the peaks characteristic of the carbonyl group in the FTIR spectra furnished further evidence for the successful esterification of HPC. The starting as well as the resulting polymers ( 1 and 2a – f ) were soluble in polar organic solvents; however, the esterification of 1 with bulky organic moieties resulted in an increased hydrophobicity as all of the amino acid‐functionalized polymers ( 2a – f ) were insoluble in water. The onset temperatures of weight loss of 2a – f were 175–230 °C, indicating fair thermal stability. The amino acid functionalization led to the enhanced polymer chain stiffness, and the glass transition temperatures of the derivatized polymers were 30–40 °C higher than that of 1 (T_g 3.9 °C; cf. T_g of 2a – f , 35.1–43.3 °C). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2326–2334, 2008     

Synthesis and radical polymerization of dissymmetric fumarates with alkoxyethyl and bulky siloxy groups

Novel dissymmetric fumarate monomers ( 1a – c ) having both an alkoxyethyl group such as 2‐methoxyethyl ( a ), 2‐(2‐methoxyethoxy)ethyl ( b ), and 2‐(2‐(2‐methoxyethoxy)ethoxy)ethyl ( c ) and a bulky 3‐[tris(trimethylsiloxy)silyl]propyl group were synthesized successfully, and their radical homopolymerizations and copolymerizations with styrene (St) were investigated. Monomer reactivities of the 1a – c in homopolymerizations were enhanced with an increase in the length of alkoxyethyl chains. The enhancement in the reactivity was explained with the suppression of the termination reaction, resulting from the increased steric hindrance induced by an increase in the size of alkoxyethyl chains. Copolymerizations of the 1a – c with St were carried out in bulk in the presence of AIBN at 60 °C, and their copolymerizations proceeded in a highly alternating tendency regardless of alkoxyethyl chain lengths. The Q, e values of the 1a – c were obtained as 0.48, +1.55 for the 1a , 0.66, +1.16 for the 1b , and 0.60, +1.16 for the 1c , respectively, from the terminal model reactivity ratios, and the 1a – c were found to be conjugative, electron‐accepting monomers. Membranes containing the 1a unit, prepared by the copolymerization of 1a with N‐vinylpyrrolidone (NVP) and terpolymerization of 1a , NVP, and 2‐hydroxyethyl methacrylate, have higher oxygen permeability than those containing no 1a unit, and also they have much better transparency compared with the membranes containing 3‐[tris(trimethylsilyloxy)silyl]propyl methacrylate unit. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 420–433, 2009     

Synthesis and characterization of soluble,fluorescent poly(arylene ether)s,poly(arylene thioether)s,and poly(arylene sulfone)s containing 1,3,5‐triphenylbenzene segments

The bisphenol 4,4″‐dihydroxy‐5′‐phenyl‐m‐terphenyl ( 4 ), containing a 1,3,5‐triphenylbenzene moiety, was synthesized from a pyrylium salt obtained by the reaction of benzaldehyde with p‐methoxyacetophenone with boron trifluoride etherate as a condensing agent. Polymers were obtained from 4 by a nucleophilic displacement reaction with various activated difluoro monomers and with K₂CO₃ as a base. A series of new poly(arylene ether)s ( 8a – 8f ) were obtained that contained phenyl‐substituted m‐terphenyl segments in the polymer chain. Polymers with inherent viscosities of 0.41–0.99 dL/g were obtained in yields greater than 96%. The polymers were soluble in a variety of organic solvents, including nonpolar solvents such as toluene. Clear, transparent, and flexible films cast from CHCl₃ showed high glass‐transition temperatures (T_g = 198–270 °C) and had excellent thermal stability, as shown by temperatures of 5% weight loss greater than 500 °C. 4 was converted via N,N‐dimethyl‐O‐thiocarbamate into the masked dithiol 4,4″‐bis(N,N′‐dimethyl‐S‐thiocarbamate)‐5′‐phenyl‐m‐terphenyl and was polymerized with activated difluoro compounds in the presence of a mixture of Cs₂CO₃ and CaCO₃ as a base in diphenyl sulfone as a solvent. A series of new poly(arylene thioether)s ( 9a – 9e ) were obtained with T_g values similar to those of 8a – 8e . 9a – 9e were further oxidized into poly(arylene sulfone)s with T_g values 40–80 °C higher than those for 8a – 8e and 9a – 9e . These polymers also had good solubility in organic solvents. A sulfonic acid group was selectively introduced onto the pendent phenyl group of polymers 8a and 8f by reaction with chlorosulfonic acid. The polymers were soluble in dipolar aprotic solvents and formed films via casting from dimethylformamide. Polymers 8a – 8f , 11a , and 11f showed blue and red fluorescence under ultraviolet–visible light with emission maxima at 380–440 nm. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 496–510, 2002; DOI 10.1002/pola.10136     

Synthesis and helicity of optically active poly(N‐propargylphosphonamidates) having chiral phosphorus center

Novel chiral N‐propargylphosphonamidate monomers (HC?CCH₂NHP(?O)R? O? menthyl, 1 : R = CH₃, 2 : R = C₂H₅, 3 : R = n‐C₃H₇, 4 : R = Ph) were synthesized by the reaction of the corresponding phosphonic dichlorides with menthol and propargylamine. Pairs of diastereomeric monomers 1 – 4 with different ratios were obtained due to the chiral P‐center and menthyl group. One diastereomer could be separated from another one in the cases of monomers 1 and 2 . Polymerization of 1 – 4 with (nbd)Rh⁺[η⁶‐C₆H₅B^?(C₆H₅)₃] as a catalyst in CHCl₃ gave the polymers with number‐average molecular weights ranging from 5000 to 12,000 in 65–85%. Poly( 1 )–poly( 4 ) exhibited quantitative cis contents, and much larger specific rotations than 1 – 4 did in CHCl₃. The polymers showed an intense Cotton effect around 325 nm based on the conjugated polyacetylene backbone. It was indicated that the polymers took a helical structure with predominantly one‐handed screw sense, and intramolecular hydrogen bonding between P?O and N? H of the polymers contributed to the stability of the helical structure. Poly( 1a ) and poly( 2a ) decreased the CD intensity upon raising CH₃OH content in CHCl₃/CH₃OH. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1515–1524, 2007     

Synthesis of dual pH/temperature‐responsive polymers with amino groups by living cationic polymerization

For the precision synthesis of primary amino functional polymers, cationic polymerization of a phthalimide‐containing vinyl ether monomer precursor, 2‐vinyloxyethyl phthalimide (PIVE), was examined using a base‐assisting initiating system. Living polymerization of PIVE in CH₂Cl₂ in the presence of 1,4‐dioxane as an added base yielded nearly monodispersed polymers (M_w/M_n < 1.1) and higher molecular weight polymers, which have never been obtained using other initiating systems. Furthermore, block copolymers with hydrophobic or hydrophilic groups could be prepared. The deprotection of the pendant phthalimide groups gave well‐defined pH‐responsive polymers with pendant primary amino groups. Dual‐stimuli–responsive block copolymers having a pH‐responsive polyamine segment and a thermosensitive segment self‐assembled in water in response to both pH and temperature. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1207–1213, 2010     

Syntheses and gas transport properties of polyarylates based on isophthalic and terephthalic acids and mixtures of bisphenol A and 1, 1 bi‐2‐naphthol

Polyarylates based on isophthalic (IA) and terephthalic (TA) acids and an equimolar mixture of the diols Bisphenol A (BPA) and 1,1 bi‐2‐naphthol (BN) were synthesized to produce BPA‐BN/IA and BPA‐BN/TA polymers and to measure their gas permeability coefficients, P(i), at several pressures and 35 °C, to the gases O₂, N₂, CH₄, and CO₂. For the BPA‐BN/IA membranes, at a 2 atm up‐stream pressure, the P(O₂) and P(CO₂) are 0.93 and 4.0 Barrers with O₂/N₂ and CO₂/CH₄ ideal separation factors of 6.7 and 27. For the BPA‐BN/TA, at a 2 atm up‐stream pressure, the P(O₂) and P(CO₂) are 2.0 and 9.9 Barrers with O₂/N₂ and CO₂/CH₄ ideal separation factors of 5.6 and 21. Comparing the selectivity–permeability balance of properties shown by the BPA/TA membranes with that shown by the copolymer BPA‐BN/TA, the balance moves in the direction of higher selectivity and lower permeability because of the incorporation of BN, which is a more rigid monomer than BPA. However, when the balance of properties for the pair O₂/N₂ shown by BPA‐BN/TA is compared with the one shown by other membranes such as those based on mixtures of diols and diacids, that is the bisphenol A‐naphthalene/I‐T polymers reported in the literature, the balance moves up and to the right of the typical selectivity–permeability trade‐off observed in the BPA‐polyarylate family. Thus, simultaneous incorporations of flexible and rigid monomers in both the diols and the diacids lead to more productive and more selective membranes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 256–263, 2006     

Synthesis and applications of 2,7‐carbazole‐based conjugated main‐chain copolymers containing electron deficient bithiazole units for organic solar cells

A series of low‐band‐gap (LBG) donor–accepor conjugated main‐chain copolymers ( P1 – P4 ) containing planar 2,7‐carbazole as electron donors and bithiazole units (4,4′‐dihexyl‐2,2′‐bithiazole and 4,4′‐dihexyl‐5,5′‐di(thiophen‐2‐yl)‐2,2′‐bithiazole) as electron acceptors were synthesized and studied for the applications in bulk heterojunction (BHJ) solar cells. The effects of electron deficient bithiazole units on the thermal, optical, electrochemical, and photovoltaic (PV) properties of these LBG copolymers were investigated. Absorption spectra revealed that polymers P1 – P4 exhibited broad absorption bands in UV and visible regions from 300 to 600 nm with optical band gaps in the range of 1.93–1.99 eV, which overlapped with the major region of the solar emission spectrum. Moreover, carbazole‐based polymers P1 – P4 showed low values of the highest occupied molecular orbital (HOMO) levels, which provided good air stability and high open circuit voltages (V_oc) in the PV applications. The BHJ PV devices were fabricated using polymers P1 – P4 as electron donors and (6,6)‐phenyl‐C₆₁‐butyric acid methyl ester (PC₆₁BM) or (6,6)‐phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM) as electron acceptors in different weight ratios. The PV device bearing an active layer of polymer blend P4:PC₇₁BM (1:1.5 w/w) showed the best power conversion efficiency value of 1.01% with a short circuit current density (J_sc) of 4.83 mA/cm², a fill factor (FF) of 35%, and V_oc = 0.60 V under 100 mW/cm² of AM 1.5 white‐light illumination. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis of highly luminescent organoboron polymers connected by bifunctional 8‐aminoquinolate linkers

New organoboron aminoquinolate‐based polymers linked by π‐conjugated bridge were prepared by Sonogashira–Hagihara coupling of organoboron aminoquinolate‐based bisiodo monomers bearing biphenyl or bithiophene moiety with 1,4‐diethynylbenzene derivatives. Tetracoordination states of boron atoms in the obtained polymers were confirmed by ¹¹B NMR spectroscopy, and they were also characterized by ¹H NMR and IR spectroscopies and size‐exclusion chromatography. Their optical properties were studied by UV–vis absorption and photoluminescence spectroscopies. In the region above 400 nm, the polymers prepared from 1,4‐diethynyl‐2,5‐dioctyloxybenzene showed bathochromic shifts when compared with those prepared from 1.4‐diethynyl‐2‐perfluorooctyl‐5‐trifluoromethylbenzene. The polymers with biphenyl moiety showed higher absolute fluorescence quantum yields (?_F = 0.28 and 0.65), whereas those with bithiophene moiety led to decreasing of the low quantum yields (?_F = 0.19 and 0.00). The density‐functional theory (DFT) and time‐dependent–DFT calculations of model compounds corresponding to the polymers were in good agreement with the results from UV–vis properties. The calculations revealed that the electronic structure of the polymer with bithiophene moiety is different from that with biphenyl moiety, and predicted the electron transfer from the bithiophene moiety to the π‐extended quinoline moiety in transition state. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3693–3701, 2010     

Synthesis of hydrocarbon polymers containing bulky dibenzobicyclic moiety by ROMP and their characteristic optical properties

The eight‐membered cyclic monomer, prepared by Diels–Alder reaction of 1,5‐cyclooctadiene and anthracene, polymerized via Ru‐catalyzed ring‐opening metathesis to efficiently afford high polymers (M_n up to 631,000). Unsaturated moieties in the main chain of the obtained polymer were hydrogenated with a homogeneous ruthenium catalyst in quantitative conversion, confirmed by ¹H‐NMR measurement. The self‐standing membranes were provided by casting the tetrahydrofuran solutions of both nonhydrogenated and hydrogenated polymers. The obtained membranes showed high transparency in the region of >300 nm with mechanical flexibility. Thermal gravimetric analysis revealed that both nonhydrogenated and hydrogenated polymers decomposed in two stages. The first‐stage decomposition starting at around 230 °C was caused by retro Diels–Alder reaction forming anthracene, proven by pyrolysis gas chromatography mass spectroscopy (GC‐MS) analyses. Mechanical grinding of the polymers induced the formation of anthracene in solid state, which transformed the polymer into blue‐luminescent materials under UV irradiation. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1392–1400     

含有联苯侧基聚乙炔的合成及其气体渗透性能

合成了含有取代联苯及烷基硅取代基的二芳基乙炔单体（1a~1d）,以TaCl5-n-Bu4Sn作催化剂聚合得到聚合物2a、2b和2d。 所得聚合物在常规有机溶剂中具有良好的溶解性。 用聚合物2a和2b的甲苯溶液浇铸制备了均质膜。 采用三氟乙酸对聚合物2a和2b膜进行去硅化反应,制备了不溶性膜3a和3b。 热重分析表明,所得聚合物均具有高的热稳定性,在空气中的热失重起始温度分别为340和430 ℃。 聚合物2a和2b的氧气渗透系数（PO2)分别为260和390 barrers,去硅化膜3a和3b的PO2分别下降至73和180 barrers。 聚合物膜的O2/N2分离系数为2.4~3.3,并随PO2的增加而减小。 由气体在聚合物膜中的扩散系数和溶解系数的测定,扩散系数的降低是导致去硅化膜气体渗透系数下降的主要原因。     

Synthesis and characterization of nitrogen‐linked carbazole‐containing fluorescent polymers

We have prepared four light‐emitting polymers bearing a chromophore composed of carbazole and fluorene by the Suzuki coupling polycondensation. Two nonconjugated polymers (P3CzBFXy and P2CzFXy) had a chromophore tethered by the p‐xylylene spacer, whose connection point between carbazole and fluorene in addition to the number of fluorene unit was systematically changed to investigate the emission wavelength and intensity. The red‐shifted absorption and emission maximum wavelengths together with the improved fluorescence quantum yield of polymers P3CzBFXy and P2CzFXy indicate that the increment of the number of para‐connected benzene rings included in the chromophore effectively extends the conjugation length. The fact that polymer P3CzBFXy has longer wavelength absorption and emission spectra also indicates the interaction of the carbazole nitrogen lone pair with the oligophenylene moiety. Other two polymers P3CzFPy and P3CzFPym having the heterocycle directly bound to the carbazole nitrogen were prepared to know the character of the carbazole nitrogen lone pair and their influence on the fluorescence behavior. The fluorescence spectra of polymer P3CzFPym bearing the pyrimidine ring gradually red‐shifted in conjunction with the decrease of fluorescence quantum yield on going from toluene solution to CHCl₃ solution because of the intramolecular charge transfer at the excited state. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3729–3735, 2010     

Aminolysis of 2,4-dinitrophenyl X-substituted benzoates and Y-substituted phenyl benzoates in MeCN: effect of the reaction medium on rate and mechanism

Second‐order rate constants (k_N) have been determined spectrophotometrically for the reactions of 2,4‐dinitrophenyl X‐substituted benzoates ( 1 a – f ) and Y‐substituted phenyl benzoates ( 2 a – h ) with a series of alicyclic secondary amines in MeCN at 25.0±0.1 °C. The k_N values are only slightly larger in MeCN than in H₂O, although the amines studied are approximately 8 pK_a units more basic in the aprotic solvent than in H₂O. The Yukawa–Tsuno plot for the aminolysis of 1 a – f is linear, indicating that the electronic nature of the substituent X in the nonleaving group does not affect the rate‐determining step (RDS) or reaction mechanism. The Hammett correlation with σ^? constants also exhibits good linearity with a large slope (ρ_Y=3.54) for the reactions of 2 a – h with piperidine, implying that the leaving‐group departure occurs at the rate‐determining step. Aminolysis of 2,4‐dinitrophenyl benzoate ( 1 c ) results in a linear Brønsted‐type plot with a β_nuc value of 0.40, suggesting that bond formation between the attacking amine and the carbonyl carbon atom of 1 c is little advanced in the transition state (TS). A concerted mechanism is proposed for the aminolysis of 1 a – f in MeCN. The medium change from H₂O to MeCN appears to force the reaction to proceed concertedly by decreasing the stability of the zwitterionic tetrahedral intermediate (T^±) in aprotic solvent.     

Synthesis and characterization of fluorine‐containing polybenzimidazole for proton conducting membranes in fuel cells

Two new kinds of fluorine‐containing polybenzimidazoles (PBI), poly(2,2′‐(tetrafluoro‐p‐phenylene)‐5,5′‐bibenzimidazole) and poly(2,2′‐tetradecafluoroheptylene‐5,5′‐bibenzimidazole), were synthesized by condensation polymerization of 3,3′‐diaminobenzidine and perfluoroterephthalic acid (or perfluoroazelaic acid), with polyphosphoric acid as solvent. Thermogravimetric analysis results show that the fluorine‐containing polymers synthesized exhibit promising thermal stability. The film‐forming properties of the fluorine‐containing polymers are improved over nonfluorinated PBI. The introduction of fluorine into the backbone of the polymers has significant positive affection on their chemical oxidation stability demonstrated by Fenton test. Compared with poly(2,2′‐(m‐phenylene)‐5,5′‐bibenzimidazole)/phosphoric acid (PA) composite membrane, the resulting fluorinated membranes with a same PA doping level exhibit better flexibility and higher proton conductivity. The maximum proton conductivity gained is 3.05 × 10^?2 S/cm at 150 °C with a PA doping level of 7. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2115–2122, 2010     

Novel organosoluble aromatic polyimides bearing pendant methoxy‐substituted triphenylamine moieties: Synthesis,electrochromic, and gas separation properties

Four series of polyimides I – VI with pendent triphenylamine (TPA) units having inherent viscosities of 0.44–0.88 dL/g were prepared from four diamines with two commercially available tetracarboxylic dianhydrides via a conventional two‐step procedure that included a ring‐opening polyaddition to give polyamic acids, followed by chemical cyclodehydration. These polymers were amorphous and could afford flexible films. All the polyimides had useful levels of thermal stability associated with high softening temperatures (279–300 °C), 10% weight‐loss temperatures in excess of 505 °C, and char yields at 800 °C in nitrogen higher than 58%. The hole‐transporting and electrochromic properties were examined by electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the polyimide films cast onto an indium‐tin oxide (ITO)‐coated glass substrate exhibited a or two reversible oxidation couples at 0.65–0.78 and 1.00–1.08 V versus Ag/AgCl in acetonitrile solution. The polymer films revealed electrochromic characteristics with a color change from neutral pale yellowish to blue doped form at applied potentials ranging from 0.00 to 1.20 V. The CO₂ permeability coefficients (P) and permeability selectivity (P/P) for these polyimide membranes were in the range of 4.73–16.82 barrer and 9.49–51.13, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7937–7949, 2008