Synthesis and properties of sulfonated poly(siloxane imide)s bearing dimethyl siloxane oligomers for fuel cell applications

A series of sulfonated poly(siloxane imide)s (SPSIs) were synthesized from 4,4′‐ketone dinaphthalene 1,1′,8,8′‐tetracarboxylic dianhydride (KDNTDA), a dimethyl siloxane oligomer‐based diamine, and a sulfonated diamine. The reduced viscosities ranged from 1.0 to 3.5 dL/g at 35°C in the triethylamine (TEA) salt form. The SPSIs showed anisotropic membrane swelling with larger swelling in thickness than in plane. They displayed reasonably high proton conductivity, thermal stability and good mechanical properties. The KDNTDA‐based SPSIs showed good solubility in common aprotic solvents not only in TEA salt form but also in proton form. The ¹H‐NMR results indicated that the molar content of the dimethyl siloxane oligomer in the SPSIs was 50–80% of that in the feed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Novel trifluoromethyl‐containing poly(amide–imide)s: Organosolubility,optical behavior,thermostability, and crystallinity

A new dicarboxylic acid monomer, 2,6‐bis(1,3‐dioxo‐5‐carboxyisoindolin‐2‐yl)‐4,4′‐bis(trifluoromethyl)‐1,1′‐diphenyl ether (IFDPE), bearing two preformed imide rings was synthesized via a three‐step manner from 4‐(trifluoromethyl)phenol and 4‐chloro‐3,5‐dinitrobenzotrifluoride. The monomer IFDPE was then used to prepare a series of novel trifluoromethyl‐containing poly(amide–imide)s via a direct phosphorylation polycondensation with various aromatic diamines. The intrinsic viscosities of the polymers were found to be in the range 0.86–1.02 d/g. The weight‐ and number‐average molecular weights of the resulting polymers were determined with gel permeation chromatography. The polymeric samples were readily soluble in a variety of organic solvents and formed low‐color, flexible thin films via solution casting. The values of the absorption edge wavelength were determined by ultraviolet–visible spectroscopy, and all of the resulting poly (amide–imide)s films exhibited high optical transparency. The resulting polymers showed moderately high glass‐transition temperatures in the range 295–324°C and had 10% weight loss temperatures in excess of 524°C in nitrogen. The crystallinity extents were qualitatively investigated with wide‐angle X‐ray diffraction measurements. Scanning electron microscopy images revealed an agglomerated bulk with nonuniformity on the surface. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis of vinyl substitute poly(silphenylene‐siloxane) via silyl hydride‐dialkoxysilane process

The synthesis of vinyl‐substituted silphenylene‐siloxane polymer through B(C₆F₅)₃ catalyzed polycondensation of 1,4‐bis(dimethylsilyl)benzene and vinylmethyldimethoxysilane is described. ¹H‐NMR, ²⁹Si‐NMR, and UV spectroscopy indicate that the vinyl groups remain undamaged during the polycondensation reaction. No hydrosilylation side reaction is observed under the reaction conditions. The microstructure of the polymer is not perfectly alternating with a randomization of 20%. The temperature for 5% mass loss is 430°C in inert atmosphere and 417°C in oxidative atmosphere with a residue of 56% at 700°C. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Characteristics of the degradation and improvement of the thermal stability of poly(siloxane urethane) copolymers

This work investigates the characteristics of the thermal degradation of poly(ether urethane) (E‐PU) and poly(siloxane urethane) (S‐PU) copolymers by thermogravimetric analysis (TGA) and thermogravimetric analysis/Fourier transform infrared spectroscopy (TG–FTIR). The stage of initial degradation for E‐PU was demonstrated as a urethane‐B segment consisting of 4,4′‐diphenylmethane diisocyanate (MDI) and 1,4‐butanediol. Moreover, the urethane‐B segment in the copolymers had the lowest temperature of degradation (ca. 200°C). The degradation of E‐PU was determined by TGA and TG–FTIR analyses and had three stages including seven steps. Although the soft segment of S‐PU possessed the thermal stability of polydimethylsiloxane (PDMS), the unstable urethane‐B segment existed in S‐PU. Therefore, the initial degradation of S‐PU appeared around 210°C. The four stages of degradation of S‐PU involved eight steps, as revealed by TG–FTIR, which identified the main decomposition products: CO₂, tetrahydrofuran, and siloxane decomposition products. The imide group with high thermal stability was to replace the urethane‐B segment of S‐PU, which had the lowest thermal stability herein. The poly(siloxane urethane imide) (I‐PU) copolymer around 285°C exhibited a high initial temperature of degradation, and the initial degradation occurred at the urethane‐S segment consisting of MDI and PDMS. The degradation of I‐PU was similar to that of S‐PU and had four stages including six steps. Moreover, the degradation region of the imide group between 468 and 625°C was merged into the degradation stage of the siloxane decomposed products. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of poly(N‐isopropylacrylamide)s initiated with siloxane oligomer–(NH4)2Ce(NO3)6 redox pair

Poly(N‐isopropylacrylamide)s (PNIPAAM)s were synthesized via free‐radical polymerization using a ceric ammonium nitrate, Ce(IV)–α‐ω‐dihydroxy(polydimethylsiloxane) (Tegomer H‐Si 2111, PDMS) redox pair in hexane at 30°C in a nitrogen atmosphere. The dependence of the initiation and termination steps on the [NIPAAM]/[Ce(IV)] and [NIPAAM]/[PDMS] ratios were studied using gravimetry and FTIR, ¹H‐NMR, UV‐vis, and GFAA spectroscopy techniques. Gravimetric results indicated that, in the case of high concentrations of PDMS, the percentage of the solid portions of the products decreased while the amount of the oligomeric NIPAAM chains increased, that is, as the amount of PDMS in hexane was increased, the number of the short NIPAAM chains having PDMS segments at the two ends, also increased. UV‐vis results showed that the LCST of PNIPAAM initiated with Ce(IV) alone was higher than those of the ones that were synthesized using common initiator systems such as an ammonium persulfate–N,N,N′,N′‐tetramethylethylenediamine redox pair and azobis(isobutyronitrile). Further, it was observed that both siloxane blocks and ? NH? groups forming coordination bonds with free Ce(IV) ions and/or metal–ligand complexes had an important effect on the aggregation process of the chains. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1248–1254, 2003     

Synthesis and characterization of thermoplastic poly(ester–siloxane)s

Two series of thermoplastic poly(ester–siloxane)s, based on poly(dimethylsiloxane) (PDMS) as the soft segment and poly(butylene terephthalate) as the hard segment, were synthesized by two‐step catalyzed transesterification reactions in the melt. Incorporation of soft poly(dimethylsiloxane) segments into the copolyester backbone was accomplished in two different ways. The first series was prepared based on dimethyl terephthalate, 1,4‐butanediol and silanol‐terminated poly(dimethylsiloxane) (PDMS‐OH). For the second series, the PDMS‐OH was replaced by methyl diesters of carboxypropyl‐terminated poly(dimethylsiloxane)s. The syntheses were optimized in terms of both the concentration of catalyst, tetra‐n‐butyl‐titanate (Ti(OBu)₄), and stabilizer, N,N′‐diphenyl‐p‐phenylene‐diamine, as well as the reaction time. The reactions were followed by measuring the inherent viscosities of the reaction mixture. The molecular structures of the synthesized poly(ester–siloxane)s were verified by ¹H NMR spectroscopy, while their thermal properties were investigated using differential scanning calorimetry. © 2001 Society of Chemical Industry     

聚(四甲基对硅亚苯基-二甲基)硅氧烷共聚物的制备及其热性质

以对二溴苯为起始原料,在超声辐照下制备得到对二溴苯双格氏试剂,然后与二甲基氢氯硅烷制备得到1,4-双(二甲基硅基)苯)(BDSB)。以B(C6F5)3为催化剂,BDSB与二甲基二甲氧基硅烷缩聚制备得到聚(四甲基对硅亚苯基-二甲基)硅氧烷共聚物(PTMPS-DMS),并对催化剂浓度、反应温度对反应速率的影响进行了研究。29SiNMR表明产物不是严格交替共聚物,具有38%～49%的嵌段结构。PTMPS-DMS的Tg=-56.2℃,起始降解温度氮气、空气中分别为334℃、345℃。在氮气中PTMPS-DMS出现一步热失重,最大热失重温度是529℃,在空气中则分别在539℃、559℃、662℃出现多步热失重。     

Preparation and properties of poly(dimethyl siloxane)–colloidal silica/functionalized colloidal silica nanocomposites

Aqueous spherical colloidal silica (CS) particles with a diameter of 15 ± 5 nm were modified with three different types of monofunctional silane coupling agents to prepare functionalized colloidal silica (FCS) particles. The effects of the surface chemistry of the FCS were studied as a function of the CS/FCS loading in the poly(dimethyl siloxane) (PDMS) polymer. The prepared PDMS–CS/FCS composites were investigated for their physical properties both in the cured and uncured states. The extent of filler–filler and filler–polymer interactions was found to vary with the type of functionalizing agent used to treat the surface of the CS. The filler–filler interaction appeared to be predominant in the PDMS–CS composites, and improved filler–polymer interaction was indicated in the case of the PDMS–FCS composites. The composites containing CS treated with methyltrimethoxysilane exhibited relatively better optical and mechanical properties compared to the other PDMS–FCS composites. This study highlighted the importance of judiciously choosing functionalizing agents to achieve PDMS–FCS composites with predetermined optical and mechanical properties. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The effect of segment length on some properties of thermoplastic poly(ester–siloxane)s

A series of novel thermoplastic elastomers, based on poly(dimethylsiloxane) (PDMS) as the soft segment and poly(butylene terephthalate) (PBT) as the hard segment, were synthesized by catalyzed two‐step, melt transesterification reactions of dimethyl terephthalate and methyl esters of carboxypropyl‐terminated poly(dimethylsiloxane)s (M?_n = 550–2170 g mol^?1) with 1,4‐butanediol. The lengths of both the hard and soft segments were varied while the weight ratio of the hard to soft segments in the reaction mixture was maintained constant (57/43). The molecular structure, composition and molecular weights of the poly(ester–siloxane)s were examined by ¹H NMR spectroscopy. The effectiveness of the incorporation of the methyl‐ester‐terminated poly(dimethylsiloxane)s into the copolymer chains was verified by chloroform extraction. The effect of the segment length on the transition temperatures (T_m and T_g) and the thermal and thermo‐oxidative degradation stability, as well as the degree of crystallinity and hardness properties of the synthesized TPESs, were studied. Copyright © 2003 Society of Chemical Industry     

Thermal behavior of aliphatic–aromatic poly(ether-amide)s

The thermal properties of a set of experimental aliphatic–aromatic polyamides containing ether linkages were examined as a function of their chemical structure. Variations of the glass transition temperature (T_g) and melting temperature (T_m) could be correlated with the length of the aliphatic spacers and with the orientation of the phenylene rings. Polymers with a high concentration of p-oriented phenylene units showed a higher T_g than those containing mainly m-oriented ones; T_g values ranged from 110 to 155°C. Surprisingly, a negligible dependence of T_gs on the nature of flexible spacers was observed. For all of the polymers, the thermal stability was virtually the same, about 440°C, when tested by dynamic thermogravimetric analysis (TGA). However, quite different levels of thermal stability were found by isothermal TGA analysis for polyamides with different flexible spacers. Moreover, the poly(ether-amide)s described here compare fairly well with wholly aromatic polyamides when measured by dynamic TGA; but isothermal TGA measurements clearly demonstrated that they decompose faster than aromatic polyamides. Treatment of the TGA curves by the method of McCallum provided kinetic data that confirmed a better long-term stability for poly(ether-amide)s with a higher proportion of para-oriented phenylene rings. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:975–981, 1998     

Synthesis and characterization of pyridine‐containing poly(imide‐siloxane)s and their adhesion to copper foil

A series of pyridine‐containing poly(imide‐siloxane) (PIS) copolymers with different amounts of PDMS with various segmental lengths were synthesized from 2,6‐diaminopyridine (DAP), α,ω′‐aminopropylpoly(dimethylsiloxane) (PDMS), 1,3‐bis(4‐aminophenoxy)benzene (APB), and 4,4′‐oxydiphthalic dianhydride (ODPA). A modified synthetic approach was applied instead of approaches commonly reported in the literature, to ensure the incorporation of DAP and PDMS. The effects of the content and the segmental length of PDMS on the thermal glass transition temperature (T_g), dielectric constant, and surface electrical resistivity of the copolymer are investigated. The copolymers were attached to copper foil by hot‐pressing, and changes in wettability caused the peel strength of the laminates to increase with the PDMS content, but to decrease as the DAP content increased. Furthermore, X‐ray photoelectron spectroscopy was employed to determine the loci of failures (LOF) of the laminates and to monitor the movement of LOF, which varies with the PDMS content. For those laminates with good peel strengths, the LOF occur in the interior of PIS layer, indicating that the adhesion is cohesive rather than adhesive. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Thermooxidative degradation of poly(vinyl chloride)/acrylonitrile–butadiene–styrene blends

The thermal degradation process of poly(vinyl chloride)/acrylonitrile–butadiene–styrene (PVC/ABS) blends was investigated by dynamic thermogravimetric analysis in the temperature range 50–650°C in air. The thermooxidative degradation of PVC/ABS blends of different composition takes place in three steps. In this multistep process of degradation the first step, dehydrochlorination, is the most rapid. The maximal rate of dehydrochlorination for the PVC blends containing up to 20% ABS-modifier is achieved at average conversions of 23.5–20.0%, i.e., at 13.5% for the 50/50 blend. The apparent activation energies (E = 103–116 kJ mol⁻¹) and preexponential factors (Z = 2.11 × 10⁹−3.45 × 10¹⁰min⁻¹) for the first step of the degradation process were calculated after the Kissinger method. © 1996 John Wiley © Sons, Inc.     

Novel thermally stable poly(ether imide ester)s from 2,6‐bis (4‐aminophenoxy) pyridine

2,6‐Bis (4‐aminophenoxy) pyridine was prepared via reaction of 4‐aminophenol with 2,6‐dichloropyridine in the presence of potassium carbonate in N‐methyl‐2‐pyrrolidone (NMP). This pyridine‐based ether diamine was reacted with two moles of trimellitic anhydride to synthesize related diimide‐diacid (DIDA). A high temperature solution polycondensation reaction of DIDA with different diols in the presence of triethylamine hydrochloride in dichlorobenzene resulted in different poly(ether imide ester)s. The monomer and polymers were fully characterized, and the physical and thermal properties of the polymers were studied. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 570–576, 2005     

Synthesis and properties of PMR type poly(benzimidazopyrrolone‐imide)s

PMR type poly(benzimidazopyrrolone‐imide) or poly(pyrrolone‐imide) (PPI) matrix resin was synthesized using the diethyl ester of 4,4′‐(hexafluoroisopropylidene)diphthalic acid (6FDE), 3,3′‐diaminobenzidine, para‐phenylenediamine, and monoethyl ester of cis‐5‐norbornene‐endo‐2,3‐dicarboxylic acid (NE) in anhydrous ethyl alcohol with N‐methylpyrrolidone. The homogeneous matrix resin solution (40–50% solid) was stable for a storage period of 2 weeks and showed good adhesion with carbon fibers, which ensured production of prepregs. The chemical and thermal processes in the polycondensation of the monomeric reactant mixture were monitored by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, etc. Thermosetting PPI as well as short carbon fiber‐reinforced polymer composites was accomplished at optimal thermal curing conditions. The polymer materials, after postcuring, showed excellent thermal stability, with an initial decomposition temperature > 540°C. Results of MDA experiments indicate that the materials showed > 70–80% retention of the storage modulus at 400°C and glass transition temperatures as high as 440–451°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1600–1608, 2001     

Preparation of novel pyridine‐based,thermally stable poly(ether imide)s

Two aromatic, pyridine‐based ether diamines were prepared by the nucleophilic aromatic substitution reaction of 4‐aminophenol and 5‐amino‐1‐naphthol with 2,6‐dichloropyridine in N‐methyl‐2‐pyrrolidone as a solvent. Polycondensation reactions of the obtained diamines with pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride, and hexafluoroisopropylidene diphthalic anhydride resulted in six pyridine‐based, thermally stable poly(ether imide)s. The prepared monomers and polymers were characterized by common spectroscopic methods. The physical and thermal properties of the polymers, including the thermal behavior, thermal stability, solubility, and solution viscosity, were studied. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 22–26, 2004     

Synthesis of novel poly(ether ketone diphenyl ketone ether ketone ketone)s by electrophilic Friedel–Crafts solution polycondensation

4,4′‐Bis(4‐phenoxybenzoyl)diphenyl was prepared by the Friedel–Crafts reaction of 4‐bromobenzoyl chloride and diphenyl followed by condensation with potassium phenoxide. Novel aromatic poly(ether ketone diphenyl ketone ether ketone ketone)s were obtained by the electrophilic Friedel–Crafts solution copolycondensation of 4,4′‐bis(4‐phenoxybenzoyl)diphenyl with a mixture of isophthaloyl chloride and terephthaloyl chloride over a wide range of isophthaloyl chloride/terephthaloyl chloride molar ratios in the presence of anhydrous aluminum chloride and N‐methylpyrrolidone in 1,2‐dichloroethane. The influence of the reaction conditions on the preparation of the copolymers was examined. The copolymers were characterized with different physicochemical techniques. Because of the incorporation of diphenyl, the resulting copolymers exhibited outstanding thermal stability. The glass‐transition temperatures were above 174°C, the melting temperatures were above 342°C, and the 5% weight loss temperatures were above 544°C in nitrogen. All these copolymers were semicrystalline and insoluble in organic solvents. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and properties of novel poly(benzimidazopyrrolone amide)s containing pyridine moieties

A series of new poly(benzimidazopyrrolone amide) (PPA) copolymers were synthesized by a two‐step procedure, which was the solution polycondensation of a novel pyridine‐containing tetraamine with various aromatic dianhydrides at a room temperature and cyclization of the resulting prepolymers at a high temperature, respectively. The resulting prepolymers from the solution polycondensation, that is, poly(amide amino acid)s (PAAAs), had inherent viscosities of 0.82–0.91 dL/g; then, tough and flexible PPA films could be successfully prepared by the casting of the PAAA solutions onto a glass substrate followed by thermal curing with a program temperature procedure up to 350°C. The obtained PPA films exhibited not only excellent thermal properties with onset decomposition temperatures in the range 502–521°C, glass‐transition temperatures in the range 299–337°C, and residual weight retentions at 700°C in air of 29.1–34.8% but also good mechanical properties with tensile strengths of 102.1–115.9 MPa and elongations at break of 6.8–7.4%. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Fluorinated poly(aryl thioether)s and poly(aryl sulfone)s derived from 2,3,4,5,6‐pentafluorobenzoic acid

Poly(aryl thioether)s (F‐PTEs) containing 2,3,5,6‐tetrafluoro‐1,4‐phenylene moiety and polar moiety, such as 1,3,4‐ozadiazole, ether ketone, and amide groups, were synthesized by nucleophilic aromatic substitution reaction of aryl fluorides and 4,4′‐thiobisbenzenthiol. F‐PTEs were amorphous with good thermal properties including high glass transition temperature (T_g) and thermal stability, solubility, and hydrophobicity. F‐PTEs were transformed into poly(aryl sulfone)s (F‐PSs) by the oxidation reaction with hydrogen peroxide in acetic acid. Because of the sulfone group, the T_gs of the F‐PSs were 30–40°C higher than those of the corresponding F‐PTEs. F‐PSs maintained solubility in polar aprotic solvents and exhibited hydrophobicity in spite of the content of polar sulfone groups due to the highly substituted fluorine atoms. These F‐PTEs and F‐PSs were a new class of high‐performance polymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of ultraviolet/ozone treatment on the surface and bulk properties of poly(dimethyl siloxane) and poly(vinylmethyl siloxane) networks

We present a comparative study aiming at comprehending the effect of ultraviolet/ozone treatment on the modification of poly(dimethyl siloxane) (PDMS) and poly(vinylmethyl siloxane) (PVMS) silicone elastomers networks (SENs). Both PDMS and PVMS SENs undergo dramatic changes in their properties when exposed to UVO. The surface chemical composition of both PDMS and PVMS at long UVO treatment times changes substantially and features a high density of hydrophilic groups. There are two major differences in behavior in the two classes of materials. First, relative to PDMS, the PVMS-based SENs get modified throughout the entire bulk. Second, the physico-chemical changes detected in PVMS take place on much shorter time scale relative to PDMS. These results are in accord with our earlier reports that indicated that when exposed to UVO, the topmost ≈5 nm of PDMS gets converted into a silica-like material, which then acts as a barrier for diffusion of atomic oxygen. In this case, the bulk of PDMS maintains its elasticity. In contrast, both the surface and bulk of PVMS films undergo substantial changes in properties when exposed to UVO. First, the surface modification of PVMS SENs takes place after only a few seconds of the UVO treatment. In addition, we register substantial modification of bulk properties, including the complete densification accompanied with increased bulk modulus. Likely, the susceptibility of the vinyl bonds to radical reactions is responsible for this effect.     

Thermal and microwave‐assisted oxidative degradation of poly(ethylene oxide)

The kinetics of the thermal and microwave‐assisted oxidative degradation of poly(ethylene oxide) were determined with potassium persulfate as the oxidizing agent. Gel permeation chromatography was used to determine the variation of the molecular weight with time. The degradation was studied as a function of the temperature and persulfate concentration, and it was found that the degradation rate increased with the temperature and concentration of persulfate. Continuous distribution kinetics were used to determine the rate coefficients for the degradation process, and the activation energies were obtained. The results indicated that the microwave‐assisted process had a lower activation energy of 10.3 kcal/mol, whereas that of the thermal degradation was 25.2 kcal/mol. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2090–2096, 2005