Synthesis of epoxy‐functionalized hyperbranched poly(phenylene oxide) and its modification of cyanate ester resin

High curing temperature is the key drawback of present heat resistant thermosetting resins. A novel epoxy‐functionalized hyperbranched poly(phenylene oxide), coded as eHBPPO, was synthesized, and used to modify 2,2′‐bis (4‐cyanatophenyl) isopropylidene (CE). Compared with CE, CE/eHBPPO system has significantly decreased curing temperature owing to the different curing mechanism. Based on this results, cured CE/eHBPPO resins without postcuring process, and cured CE resin postcured at 230°C were prepared, their dynamic mechanical and dielectric properties were systematically investigated. Results show that cured CE/eHBPPO resins not only have excellent stability in dielectric properties over a wide frequency range (1–10⁹Hz), but also show attractively lower dielectric constant and loss than CE resin. In addition, cured CE/eHBPPO resins also have high glass transition temperature and storage moduli in glassy state. These attractive integrated performance of CE/eHBPPO suggest a new method to develop high performance resins. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Kinetics of the thermal degradation of hyperbranched poly(phenylene sulfide)

An advanced heat‐resistant hyperbranched poly(phenylene sulfide) (HPPS) had been subjected to dynamic thermogravimetric analysis (TGA) in nitrogen. The presence of a single peak in the DTG cures suggested that weight loss occurs in a single stage. The thermal decomposition kinetics had been analyzed by applying the Kissinger, Friedman and Ozawa‐Flynn methods. The E values determined for the hyperbranched PPS using these analyses were found to be 183.1, 189.2, 193.9 kJ mol^?1, respectively. Coats‐Redfern method was used to discuss the probable degradation mechanisms. The solid‐state decomposition mechanism followed by the degradation stage of HPPS was Phase boundary controlled mechanism (R₁). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Mechanical and dielectric properties of cured 1,2‐bis(vinylphenyl)ethane resin modified with poly(phenylene oxide)

1,2‐Bis(vinylphenyl)ethane (BVPE) could be cured without curing agents at relatively low temperatures (～ 180°) in a nitrogen atmosphere. Cured BVPE (CBVPE) resin showed exceptionally low dielectric constant (? = 2.50 at 10 GHz) and low dielectric loss tangent (tan δ = 0.0012 at 10 GHz), and had excellent thermal resistance. Its 5 wt % weight‐loss temperature was 425°C in a nitrogen atmosphere and glass transition temperature was over 400°C. Poly(phenylene oxide) (PPO) was used to improve the toughness of CBVPE resin. PPO was an effective modifier to toughen CBVPE resin: when using 30 wt % of the modifier, the tensile strength and elongation of the modified CBVPE resin were 75 MPa and 26%, respectively. The modified CBVPE resin also showed excellent dielectric properties (? = 2.45 at 10 GHz, tan δ = 0.0015 at 10 GHz). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1252–1258, 2004     

Curing behavior and dielectric properties of hyperbranched poly(phenylene oxide)/cyanate ester resins

A novel hyperbranched poly(phenylene oxide) (HBPPO) modified 2,2′‐bis(4‐cyanatophenyl) isopropylidene (BCE) resin system with significantly reduced curing temperature and outstanding dielectric properties was developed, and the effect of the content of HBPPO on the curing behavior and dielectric properties as well as their origins was thoroughly investigated. Results show that BCE/HBPPO has significantly lower curing temperature than BCE owing to the different curing mechanisms between the two systems, the difference also brings different crosslinked networks and thus dielectric properties. The dielectric properties are frequency and temperature dependence, which are closely related with the content of HBPPO in the BCE/HBPPO system. BCE/2.5 HBPPO and BCE/5 HBPPO resins have lower dielectric constant than BCE resin over the whole frequency range tested, while BCE/10 HBPPO resin exhibits higher dielectric constant than BCE resin in the low frequency range (<10⁴ Hz) at 200°C. At 150°C or higher temperature, the dielectric loss at the frequency lower than 10² Hz becomes sensitive to the content of HBPPO. These phenomena can be attributed to the molecular relaxation. Two relaxation processes (α‐ and β‐relaxation processes) are observed. The β‐relaxation process shifts toward higher frequency with the increase of temperature because of the polymer structure and chain flexibility; the α‐relaxation process appears at high temperature resulting from the chain‐mobility effects. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

多马来酰亚胺改性聚苯醚树脂的热分解动力学研究

采用热重分析法对自制的3,3′-二乙基-4,4′-二苯甲烷型多马来酰亚胺(PEDM)改性烯丙基化聚苯醚(PPO)固化树脂的热分解动力学进行了研究。结果表明:在热作用下,共聚交联体系在PPO的苯氧醚键处首先断链,并按无规断链或自由基引发断链方式迅速进行,交联网络被破坏成许多线形分子链,但其他键受影响很小,热分解表现为一级反应,且失重速率很快;随温度升高,当体系的苯氧醚键基本上断裂完毕后,线形分子链上的马来酰亚胺环的羰基或其他能量相近的键也开始逐渐断裂,此时热分解也表现为一级反应,但速率比第1步慢得多。     

超支化聚苯硫醚与线性聚苯硫醚的对比表征

以2,4-二氯苯硫酚为原料,采用一步法合成超支化聚苯硫醚。笔者运用红外光谱、拉曼光谱、荧光光谱、示差扫描量热分析、热重分析、广角X-射线衍射、溶解实验等分析手段,对超支化聚苯硫醚和线性聚苯硫醚的基本性能进行了对比。由于两者结构上的差异,使得两者表现出不同的特性。超支化聚苯硫醚具有三取代苯结构,具有很强的荧光效应、完全的不结晶、溶于有机溶剂、热降解温度低于线性聚苯硫醚约60℃等特性。广角X-射线衍射谱图也和结晶、无定型线性聚苯硫醚有很大不同。     

The preparation of microporous membranes from blends of poly(2,6‐dimethyl‐1,4‐phenylene oxide) and sulfonated poly(2,6‐dimethyl‐1,4‐phenylene oxide)

Poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) is a chemically resistant polymer and, therefore, an attractive material for the formation of membranes. However, membranes of unmodified PPO prepared by an immersion precipitation possess very low hydraulic permeabilities at the filtration processes. The membranes with higher hydraulic permeabilities can be prepared from sulfonated PPO and/or from blends of unsulfonated PPO and sulfonated PPO. In conclusion, the mechanism of the formation of membranes from blends of unsulfonated PPO and sulfonated PPO is suggested. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 161–167, 1999     

Novel hyperbranched poly(phenylene oxide)s with phenolic terminal groups: synthesis, characterization, and modification

Novel hyperbranched poly(phenylene oxide)s (HPPOs) with phenolic terminal groups were prepared from 4-bromo-4′,4″-dihydroxytriphenylmethane via a modified Ullmann reaction. This monomer was treated with potassium carbonate or sodium hydroxide as a base and copper chloride as a catalyst in an aprotogenic solvent, either dimethylsulphoxide (DMSO) or sulfolane. The sulfolane/NaOH system at higher temperature led to more rapid polymerization, and a relative high molecular weight. The degrees of branching of these HPPOs from the DMSO/K₂CO₃ and sulfolane/NaOH systems were 71 and 48%, respectively, as determined by ¹H NMR integration experiments. The phenolic terminal groups underwent facile modification, furnishing hyperbranched polymers with a variety of functional chain ends. The nature of the chain-end groups had a significant influence on the solubility of the hyperbranched poly(phenylene oxide)s. The resulting polymers were characterized by NMR, Fourier transform infrared, gel permeation chromatography (GPC), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC).     

Preparation and thermal stability of new cellulose‐based poly(propylene imine) and poly(amido amine) hyperbranched derivatives

New cellulose‐based hyperbranched derivatives having different degrees of branching were prepared via reaction of cellulose with acrylonitrile followed by reduction of nitrile groups and successive reaction with acrylonitrile or methylacrylate. First‐ (G = 1) and half‐ (G = 0.5) generation cellulose‐based hyperbranched poly(propylene imine) or poly(amido amine) derivatives have been prepared with high reaction yield. The structure of the prepared derivatives was confirmed by Fourier transform infrared and ¹³C nuclear magnetic resonance (¹³C NMR). Thermal stability of the different cellulose‐based hyperbranched derivatives were examined using thermogravimetric analysis to study the effect of branching on the thermal decomposition parameters. The onset degradation temperature and the activation energy of the thermal degradation decreased with increasing the branching of the cellulose‐based hyperbranched derivatives. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2079–2087, 2006     

Electrodeposition of insulating poly(phenylene oxide) films with variable thickness

Ability to control key characteristics of electrodeposited polymers plays a vital role for their applications. In this work the results on tailoring the thickness of electronically insulating poly(phenylene oxide) (PPO) type polymer films have been showed. Pinhole‐free PPO films with variable thickness in the range of 10–50 nm were grown by controlling the potential applied during the electrochemical polymerization on the surface of titanium nitride (TiN) substrates. The insulating properties of the PPO film were confirmed by testing its permeability to redox species by cyclic voltammetry. Thermal stability of the PPO films with different thicknesses was investigated by in‐situ spectroscopic ellipsometry up to 400 °C in various environments. This insight is important for the optimization of the PPO anneal conditions in order to remove the residual solvent and potentially improve the polymer chains stacking. Our results provide the basis for electrodeposition of PPO films with variable thickness for diverse applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44533.     

Thermal,mechanical, and morphological characterization studies of poly(2,6‐dimethyl‐1,4‐phenylene oxide) blends with polystyrene and brominated polystyrene

The miscibility of the binary and ternary blends of poly(2,6‐dimethyl‐1,4‐phenylene oxide), brominated polystyrene, and polystyrene was investigated using a differential scanning calorimeter. The morphology of these blends was characterized by scanning electron microscopy. These studies revealed a close relation between the blend structure and its mechanical properties. The compatibilizing effect of poly(2,6‐dimethyl‐1,4‐phenylene oxide) on the miscibility of the polystyrene/brominated polystyrene blends was examined. It was found that poly(2,6‐dimethyl‐1,4‐phenylene oxide), which was miscible with polystyrene and partially miscible with brominated polystyrene, compatibilizes these two immiscible polymers if its contention exceeds 33 wt %. Upon the addition of poly(2,6‐dimethyl‐1,4‐phenylene oxide) to the immiscible blends of polystyrene/brominated polystyrene, we observed a change in the morphology of the mixtures. An improvement in the mechanical properties was noticed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 225–231, 2000     

Preparation and performance testing of sulfonated poly(phenylene oxide) based composite membranes for nanofiltration

Sulfonated brominated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (SPPOBr) was synthesized by a sequence of bromination and sulfonation. A thin film of SPPOBr was coated on top of a commercial poly(ether sulfone) membrane. Pure butoxyethanol (BE) solvent or a BE/isopropyl alcohol (IPA) solvent mixture was used to dissolve SPPOBr in the coating process. The thin film composite membranes so prepared were then tested for the separation of carbohydrate and electrolyte solutes. We found that the flux and the carbohydrate separation both increased significantly with increasing IPA content in the solvent mixture. However, the separation of electrolyte solutes did not change significantly. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2624–2628, 2004     

Reactive blend of epoxy‐novolac resin and epoxide‐terminated low‐molecular‐weight poly(phenylene oxide)

The epoxide‐terminated low‐molecular‐weight poly(phenylene oxide) (PPO), EPPO, was synthesized by modifying the terminal hydroxyl group of PPO and it was reactively blended with epoxy‐novolac resin (EPN). The curing kinetics, phase morphology, thermal stability, dielectric property, and water absorption behavior of the cured EPN/EPPO blends were investigated and compared with the unmodified EPN/PPO blends. As revealed by the FTIR and DSC analysis, EPPO takes part in the curing reaction and forms a reactive blend with EPN. The curing rate of both EPN/PPO and EPN/EPPO blends first increases and then decreases with increasing the PPO or EPPO fraction. The blends have lower degree of curing than neat EPN, due to the steric hindrance effects of PPO or EPPO. Because of the reaction between blend components, EPN/EPPO blends show faster curing rate and higher degree of curing than the corresponding EPN/PPO blends. The reactive blending improves the dispersion of EPPO in EPN matrix and the EPN/EPPO blend forms a co‐continuous morphology even at a low EPPO content, compared to the typical sea‐island morphology of the EPN/PPO blend. The EPN/EPPO blend has remarkable smaller dielectric constant, dissipation factor, and water absorption than neat EPN. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

High‐resolution thermogravimetry of poly(phenylene sulfide) film under four atmospheres

The thermal degradation of poly(phenylene sulfide) (PPS) film is investigated in air, nitrogen, helium, and argon with different physical and reactive characteristics at room temperature to 790°C as ascertained by high‐resolution thermogravimetry (TG) at a variable heating rate in response to the changes in the sample's weight‐loss rate. Only a one‐step degradation process of the PPS is observed in nitrogen and argon, but a two‐step degradation process of PPS is found in helium. A four‐step degradation process of the PPS, which is hardly ever revealed by traditional TG, is found in this investigation, especially in air. The initial thermal degradation temperature and temperature at the first maximum weight‐loss rate of the PPS increase in the following order: helium < nitrogen < argon < air. The first maximum weight‐loss rate also increases with the variation of the atmosphere in the order nitrogen < air < argon < helium. The char yield at 700°C increases in the order air < helium < nitrogen < argon. The activation energy of the major degradation process of PPS, as calculated based on the high‐resolution TG data, is very high and increases in the order nitrogen < argon < helium < air. The thermal decomposition parameters of the PPS determined by the high‐resolution TG are systematically compared with those by traditional TG at a constant heating rate. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1940–1946, 2002     

Photooxidative stability of substituted poly(phenylene vinylene) (PPV) and poly(phenylene acetylene) (PPA)

The addition of side groups to improve the photooxidative stability of polymers used in polymer-based light-emitting diodes (LEDs) is explored. Infrared spectroscopy and computational chemistry techniques are used to study the effects of chemical substitution of the reactive vinylene moiety in poly(phenylene vinylene) (PPV). The bond order of the vinylene group in small oligomers is calculated using semiempirical techniques to assess the improvement in stability toward oxidants such as singlet oxygen. We find that PPV dimers allow relative comparisons across a range of possible substitutions. Experimental results correlate well with these calculations. The addition of electron-withdrawing substituents, such as nitrile groups, to the vinylene moiety is found to be particularly effective in reducing the reactivity of alkoxy-substituted PPV toward singlet oxygen. The photooxidative stability of a poly(phenylene acetylene) (PPA) derivative is also studied. It appears that this family of polymers is more stable toward photooxidation than are its PPV analogs. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2451–2458, 1998     

Ion‐exchange membranes prepared by blending sulfonated poly(2,6‐dimethyl‐1,4‐phenylene oxide) with polybenzimidazole

New ion‐exchange acid/base‐blend (SPPO/PBI) membranes were prepared by mixing N,N‐dimethylacetamide (DMA) solutions of sulfonated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (SPPO) in the ammonium form and of polybenzimidazole (PBI), casting the solution as a thin film, evaporating the solvent, and treating the membrane with aqueous hydrochloric acid. The resulting membranes were found insoluble in DMA. The preliminary tests of the membranes were carried out in an H₂/O₂ fuel cell at room temperature. Their performance in the fuel cell increased with the increase in the concentration of SPPO sulfonic acid groups in the blend, but the membranes formed with the highly sulfonated SPPO alone or predominanting, which swelled excessively in water, did not give reproducible results, and their performance was usually inferior to that of the membranes having an optimum ratio of both components. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1118–1127, 2002     

New poly(phenylene oxide)/polystyrene blend nanocomposites with clay: Intercalation,thermal and mechanical properties

We present the first study and results on the preparation and characterization of montmorillonite clay filler based polymer blend nanocomposites of the miscible poly(phenylene oxide)/polystyrene blend. Intercalated nanocomposites, prepared by a melt‐processing method with 2–6 wt % commercially available organically modified sodium montmorillonite, have been characterized with wide‐angle X‐ray diffraction, transmission electron microscopy analysis, thermal analysis (thermogravimetric analysis and differential scanning calorimetry), and mechanical tensile tests. We show that nanocomposites can be successfully prepared in a batch mixer at temperatures much below the conditions conventionally used for this blend without organic degradation. Thermal stability is enhanced by nanoscale hybrid formation. The level of intercalation (change in the d‐spacing) does not change with the clay loading. Better dispersion of clay in the blend matrix has been observed at a low level of clay content. The nanocomposites show improved tensile modulus (by 31%) in comparison to the blend, whereas the tensile strength (stress at break) and elongation decrease in the presence of the filler with an increase in the clay loading. The Halpin–Tsai model is able to predict the modulus of the nanocomposites in very good agreement with the experimental data. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Crosslinkable poly(phenylene oxide) containing pendent 1,2-diphenylcyclopropane groups

Crosslinkable poly(phenylene oxide)s containing pendent 1,2-diphenylcyclopropane groups have been synthesized by oxidative polymerization from four new phenols containing the 1,2-diphenylcyclopropane group. The monomers were prepared by base-catalysed decomposition of the corresponding hydroxy-substituted 3,5-diphenyl-2-pyrazolines, which were the products of the reaction between hydroxy-substituted chalcones and hydrazine monohydrate. Characterization of and crosslinking studies on these polymers were carried out utilizing differential scanning calorimetry, thermogravimetric analysis, gel permeation chromatography and nuclear magnetic resonance. The polymers can be thermally cross-linked when heated to 350°C and the glass transition temperatures (T_g) of the polymers increase after crosslinking. The resulting crosslinked networks are insoluble in all solvents examined. Thermogravimetric analysis shows that no significant weight loss accompanies the crosslinking reaction.     

Synthesis of bismaleimide resin containing the poly(ethylene glycol) side chain: Curing behavior and thermal properties

Two maleimido end‐capped poly(ethylene glycol) (m‐PEG) of different molecular weights were synthesized and blended at various proportions with bismaleimide resin (4,4′‐bismaleimido diphenylmethane) (BDM). The curing behavior and the thermal properties of the m‐PEG/BDM blends were studied and presented here. It was found that the addition of m‐PEG enhanced the processability of the BDM resin significantly. The processing window of the BDM resin was increased from approximately 20 to 80°C. The addition of m‐PEG modified resins, however, resulted not only in the reduction in the thermal stability of the blended BDM resin but also elevation of the coefficients of thermal expansion. The changes in thermal/mechanical properties of the blends were found to be proportional to the amounts of m‐PEG incorporated. It was observed that the curing behavior, and thermal and mechanical properties, of the blends were independent of the molecular weight of the PEG segment. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2935–2945, 2002