Cross-linked poly(benzoxazole-co-siloxane) networks with high thermal stability and low dielectric constant based on a new ortho-amide functional benzoxazine

In this study, an amide functionalized bis-benzoxazine (AI-al) has been synthesized using allylamine, ortho-amide functional bis-phenol and paraformaldehyde as raw materials via Mannich condensation. This newly obtained benzoxazine has been used to react with polydimethylsiloxane (PDMS) through hydrosilylation to form poly(benzoxazine-co-amide-co-siloxane) (AI-al-PDMS) featuring siloxane, amide and benzoxazine as repeating units. The chemical structures of both oxazine ring-containing monomer and copolymer are confirmed by NMR and FT-IR spectroscopies. Besides, the thermally activated polymerization behaviors of AI-al and AI-al-PDMS are investigated by DSC, and the subsequent conversion of benzoxazole formation is studied by in situ FT-IR. Moreover, dynamic mechanical analysis and thermogravimetric analysis are used to determine the thermal properties of the cross-linked polymers. The resulting cross-linked poly(benzoxazole-co-siloxane) derived from AI-al-PDMS shows excellent thermal stability (no T_g can be observed before 400°C; Td5 of 393°C) and low dielectric constants (2.52–2.13 in the frequency range of 1 Hz to 1 MHz), evidencing its great potential applications in electronic packing, aerospace, and other high-performance fields.     

Preparation and characterization of crosslinked polyurethane‐block‐poly(trifluoropropylmethyl)siloxane elastomers with potential biomedical applications

A series of crosslinked polyurethane‐block‐poly(trifluoropropylmethyl)siloxane elastomers were prepared via two steps. First, poly(trifluoropropylmethyl)siloxane polyurethane (FSPU) prepolymers were synthesized with α,ω‐bis(3‐aminopropyldiethoxylsilane) poly(trifluoropropylmethyl)siloxane (APFS) and toluenediisocyanate (TDI) and then capped with butanediol to generate the macromolecular FSPU diol extender. Second, polyurethane prepolymers synthesized from poly(tetramethylene oxide) and TDI were reacted with FSPU diol extenders with different ratios. The copolymers formed films through moisture curing and were characterized by Fourier transform infrared spectroscopy, DSC, dynamic mechanical analysis, TGA, mechanical testing etc. It is found that the equivalent ratio of reactants gives rise to a high molecular weight of copolymers and that low molecular weight APFS in the copolymers can form a certain number of silicon–oxygen crosslinks resulting from silicon alkoxy to produce higher tensile strength elastomers. The material thus has higher thermal stability and a more stable surface performance. The copolymers are then good candidates for biomedical applications.© 2013 Society of Chemical Industry     

Morphology and properties of poly(benzoxazine‐co‐urethane)s based on bisphenol‐S/aniline benzoxazine

Poly(benzoxazine‐co‐urethane) was prepared by melt‐blending bisphenol‐S/aniline‐type benzoxazine (BS‐a) with isocyanate‐terminated polyurethane (PU) prepolymer based on 2,4‐toluene diisocyanate and poly(ethylene glycol), followed by thermally activated polymerization of the blend. The copolymerization reaction between BS‐a and PU prepolymer was monitored using Fourier transform infrared spectroscopy. The morphology, dynamic mechanical properties, and thermal stability of the poly(benzoxazine‐co‐urethane) were studied using scanning electron microscopy, dynamic mechanical analysis, and thermogravimetry. Homogeneous morphology is shown in scanning electron micrographs of the fracture surfaces of poly(benzoxazine‐co‐urethane)s with different urethane weight fractions, and the roughness of the surface increases with urethane content increasing. Correspondingly, a single glass transition temperature (T_g) is shown on the dynamic mechanical analysis curves of the poly(benzoxazine‐co‐urethane)s, and the T_g is higher than that of the polybenzoxazine. With increase in the urethane content, the T_g and water absorption of poly(benzoxazine‐co‐urethane) increase, whereas the storage modulus and thermal stability decrease. POLYM. ENG. SCI., 53:2633–2639, 2013. © 2013 Society of Plastics Engineers     

Comparison of thermomechanical properties of statistical, gradient and block copolymers of isobornyl acrylate and n-butyl acrylate with various acrylate homopolymers

Well-defined statistical, gradient and block copolymers consisting of isobornyl acrylate (IBA) and n-butyl acrylate (nBA) were synthesized via atom transfer radical polymerization (ATRP). To investigate structure-property correlation, copolymers were prepared with systematically varied molecular weights and compositions. Thermomechanical properties of synthesized materials were analyzed via differential scanning calorimetry (DSC), dynamic mechanical analyses (DMA) and small-angle X-ray scattering (SAXS). Glass transition temperature (T_g) of the resulting statistical poly(isobornyl acrylate-co-n-butyl acrylate) (P(IBA-co-nBA)) copolymers was tuned by changing the monomer feed. This way, it was possible to generate materials which can mimic thermal behavior of several homopolymers, such as poly(t-butyl acrylate) (PtBA), poly(methyl acrylate) (PMA), poly(ethyl acrylate) (PEA) and poly(n-propyl acrylate) (PPA). Although statistical copolymers had the same thermal properties as their homopolymer equivalents, DMA measurements revealed that they are much softer materials. While statistical copolymers showed a single T_g, block copolymers showed two T_gs and DSC thermogram for the gradient copolymer indicated a single, but very broad, glass transition. The mechanical properties of block and gradient copolymers were compared to the statistical copolymers with the same IBA/nBA composition.     

Crystalline structures and thermal properties of poly(ethylene-co-α,ω-nonconjugated diene)s prepared by zirconocene catalysts

Crystalline structures and thermal properties of poly(ethylene-co-α,ω-nonconjugated diene)s, [diene=1,5-hexadiene (HD), 1,7-octadiene (OD), and 1,9-decadiene (DD)] have been investigated in relation to insertion mode of the dienes. In the case of poly(ethylene-co-HD), the copolymer containing high cis-1,3-cyclopentane units shows lower melting point depression with increasing the comonomer content than the copolymers containing high trans-1,3-cyclopentane units. In the case of poly(ethylene-co-OD) and poly(ethylene-co-DD), the copolymers containing pendant vinyl groups show higher ΔH_m than that of the copolymers with cyclic units or branching structures. Thermal degradation of the copolymers has been investigated under nitrogen atmosphere and the degradation of the copolymers containing the cyclic structures begins at lower temperature than the copolymers containing pendant vinyl groups.     

Effect of hydroxyl content on the morphology and properties of epoxy/poly(styrene-co-allylalcohol) blends

Blends based on epoxy resin and random copolymers, poly(styrene-co-allylalcohol) (PS-co-PA), were studied. Two PS-co-PA copolymers, with different hydroxyl content, and a polyallylalcohol (PA) homopolymer were used to analyze the effect of polyalcohol content. The polymers presented similar values of molar mass. The miscibility of noncured mixtures and the thermal transition behavior of cured blends were investigated by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). Its morphology was studied using both scanning and transmission electron microscopy (SEM and TEM). While the epoxy/PA blends are homogenous materials, because of the epoxy/hydroxyl reaction, PS-co-PA/epoxy blends shows separated phases. In these blends, the presence of a third glass transition, whose value is an intermediate between those of pure components, and the presence of a well-defined interfacial layer between PS-co-PA domains and epoxy matrix indicates a secondary epoxy/hydroxyl reaction. The modification of epoxy resin with PS-co-PA provides significant increase in the storage modulus measured by DMTA. POLYM. ENG. SCI., 47:1580–1588, 2007. © 2007 Society of Plastics Engineers     

Poly(hydroxyether of bisphenol A) ‐alt‐polydimethylsiloxane: a novel thermally crosslinkable alternating block copolymer

BACKGROUND: An important strategy for making polymer materials with combined properties is to prepare block copolymers consisting of well‐defined blocks via facile approaches. RESULTS: Poly(hydroxyether of bisphenol A)‐block‐polydimethylsiloxane alternating block copolymers (PH‐alt‐PDMS) were synthesized via Mannich polycondensation involving phenolic hydroxyl‐terminated poly(hydroxyether of bisphenol A), diaminopropyl‐terminated polydimethylsiloxane and formaldehyde. The polymerization was carried out via the formation of benzoxazine ring linkages between poly(hydroxyether of bisphenol A) and polydimethylsiloxane blocks. Differential scanning calorimetry and small‐angle X‐ray scattering show that the alternating block copolymers are microphase‐separated. Compared to poly(hydroxyether of bisphenol A), the copolymers displayed enhanced surface hydrophobicity (dewettability). In addition, subsequent crosslinking can occur upon heating the copolymers to elevated temperatures owing to the existence of benzoxazine linkages in the microdomains of hard segments. CONCLUSION: PH‐alt‐PDMS alternating block copolymers were successfully obtained. The subsequent self‐crosslinking of the PH‐alt‐PDMS alternating block copolymers could lead to these polymer materials having potential applications. Copyright © 2008 Society of Chemical Industry     

Synthesis,characterization and corrosion protection properties of poly(N-vinyl carbazole-co-glycidyl methacrylate) coatings on low nickel stainless steel

Methacrylate based copolymers are considered as one of the best organic coating materials for anticorrosive application. Poly(N-vinyl carbazole-co-glycidyl methacrylate) have been synthesized by free radical solution polymerization technique from different mole ratios of N-vinyl carbazole (N-Vc) and glycidyl methacrylate (GMA) and characterized using Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (¹H NMR and ¹³C NMR). Thermal analyses of the poly(N-Vc-co-GMA) were performed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The number average molecular weight (M_n) of different compositions of the same was determined by gel permeation chromatography (GPC). The corrosion performances of low nickel stainless steel specimens coated with different composition of copolymers were investigated in 1 M H₂SO₄ using potentiodynamic polarization, electrochemical impedance spectroscopic (EIS) method, scanning electron microscopic (SEM) and energy dispersive X-ray analysis (EDAX). Poly(N-Vc-co-GMA) have been provided in order to achieve adherent, low permeability to aggressive ions as well as environmentally favored good anticorrosive coating. Electrochemical corrosion test and surface analysis results clearly showed that poly(N-Vc-co-GMA) coatings served as a stable host matrix on low nickel stainless steel against corrosion. It was also observed that the coatings of poly(N-Vc-co-GMA) with equal mole ratio of N-Vc and GMA exhibited the best corrosion resistance among all combinations.     

Gelation behavior of near‐zero shrinkage polybenzoxazines

A new class of phenolic thermosetting resins is developed that is based on the ring‐opening polymerization of a benzoxazine precursor. These new materials seek to combine the thermal properties and flame retardance of phenolics with the mechanical performance and molecular design flexibility of advanced epoxy systems. These materials overcome many of the traditional shortcomings of conventional novolac and resole‐type phenolic resins, while retaining their benefits. The viscoelastic behavior of the polybenzoxazines during isothermal cure is monitored by dynamic mechanical analysis. Isochronic measurements show that although the aniline‐based benzoxazine has a lower activation energy for the gelation process than the methylamine‐based resin, it has a slower rate of reaction. The purified monomer and as‐synthesized precursor for each benzoxazine are found to polymerize by the same mechanism, despite the absence of an initiating species in the purified resins. The chemical gelation phenomenon of the methylamine‐based resin is probed by a multifrequency dynamic cure analysis that allows determination of the instant of chemical gelation, as well as the network relaxation exponent, n. The constant value of the exponent regardless of cure temperature demonstrates that chemical gelation is, in fact, an isoconversion event for the methylamine‐based benzoxazine. The multifrequency and isochronic analyses are shown to produce very similar gel times and activation energies for the gelation process. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 406–417, 2001     

Enzymatic synthesis,thermal and crystalline properties of a poly(β–amino ester) and poly(lactone-co-β–amino ester) copolymers

Ethyl 3-(4-(hydroxymethyl)piperidin-1-yl)propanoate (EHMPP) was prepared in quantitative yield under mild conditions via Michael addition reaction of 4-piperidinemethanol with ethyl acrylate. EHMPP underwent condensation polymerization in the presence of a lipase catalyst (CALB) to form poly[3-(4-(methylene)piperidin-1-yl)propanoate] (poly(MPP) or PMPP). Ring-opening and condensation copolymerization of EHMPP with ω-pentadecalactone (PDL) led to the synthesis of novel poly(PDL-co-MPP) copolymers, whose compositions were readily controlled by varying the monomer feed ratio. NMR analyses, including statistical analysis on repeating unit sequence distribution, indicate that the copolymers are totally random polymers. TGA analysis revealed that the degradation temperature of PMPP is approximately 160 °C lower than that of PPDL and that all poly(PDL-co-MPP) copolymers degrade in two well defined weight loss steps attributable to thermal degradation of MPP and PDL unit fractions in the polymers. The crystallinity of the polymers was studied by DSC analysis. Although PMPP and the copolymers rich in MPP units do not easily crystallize upon cooling from melt, the homopolymer and all copolymers obtained via precipitation from solution are semi-crystalline materials. WAXS analysis showed that the copolymers rich in PDL (≥51 mol%) crystallize in PPDL lattice and those with ≤21 mol% PDL content develop PMPP-type crystals while in the copolymer with 36 mol% PDL, PMPP-type and PPDL-type crystals co-exist. PMPP and poly(PDL-co-MPP) represent a new type of biodegradable poly(β–amino esters) that are potentially useful biomaterials for specific biomedical applications (e.g., gene delivery).     

Synthesis of comb-shaped copolymers by combination of reversible addition-fragmentation chain transfer polymerization and cationic ring-opening polymerization

Comb-shaped graft copolymers with poly(methyl acrylate) as a handle were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization and ring-opening polymerization (ROP) techniques in three steps. First, copolymers of poly(styrene-co-chloromethyl styrene), poly(St-co-CMS), were prepared by RAFT copolymerization of St and CMS using 1-(ethoxycarbonyl)prop-1-yl dithiobenzoate (EPDTB) as RAFT agent. Second, the polymerization of MA using poly(St-co-CMS)-SC(S)Ph as macromolecular chain transfer agent produced block copolymer poly(St-co-CMS)-b-PMA. Third, cationic ring-opening polymerization of THF was performed using poly(St-co-CMS)-b-PMA/AgClO₄ as initiating system to produce comb-shaped copolymers. The structures of the poly(St-co-CMS), poly(St-co-CMS)-b-PMA and final comb-shaped copolymers were characterized by ¹H NMR spectroscopy and gel permeation chromatography (GPC).     

苯并噁嗪/含磷环氧/含氮酚醛共混体系结构与性能的研究

针对双酚A型苯并噁嗪无法满足较高阻燃要求的缺陷,在双酚A型苯并噁嗪中引入含磷环氧、含氮酚醛,制备了三元共混浇铸体,通过测定凝胶化时间、差示扫描量热仪(DSC)、动态热机械分析(DMA)、热失重分析(TGA)、垂直燃烧、锥形量热等测试手段研究了共混体系固化反应及结构与性能间的关系。研究表明:在共混体系中,随着环氧树脂含量的增加,固化产物的初始储能模量和玻璃化转变温度均减小,同时还有效地发挥了固相、气相阻燃的作用;含氮酚醛的引入,除有效催化固化反应和降低固化反应温度外,还发挥了气相阻燃的作用。含磷环氧和含氮酚醛均能有效提高热稳定性和阻燃性能;含氮酚醛中的氮源比苯并噁嗪中的氮源对阻燃、提高热稳定性等性能所发挥的作用更明显。     

Thermal energy storage by poly(styrene-co-p-stearoylstyrene) copolymers produced by the modification of polystyrene

A series of poly(styrene-co-p-stearoyl styrene) copolymers as novel polymeric solid–solid phase-change materials (SSPCMs) were synthesized by the modification of polystyrene with stearoyl chloride. The chemical structure and crystalline morphology of the synthesized copolymers were determined with Fourier transform infrared spectroscopy and polarized optical microscopy, respectively. The thermal energy storage properties and thermal stability of the SSPCMs were investigated with differential scanning calorimetry and thermogravimetric analysis, respectively. In addition, the thermal conductivity of the SSPCMs was measured with a thermal property analyzer. Moreover, thermal cycling tests showed that the copolymers had good thermal reliability and chemical stability after being subjected to 5000 heating/cooling cycles. The synthesized poly(styrene-co-stearoyl styrene) copolymers as novel SSPCMs have considerable potential for thermal energy storage and temperature-control applications. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis of electrically conducting copolymers of aniline with o/m-amino benzoic acid by an inverse emulsion pathway

Copolymers of aniline and ortho/meta-amino benzoic acid were synthesized by chemical polymerization using an inverse emulsion pathway. The copolymers are soluble in organic solvents, and the solubility increases with the amino benzoic acid content in the feed. The reaction conditions were optimized with emphasis on high yield and relatively good conductivity (2.5×10⁻¹ S cm⁻¹). The copolymers were characterized by a number of techniques including UV-vis, FT-IR, FT-Raman, EPR and NMR spectroscopy, thermal analysis, SEM and conductivity. The influence of the carboxylic acid group ring substituent on the copolymers is investigated. The spectral studies reveal that the amino benzoic acid groups restrict the conjugation along the polymer chain. The SEM micrographs of the copolymers reveal regions of amorphous and crystalline domain. Thermal studies indicate a marginally higher thermal stability for poly(aniline-co-m-amino benzoic acid) compared to poly(aniline-co-o-amino benzoic acid).     

Resins with the ability to bind copper and uranyl ions

Crosslinked poly(1‐vinyl imidazole‐co‐acrylic acid) and crosslinked poly(1‐vinylmidazole‐co‐2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) were synthesized by radical polymerization and characterized by elemental analysis and FTIR spectroscopy. The polymerization yields were 79 and 99%, respectively. The metal ion binding properties for copper(II) and uranium(VI) were studied under noncompetitive and competitive conditions by Batch equilibrium procedure. The resin crosslinked poly(1‐vinyl imidazole‐co‐acrylic acid) showed a higher dependence on pH than crosslinked poly(1‐vinylmidazole‐co‐2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid). The retention of uranyl ions for the latter resin was close to 100% at pH 5.0. The higher maximum retention capacity was close to 0.8 mmol/g dry resin at pH 5.0. Regeneration of the resin was possible by treatment with basic eluent. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 706–711, 2006     

Improving the electrochemical performance of polyaniline electrode for supercapacitor by chemical oxidative copolymerization with p-phenylenediamine

A series of poly(aniline-co-p-phenylenediamine) (P(ANI-co-PPDA)) copolymers were synthesized via the chemical oxidative polymerization of aniline with p-phenylenediamine (PPDA) as the comonomer. The structure and morphology of the P(ANI-co-PPDA) copolymers prepared with different feeding ratio of PPDA under different polymerizing temperature were compared with the two homopolymers polyaniline (PANI) and poly(p-phenylenediamine) (PPPDA). It is interesting to find that the electrical conductivity, specific capacitance and cycling stability of the P(ANI-co-PPDA) copolymer electrode materials were obviously improved with certain feeding ratio of PPDA, compared with those two homopolymers.     

Improvement of dimensional stability of nylon-6 block copolymer using phenolic resin by reaction injection molding

In order to decrease moisture uptake and hence provide rigidity and dimensional stability in a nylon-6 block copolymer (NBC), powdered phenolic resin was incorporated into the formulation as a filler and processed by reaction injection molding. A novolac resin was cured with hexamethylenetetramine to produce the phenolic resin, which was modified with diethylamine in order to remplaced the  OH groups by diethylamine groups. 5% by weight of modified and unmodified powdered phenolic resin was used as a filler in the nylon-6 block copolymers, and reinforced-nylon-6 block copolymer plaques were produced by reaction injection molding at 145°C. The materials were characterized by dynamic mechanical thermal analysis (DMTA), and their flexural modulus, impact test, and dimensional stability were evaluated. In unmodified phenolic-resin-reinforced nylon-6 block copolymer, water absorption was decreased by 90% compared with the NBC without filler. Two mechanisms of interaction between the NBC and the phenolic resin have been proposed. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1811–1816, 1998     

Poly(2‐alkyloyloxyethylacrylate) and poly(2‐alkyloyloxyethylacrylate‐co‐methylacrylate) comblike polymers as novel phase‐change materials for thermal energy storage

A series of poly(2‐alkyloyloxyethylacrylate) and poly(2‐alkyloyloxyethylacrylate‐co‐methylacrylate) polymers as novel polymeric phase‐change materials (PCMs) were synthesized starting from 2‐hydroxyethylacrylate and fatty acids. The chemical structure and crystalline morphology of the synthesized copolymers were characterized with Fourier transform infrared and ¹H‐NMR spectroscopy and polarized optical microscopy, respectively, and their thermal energy storage properties and thermal stability were investigated with differential scanning calorimetry and thermogravimetric analysis, respectively. The thermal conductivities of the PCMs were also measured with a thermal property analyzer. Moreover, thermal cycling testing showed that the copolymers had good thermal reliability and chemical stability after they were subjected to 1000 heating/cooling cycles. The synthesized poly(2‐alkyloyloxyethylacrylate) polymers and poly(2‐alkyloyloxyethylacrylate‐co‐methylacrylate) copolymers as novel PCMs have considerable potential for thermal energy storage and temperature‐control applications. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

A comparative study on corrosion-resistant performance of halogenated copolymers

Methacrylate-based copolymers are frequently used as anticorrosive organic coatings. Polymeric coating on metallic surfaces provides protection by a barrier action. Thermal properties have a significant influence on corrosion-resistance. This paper deals with the effect of thermal properties of 2,4,6-tribromophenyl methacrylate-co-glycidyl methacrylate and N-(p-bromophenyl)-2-methacrylamide-co-glycidyl methacrylate copolymers in corrosion-resistant behavior on low nickel stainless steel (LNSS). Hence attempts have been made to synthesize a set of copolymers by free radical polymerization and compare their corrosion-resistance properties. The copolymers were structurally characterized by Fourier transform-infrared, and ¹H-nuclear magnetic resonance spectroscopic techniques. The molecular weight of the copolymers was determined by gel permeation chromatography. Thermal studies were carried out using thermogravimetric analysis and differential scanning calorimetry. Corrosion performances of LNSS coated with two different copolymers was investigated in 1 M H₂SO₄ using potentiodynamic polarization and electrochemical impedance spectroscopic methods. The corrosion study reveals that poly(TBPMA-co-GMA) showed better corrosion-resistance than poly(PBPMA-co-GMA).     

Thermal and mechanical properties of poly(urethane‐imide)/epoxy/silica hybrids

Improving properties of polyurethane (PU) elastomers have drawn much attention. To extend the properties of the modified PU composite, here a new method via the reaction of poly(urethane‐imide) diacid (PUI) and silane‐modified epoxy resin (diglycidyl ether of bisphenol A) was developed to prepare crosslinked poly (urethane‐ imide)/epoxy/silica (PUI/epoxy/SiO₂) hybrids with enhanced thermal stability. PUI was synthesized from the reaction of trimellitic anhydride with isocyanate‐terminated PU prepolymer, which was prepared from reaction of polytetramethylene ether glycol and 4,4′‐diphenylmethane diisocyanate. Thermal and mechanical properties of the PUI/epoxy/SiO₂ hybrids were investigated to study the effect of incorporating in situ SiO₂ from silane‐modified epoxy resin. All experimental data indicated that the properties of PUI/epoxy/SiO₂ hybrids, such as thermal stability, mechanical properties, were improved due to the existence of epoxy resin and SiO₂. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010