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A novel series of ablative composites containing a hyperbranched polyazomethine synthesized inside a carbon fiber preform (HyPAZA) were prepared, which have similar density to phenolic impregnated carbon ablators (∼0.3 g/cc). A novel method of synthesizing strong hyperbranched polyazomethine thermosets has been developed, enabling polyazomethines to be studied in ablators for the first time. Several formulations of HyPAZA perform better than the phenolic impregnated carbon ablator in terms of polymer char yield, composite mechanical strength, CO2 laser ablation tests at heat fluxes of 550 and 1100 W/cm2, and small-scale arcjet testing at a heat flux of 400 W/cm2. Char yields of hyperbranched polyazomethines were as high as 79% at 1000°C by thermogravimetric analysis. This is one of the highest char yields ever reported for a fully organic polymer. Some HyPAZA composites are over 10 times stronger than the carbon fiber preform, as determined by compression tests. Specimens were also tested in an arcjet ...

A series of poly(arylene ether triazine) homopolymers were synthesized that contain pendant diphenylamine groups. The polymers had inherent viscosities from 0.66 to 1.01 dL/g in DMAc at 25 °C, thermal stabilities >500 °C in air, glass transition temperatures from 156 °C to 309 °C, and solubilities that depended upon the bis(4-fluorophenyl) monomer that was used for polymerization. Polymers could be sulfonated with chlorosulfonic acid exclusively at the para position of the diphenylamine rings, with ion exchange capacities from 1.88 to 2.12 meq/g. Transmission electron microscopy images show that the morphology of the sulfonated polymer films depends on the functional group in the polymer backbone. Polymers containing sulfone groups exhibited small ionic clusters within a uniform ion-containing background, while polymers with ketone and isophthaloyl groups exhibited phase separation with different sizes of spherical hydrophilic clusters. The uniform distribution of ionic groups within polymers that contain sulfone groups resulted in higher proton conductivity, 0.11 S/cm at 90 °C and 100% relative humidity, in spite of having a lower degree of sulfonation and water uptake. Small angle neutron scattering data also shows this film has a robust morphology that does not change as a function of temperature or by counterion exchange. Films cast from unsulfonated polymers that contained phosphine oxide groups in the polymer backbone, as well polymer blends with polybenzimidazole soaked in 85% phosphoric acid at 75 °C, had phosphoric acid uptakes above 350 wt%, and as high as 830 wt%. However, these films lost dimensional stability at elevated temperatures.

In this work, a novel, high modulus sulfonated polymer is utilized as an ionomer for ionic liquid containing micro. ionic actuators (ionogel) is presented. The ionic polymer is composed of one. to. one ratio 4,6-bis(4-hydroxyphenyl)-N,N-diphenyl. 1,3,5-triazin-2-amine and 4,4'-biphenol with bis(4-fluorophenyl) sulfone (DPA-PS: BP). The ionogel maintains a relatively higher modulus (700 MPa for 120 wt% of ionic liquid) compared to other widely used ionomers. High modulus of ionogel enables to realize thin films through solution casting. As an initial demonstration of a micro-ionic actuator, an ionic micro cantilever (200 mu m x 33 mu m x 5 mu m) has been micromachined by using focused ion beam (FIB) milling on the substrate. The micro cantilever performance under DC actuation is tested using optical profilometer and a maximum tip displacement is 42 mu m at 1.6V was obtained. (C) 2011 Published by Elsevier Ltd.

A series of novel fully aromatic poly(arylene ether sulfone)s that contain 1,3,5-s-triazine groups were synthesized by the reaction of triazine-containing bisphenols with bis(4-fluorophenylsulfone) to study the effects of branching groups on solubility as well as thermal and mechanical properties. Polymers had inherent viscosities from 0.43 to 1.10 dL/g, thermal stabilities >500 °C in air, glass transition temperatures from 136 to 289 °C, and good film forming abilities. The polymer with pendant diphenylamine groups on the triazine ring were further investigated for use in proton exchange membranes based on solubility, thermo-oxidative stability, and ease of monomer synthesis. A series of copolymers made from 4,6-bis(4-hydroxyphenyl)-N,N-diphenyl-1,3,5-triazin-2-amine and 4,4′-biphenol were sulfonated with chlorosulfonic acid to achieve ion exchange capacities up to 2.62 mmol/g. The homopolymer was sulfonated exclusively on the diphenylamine branch and had the highest proton conductivity (0.11 S/cm at 95 ...

Solvent free polymer electrolytes were made consisting of Li(+) and pyrrolidinium salts of trifluoromethanesulfonimide added to a series of hyperbranched poly(ethylene oxide)s (PEO). The polymers were connected by triazine linkages and crosslinked by a sol-gel process to provide mechanical strength. The connecting PEO groups were varied to help understand the effects of polymer structure on electrolyte conductivity in the presence of ionic liquids. Polymers were also made that contain poly(dimethylsiloxane) groups, which provide increased flexibility without interacting with lithium ions. When large amounts of ionic liquid are added, there is little dependence of conductivity on the polymer structure. However, when smaller amounts of ionic liquid are added, the inherent conductivity of the polymer becomes a factor. These electrolytes are more conductive than those made with high molecular weight PEO imbibed with ionic liquids at ambient temperatures, due to the amorphous nature of the polymer.

A series of polymers was synthesized that contain a rigid aromatic backbone connected through triazine linkages that are cross-linked by flexible diamine-terminated poly(ethylene oxide) oligomers. Polymers were made that contained both hydrophilic sulfonated aromatic and hydrophobic pyridinium triflate backbones. Thermal and mechanical properties of the resulting polymer films were studied, as well as uptake of water and protic ionic liquids. Ionic liquid uptake varied from 41 to 440%, depending upon the nature of the polymer. The ionic liquid-doped films were analyzed for proton conductivity at high temperatures (>150 °C) under non-humidified conditions. Conductivities as high as 5×10 −2 S/cm were observed at 150 °C.

A new series of polymer electrolytes for use as membranes for lithium batteries are described. Electrolytes were made by polymerization between cyanuric chloride and diamino-terminated poly(ethylene oxide)s, followed by cross-linking via a sol-gel process. Thermal analysis and lithium conductivity of freestanding polymer films were studied. The effects of several variables on conductivity were investigated, such as length of backbone PEO chain, length of branching PEO chain, extent of branching, extent of cross-linking, salt content, and salt counterion. Polymer films with the highest percentage of PEO were found to be the most conductive, with a maximum lithium conductivity of 3.9 x 10(exp -5) S/cm at 25 C. Addition of plasticizer to the dry polymers increased conductivity by an order of magnitude.

A series of poly(pyridinium triflate)s with alkyl and aromatic spacer groups were prepared by ring transformation polymerizations between various pyrylium triflates and diamines. The polymers are soluble in polar aprotic solvents and form tough, clear, flexible films. These novel polymers were characterized by IR, NMR, UV, DSC, TMA, and TGA. The polymers were thermally stable to 340 °C under nitrogen, and had softening points that ranged from 151 to 255 °C. Thin films were shown to display electrostrictive behavior in the presence of an applied electric field, with the amount of transverse strain being proportional to the concentration of charge in the polymer.

In this work we explore the use of room temperature ionic liquid doped ionomers as the sensing material for volatile organic compounds (VOCs). Pixels of a monolithic, micromachined quartz crystal resonator (μQCR) array were functionalized using a sulfonated, aromatic, high thermal stability polymer as a template which is able to contain high amount of ionic liquids (up to 200 wt %). Ionic liquid: [C 4 mim][BF 4 ] (1-butyl-3-methylimidazolium tetrafluoroburate) was used as the detection material. Exposure to VOCs results in mass loading and changes in the viscoelastic properties of the ionomer and manifests as changes in the frequency and phase of the quartz resonators.

A high modulus, sulfonated polymer synthesized from one-to-one ratio 4,6-bis(4-hydroxyphenyl)-N, N-diphenyl-1,3,5-triazin-2-amine and 4,4′-biphenol with bis(4-fluorophenyl) sulfone (DPA-PS:BP) is exploited as an ionomer for micro-ionic actuators. A unique and attractive feature of the ionomer is that it can contain high amounts of ionic liquid (IL) as an electrolyte while maintaining a high elastic modulus (i.e 600 MPa for 150 wt% uptake), which is more than one order of magnitude higher than the state-of-the-art of ionomers with working electrolytes. Such a high modulus makes it possible for the ionomer to be fabricated into micro-actuators with high uptake of ILs and low operation voltage (< 4 V), in various free standing forms with ion milling techniques, which are attractive for MEMS applications. As an initial demonstration of a DPA-PS:BP based ionic micro-actuator, a cantilever (200 μm x 33 μm x 5 μm) is manufactured by Focused Ion Beam (FIB) and characterized. Under the voltage of 1.6 V, the bending actuator exhibits an intrinsic strain from the active ionomer of 1.1% and a corresponding blocking force of 27 μN.

A high modulus, sulfonated ionomer synthesized from 4,6-bis(4-hydroxyphenyl)-N,N-diphenyl-1,3,5-triazin-2-amine and 4,4'-biphenol with bis(4-fluorophenyl)sulfone (DPA-PS:BP) is investigated for ionic polymer actuators. The uniqueness of DPA-PS: BP is that it can have a high ionic liquid (IL) uptake and consequently generates a high intrinsic strain response, which is >1.1% under 1.6 V while maintaining a high elastic modulus (i.e. 600 MPa for 65 vol% IL uptake). Moreover, such a high modulus of the active ionomer, originating from the highly aromatic backbone and side-chain-free structure, allows for the fabrication of free-standing thin film micro-actuators (down to 5 mu m thickness) via the solution cast method and focused-ion-beam milling, which exhibits a much higher bending actuation, i.e. 43 mu m tip displacement and 180 kPa blocking stress for a 200 mu m long and 5 mu m thick cantilever actuator, compared with the ionic actuators based on traditional ionomers such as Nafion, which has a much lower elastic modulus (50 MPa) and actuation strain.

A highly cross-linked polyimide-polyethylene oxide copolymer has been synthesized that is capable of holding large volumes of liquid component, simultaneously maintaining good dimensional stability. An amine end capped oligomer was made that was imidized in solution, followed by reaction with a triisocyanate in the presence of desired additives at ambient temperature. Polymer films are able to hold over 4 times their weight in room temperature ionic liquid RTIL or carbonate solvent. Electrolytes were studied that contained varying amounts of RTIL, lithium trifluoromethanesulfonimide LiTFSi, and alumina nanoparticles. Electrochemical stability of these electrolytes with lithium metal electrodes was studied by galvanic cycling and impedance spectroscopy. Improved cycling stability and decreased interfacial resistance were observed when increasing amounts of RTIL and LiTFSi were added. The addition of small amounts of alumina further decreased interfacial resistance by nearly an order of magnitude. During the course of the study, cycling stability increased from less than 3 to greater than 1000 h at 60 C and 0.25 mA/cm2 current density.

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