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A variety of perfluorocycloalkenyl (PFCA) aryl ether monomers and polymers with enchained triarylamine units were successfully synthesized, characterized and reported here. These polymers are highly thermally stable and show variable thermal properties. Successful conversion of the newly synthesized TAA enchained perfluorocyclopentenyl (PFCP) aryl ether polymers via formylation and EAS demonstrates the synthetic versatility of TAA moiety and provides an excellent option for application specific post polymerization reactions. The cross-linking behavior of PFCP aryl ether polymers was studied under different reaction conditions. The combination of processability, thermal stabilities, and tailorability makes these polymers suitable for a wide variety of applications including electro-optics, proton exchange membranes and super-hydrophobic applications.

Platinum catalysts for electrochemical oxygen reduction were prepared on mesoporous carbon supports, some of which included embedded zirconia nanoparticles, by borohydride reduction of hexachloroplatinic acid in ethylene glycol solution. The resulting materials are approximately 20 percent platinum by weight and consist of platinum particles having diameters in the 2-3 nm range, evenly distributed throughout the support structure. Electrochemical surface areas for platinum were measured by hydrogen adsorption/desorption and carbon monoxide stripping and were found to be lower for platinum on carbon containing zirconia than for carbon without zirconia. This finding is thought to reflect a slightly larger platinum particle size and also a higher degree of particle aggregation for platinum on the carbon support containing zirconia, possibly caused by localized patches of positive charge on zirconia particles under the acidic conditions used to deposit platinum. Zirconia-containing carbon supports that had been treated with platinum were subsequently treated with polymer electrolytes having terminal aryl phosphonate groups that can covalently bind to exposed zirconia sites, thereby producing composite materials having intimately integrated platinum catalysts and polymer electrolytes immobilized within a mesoporous carbon support structure. Electrochemical ORR activity of these materials as thin-film electrodes was assessed using rotating disk electrode voltammetry in aqueous sulfuric acid solutions. Activity for platinum on a mesoporous carbon support without zirconia is comparable to that of benchmark materials, e.g., platinum on Vulcan carbon XC-72, but is diminished on the mesoporous carbon support containing zirconia. Remarkably, the platinum ORR activity is fully recovered and slightly enhanced on zirconia-containing supports following treatment with polymer electrolyte. Possible reasons for the recovery of the platinum ORR activity upon polymer electrolyte treatment, and implications for possible application in polyelectrolyte membrane fuel-cell technology, are discussed.

A new method for the surface modification of used tire rubber (UTR) is being developed. The method involves hydrosilylation of ground UTR particles with trichlorosilane (TCS) under various reaction conditions. The reaction has been carried out with and without solvents and catalysts (Karsted's/Pt catalyst). TCS treated UTR particles are then hydrolyzed to obtain silanol functionalized hydrosilylated rubber powder. Attenuated total reflection–Fourier transform infrared, solid-state 13C NMR spectroscopy, and thermogravimetric analysis are provided as evidence of hydrosilylation onto rubber particles.

New thermally cross-linkable and/or post-functionalizable perfluorocyclobutyl (PFCB) polymers containing Meldrum's acid moieties have been successfully prepared via the thermal cyclopolymerization of a new Meldrum's acid functionalized aromatic trifluorovinyl ether (TFVE) monomer.

A new class of heteroatom terminated bis-ortho-diynyl arene (BODA) compounds have been synthesized via efficient in situ palladium catalyzed cross coupling between tetra alkynyl silanes and aryl bromides and iodides. BODA monomers undergo Bergman-type cyclization upon heating, and afford processable intermediates and ultimately network polymers. The new heterocycle terminated oligomers are compared to phenyl terminated derivatives and exhibit bathochromic shifts (25 nm) in their emission spectra.

Water-soluble perfluorocyclobutyl (PFCB) aryl ether ionomers bearing sulfonic acid groups in the main chain and phosphonic acid end groups were prepared and used to modify the surfaces of mesoporous carbon materials containing dispersed zirconia nanoparticles. Ionomer surface grafting occurred via phosphonate bonding onto the zirconia particle surfaces.

The structure of 2,2,4,4,9,9,11,11-octamethyl-3,10-dioxa-2,4,9,11-tetrasilatricyclo[10.2.2.2 5,8 ]octadeca-1(14),5,7,12,15,17-hexaene (I) consists of molecules located on crystallographic centers of inversion (half a molecule in the asymmetric unit). The two phenyl rings are parallel to each other with a separation of 3.63 A. The title compound (I) has been considered as a monomer for catalytic ring-opening polymerization. It was synthesized, using allyl(chloro)dimethylsilane, by the condensation of bis(hydroxydimethylsilyl)benzene

Unsaturated poly(carbosiloxane)s ([SiO(Me) 2 ] 2 Si(Me) 2 CH 2 CH=CHCH 2 ) n , [SiO(Me) 2 Si(Me) 2 (CH 2 ) 3 CH=CH(CH 2 ) 3 ] n , [SiO(Me) 2 Si(Me) 2 PhSiO(Me) 2 Si(Me) 2 CH 2 CH=CHCH 2 ] n and [(SiO(Me) 2 Si(Me) 2 [CH 2 ] 4 ) x SiO(Me) 2 Si(Me) 2 (CH 2 ) 3 CH=CH(CH 2 ) 3 ] n and The synthesis of unsaturated poly(carbosiloxane)s, a new class of were synthesized by bulk acyclic diene metathesis polymerization catalyzed by [(CF 3 ) 2 CH 3 CO] 2 (N-2,6-C 6 H 3 -i-Pr 2 )Mo

Diallyldimethylsilane, 4,4,7,7-tetramethyl-4,7-disiladeca-1,9-diene and 1,4-bis(allyldimethylsilylbenzene) undergo acyclic diene metathesis polymerization when catalyzed by highly active tungsten alkylidenes to give poly(1,1-dimethyl-1-silapent-3-ene), poly(1,1,4,4-tetramethyl-1,4-disilaoct-6-ene) and poly[1-(dimethylsilyl)-4-(1,1-dimethylsilapent-3-en-1-yl)phenylene], respectively. Dimethyldivinylsilane copolymerizes with 1,9-decadiene to give poly(1,1-dimethyl-1-silapropene)-co-octenamer.

New fluorinated polyhedral oligomeric silsesquioxane (F-POSS) structures possessing a high degree of hydrophobicity have been prepared via a facile corner-capping methodology.

A series of 19 p-substituted aromatic trifluorovinyl ether compounds were prepared from versatile intermediate p-Br-C(6)H(4)-O-CF=CF(2) and underwent thermal radical mediated cyclodimerization to new difunctional compounds containing the 1,2-disubstituted perfluorocyclobutyl (PFCB) linkage. The synthetic scope demonstrates the functional group transformation tolerance of the fluorovinyl ether, and the dimers are useful as monomers for traditional step-growth polymerization methods. (19)F NMR spectra confirmed that p-substitution affects the trifluorovinyl ether group chemical shifts. The first kinetic studies and substituent effects on thermal cyclodimerization were performed, and the results indicated that electron-withdrawing groups slow the rate of cyclodimerization. The data were further analyzed using the Hammett equation, and reaction constants (rho) of -0.46 at 120 degrees C and -0.59 at 130 degrees C were calculated. This study presents the first liner free energy relationship reported for the cyclodimerization of aromatic trifluorovinyl ethers to PFCB compounds.

Hexa-peri-hexabenzocoronene (HBC) derivatives possess many interesting properties ranging from liquid crystallinity, to hole transport, to variable emission behavior, yet are plagued by insolubility and general accessibility of polymerizable substituents. The first synthesis of trifluorovinyl ether-substituted hexabenzocoronene and its polymerization to perfluorocyclobutyl (PFCB) polymers and copolymers is shown. Unlike hydrocarbon ethers, fluoro vinyl ethers are stable under HBC oxidation conditions. Discrete HBC units in PFCB polymers provide access to potentially processable HBC optical materials.

The olefin metathesis reaction is of great synthetic utility in polymer chemistry. The recent development of ring-opening (ROMP) and acyclic diene (ADMET) metathesis polymerization reactions has opened new avenues for the synthesis of novel polymeric materials. Recently the authors used ADMET to synthesize several photochemically active poly(keto olefins) using the catalyst Mo(CHCMe[sub 2]Ph)(NAr)(OCMe(CF[sub 3])[sub 2])[sub 2] (Ar = 2,6-diisopropylphenyl) (1) developed by Schrock and co-workers in 1990. In the course of that work, they discovered that neat samples of highly substituted dienes will cyclize quantitatively via metathesis to give difunctional five- and seven-membered rings instead of the expected linear polymer. Examples of substituted diene cyclizations by metathesis even in the presence of a solvent are rare. Their systematic exploitation in organic synthesis has therefore been limited to two recent studies by Fu and Grubbs, who cyclized several substituted diene ethers, amines, and amides to unsaturated oxygen and nitrogen heterocycles. Cyclization of unsubstituted dienes in various solvents has been reported, but complete conversion occurred in only a few cases. Formation of cyclic alkene oligomers from back-biting during the ROMP reaction is also known. The reactions reported here are unusual in that they are intermolecular between catalyst and substrate, yet can givemore » 100% yield of product solely from the monomer in the absence of solvent. 13 refs.« less

Enediynes were first studied by Bergman and are known to undergo thermal intramolecular cyclization to benzene 1,4diradical or “dehydroaromatic” intermediates.1 While the primary impetus for enediyne research remains focused on their biological activity as antitumor agents,2 others have reported using enediynes in a polymerization scheme.3,4 Tour detailed the synthesis of linear poly(phenylenes) and poly(naphthalenes) by thermolysis of substituted enediynes and 1,2-dialkynylbenzenes (Scheme 1).3 This work extended earlier accounts4 and revealed the Bergman cyclization as a viable polymerization reaction in detail. Polynaphthalenes prepared by Bergman cyclopolymerization to date have been limited to linear systems of soluble, low molecular weight oligomers with fair thermal stability, or high molecular weight polymers exhibiting exceptional thermal stability yet are insoluble and not easily processed.3,4 In addition, the preparation of 1,2-dialkynyl monomers is typically accomplished by the palladium-catalyzed coupling of terminal alkynes with difficult to prepare 1,2-dibromo or -diiodo aromatics.3-5 We have found, however, that bis(o-di(phenylethynyl)phenyl) monomers 1-4 (Scheme 2) overcome both monomer synthetic obstacles and the processability/performance “tradeoff” issues common to linear polyarylenes.6 We have developed a general multi hundred gram preparation of these compounds in three steps from commodity starting materials and reagents. When heated, monomers 1-4 undergo Bergman cyclopolymerization to reactive oligomers which can be melt or solution processed and thermally cured providing a new class of polynaphthalene networks. Other polymers containing naphthalene linkages are also known.7 Our polynaphthalene networks were designed specifically to replace current dielectric materials used in integrated circuits.8 Monomer intermediates were prepared by selective o-bromination followed by quantitative trifluoromethanesulfonate (triflate) esterification of the corresponding bisphenols and gave aryl dibromide ditriflate intermediates in good yield (>75%). Sonogoshira-type9 palladium coupling with phenylacetylene produced tetraynes 1-4 in isolated yields usually >80% (Scheme 2).10 Our method does not use a copper cocatalyst, common to aryl alkyne couplings, thereby eliminating the potentially hazardous formation of copper acetylide.11 All monomers were isolated as lightly colored crystalline solids with sharp melting points (Table 1). Neat exothermic polymerizations of 1-4 are detected by differential scanning calorimetry (DSC, 10 °C/min) at 200-210 °C, giving reaction profiles consistent with known phenylsubstituted aryldiynes.4 For example, the polymerization of 1,2,4,5-tetrakis(phenylethynyl)benzene and poly(arylene-1,2-ethynylene) each containing four acetylene linkages, gave a DSCmeasured -∆H ) 29 kcal/mol alkyne, whereas the thermolysis of 1-3 gave -∆H ) 27, 29, and 27 kcal/mol alkyne, respectively. Fluorenyl monomer 4 exhibited a significantly lower -∆H ) 18 kcal/mol alkyne, due to incomplete conversion. Bergman cyclopolymerization kinetics, and thus rheological properties, are controlled by tetraphenyl substitution and provide

New fluorovinylene aromatic ether polymers, possessing dual reactivity, have been successfully prepared via the step-growth polymerization of commercial bis(trifluorovinyl) aromatic ethers and bisphenols.