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A modification of the method for synthesis of well-defined mono- and ditelechelic polyphosphazenes via the living, cationic polymerization of phosphoranimines has been developed. This process provides access to phosphazene block, comb, and graft copolymers that contain organic or organosilicon macromolecules. Several alkoxy and aryloxy phosphoranimines, RO(CF3CH2O)2P&dbd;NSiMe3 (R = Ph, MeOPh, C10H7, BOC−NH−CH2CH2, t-BuMe2SiO(CH2)5, C8H11, and CH2&dbd;CH−C6H4), were synthesized via the reaction between a bromophosphoranimine and the appropriate sodium alkoxide or aryl oxide. These species are potential initiators or terminators, useful for the synthesis of telechelic polyphosphazenes with etheric linkages rather than the amino linkages used previously. Ditelechelic polymers, RO[(CF3CH2O)2P&dbd;N]n−P(OCH2CF3)3OR, were prepared by terminating living poly(dichlorophosphazene) chains, [Cl3P&dbd;N−(Cl2P&dbd;N)n−PCl3]⁺[PCl6]^-, with these alkoxy or aryloxy phosphoranimines. Alternatively, monotelechelic polyphosphazenes were produced through the termination of the polymer [(CF3CH2O2)3P&dbd;N−(Cl2P&dbd;N)n−PCl3]⁺[PCl6]^- with the appropriate alkoxy or aryloxy phosphoranimines. In all cases, hydrolytically stable telechelic polymers with controlled molecular weights and low polydispersities were obtained in good yield after macromolecular replacement of labile chlorine atoms with sodium trifluoroethoxide.

The micellar characteristics of the amphiphilic diblock copolymers based on a hydrophobic polyphosphazene (PN) and hydrophilic poly(ethylene oxide) (PEO) were investigated by using fluorescence techniques, dynamic light scattering, and transmission electron microscopy. The two diblock copolymers with different ratios of the length of block components form spherical micellar aggregates in an aqueous phase. The critical micelle concentrations of PN−PEO 1 and PN−PEO 2, determined by a fluorescence technique, were 12.4 and 5.2 mg/L, respectively. The mean diameters of the micelles of PN−PEO 1 and PN−PEO 2, measured by dynamic light scattering, were 100 and 120 nm. The steady-state fluorescence anisotropy values (r) of 1,6-diphenyl-1,3,5-hexatriene (DPH) were 0.103 for PN−PEO 1 and 0.108 for PN−PEO 2. The low anisotropy values for PEO−PN compared to those for other polymeric amphiphiles may be due to the intrinsic flexibility of the trifluoroethoxy-substituted polyphosphazene block, which would allow enhanced rotational diffusion of the probe.

Linear A−B, A−B−A, and B−A−B block copolymers containing polyphosphazenes and polysiloxanes were synthesized and characterized. Two methods were used in the synthesis of these novel block copolymers. The first utilized hydrosilylation chemistry to couple monotelechelic polyphosphazenes with commercially available dihydride-terminated poly(dimethylsiloxane) (PDMS). The second involved the termination of living poly(dichlorophosphazene) chains with phosphoranimine-terminated PDMS. The semicrystalline, hydrophobic copolymers, [(CF3CH2O)2P&dbd;N]x−[(Me)2Si−O]y, and the water-soluble copolymers, [(CH3OCH2CH2OCH2CH2O)2P&dbd;N]x−[(Me)2Si−O]y, were prepared by the linkage of either hydrophobic or hydrophilic organic groups to the polyphosphazene backbone. These materials, with a polyphosphazene content from 19 to 73 mol % (43−90 wt %) were obtained with controlled molecular weights that ranged from 5600 to 108 900 Da. The syntheses, characterization, and physical properties of the linear polyphosphazene−polysiloxane block copolymers are reported.

The synthesis of polyphosphazene-co-poly(ethylene oxide) block copolymers with well-defined molecular weights has been accomplished via end-functionalized polymer intermediates. Mono- and diamine-terminated poly(ethylene oxides) (PEO = (CH2CH2O)n−CH2CH2−) were used to produce polymer-based phosphoranimines, CH3O−(CH2CH2O)n−CH2CH2−NH(CF3CH2O)2P&dbd;NSiMe3 and Me3SiN&dbd;P(OCH2CF3)NH−(CH2CH2O)n−CH2CH2−NH(CF3CH2O)2P&dbd;NSiMe3. These were then converted to macroinitiators via reaction with PCl5 to produce CH3O−PEO−NH[(CF3CH2O)2P&dbd;NPCl3]⁺[PCl6]^- and [Cl3PN&dbd;P(OCH2CF3)NH−PEO−NH[(CF3CH2O)2P&dbd;NPCl3]²⁺[PCl6]2^-, respectively. These macroinitiators were used to polymerize Cl3P&dbd;NSiMe3 in a living manner to produce diblock copolymers of polyphosphazenes with poly(ethylene oxide) or triblock copolymers with poly(ethylene oxide) blocks flanked by polyphosphazene components. In addition, the monophosphoranimine-terminated PEO was employed as a terminator in the living, cationic polymerization of Cl3P&dbd;NSiMe3 to produce triblock copolymers with a polyphosphazene block flanked by two poly(ethylene oxide) blocks. Polymers for use as solid−ionic conduction media or hydrogels were produced by nucleophilic replacement of the chlorine atoms along the polyphosphazene segments by methoxyethoxyethoxy units. The ionic conductivities of these materials, after complexation with varying ratios of lithium triflate, ranged from 7.6 × 10^-6 to 1.0 × 10^-4 S cm^-1 for a temperature range of 20−80 °C.

Mono- and ditelechelic linear polyphosphazenes, functionalized with a norbornene end group, were synthesized through the termination of living poly(dichlorophosphazene) with norbornenyl phosphoranimines. These materials were employed as macromonomers for the synthesis of graft copolymers via the ring-opening metathesis polymerization (ROMP) of the terminal norbornenyl component. Norbornenyl monotelechelic polyphosphazenes with various molecular weights yielded un-cross-linked graft copolymers when subjected to ROMP. The ditelechelic polyphosphazenes yielded branched or cross-linked materials due to the multiple reactive sites. In addition, the 5-norbornene-2-methoxy phosphoranimine was polymerized via ROMP to yield materials that consisted of a polynorbornene backbone with phosphoranimine pendent side groups.

We present ground-based observations of the jovian ionospheric H+3 emission at 4 micrometers, using the CSHELL facility long-slit spectrograph at the NASA Infrared Telescope Facility (IRTF) in Hawaii. The data were obtained during four consecutive nights from July 13 to July 16, 1996. The 30-arcsec length slit of the spectrograph was aligned with the jovian CML, in order to get high-spatial, high-spectral resolution latitudinal profiles of the jovian H+3 emission. A self-consistent multi-emission-component (MEC) model, developed for the analysis of these latitudinal profiles, simulates the emission from the vertical distribution of the ionization components known to produce H+3. We initially identify these as solar-EUV photo-ionization, auroral oval precipitation, and diffuse auroral precipitation. A fourth component, mid-to-low (MTL)-latitude ionization is derived, and then fitted. InfraRed H+3 auroral ovals follow closely the UV ovals as observed with the HST instruments WFPC2 and FOC. Our model shows that the auroral production rate is generally between a few and a few tens of times the EUV rate. The MTL component production rate is 1 to 40% of the auroral rate in the north, and 2 to 16% in the south. Input and output energies are scaled to solar EUV values. We assume an EUV insolation of 60 μW/m2, equivalent to a total jovian EUV insolation of 1012W. Scaled to the EUV input, planetwide integration of the components of our model produces the total hemispheric energy inputs associated with the aurora, the diffuse emission, and the MTL emission. The results are 1.22(±.25)×1012W, 0.37(±.15)×1012W, and 0.65(±.32)×1012W, respectively, for the north and 1.15(±.30)×1012W, 0.21(±.10)×1012W, and 0.64 (±.32)×1012W for the south, respectively. We discusss the limitations of our scaling process, introducing the notion of emission efficiency with respect to a nominal 1000K/LTE H+3 emitter. The overall auroral emission is approximately 43 (+107, −23)% of that measured in 1993. Our results show that H+3 controls the energy balance of the auroral regions above the homopause, as well as the equatorial regions.

A new polyphosphazene, [N&dbd;PPh(CF3)]n, has been prepared via the PCl5-induced cationic polymerization of Me3SiN&dbd;P(CF3)(Ph)Br. In addition, the cationic route has been used to produce [N&dbd;PPh(Me)]n with controlled molecular weights and narrow polydispersities. By contrast, the new monomer Me3SiN&dbd;P(t-Bu)(Ph)F failed to polymerize under any conditions but was used as an initiator and terminator to prepare both mono- and ditelechelic polymers. This monomer was also used to prepare [F(Ph)(t-Bu)P&dbd;N(PCl2&dbd;N)P(t-Bu)(Ph)F]⁺, which was used as a substrate for reactions with alkoxy and aryloxy groups to yield the hydrolytically stable materials, [R(Ph)(t-Bu)P&dbd;N(PR2&dbd;N)P(t-Bu)(Ph)R2].

A method for the synthesis of well-defined mono-, di-, and mixed-telechelic polyphosphazenes produced via a living cationic polymerization of phosphoranimines is described. Amino phosphoranimines R−NH(CF3CH2O)2P&dbd;NSiMe3 (R = Ph−, p-BrPh−, p-H3CPh−, CH2&dbd;CHCH2−, and CH2&dbd;CHPh−) were synthesized via a reaction between a bromophosphoranimine and the appropriate organic amine. Ditelechelic polymers [R−NH]2−[Cl2P&dbd;N]n were prepared by quenching living poly(dichlorophosphazene) chains, [Cl3P&dbd;N(Cl2P&dbd;N)n−PCl3]⁺[PCl6]^- with small quantities of the amino phosphoranimines. Cationic initiators of the amino phosphoranimines were also generated using PCl5 and were used to polymerize Cl3P&dbd;NSiMe3, to give monotelechelic poly(dichlorophosphazenes). In addition, a mixed telechelic system was produced by the termination of an allylamino monotelechelic poly(dichlorophosphazene) chain with a bromoanilino phosphoranimine. In all cases, displacement of the chlorine atoms with sodium trifluoroethoxide yielded hydrolytically stable telechelic polymers with controlled molecular weights and low polydispersities.

The protein‐coding region of the essential Saccharomyces cerevisiae YPT1 gene coding for a ras‐related, guanine‐nucleotide‐binding protein was exchanged in chromosome VI by the protein‐coding segment of either the mouse ypt1 gene or the v‐Ki‐ras gene, and different chimeric YPT1‐v‐Ki‐ras genes. The mouse ypt1 protein with 71% of identical residues compared with the yeast Ypt1 protein could functionally fully replace its yeast homologue as long as the mouse gene was overexpressed under transcriptional control of the inducible GAL10 promoter. In contrast, neither the viral Ki‐ras nor the hybrid proteins were able to substitute for the loss of YPT1 gene function. This study suggests that different parts of the yeast Ypt1 protein are required for the interaction with cellular targets and that these essential parts are conserved in the mammalian ypt1 protein.

The Saccharomyces cerevisiae YPT1 gene codes for a ras‐like, guanine nucleotide‐binding protein which is essential for cell viability. The functional significance of two consecutive cysteines at the very carboxyl‐terminal end of this protein and in ypt homologues of other eukaryotic species was examined. YPT1 gene mutations were generated that either led to substitutions by serine or the deletion of one or both C‐terminal cysteines. The consequences of the mutations were checked in cells after replacing the wild type with the mutant genes. It was found that as long as one of the cysteines was retained, the protein was fully functional. The YPT1 protein could be labelled with [3H]palmitic acid that appeared to be bound in an ester linkage. The wild‐type protein was evenly distributed between soluble and membrane‐associated proteins, the palmitoylated form was predominantly in the crude membrane fraction. The mutant protein lacking the C‐terminal cysteines was not palmitoylated and was exclusively found in the soluble fraction. The extension by three residues, ‐Val‐Leu‐Ser, generating a ras‐typical C‐terminal end, did not interfere with the mutant YPT1 protein's function although it resulted in a reduced labelling with palmitic acid.

Rumen propionate production in steers fed either a control or monensin supplemented diet was measured by an isotope dilution technique. The feeding of the control ration (5.9 kg hay, 2.5 kg concentrate) gave a typical high acetate type fermentation, while supplementing the same ration with monensin at a level of 33 ppm significantly increased the molar proportion of rumen propionate (19.1 vs24.7%). Monensin supplementation increased propionate production from 7.74 moles/day to 11.18 moles/day. These results show that the change in the molar proportions of the volatile fatty acids resulting from monensin supplementation can be explained on the basis of an increase in propionate production.