LetG be a complex connected reductive group. Well known wonderfulG-varieties are those of rank zero, namely the generalized flag varietiesG/P, those of rank one, classified in [A], and certain complete symmetric varieties described in [DP] such as the famous space of complete conics. Recently, there is a renewed interest in wonderful varieties of rank two since they were shown to hold a keystone position in the theory of spherical varieties, see [L], [BP], and [K].

The conductivity enhancement in polydiacetylene (PDA) crystals due to chemical doping and ion implantation was measured and analyzed in relation to their spin concentration and photocurrent decay based on the structural and optical information obtained through infrared and visible reflectivity spectra. A conductivity jump was observed upon slight increase of the spin concentration at low doping levels of chemically doped PDAs, suggesting the formation of spinless carriers in chemically doped PDAs, as in trans-polyacetylene and poly(p-phenylene). In contrast, in ion-implanted samples, a great difference in the magnitudes (by more than five orders of magnitude) was observed between the conductivity enhancement for two PDAs having different side chain species. Furthermore, the photocurrent decay time measurements reveal different distributions of implantation-induced trap levels between ion-implanted poly [2,4-hexadiyne-1,6-diol-bis-(p-toluene sulfonate)] (PTS) and poly[2,4-hexadiyne-1,6-di(N-carbazolyl)] (DCH). A conduction mechanism which could explain the significant difference in conductivity enhancement between PTS and DCH is suggested. Because the enhanced conductivity by ion-implanted PTS showed no orientational effect associated with the polymer chain direction, a conductive path and network formation by the implantation-induced defects is more plausible for the conduction mechanism than carrier introduction into the backbone chain band from side chain defect levels.

Current transient measurements are carried out on ion‐implanted polymers to provide new information on the mechanism for the implantation‐induced conductivity. Using metal‐oxide‐semiconductor field‐effect transistor devices in which implanted polymer films form part of the metal‐oxide‐semiconductor structure, the dispersion parameter α is measured as a function of ion fluence and temperature. The fluence dependent measurements provide evidence for trapping sites and support a trap‐controlled hopping mechanism for ion‐implanted polymers. The temperature‐dependence measurements favor conduction by hopping between traps in the defect band in the mobility gap rather than between traps in the mobility edges. New results are also presented on the dc conductivity of polymers implanted at low temperature (77 K), the same samples as were used for the current transient measurements.

Journal of Polymer Science: Polymer Letters EditionVolume 23, Issue 12 p. 609-612 Article Ion implantation of a polyquinoline G. E. Wnek, G. E. Wnek Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139Search for more papers by this authorB. Wasserman, B. Wasserman Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139Search for more papers by this authorM. S. Dresselhaus, M. S. Dresselhaus Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139Search for more papers by this authorS. E. Tunney, S. E. Tunney Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523Search for more papers by this authorJ. K. Stille, J. K. Stille Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523Search for more papers by this author G. E. Wnek, G. E. Wnek Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139Search for more papers by this authorB. Wasserman, B. Wasserman Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139Search for more papers by this authorM. S. Dresselhaus, M. S. Dresselhaus Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139Search for more papers by this authorS. E. Tunney, S. E. Tunney Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523Search for more papers by this authorJ. K. Stille, J. K. Stille Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523Search for more papers by this author First published: December 1985 https://doi.org/10.1002/pol.1985.130231201Citations: 9AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume23, Issue12December 1985Pages 609-612 RelatedInformation

The effect of ion implantation on the polymers PAN (polyacrylonitrile), PPO (poly 2,6-dimethylphenylene oxide) and PPS (p-polyphenylene sulfide) is studied using electron spin resonance. ESR measurements on these polymers were performed as a function of ion species and fluence in the temperature range 10 <T< 300 K. The unpaired carrier concentration increases with increasing fluence and is independent of the ion species used for implantation in this study (84Kr,80Br,75As,40Ar and14N). It is therefore concluded that the carrier concentration is related to the structural damage and not to chemical doping effects. From the shape of the ESR line, the ratio of the relaxation times for one-dimensional to three-dimensional spin diffusion is determined to be larger than 1000. The temperature dependence of the unpaired carrier concentration shows a strong deviation from a Curie law behavior, which can be explained by assuming that a defect band is formed with a bandgap due to strong Coulomb interaction between electrons on the defect sites.

We have studied the H-D exchange reaction on a series of ${\mathrm{Ni}}_{1\ensuremath{-}x}{\mathrm{Cu}}_{x}$ alloys, with $0.17\ensuremath{\le}x\ensuremath{\le}0.33$. Large increases in reaction rate occur as the temperature is raised through the alloy Curie temperature ${T}_{C}$. These observations can be explained by a model based on the existence of two alternative hydrogen---surface-atom complex configurations that differ in reactivity. At temperature below ${T}_{C}$, the less reactive configuration has the lower free energy (including surface magnetic energy) and therefore has the larger population. As the alloy temperature is raised through ${T}_{C}$, the surface magnetic free energy vanishes, and the free-energy balance favors an increase in population of the more reactive configuration.

Ion implantation causes an increase by ∼14 orders of magnitude in the electrical conductivity of normally insulating polymers such as polyacrylonitrile (PAN), poly(2,6 dimethyl phenylene-oxide) (PPO), and poly (pphenylene sulfide) (PPS), after ion implantation with Br at fluences of 3 × 1015 ions/cm2. The temperature dependence of the dc conductivity was measured in the range 23 < T < 293 K and results show an exponential law σ ∼ exp(−To/T)α) for PAN, PPO and PPS with α = 1/2, suggesting a one-dimensional hopping mechanism. The temperature dependence of the thermoelectric power (TEP) identifies the sign of the dominant carrier type. The TEP exhibits linear metallic behavior, with small magnitudes (∼3µV/K), and shows Br implantation to yield p-type material in PPS and n-type material in PAN with extremely low values of mobility (< 10−3 cm2/V sec) and correspondingly very high values of the carrier concentration estimated to be 5 × 1022 cm−3. Results are also reported for the frequency dependence of the AC conductivity and of similarly implanted PPS and PAN samples.

The rate of ethylene hydrogenation has been measured as a function of temperature for a series of Ni1-xCux powder catalysts ( 20 < Tc < 150°C). For each alloy the reaction rises rapidly as Tc is approached. The experimental data have been fit using a model which assumes ethylene to be adsorbed on the alloy surface in two alternative configurations that differ in reactivity, and which attributes variations in reaction rate to changes in the relative populations of these two forms. Below Tc, the more reactive form has the higher total free energy (and therefore the lower equilibrium population) because it has the larger surface magnetic free energy due to interaction with the alloy. Above Tc, where there is no magnetic interaction, the more reactive form has the lower total free energy. Consequently its relative population and the reaction rate are increased.

Ion implantation of selected polymer films leads to the formation of semiconductive (σ ∼ 10−4 S/cm) derivatives, which are presumably partially carbonacėous products derived from gross structural rearrangements. In support of this contention we find that Br-implanted polyacrylonitrile, PAN, exhibits a narrow ESR signal with a g-value of 2.0033, consistent with the presence of free radicals delocalized within a П-electron system. Thermopower measurements reveal that the sign of the majority carrier is dependent upon the molecular structure of the parent polymer. For example, implantation of PAN with Br+ affords n-type derivatives while under similar conditions poly(p-phenylene sulfide), PPS, and poly(2,6-dimethylphenylene-oxide), PPO, yield p-type semiconductors. It is suggested that the majority carriers arethe ions (carbenium ions or carbanions) which are best stabilized by the parent polymerstructure, remnants of which presumably exist after implantation. Resonance and/or inductive effects are invoked to explain the data. For example, the rather electron-rich backbone of PPQ is expected to stabilize holes more effectively than electrons, and the observed p-type behavior is consistent with this prediction.

ABSTRACTIon implantation provides a mechanism for radically modifying the electronic and transport properties of a variety of polymers that are normally insulating. By using masks and tailoring the implanted species and ion energies, conducting paths in an insulating medium can be fabricated between specific reference points, an application of obvious relevance to the microelectronics industry. Specific results are reported for modification of the structure, electrical conductivity, thermoelectric-power, optical transmission and electron spin resonance for several polymers under a variety of implantation conditions. The temperature and frequency dependence of the conductivity suggest a onedimensional variable range hopping mechanism for conduction along the polymer chains. Comparison is made between implantation in the 200 keV and 2 MeV energy ranges.

A fast and efficient procedure for the purification of plasma membranes from Saccharomyces cerevisiae is described. Protoplasts served as starting material. They were coated with cationic silica microbeads. After lysis, the plasma membranes were washed free from debris and cell organelles. This procedure resulted in a high yield (about 85%) of plasma membranes, as judged by measuring vanadate-sensitive ATPase as a plasma membrane marker. The enzyme was enriched 12-fold relative to the homogenate after lysis. Its specific activity was 1.5–2.0 μmol/min per mg protein, the pH optimum was 6.5, and 10 μM vanadate was sufficient to obtain maximum inhibition. Based on the assay of internal markers and electron microscopic studies, we found our preparation essentially free of contamination from other cell organelles.