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ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTheory of the grafted polymer brushS. T. Milner, T. A. Witten, and M. E. CatesCite this: Macromolecules 1988, 21, 8, 2610–2619Publication Date (Print):August 1, 1988Publication History Published online1 May 2002Published inissue 1 August 1988https://pubs.acs.org/doi/10.1021/ma00186a051https://doi.org/10.1021/ma00186a051research-articleACS PublicationsRequest reuse permissionsArticle Views8421Altmetric-Citations1328LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

<div class="htmlview paragraph">A consortium of CONCAWE, EUCAR and the EU Commission's JRC carried out a Well-to-Wheels analysis of a wide range of automotive fuels and powertrains. The study gives an assessment of the energy consumption and greenhouse gas emissions for each pathway. It also considers macroeconomic costs and the market potential of alternative fuels.</div>

The interactions between charged colloidal particles with sufficient strength to cause crystallization are shown to be describable in terms of the usual Debye–Huckel approximation, but with a renormalized charge. The effective charge in general is smaller than the actual charge. We calculate the relationship between the actual charge and the renormalized charge by solving the Boltzmann–Poisson equation numerically in a spherical Wigner–Seitz cell. We then relate the numerical solutions and the effective charge to the osmotic pressure and the bulk modulus of the crystal. Our calculations also reveal that the renormalization of the added electrolyte concentration is negligible, so that the effective charge computations are useful even in the presence of salts.

<div class="htmlview paragraph">Recently, the smokeless rich diesel combustion had been demonstrated [<span class="xref">1</span>]. This can realize smokeless and NOx-less combustion by using a large amount of cooled EGR under a near stoichiometric and even in a rich operating condition. We focus on the effects of reducing diesel combustion temperature on soot reduction. In this paper, the smoke suppression mechanism in the smokeless rich combustion, where the temperature is reduced by higher EGR rate, is analyzed by the following procedure.</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"><span class="li-label">(1)</span><div class="htmlview paragraph">ϕ (equivalence ratio) - T (temperature) map, which shows soot formation tendencies as a function of ϕ and T, was made using zero dimensional calculations with a detailed chemical kinetic model including PAH (polycyclic aromatic hydrocarbons) formation, soot particle nucleation, growth and surface oxidation.</div></li> <li class="list-item"><span class="li-label">(2)</span><div class="htmlview paragraph">The combustion processes of the smokeless and conventional diesel combustion were simulated by the 3D-CFD KIVA2 code.</div></li> <li class="list-item"><span class="li-label">(3)</span><div class="htmlview paragraph">In-cylinder conditions of smokeless and conventional combustion predicted by 3D-CFD were plotted on the ϕ -T map to investigate their behaviors and differences on the map.</div></li> </ol> </div> <div class="htmlview paragraph">The following results were obtained.</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"><span class="li-label">(a)</span><div class="htmlview paragraph">According to 3D-CFD, there is little difference in mixture formation between the smokeless and conventional combustion. It is calculated that the temperature of the smokeless combustion with higher EGR rate is significantly reduced compared with that of conventional one.</div></li> <li class="list-item"><span class="li-label">(b)</span><div class="htmlview paragraph">The smokeless combustion proceeds so as to avoid soot formation regions on the ϕ -T map in contrast to the conventional one, due to this significant temperature reduction.</div></li> <li class="list-item"><span class="li-label">(c)</span><div class="htmlview paragraph">The smoke suppression is realized by the combustion taking place at temperatures below that needed to form soot. In such lower temperature region, the soot formation itself can be suppressed because the reactions forming soot particles from PAH do not progress even if the rich combustion occurs. This shows the reason why the smokeless rich combustion was realized without regard to the improvement of the mixture formation.</div></li> </ol> </div>

OVERVIEW:Eight companies that were Process Effectiveness Network members of the Industrial Research Institute attempted to collectively determine the best practices of the Fuzzy Front End (FFE) of innovation. Comparing one company's processes to those of another proved insurmountable because there was neither a common language nor clear and consistent definition of the key elements of the front end. As a result, the group developed a theoretical construct, defined as the New Concept Development (NCD) model, in order to provide a common language and insights on the front end activities. The model consists of three key parts: five front end elements, the engine that powers the elements, and external influencing factors. Proficiency of the FFE was evaluated at 19 companies by using the NCD model. Highly innovative companies were found to be more proficient in the FFE and in several elements of the NCD model.

Tailoring of porous materials involves not only chemical synthetic techniques for tailoring microscopic properties such as pore size, pore shape, pore connectivity, and pore surface reactivity, but also materials processing techniques for tailoring the meso- and the macroscopic properties of bulk materials in the form of fibers, thin films, and monoliths. These issues are addressed in the context of five specific classes of porous materials: oxide molecular sieves, porous coordination solids, porous carbons, sol−gel-derived oxides, and porous heteropolyanion salts. Reviews of these specific areas are preceded by a presentation of background material and review of current theoretical approaches to adsorption phenomena. A concluding section outlines current research needs and opportunities.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTFluorous Biphase ChemistryIstván T. HorváthView Author Information Corporate Research, Exxon Research and Engineering Company, Route 22 East, Annandale, New Jersey 08801 Cite this: Acc. Chem. Res. 1998, 31, 10, 641–650Publication Date (Web):August 8, 1998Publication History Received12 December 1997Published online8 August 1998Published inissue 1 October 1998https://pubs.acs.org/doi/10.1021/ar970342ihttps://doi.org/10.1021/ar970342iresearch-articleACS PublicationsCopyright © 1998 American Chemical SocietyRequest reuse permissionsArticle Views2937Altmetric-Citations680LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Catalysts,Chemical reactions,Hydrocarbons,Reagents,Solvents Get e-Alerts

A method to grow carbon microtubules with fullerene structure (buckytubes) has been identified. The method consists of the catalytic decomposition of acetylene over iron particles at 700 °C. Carbon microtubules of up to 50 μm in length are synthesized by this method. Electron diffraction and high resolution electron microscopy studies demonstrate that the structure of these microtubules corresponds to the helical structure recently reported by S. Iijima, Nature 354, 56(1991), prepared using an arc-discharge evaporation method.

<div class="htmlview paragraph">Computational fluid dynamic (CFD) simulations that include realistic combustion/emissions chemistry hold the promise of significantly shortening the development time for advanced high-efficiency, low-emission engines. However, significant challenges must be overcome to realize this potential. This paper discusses these challenges in the context of diesel combustion and outlines a technical program based on the use of surrogate fuels that sufficiently emulate the chemical complexity inherent in conventional diesel fuel. The essential components of such a program are discussed and include: (a) surrogate component selection; (b) the acquisition or estimation of requisite elementary chemical kinetic, thermochemical, and physical property data; (c) the development of accurate predictive chemical kinetic models, together with the measurement of the necessary fundamental laboratory data to validate these mechanisms; and (d) mechanism reduction tools to render the coupled chemistry/flow calculations feasible. In parallel to these efforts, the need exists to develop similarly robust models for fuel injection and spray processes involving multicomponent mixtures of wide distillation character, as well as methodologies to include all of these high fidelity submodels in computationally efficient CFD tools. Near- and longer-term research plans are proposed based on an application target of premixed diesel combustion. In the near term, the recommended surrogate components include n-decane, iso-octane, methylcyclohexane, and toluene. For the longer term, n-hexadecane, heptamethylnonane, n-decylbenzene, and 1-methylnaphthalene are proposed.</div>

Carbonate (limestone and dolomite) reservoirs account for approximately 50% of oil and gas production worldwide. However, seismic responses in carbonate rocks are poorly understood. In addition, DHI ranking and AVO classification systems developed for clastic rocks are unlikely to be applicable to carbonate rocks. An accurate and physically sound carbonate rock physics model is needed to address these technical issues.

The ability of Thlaspi goesingense Hálácsy to hyperaccumulate Ni appears to be governed by its extraordinary degree of Ni tolerance. However, the physiological basis of this tolerance mechanism is unknown. We have investigated the role of vacuolar compartmentalization and chelation in this Ni tolerance. A direct comparison of Ni contents of vacuoles from leaves of T. goesingense and from the non-tolerant non-accumulator Thlaspi arvense L. showed that the hyperaccumulator accumulates approximately 2-fold more Ni in the vacuole than the non-accumulator under Ni exposure conditions that were non-toxic to both species. Using x-ray absorption spectroscopy we have been able to determine the likely identity of the compounds involved in chelating Ni within the leaf tissues of the hyperaccumulator and non-accumulator. This revealed that the majority of leaf Ni in the hyperaccumulator was associated with the cell wall, with the remaining Ni being associated with citrate and His, which we interpret as being localized primarily in the vacuolar and cytoplasm, respectively. This distribution of Ni was remarkably similar to that obtained by cell fractionation, supporting the hypothesis that in the hyperaccumulator, intracellular Ni is predominantly localized in the vacuole as a Ni-organic acid complex.

Research Article| March 01, 1998 Hydroplaning of subaqueous debris flows David Mohrig; David Mohrig 1St. Anthony Falls Laboratory, University of Minnesota, Mississippi River at 3rd Avenue S.E., Minneapolis, Minnesota 55414 Search for other works by this author on: GSW Google Scholar Chris Ellis; Chris Ellis 1St. Anthony Falls Laboratory, University of Minnesota, Mississippi River at 3rd Avenue S.E., Minneapolis, Minnesota 55414 Search for other works by this author on: GSW Google Scholar Gary Parker; Gary Parker 1St. Anthony Falls Laboratory, University of Minnesota, Mississippi River at 3rd Avenue S.E., Minneapolis, Minnesota 55414 Search for other works by this author on: GSW Google Scholar Kelin X. Whipple; Kelin X. Whipple 2Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307 Search for other works by this author on: GSW Google Scholar Midhat Hondzo Midhat Hondzo 3School of Civil Engineering, Purdue University, West Lafayette, Indiana 47907-1284 Search for other works by this author on: GSW Google Scholar Author and Article Information David Mohrig 1St. Anthony Falls Laboratory, University of Minnesota, Mississippi River at 3rd Avenue S.E., Minneapolis, Minnesota 55414 Chris Ellis 1St. Anthony Falls Laboratory, University of Minnesota, Mississippi River at 3rd Avenue S.E., Minneapolis, Minnesota 55414 Gary Parker 1St. Anthony Falls Laboratory, University of Minnesota, Mississippi River at 3rd Avenue S.E., Minneapolis, Minnesota 55414 Kelin X. Whipple 2Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307 Midhat Hondzo 3School of Civil Engineering, Purdue University, West Lafayette, Indiana 47907-1284 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1998) 110 (3): 387–394. https://doi.org/10.1130/0016-7606(1998)110<0387:HOSDF>2.3.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation David Mohrig, Chris Ellis, Gary Parker, Kelin X. Whipple, Midhat Hondzo; Hydroplaning of subaqueous debris flows. GSA Bulletin 1998;; 110 (3): 387–394. doi: https://doi.org/10.1130/0016-7606(1998)110<0387:HOSDF>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract We report laboratory experiments that demonstrate that the fronts of subaqueous debris flows can hydroplane on thin layers of water. The hydroplaning dramatically reduces the bed drag, thus increasing head velocity. These high velocities promote sediment suspension and turbidity-current formation. Hydroplaning causes the fronts of debris flows to accelerate away from their bodies to the point of completely detaching from the bodies, producing surging. Instigation of hydroplaning is controlled by the balance of gravity and inertia forces at the debris front and is suitably characterized by the densimetric Froude number. The laboratory flows constrain hydroplaning to cases where the calculated densimetric Froude number is greater than 0.4. The presence of a basal lubricating layer of water underneath hydroplaning debris flows and slides offers a possible explanation for the long run-out distances of many subaqueous flows and slides on very low slopes. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe melt viscosity-molecular weight relationship for linear polymersRalph H. Colby, Lewis J. Fetters, and William W. GraessleyCite this: Macromolecules 1987, 20, 9, 2226–2237Publication Date (Print):September 1, 1987Publication History Published online1 May 2002Published inissue 1 September 1987https://pubs.acs.org/doi/10.1021/ma00175a030https://doi.org/10.1021/ma00175a030research-articleACS PublicationsRequest reuse permissionsArticle Views7240Altmetric-Citations333LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

Research Article| December 01, 1998 Two or four Neoproterozoic glaciations? Martin J. Kennedy; Martin J. Kennedy 1Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095-1567 Search for other works by this author on: GSW Google Scholar Bruce Runnegar; Bruce Runnegar 1Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095-1567 Search for other works by this author on: GSW Google Scholar Anthony R. Prave; Anthony R. Prave 2School of Geography and Geosciences, University of St. Andrews, Fife KY16 9ST, Scotland Search for other works by this author on: GSW Google Scholar K.-H. Hoffmann; K.-H. Hoffmann 3Geological Survey of Namibia, P.O. Box 2168, Windhoek, Namibia Search for other works by this author on: GSW Google Scholar Michael A. Arthur Michael A. Arthur 4Department of Geosciences and Earth System Science Center, Pennsylvania State University, University Park, Pennsylvania 16802 Search for other works by this author on: GSW Google Scholar Geology (1998) 26 (12): 1059–1063. https://doi.org/10.1130/0091-7613(1998)026<1059:TOFNG>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Martin J. Kennedy, Bruce Runnegar, Anthony R. Prave, K.-H. Hoffmann, Michael A. Arthur; Two or four Neoproterozoic glaciations?. Geology 1998;; 26 (12): 1059–1063. doi: https://doi.org/10.1130/0091-7613(1998)026<1059:TOFNG>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract A thick Neoproterozoic carbonate and glaciogenic succession of the southern Congo craton has yielded δ13C and 87Sr/86Sr records through the later Cryogenian (ca. 750–600 Ma) and earlier part of the Terminal Proterozoic (ca. 600–570 Ma). Sizeable negative δ13C excursions (to less than–5‰) occur above each of two glacial intervals and the 87Sr/86Sr values of marine carbonates shift from ∼0.7072 to ∼0.7079 at the upper glacial level. These geochemical constraints provide a Marinoan (younger Varanger) age for the upper glacial interval, previously regarded as a second phase of the Sturtian glaciation. The δ13C record from the Congo craton is therefore incompatible with recent global δ13C syntheses that have identified four or more separate ice ages during the Neoproterozoic. A cladistic analysis of geologic and geochemical characters of 12 Neoproterozoic glacial deposits identifies two distinct groups that are found in a consistent stratigraphic order whenever two glacial units occur within a single succession. We use δ13C and 87Sr/86Sr records from the Congo craton and other key successions to test the null hypothesis that there were only two global glaciations (Sturtian and Marinoan) during the Neoproterozoic. Placing the GSSP (global stratotype section and point) for the base of the Terminal Proterozoic within or just above a cap carbonate of the younger (Marinoan) glaciogenic succession would confine all known Neoproterozoic glaciations to the Cryogenian. The rapid shift in marine 87Sr/86Sr to more radiogenic values during the Marinoan glaciation is opposite that predicted by the snowball Earth scenario which calls for continental runoff to cease during glaciation, resulting in a shift to less radiogenic values. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

&lt;div class="htmlview paragraph"&gt;The development of surrogate mixtures that represent gasoline combustion behavior is reviewed. Combustion chemistry behavioral targets that a surrogate should accurately reproduce, particularly for emulating homogeneous charge compression ignition (HCCI) operation, are carefully identified. Both short and long term research needs to support development of more robust surrogate fuel compositions are described. Candidate component species are identified and the status of present chemical kinetic models for these components and their interactions are discussed. Recommendations are made for the initial components to be included in gasoline surrogates for near term development. Components that can be added to refine predictions and to include additional behavioral targets are identified as well. Thermodynamic, thermochemical and transport properties that require further investigation are discussed.&lt;/div&gt;

In this paper, we examine the melt rheology of well-defined, model polymers where the long chain branching (LCB) is precisely known from the synthesis. All of these are made by the hydrogenation of polybutadiene, but they vary greatly in the level and type of LCB present. We find that all polymers that have LCB show a greater degree of shear thinning than linear chains. This applies both to those with a single branch (stars) and also to those with multiple branches per chain (such as combs). However, only molecules with multiple branches induce extensional thickening in a sample. Only a small amount of these comblike molecules, on the order of 5%, are needed to show this effect. We also show here how a new method of treating the shear data, the so-called Van Gurp−Palmen analysis, can give a more easily interpreted form of the results that can reveal the length and amount of branches in a sample. The insights generated from this work show the importance of access to well-defined polymers with several kinds of branching architecture for the development of a deeper understanding of polymer rheology.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffects of polydispersity in the end-grafted polymer brushS. T. Milner, T. A. Witten, and M. E. CatesCite this: Macromolecules 1989, 22, 2, 853–861Publication Date (Print):February 1, 1989Publication History Published online1 May 2002Published inissue 1 February 1989https://doi.org/10.1021/ma00192a057RIGHTS & PERMISSIONSArticle Views1490Altmetric-Citations293LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

Sp and Ps converted seismic waves at 93 permanent seismic stations are used to image upper mantle velocity discontinuities across the contiguous United States and portions of southeast Canada and northwest Mexico. Receiver functions are calculated with frequency‐domain deconvolution and migrated with 1D models that account for variations in crustal structure and mantle velocities between stations. Strong positive Ps phases from the Moho are observed and agree well with previous crustal thickness estimates. In the tectonically active western U.S., high amplitude, negative Sp phases are interpreted as the lithosphere‐asthenosphere boundary (LAB) at depths of 51–104 km. These phases indicate a large and rapid LAB velocity gradient and are consistent with an anomalously hot asthenosphere that is rich in water or contains partial melt. In the regions of the Phanerozoic southern and eastern U.S where Sp phases are interpretable as the LAB, the discontinuity lies at depths of 75–111 km and is also too sharp to be explained by temperature alone. In contrast, no Sp phases are observed at depths comparable to the base of the thick high velocity lithosphere that lies beneath cratonic North America and certain portions of the Phanerozoic eastern U.S. At these stations, negative Sp phases occur at depths of 59–113 km and are interpreted as the top of a low velocity zone internal to the lithosphere. The absence of an observable LAB discontinuity in regions of thick lithosphere indicates that the LAB velocity gradient is distributed over more than 50–70 km in depth and is consistent with a purely thermal boundary.

Abstract The concept of Mechanical Specific Energy (MSE) has been used effectively in lab environments to evaluate the drilling efficiency of bits. MSE analysis has also been used in a limited manner to investigate specific inefficiencies in field operations.3,4 In early 2004, the operator initiated a pilot to determine whether the concept might be used more broadly by rig-site personnel as a real-time tool to maximize the rate of penetration. The results have exceeded expectations. The average ROP on the six rigs selected for the three-month pilot was increased by 133% and new field records were established on 10 of 11 wells. The MSE surveillance process provides the ability to detect changes in the efficiency of the drilling system, more or less continuously. This has improved performance by 1) allowing the optimum operating parameters to be identified easily, and 2) providing the quantitative data needed to cost-justify design changes to extend the current limits of the system. MSE analysis has resulted in redesign in areas as diverse as well control practices, bit selection, BHA design, makeup torque, directional target sizing and motor differential ratings. The use of MSE surveillance is a key feature in a family of well planning and operational practices that are referred to as the ExxonMobil Fast Drill Process (FDP). These are now being introduced in other operating areas throughout the global organization.

We report the results of light scattering, absorption, excitation, and emission spectroscopy of three polyphenylene vinylene (PPV) derivatives; poly[2-methoxy, 5-(2′-ethyl-hexyloxy-p-phenylene- vinylene] (MEH-PPV), poly[2-butoxy, 5-(2′-ethyl-hexyloxy-p-phenylene-vinylene] (BEH-PPV), and poly[2-dicholestanoxy-p-phenylene-vinylene] (BCHA-PPV) in solution with p-xylene. We find that increasing the size of the solubilizing side chains increases the intrinsic persistence length of the polyphenylene vinylene backbone and that this change in stiffness has dramatic effects on the photoluminescence of polyphenylene vinylene. We have determined the luminescence quantum efficiencies of the polyphenylene vinylene derivatives relative to a known standard, Rhodamine 6G, and find that the photoluminescence can be greatly enhanced by increasing the intrinsic stiffness of the polymer backbone. The stiffest polymer, poly[2-dicholestanoxy-p-phenylene-vinylene] (BCHA-PPV), has a quantum efficiency of 0.66±0.05. The quantum efficiency decreases to 0.22±0.05 for poly[2-butoxy, 5-(2′-ethyl-hexyloxy-p-phenylene-vinylene] (BEH-PPV) and 0.20±0.05 for poly[2-methoxy, 5-(2′-ethyl-hexyloxy-p-phenylene-vinylene] (MEH-PPV), the most coiled derivative. Excitation profiles of the three derivatives also show an increase in nonradiative decay at high energies when the polymer assumes a more coiled comformation. Thus, the quantum yields are dependent on pump energy.