Abstract The hydride reagent (I) formed from LiAlH 4 , dimethylphenol, and polymer‐bound l‐ephedrine reduces acetophenone (II) enantioselectively to form (III).
Abstract Die K0enigs‐Knorr‐Kondensation (Helferich‐Modifikation) des α‐Glucosylpyranosylbromides (I) mit den anomeren galacto‐Nitrozuckern (IIa) bzw. (IIb) liefert die Disaccharide (IIIa) bzw. (IIIb); mit den gluco‐Nitrozuckern (IVa) bzw. (IVb) werden jeweils Gemische der α‐ (vorherrschender Anteil) und β‐glykosidisch verknüpften Disaccharide erhalten: a) Das Produktgemisch (Va) ist schwertrennbar; b) im Falle der Reaktion von (I) mit (IVb) kann nur das α‐verknüpfte Produkt (Vb) isoliert werden.
A new approach to the controlled synthesis of multicomponent dendrimers is presented, in which three oligonucleotide-dendron conjugates were synthesized using solid phase techniques and hybridized to create a second generation polyester dendrimer with DNA as a core and bearing two types of peripheral functional groups.
The process, chemistry, and characterization of the silylation and dry-development of acid catalyzed resist is described. The resist is sensitive to deep-UV, x ray, and e-beam exposure and its sensitivity can be tailored by the relative concentration of its components. The resist is positive or negative for dry or wet development, respectively. Two silylation agents were studied: Hexamethyldisilazane (HMDS) and N,N-Dimethylaminotrimethylsilane (DMATMS). The silylation was characterized by Fourier-transform-infrared (FTIR) transmission spectroscopy and Rutherford-backscattering spectrometry (RBS). FTIR revealed the total number of OH and SiO bonds, while RBS revealed the composition profile in various regions of the resist. The silylation by HMDS was not well controlled and was characterized by a large incubation period followed by fast penetration. The DMATMS silylation process, however, was well controlled and reproducible. The penetration of the silicon atoms monotonically increased with time until it reached saturation. Films patterned by deep-UV (254 nm) exposure were silylated with DMATMS and were etched by an oxygen plasma in a magnetron ion etcher (MIE). The etch rate of the oxygen plasma was characterized for the unexposed, silylated regions, as well as for the exposed, unsilylated regions. The optimized dry-development process is described and SEM cross sections of lines as narrow as 0.4 micrometers wide are presented.
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
In this paper the design of radiation sensitive polymeric imaging systems is reviewed. Advances in design have led to systems that function on the basis of radiation‐induced changes in the polarity of polymer repeating units rather than cross‐linking. These new systems offer improved resolution, since they do not swell during development. Improvement in sensitivity has been achieved by designing systems that incorporate chemical amplification. The design principles leading to amplification and examples of systems that demonstrate amplification are presented.
A series of cyclopolymers designed for use in 193 nm photoresist materials has been synthesized and characterized. These novel materials that provide both optical transparency at 193 nm and also reactive ion etch resistance are obtained via cyclopolymerization of suitably designed bifunctional monomers incorporating acrylic and olefinic double bonds. The approach is highly versatile and allows the preparation of a broad array of structurally related materials with different substituents providing the imaging function and the desired level of etch resistance. The cyclopolymerization process is experimentally forgiving, enabling control of the molecular weight as well as the incorporation of comonomers such as acrylic acid or maleic anhydride to fine-tune the lithographic properties.
A chemically amplified resist material consisting of poly[2-cyano-2-(p-vinylphenyl) butanoic acid] and bis[[(2-nitrobenzyl)oxy]carbonyl]hexane-1,6-diamine has been designed and tested in negative and positive tone imaging. The resist operates on the principle of base-catalyzed decarboxylation. Amine generated by exposure to UV radiation catalyzes the thermal loss of carbon dioxide from the polymer side chain thereby changing the solubility of the resist film in aqueous base developer. Image reversal is accomplished by in situ silylation of the exposed and thermolyzed film followed by dry development using an oxygen plasma. The resist shows high sensitivity to deep UV irradiation, ca. 10 mJ/cm2, while image contrast is excellent.
Abstract The preparation of monodisperse polymer particles formed by a dispersion copolymerization of a system containing styrene, butyl methacrylate, and nonpolymerizable dyes has been studied. Both the polarity of the ethanol–water dispersion medium and the polymerization rate were found to have a significant effect on the particle size. Experimental conditions have been determined that enable the preparation of colored beads having a narrow size distribution. While the benzoyl peroxide initiated polymerization is seriously inhibited by the presence of dyes, polymerization with azobisisobutyronitrile in presence of the black dye Nigrosin affords monodisperse beads in a high yield. © 1995 John Wiley & Sons, Inc.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMolecular Ball Bearings: The Unusual Melt Viscosity Behavior of Dendritic MacromoleculesCraig J. Hawker, Peter J. Farrington, Michael E. Mackay, Karen L. Wooley, and Jean M. J. FrechetCite this: J. Am. Chem. Soc. 1995, 117, 15, 4409–4410Publication Date (Print):April 1, 1995Publication History Published online1 May 2002Published inissue 1 April 1995https://pubs.acs.org/doi/10.1021/ja00120a028https://doi.org/10.1021/ja00120a028research-articleACS PublicationsRequest reuse permissionsArticle Views782Altmetric-Citations206LEARN 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
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTNeutron Reflectivity and Structure of Polyether Dendrimers as Langmuir FilmsP. M. Saville, P. A. Reynolds, J. W. White, C. J. Hawker, J. M. J. Frechet, K. L. Wooley, J. Penfold, and J. R. P. WebsterCite this: J. Phys. Chem. 1995, 99, 20, 8283–8289Publication Date (Print):May 1, 1995Publication History Published online1 May 2002Published inissue 1 May 1995https://pubs.acs.org/doi/10.1021/j100020a062https://doi.org/10.1021/j100020a062research-articleACS PublicationsRequest reuse permissionsArticle Views280Altmetric-Citations97LEARN 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 options Get e-Alerts
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSupramolecular Liquid-Crystalline Complexes Exhibiting Room-Temperature Mesophases and Electrooptic Effects. Hydrogen-Bonded Mesogens Derived from Alkylpyridines and Benzoic AcidsTakashi Kato, Mitsuo Fukumasa, and Jean M. J. FrechetCite this: Chem. Mater. 1995, 7, 2, 368–372Publication Date (Print):February 1, 1995Publication History Published online1 May 2002Published inissue 1 February 1995https://pubs.acs.org/doi/10.1021/cm00050a021https://doi.org/10.1021/cm00050a021research-articleACS PublicationsRequest reuse permissionsArticle Views475Altmetric-Citations115LEARN 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
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTControl of Porous Properties and Surface Chemistry in "Molded" Porous Polymer Monoliths Prepared by Polymerization in the Presence of TEMPOEric C. Peters, Frantisek Svec, Jean M. J. Fréchet, Camilla Viklund, and Knut IrgumView Author Information Department of Chemistry, University of California, Berkeley, California 94720-1460 Department of Analytical Chemistry, University of Umeå, Umeå S-901 87, Sweden Cite this: Macromolecules 1999, 32, 19, 6377–6379Publication Date (Web):August 19, 1999Publication History Received9 April 1999Revised16 June 1999Published online19 August 1999Published inissue 1 September 1999https://pubs.acs.org/doi/10.1021/ma990538thttps://doi.org/10.1021/ma990538trapid-communicationACS PublicationsCopyright © 1999 American Chemical SocietyRequest reuse permissionsArticle Views835Altmetric-Citations102LEARN 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:Catalyst supports,Monomers,Polymerization,Polymers,Radical polymerization Get e-Alerts
A continuous rod of porous poly(glycidyl methacrylate-co-ethylene dimethacrylate) has been prepared by a free radical polymerization within the confines of a 300 x 8 mm I.D. chromatographic column. The epoxide groups of the rod have been modified by a reaction with diethylamine that affords ionizable functionalities required for the ion-exchange chromatographic mode. The properties of this rod column have been characterized and the column has been used successfully for the chromatographic separation of proteins. The column exhibits a dynamic capacity that exceeds 300 mg at a flow velocity of 200 cm/min. An excellent selectivity allows the separation of up to 300 mg of a protein mixture in a single run.
Read moreAbstract The dispersion copolymerization of styrene and butyl methacrylate in ethanol‐water medium to afford micrometer‐size monodisperse beads has been investigated. Hydroxypropyl cel‐lulose, poly (acrylic acid), and poly (vinylpyrrolidone) have been used as steric stabilizers, benzoyl peroxide and azobisisobutyronitrile as initiators. A novel steric stabilizing system consisting of a mixture of poly (acrylic acid) and hydroxypropyl cellulose has also been shown to lead to monodisperse beads for which the surface charge can be controlled by the relative ratio of steric stabilizers. The effect of several variables, such as the solvency of the medium, the concentration of co‐monomers, the reaction temperature, and the type of steric stabilizer and initiator used on the bead size and size distribution are discussed. © 1995 John Wiley & Sons, Inc.
Read moreA novel class of photoiabile amino protecting groups, based on [(3′,5′-dimethoxybenzoinyl)oxy]carbonyl groups, is presented and their scope and versatility demonstrated by the photogeneration of free primary and secondary amines.
Read moreADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTKinetic Control of Pore Formation in Macroporous Polymers. Formation of "Molded" Porous Materials with High Flow Characteristics for Separations or CatalysisFrantisek Svec and Jean M. J. FrechetCite this: Chem. Mater. 1995, 7, 4, 707–715Publication Date (Print):April 1, 1995Publication History Published online1 May 2002Published inissue 1 April 1995https://pubs.acs.org/doi/10.1021/cm00052a016https://doi.org/10.1021/cm00052a016research-articleACS PublicationsRequest reuse permissionsArticle Views1458Altmetric-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 InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
Read moreThe formation of ether bonds by reaction of benzylic bromides with phenyl silyl ethers has been investigated as an alternative to the classical Williamson ether synthesis. The reaction has been applied to the synthesis of high-molecular-weight polyethers that are not readily obtained by other methods. An AB-type monomer, such as 3-bromomethyl-trimethylsilyloxybenzene, reacts in the presence of a stoichiometric amount of carbonate to afford the corresponding polyether with molecular weight as high as 300 000 depending on the reaction conditions. While the polyetherification reaction of 3-bromomethyi phenol under classical conditions leads to polymers rich in C-alkylated and branched units, conditions may be found to reduce or prevent C-alkylation and branching with 3-bromomethyl-trimethylsilyloxybenzene. The reaction is believed to proceed via activation of the OSi bond through carbonate addition to afford a species containing a pentacoordinate silicon. The role of carbonate and the stoichiometry and mechanism of the reaction have been investigated with the help of a model etherification reaction.
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