Abstract A novel end-reactive AB4 dendron with four phenolic coupling sites and a benzyl alcohol functionality at the focal point has been prepared by a chemoselective amidation process that requires no functional group protection. The usefulness of the end-reactive dendron for the accelerated synthesis of dendritic polymers has been demonstrated in the preparation of several poly(amide-ether) dendritic macromolecules with carboxylate chain-ends. The new dendritic polymers have been characterized by NMR and MALDI mass spectrometry, size exclusion chromatography, and thermal analysis methods.

New mid UV resist systems based on poly(p-vinylbenzoates) sensitized with diphenyl-4-thiophenoxyphenylsulfonium hexafluoroantimonate are described. t-Butyl, cyclohexenyl, a-methylbenzyl, and a-methylallyl esters are converted upon postbake to poly(p-vinylbenzoic acid) through thermolysis reaction catalyzed by the photochemically generated Bronsted acid, inducing a large change in the polarity of the repeating units. Thus, development in aqueous base such as MF312/water or alcohol provides a positive tone image of the mask, while the use of a nonpolar organic developer allows a negative tone imaging. Because the glass transition temperature of poly(p-vinylbenzoic acid) is ca. 250° C, the negative image is devoid of thermal flow to this temperature even without any hardening processes. Another interesting feature of the benzoate resists is their high opacity in the deep UV region. The optical density of a 1μ thick film of poly(p-vinylbenzoic acid) is 3.5 at 254 nm and the benzoate polymers are as absorbing as the acid polymer. This high deep UV absorption of the resin necessitates the imaging above 300 nm for good light penetration (or by e-beam or X-ray) and makes the use of this resist as an imaging layer in the PCM scheme very attractive. This imaging layer is especially useful when employed in conjunction with a planarizing layer absorbing above 240 nm (for example, PMGI) as addition of a dye is not required.

Further investigation of the mesomorphism of hydrogen bonded complexes formed between alkoxystilbazoles and benzenedicarboxylic acids has led to a reinterpretation of the phase behaviour. We have found unexpectedly that the most stable complex is at an equimolar ratio.

The search for advanced resists that can provide the high density of circuits and high throughput required for the new generations of microelectronic devices requires that highly stable chemically amplified materials be developed. In view of the high susceptibility of resists based on photoacid generation to environmental contamination, resulting in lessened performance, a program aiming at the development of chemically amplified resists utilizing photobase generation has been undertaken. In a first approach, the photogenerated amines we developed in the first stage of this project were used as catalysts for the decarboxylation of totally new resist systems containing active carboxylic acid pendant groups. The resists materials could be developed to afford negative tone images through wet development in aqueous base, or positive tone images through dry development using a gas-phase silylation reaction followed by oxygen plasma etching. The first patterning experiments carried out with two new resists utilizing photogenerated base have confirmed the validity of the approach.

Abstract Die Cinchona Alkaloide (IIa)‐(IId) lassen sich befriedigend über ihre Vinylgruppen mit den Thiolgruppen enthaltenden vernetzten Polymeren (I) verknüpfen; die so gebildeten Produkte (III)‐(VIII) werden dann eingesetzt, um die Michael‐Additionsreaktionen der Verbindungen (IXa), (IXb) bzw. (XIII) mit dem Enon (X) [= Reaktionen (1)‐(3) bzw. (l′)‐(3′)] bzw. (XV) mit Nitrostyrol (XVI) [= Reaktion (4) bzw. (4′)]‐ unter Bildung der Produkte (XI), (XII), (XIV) bzw. (XVII) zu katalysieren.

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTLight-Driven Catalysis within Dendrimers: Designing Amphiphilic Singlet Oxygen SensitizersStefan Hecht and Jean M. J. FréchetView Author Information Department of Chemistry, University of California Berkeley, California 94720-1460 Cite this: J. Am. Chem. Soc. 2001, 123, 28, 6959–6960Publication Date (Web):June 20, 2001Publication History Received24 April 2001Published online20 June 2001Published inissue 1 July 2001https://pubs.acs.org/doi/10.1021/ja016076shttps://doi.org/10.1021/ja016076srapid-communicationACS PublicationsCopyright © 2001 American Chemical SocietyRequest reuse permissionsArticle Views1383Altmetric-Citations100LEARN 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-AlertscloseSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Catalysts,Dendrons,Hydrocarbons,Hydrophobicity,Redox reactions Get e-Alerts

Abstract Die Methanolyse der Halogenide (Ia), (Ib) (bekannte Verbindungen), (Ic), (VIIc) und (VIId) unter verschiedenen Bedingungen [ a), b), c) bzw. d)] wird untersucht.

The ability of a dendritic shell to afford site isolation to a porphyrin core was evaluated using electron-transfer experiments with a series of porphyrin-core dendrimers. Cyclic voltammograms show that surrounding a porphyrin site with even a small generation (G ∼ 2) dendrimer can significantly lower the rate of interfacial electron transfer, ostensibly by decreasing the proximity of the porphyrin core to the electrode surface. This inhibition of electron transfer is more pronounced when larger generation dendrimers are employed. While a significant measure of site isolation is achieved with respect to an electrode surface, no hindrance to penetration of a small molecule is afforded by the dendritic shell surrounding the porphyrin core, an encouraging result if dendrimers are to be designed as macromolecular hosts with a functioning catalyst at the core. Stern−Volmer analysis was used to investigate the accessibility of a small molecule, benzylviologen, to the porphyrin core. For generations 1−3, the den...

A macroporous poly(styrene-co-divinylbenzene) rod has been prepared by a free-radical polymerization of a mixture containing monomers, initiator, and porogenic solvent in the confines of a chromatographic column and used for the first time in the very fast reversed-phase HPLC of proteins. Characterization of the pore structure of the continuous rod by mercury intrusion porosimetry revealed a large volume of pores with a diameter of about 1 micron to pores below 100 nm. Size exclusion chromatography and scanning electron microscopy confirmed the unusual pore size distribution. The presence of large pores make the rod easily permeable to eluents, and therefore, the back pressure of the rod column is modest even at high flow rates. The efficiency of the polymerized column is almost independent of the flow rate. The slope of the line showing capacity factor vs composition of the mobile phase was determined for several proteins, and a gradient for the separation of their mixtures was developed. Excellent separation was achieved even at a high flow rate of 25 mL/min as documented by the resolution data. Tripling the length of the column did not improve the column resolution in protein separation.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTConcurrent stabilization and imaging of a novel polymer for second harmonic generation via in situ photopolymerizationJody E. Beecher, Jean M. J. Frechet, Craig S. Willand, Douglas R. Robello, and David J. WilliamsCite this: J. Am. Chem. Soc. 1993, 115, 25, 12216–12217Publication Date (Print):December 1, 1993Publication History Published online1 May 2002Published inissue 1 December 1993https://pubs.acs.org/doi/10.1021/ja00078a091https://doi.org/10.1021/ja00078a091research-articleACS PublicationsRequest reuse permissionsArticle Views98Altmetric-Citations12LEARN 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 ISSUEPREVArticleNEXTHydrogen-bonded liquid crystals. Novel mesogens incorporating nonmesogenic bipyridyl compounds through complexation between hydrogen-bond donor and acceptor moietiesTakashi Kato, Jean M. J. Frechet, Paul G. Wilson, Takeshi Saito, Toshiyuki Uryu, Akira Fujishima, Chihiro Jin, and Fumiko KaneuchiCite this: Chem. Mater. 1993, 5, 8, 1094–1100Publication Date (Print):August 1, 1993Publication History Published online1 May 2002Published inissue 1 August 1993https://pubs.acs.org/doi/10.1021/cm00032a012https://doi.org/10.1021/cm00032a012research-articleACS PublicationsRequest reuse permissionsArticle Views1441Altmetric-Citations253LEARN 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 ISSUEPREVArticleNEXTChemical modification of polystyrene resins. Approaches to the binding of reactive functionalities to polystyrene resins through a two-carbon spacerGraham D. Darling and Jean M. J. FrechetCite this: J. Org. Chem. 1986, 51, 12, 2270–2276Publication Date (Print):June 1, 1986Publication History Published online1 May 2002Published inissue 1 June 1986https://doi.org/10.1021/jo00362a020RIGHTS & PERMISSIONSArticle Views348Altmetric-Citations35LEARN 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

Abstract Size monodispersed poly(styrene-divinylbenzene) particles with a variety of pore size and pore size distribution were prepared by a multi-step swelling and polymerization method and utilized as packing materials in high performance liquid chromatography (HPLC). As an application of these packing materials, separation of carbon clusters C60 and C70 were examined in a mixture of hexane and benzene and an influence of the pore size and the pore size distribution of the polymer-based packing materials on the separation was investigated. Although carbon clusters are sterically bulky molecules, packing materials with smaller pores showed better separation than those with larger pores. Completely separated peaks and the good peak shape suggest possible isolation of carbon clusters on relatively cheap polymer-based packing materials.

Abstract Aus handelsüblichem Polystyrol, vernetzt mit Divinylbenzol, wird nach Merrifield das Chlormethylderivat (Ia), in dem 10‐15% der Einheiten p‐chlormethyliert sind, dargestellt.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTBromination and lithiation: two important steps in the functionalization of polystyrene resinsM. Jean Farrall and Jean M. J. FrechetCite this: J. Org. Chem. 1976, 41, 24, 3877–3882Publication Date (Print):November 1, 1976Publication History Published online1 May 2002Published inissue 1 November 1976https://pubs.acs.org/doi/10.1021/jo00886a023https://doi.org/10.1021/jo00886a023research-articleACS PublicationsRequest reuse permissionsArticle Views2604Altmetric-Citations324LEARN 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