Abstract Novel separation media for the direct injection of complex samples have been prepared from porous 10 μrn uniformly sized poly(glycidyl methacrylate-co-ethylene dimethacrylate) beads. The simple hydrolysis of all epoxide groups produces beads with separation characteristics similar to those of some restricted access media. The use of a novel size-specific modification of porous materials provides separation media with even better chromatographic properties. In this approach, hydrolysis of the epoxide groups to diols can be carried out exclusively within the large pores of the medium through the use of a polymeric catalyst. The epoxide groups remaining in the small pores after hydrophilization of the large pores were then transformed either to hydrophobic C18 or phenyl groups, or to more polar diethylamino groups. Due to the size specific characteristics of the modification process used in the preparation of the beads which renders the large pores hydrophilic, no protein interaction with the surface of the pores was observed, the protein recovery was high, and the retention times of proteins and of a non-retained probe was similar. Examples of separations of drugs from plasma document the good efficiency and excellent selectivity of columns packed with the novel separation medium.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSolid-phase synthesis of oligosaccharides. I. Preparation of the solid support. Poly[p-(1-propen-3-ol-1-yl)styrene]Conrad Schuerch and Jean M. FrechetCite this: J. Am. Chem. Soc. 1971, 93, 2, 492–496Publication Date (Print):January 1, 1971Publication History Published online1 May 2002Published inissue 1 January 1971https://pubs.acs.org/doi/10.1021/ja00731a031https://doi.org/10.1021/ja00731a031research-articleACS PublicationsRequest reuse permissionsArticle Views1278Altmetric-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 ISSUEPREVArticleNEXTAdditions and Corrections - Chemical Synthesis and Structure Proof of a Stereoregular Linear Mannan, Poly-α-(1→6')-anhydro-D-mannopyranose Jean Frechet and Conrad SchuerchCite this: J. Am. Chem. Soc. 1969, 91, 20, 5697Publication Date (Print):September 1, 1969Publication History Published online26 April 2004Published inissue 1 September 1969https://pubs.acs.org/doi/10.1021/ja01048a606https://doi.org/10.1021/ja01048a606research-articleACS PublicationsRequest reuse permissionsArticle Views33Altmetric-Citations-LEARN 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

A variety of substituted triphenylamine derivatives were prepared in nearly quantitative yields by the use of 18-crown-6 as a phase transfer catalyst under the Ullmann reaction conditions.

Capillaries with inner diameters of 550 microm have successfully been packed with 1.5-microm octadecyl silica particles using frits made of macroporous polymers by the UV photopolymerization of a solution of glycidyl methacrylate and trimethylolpropane trimethacrylate. This type of frit is found superior to one made of low-melting point poly(styrene-co-divinylbenzene) beads. Bubble formation is not observed to occur within these capillary columns under our experimental conditions. Separations can be achieved with sample injection volumes as high as 1 microL. To demonstrate its semipreparative use, a mixture of 500 nL of taxol (20 mM) and its precursor, baccatin III (30 mM), is separated using such a column with a Tris buffer.

Abstract For Abstract see ChemInform Abstract in Full Text.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTApplication of phase-transfer catalysis to the chemical modification of cross-linked polystyrene resinsJean M. J. Frechet, Marc D. De Smet, and M. Jean FarrallCite this: J. Org. Chem. 1979, 44, 11, 1774–1779Publication Date (Print):May 1, 1979Publication History Published online1 May 2002Published inissue 1 May 1979https://pubs.acs.org/doi/10.1021/jo01325a006https://doi.org/10.1021/jo01325a006research-articleACS PublicationsRequest reuse permissionsArticle Views430Altmetric-Citations108LEARN 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 The stability of a hydrogen-bonded complex built through inter-molecular hydrogen bonding between carboxylic acid and pyridine fragments has been examined using infrared spectroscopy. Infrared spectra as a function of temperature have been recorded for the 1:1 complex of 4-hexyloxybenzoic acid and trans-4-propoxy-4′-stilbazole from the crystalline state to the isotropic state. A dependence of the stability of the hydrogen bond on molecular orientation is observed clearly in the infrared spectra. The spectra also suggest that the hydrogen bond is an unionized type with a double minimum potential energy.

Abstract The chemical reactivity of a new elastomer based on brominated poly(isobutylene- co -4-methylstyrene) in electrophilic additions to olefins has been investigated using model compounds as well as appropriate polymers. The reactions catalyzed by zinc salts are influenced by the solubility as well as the composition of the catalyst. While the reactivity of zinc bromide is limited by its low solubility in nonpolar medium, zinc oxide and zinc stearate can afford excellent results once an induction period has elapsed. The induction period likely corresponds to the formation of more reactive zinc based moieties through interchange reactions with the benzylic bromide groups. The mechanism of the addition process involves initial formation of carbocationic complexes with the zinc salts, followed by addition to the double bonds of the olefins. The products resulting from these additions have been characterized by NMR as well as gas chromatography-mass spectrometry. A comparison of potential crosslinking processes involving olefin addition or electrophilic aromatic substitution reactions shows that the former process is preferred. The findings of this study are directly applicable to the co-curing of elastomers based on brominated poly-(isobutylene- co -4-methylstyrene) with polyolefins.

Near-field scanning optical microscopy (NSOM) has been used to investigate the photophysical characteristics of first- to fourth-generation (G1 to G4) light-harvesting dendrimer thin films containing coumarin-343 and coumarin-2 as the core and peripheral chromophores, respectively. Thin film photoluminescence (PL) spectra exhibit a significant red shift in the lower generations (G1, G2, and G3) as compared to their respective solution PL spectra, implying the formation of excimers. Spatially resolved PL NSOM images exhibit pronounced nanoscopic domains in G1, which become more homogeneous in higher generations due to site-isolation of the core chromophore. G4 exhibits complete site-isolation for these light-harvesting dendrimer films.

ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTDivergent Synthesis of Dendronized Poly(p-hydroxystyrene)Scott M. Grayson and Jean M. J. FréchetView Author Information Center for New Directions in Organic Synthesis,† Department of Chemistry, University of California, Berkeley, California 94720-1460, and Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 Cite this: Macromolecules 2001, 34, 19, 6542–6544Publication Date (Web):August 11, 2001Publication History Received23 April 2001Published online11 August 2001Published inissue 1 September 2001https://pubs.acs.org/doi/10.1021/ma010698ghttps://doi.org/10.1021/ma010698grapid-communicationACS PublicationsCopyright © 2001 American Chemical SocietyRequest reuse permissionsArticle Views880Altmetric-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-AlertscloseSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Dendrons,Materials,Organic reactions,Physical and chemical properties,Polymers Get e-Alerts

Copolymers of PEG and analogs of second generation dendrimer have been synthesized and characterized. Normal polyether dendrimers can be replaced by other branched structures with similar physical properties. Incorporation of fluorinated chains enhance the hydrophobicity of the dendrimer. Attachment of long alkyl chains to dendrimers to achieve the same goal is under investigation and applications of the amphiphilic copolymers are being explored.

Abstract Methyl‐a‐D‐glucopyranosid (II) kondensiert mit dem Harz (I), das Vinylbenzaldehydeinheiten enthält, in siedendem Dioxan in Gegenwart von p‐Toluolsulfonsäure zur polymeren Verbindung (III).

A reactive triallyl chloride moiety was prepared as a suitable core for aliphatic polyether dendrons. In addition to allowing access to fourth generation dendrimers, this core contains three alkene functionalities that can be modified after dendrimer formation and used for further dendritic growth.

Since the concept of chemical amplification in microlithography was first developed in the early 1980`s, a number of new resists based on acid catalyzed thermolysis have been developed. This report describes the first chemically amplified resist operating on the basis of photogenerated base. The concept is demonstrated with poly(2-cyano-2(p-vinylphenyl)butanoic acid) which decarboxylates readily under basic conditions. A resist system consisting of this polymer and an amine photogenerator, bis[((2,6-dinitrobenzyl)oxy)carbonyl]hexan-1,6-diamine, was formulated. The sensitivity of this resist is 1.4 mJ/cm{sup 2} with a contrast ({gamma}) of 13.7. This high sensitivity confirms that chemical amplification is achieved as the photogenerated base is not consumed in the overall decarboxylation process. The mechanistic insights of the decarboxylation reaction in a polymer matrix will also be discussed.