ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTSynthesis and Catalytic Activity of Unimolecular Dendritic Reverse Micelles with "Internal" Functional GroupsMarcelo E. Piotti, Felix Rivera,, Risha Bond, Craig J. Hawker, and Jean M. J. FréchetView Author Information IBM Almaden Research Center 650 Harry Road, San Jose, California 95120 Department of Chemistry, University of California Berkeley, California 94720-1460 Cite this: J. Am. Chem. Soc. 1999, 121, 40, 9471–9472Publication Date (Web):September 23, 1999Publication History Received7 June 1999Published online23 September 1999Published inissue 1 October 1999https://pubs.acs.org/doi/10.1021/ja991879phttps://doi.org/10.1021/ja991879prapid-communicationACS PublicationsCopyright © 1999 American Chemical SocietyRequest reuse permissionsArticle Views1180Altmetric-Citations186LEARN 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:Chemical structure,Dendrons,Functional groups,Organic compounds,Transfer reactions Get e-Alerts
ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionORIGINAL ARTICLEThis notice is a correctionOrganic Thin Film Transistors from a Soluble Oligothiophene Derivative Containing Thermally Removable Solubilizing Groups [J. Am. Chem. Soc.2004, 126, 1596−1597].Amanda R. Murphy, Jean M. J. Fréchet, Paul Chang, Josephine Lee, and Vivek SubramanianCite this: J. Am. Chem. Soc. 2004, 126, 37, 11750Publication Date (Web):August 25, 2004Publication History Published online25 August 2004Published inissue 1 September 2004https://pubs.acs.org/doi/10.1021/ja0408193https://doi.org/10.1021/ja0408193correctionACS PublicationsCopyright © 2004 American Chemical Society. This publication is available under these Terms of Use. Request reuse permissions This publication is free to access through this site. Learn MoreArticle Views569Altmetric-Citations6LEARN 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 PDF (14 KB) Get e-Alertsclose Get e-Alerts
An alpha,alpha-dimethyl-3,5-dimethoxybenzyloxycarbonyl (DDZ)-protected amine monolayer can be selectively deprotected by the application of a voltage bias from a conducting AFM tip to afford localized nanoscale patterns that can be visualized by self-assembly of dendritic molecular objects with terminal carboxylic acid groups and different aspect ratios.
The synthesis of novel dendrimers functionalized with laser dyes both at the periphery and at the core, along with all relevant model compounds necessary for accurate photophysical studies, is described. The utilized synthetic strategy involves a modular approach in which a variety of peripheral and core moieties can be placed on a dendritic structure bearing electrophilic peripheral groups and a nucleophilic core. Specifically, the target macromolecules required functionalization with the laser dyes coumarin 2 (periphery) and coumarin 343 (core) due to the possibility of energy transfer from the former to the latter dye. In addition, the preparation of a novel, highly soluble and reactive hypermonomer utilized in the rapid and efficient synthesis of high-generation dye-labeled dendrimers and model compounds is outlined.
Abstract : This report explores the preparation of photovoltaic devices with enhanced light harvesting characteristics. In particular plastic hybrid photovoltaic devices based on electroactive polymer/inorganic components are studied. Significant advances were made in polymer-nanocrystal as well as polymer-titania photovoltaic devices through the development of novel polythiophenes that enhance both the interface and electronic communications between the polymer and the inorganic.
The structural and mechanical properties of Langmuir-Blodgett monolayer and multilayer films of 3",4""-didecyl-5,2'; 5',2"; 5",2'''; 5''',2""; 5"",2'''''; 5''''',2"""-heptathiophene-4'''-acetic acid on mica have been studied by atomic force microscopy (AFM) as a function of humidity, temperature, and applied force. The molecules orient with the carboxylic acid group pointing toward the mica surface and expose the alkyl side chains to the air interface. As the load applied by the AFM tip increases, the film is compressed easily from an initial height of 2 to 1.2 nm. After compression the films can support much higher loads without loss of height. The state of aggregation of the molecules was found to be sensitive to the environmental humidity, which induced reversible changes. Annealing the samples with monolayer or multilayer films resulted in irreversible changes when the temperature exceeded approximately 100 degrees C.
Unser gestiegenes Verständnis der Struktur-Eigenschafts-Beziehungen einiger ausgewählter Biomakromoleküle hat – zusammen mit unseren verbesserten Fertigkeiten, Makromoleküle mit einer strukturellen Genauigkeit, die der der Proteine nahekommt, herzustellen – den Horizont zu einem neuen Forschungsbereich geöffnet, der die Chemie und die Materialwissenschaften mit der Biologie verbindet. Während die Natur im Laufe der Evolution kontinuierlich Prozesse wie Energietransfer oder Katalyse durch Selbstreplikations- und Reparaturfunktionen vervollkommnen konnte, hängen die Zugänglichkeit und der Nutzen synthetischer Makromoleküle in erster Linie von unserem präparativen Können und von unserer Fähigkeit ab, Struktur und Funktion in unserem Design miteinander zu verbinden. So können wir Nutzen aus unserem Verständnis der natürlichen Systeme ziehen, um strukturelle Charakteristika nachzuahmen und Funktionen zu optimieren. Um Eigenschaften zu realisieren, die im nichtorganisierten isotropen Zustand (bulk) unerreichbar wären, nutzen zahlreiche biologische Systeme das Isolationskonzept, bei dem ein aktives Zentrum oder eine katalytisch aktive Stelle innerhalb eines Proteins eingekapselt wird. Diesem Konzept folgend wurde die Fähigkeit dendritischer Hüllen, funktionelle Zentren einzuschließen und so spezifische, isolierte Nanoumgebungen zu schaffen, die die molekularen Eigenschaften des Zentrums beeinflussen, intensiv erforscht. Unter Nutzung der besonderen Eigenschaften der Dendrimerarchitektur wurden aktive Zentren mit photophysikalischen, photochemischen, elektrochemischen oder katalytischen Eigenschaften im Mittelpunkt des Dendrimers (als Dendrimerkern) platziert. Eine solche Anwendung des Isolationskonzeptes auf Probleme in der Materialforschung ist auf lange Sicht sehr viel versprechend, und bereits heute zeichnen sich erste Anwendungen u. a. beim Design verbesserter, optoelektronischer Bauelemente ab. Dieser Aufsatz konzentriert sich auf die Entwicklung dieses natürlichen Designprinzips, das wesentlich dazu beiträgt, die Lücke zwischen zwei historisch so unterschiedlichen Disziplinen wie der Biologie und den Materialwissenschaften zu schließen. Aktuelle Fortschritte sowohl in der Synthese von dendritisch eingekapselten Molekülen als auch in der Untersuchung ihrer Eigenschaften mit Hilfe einer Vielzahl von unterschiedlichen Methoden werden behandelt. Aus diesen Studien ergeben sich Erkenntnisse für viele Anwendungen, die vom Design künstlicher Enzyme und Katalysatoren sowie supermolekularer Lichtsammelsysteme bis hin zum Aufbau von isolierten molekularen Drähten, Leuchtdioden und Glasfaseroptiken reichen.
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTAn Alternative Synthetic Approach toward Dendritic Macromolecules: Novel Benzene-Core Dendrimers via Alkyne CyclotrimerizationStefan Hecht and Jean M. J. FréchetView Author Information Department of Chemistry, University of California Berkeley, California 94720-1460 Cite this: J. Am. Chem. Soc. 1999, 121, 16, 4084–4085Publication Date (Web):April 13, 1999Publication History Received7 December 1998Published online13 April 1999Published inissue 1 April 1999https://pubs.acs.org/doi/10.1021/ja9842215https://doi.org/10.1021/ja9842215rapid-communicationACS PublicationsCopyright © 1999 American Chemical SocietyRequest reuse permissionsArticle Views857Altmetric-Citations58LEARN 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:Addition reactions,Cyclization,Dendrons,Hydrocarbons,Molecules Get e-Alerts
A library of 36 L-amino acid anilides, which are potential selectors for chiral HPLC, was synthesized in solution and attached to functionalized macroporous polymer beads. The best selector from the library was identified by a deconvolution process using the HPLC separation of several racemic N-(3,5-dinitrobenzoyl)-alpha-amino acid alkylamides as a probe. In each deconvolution step, a series of chiral stationary phases (CSPs) containing a subset of the amino acid anilide selector library was screened for enantioselectivity. After the best CSP was chosen, the library was further deconvoluted until the single best selector was found. The highest selectivity was obtained with a L-proline-1-indananilide that exhibited alpha values up to 23 under normal-phase HPLC conditions. In addition, six CSPs were prepared using individual selectors from the library, and screening results indicate that the deconvolution process indeed led to the most selective receptor.
Read moreDurch den Einbau von miteinander wechselwirkenden Laserfarbstoffen an den Kettenenden und im Brennpunkt eines dendritischen Makromoleküls kann Energie unterschiedlicher Wellenlängen, die durch die große periphere Antenne des Dendrimers gesammelt wurde (siehe linkes Bild), direkt und mit hohem Wirkungsgrad auf den zentralen Kern übertragen werden (mittleres Bild), ohne daß das innere Skelett des Dendrimers am Übertragungsprozeß beteiligt ist. Die Energie wird dann als schmalbandige Fluoreszenzstrahlung vom Kern emittiert (rechtes Bild).
Read moreUltra-thin dendrimer films are effective resists for high-resolution lithography using a scanning probe. The authors describe dendritic monolayer formation via covalent attachment to a silicon wafer surface and the field-enhanced oxidation of the dendrimer monolayers using scanning probe lithography to create features with dimensions less than 60 nm. Poly-(benzyl ether) dendrimers, terminated with either benzyl or tert-butyldiphenylsilyl ether groups, were used because of their relative ease of preparation and derivatization.
Read moreA photoresist-like thermally responsive polymer has been formulated, surface micromachined and integrated into parylene microchannels to realize an inline valve. The polymer physically swells below its lower critical solution temperature and shrinks above it. Test showed a 2.5-fold polymer volume increase by changing water temperature from 25 to 10/spl deg/C. Repeated polymer swelling and shrinking were observed inside the channel with a system response time around 7 s. Pressure build-up measurements were used to demonstrate the functionality of the valve. Valve test results using DI water showed that the pressure upstream of the polymer plug increased from 15.3 to 20.3 psi with temperature change from 36/spl deg/C to 15/spl deg/C.
Read moreA symmetrical alpha,omega-substituted sexithiophene derivative containing thermally removable branched ester solubilizing groups has been prepared. These oligomers can be solution cast into thin films and then thermolyzed to remove the solubilizing group, leaving short pendant alkene groups on the oligomer. Device testing of thin film transistors shows an increase in hole mobility from 1 x 10-5 cm2/(V s) with on/off ratios of approximately 100 before thermolysis to 5 x 10-2 cm2/(V s) with on/off ratios >105 after thermolysis. This method offers an attractive route to easily processed and highly performing thiophene oligomers.
Read moreA micellar assembly of molecules constituted of poly(ethylene glycol) as the hydrophilic component and 2-diazo-1,2-naphthoquinone as the hydrophobic component was shown to be destroyed in a two-photon photoreaction triggered by infrared light with release of an encapsulated fluorescent probe molecule.
Read moreAbstract In recent years, supramolecular micellar assemblies formed from amphiphilic block copolymers have been receiving attention as potential drug carriers. The size of the carriers is ideal for avoiding rapid renal exclusion and reticuloendothelial uptake, and enables them to be targeted to certain tissues such as tumors. One important issue determining the effectiveness of a micellar drug carrier is the ability to control the time over which drug release takes place, or to possibly trigger drug release at a specific location or time. The mildly acidic pH encountered in tumor and inflammatory tissues as well as in the endosomal and lysosomal compartments of cells has inspired the development of micellar carriers capable of releasing their drug load in response to small changes in pH. One approach to the development of these systems has been to incorporate “titratable” groups such as amines and carboxylic acids into the copolymer backbone, thus altering the solubility of the polymer upon protonation and disrupting micelle formation. Another approach has been to incorporate acid-degradable linkages into the copolymer, either for direct attachment of the drug, or to cause a structural change of such magnitude that micellar integrity is lost and the drug is released.
Read moreVapor−liquid equilibria for dendritic-polymer solutions were obtained using a classic gravimetric-sorption method; the amount of solvent absorbed by the dendrimer was measured as a function of solvent vapor pressure. Three series of dendrimers, each with the same tertiary amine core structure, but different surface groups, were investigated in a variety of organic solvents in the range 50−75 °C. The dendrimer surface groups were dodecylamines, octadecyl amides, and polyisobutylene. Solvent absorption depends strongly on dendrimer composition and generation number.
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