A polythiophene derivative containing thermally removable branched ester solubilizing groups has been prepared and tested as a processable organic semiconductor polymer with tunable electronic and chemical properties for hybrid polymer-inorganic solar cells. Thermal removal of the protecting group enhances the interface between the organic and inorganic components while also contributing to better light absorption, energy transfer, and overall cell performance.
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.
High molecular weight poly(p-hydroxystyrene) (PHS) was dendronized in high yield by the divergent grafting of aliphatic polyester dendrons using acetal and ketal protected anhydride derivatives of bis(hydroxymethyl)propionic acid. Relatively low polydispersities (PDI = 1.1-1.3) were maintained throughout the dendronization process. Detailed characterization of a series of these polymers by size exclusion chromatography (SEC) and SEC with multi-angle laser light scattering (SEC-MALLS) clearly shows the effect of dendron steric bulk on the persistence length (ξ) of the polymer main chain in solution. As a result of the fixed degree of polymerization (DP), the main chain rigidification that accompanies lateral dendron growth causes an unusual relationship between Rg,z and molecular weight across a series of generations. The rodlike structure and contour length of the alkylated dendronized polymers was also characterized by scanning force microscopy (SFM) on mica, highly oriented pyrolytic graphite (HOPG), and molybdenum disulfide (MoS2) surfaces. One of the G3 dendronized polymers with an alkylated periphery showed significant physical gelation behavior at concentrations below 1 wt % in several organic solvents, which constitutes additional evidence that the solution phase rigidity of a polymer chain can be enhanced by dendronization.
Dendrimer monolayers have been designed for use as positive resists for scanning probe lithography (SPL). Several new amphiphilic poly(benzyl ether) dendrimers with carboxylic acids at either the focal point or the "periphery" have been prepared. These can form ionically bound dendrimer monolayers that may serve as either positive or negative tone resists for SPL. The amphiphilic dendrimers self-assemble onto (3-aminopropyl)silanized Si(100) wafer surfaces to afford ultrathin films. The dendrimer monolayers were characterized by AFM, ellipsometry, and contact angle goniometry. Patterning a singly charged dendrimer monolayer results in the formation of positive tone holes ∼35 nm in width. Similarly, patterning a multiply charged dendrimer monolayer in a direct-write manner with the scanning probe microscope results in the formation of negative tone oxide features ∼80 nm in width.
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.
Ultra-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.
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.
Linear copolymers that have pendant coumarin-2 and coumarin-343 chromophores were prepared as analogues to previously synthesized light-harvesting dendrimers. The chromophore ratios within these polymers were maintained similar to those of the various generation dendrimers to investigate the effect of polymer architecture on the energy-transfer efficiency between the coumarin-2 donors and coumarin-343 acceptors. Both physical and photophysical properties of these polymers were analyzed and compared to those of the analogous dendrimers. Energy-transfer efficiencies were relatively high in the polymers; however, deleterious excimer formation between the coumarin-343 chromophores diminished the quantum yield of fluorescence of the polymers when compared to the analogous dendrimers. Overall, it was found that the ultimate performance of the dendritic light-harvesting antennae was superior to that of the polymeric analogues, but the polymers were more practical in terms of synthetic accessibility. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1366–1373, 2001
Read moreADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTProton-Transfer Polymerization: A New Approach to Hyperbranched PolymersHan-Ting Chang 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, 10, 2313–2314Publication Date (Web):February 27, 1999Publication History Received2 November 1998Published online27 February 1999Published inissue 1 March 1999https://pubs.acs.org/doi/10.1021/ja983797rhttps://doi.org/10.1021/ja983797rrapid-communicationACS PublicationsCopyright © 1999 American Chemical SocietyRequest reuse permissionsArticle Views1488Altmetric-Citations109LEARN 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:Aromatic compounds,Ethers,Hydrocarbons,Monomers,Polymerization Get e-Alerts
Read moreADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTAn A2 + B3 Approach to Hyperbranched Aliphatic Polyethers Containing Chain End Epoxy SubstituentsTodd Emrick, Han-Ting Chang, and Jean M. J. FréchetView Author Information Department of Chemistry, University of California, Berkeley, California 94720-1460 Cite this: Macromolecules 1999, 32, 19, 6380–6382Publication Date (Web):August 20, 1999Publication History Received3 May 1999Revised27 July 1999Published online20 August 1999Published inissue 1 September 1999https://pubs.acs.org/doi/10.1021/ma990687bhttps://doi.org/10.1021/ma990687brapid-communicationACS PublicationsCopyright © 1999 American Chemical SocietyRequest reuse permissionsArticle Views2010Altmetric-Citations258LEARN 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:Monomers,Nuclear magnetic resonance spectroscopy,Organic polymers,Polymerization,Polymers Get e-Alerts
Read moreNanoscale patterning and electronics fabrication on flexible polymer substrates via direct nanoirnprinting of metal nanoparticles was demonstrated. The metal nanoparticle solution enables a simple one-step metal nanoirnprinting with very low pressure and temperature. Electrical and structural characterizations on flexible substrate during cyclic bending deformations verify the robustness of the nanoimprinted structures to mechanical deformation conditions.
Read moreADVERTISEMENT 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
Read morepH-Sensitive linkages designed to undergo hydrolysis at mildly acidic pH can trigger the release of therapeutics selectively at targets such as tumor and inflammatory tissues and in the endosomes and lysosomes of cells. Acetals have the potential to be used as linkages for a range of alcohol functionalities, and, by altering their chemical structure, it is possible to tune their hydrolysis rate. The syntheses of four conjugates of model drug molecules with PEO using acetals of varying chemical structure are described herein. Primary and secondary alcohols, as well as syn-1,2-diols, were incorporated in the conjugates. The hydrolysis kinetics were investigated by HPLC, and the conjugates had half-lives ranging from less than 1 min to several days at pH 5.0, with slower hydrolysis at pH 7.4 in all cases. These acetal linkages are therefore promising for use in a variety of drug delivery applications ranging from polymer-drug conjugates to pH-sensitive micelles and nanoparticulate systems.
Read moreAn 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.
Read moreADVERTISEMENT 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
Read moreThe 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.
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 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.
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