A stable free radical (SFR) mediated preparation of porous poly(styrene-co-divinylbenzene) monoliths using new types of SFRs and a novel binary porogenic solvent consisting of poly(ethylene glycol) ...
The design, structure, and properties of supramolecular liquid-crystalline side-chain polymers are described. In particular, we show how several simple H-bonding building blocks can be used for the formation of various liquid-crystalline structures. Poly[4-(6-(acryloyloxy)hexyl- and -undecyloxy)benzoic acid] (PmOBA; m = 6, 11) have been employed as polymer components. A variety of supramolecular mesogenic "copolymers" based on one polymeric component have been designed and prepared by simple self-assembly. Cooperation of the hydrogen bond and electron donor−acceptor interactions results in the mesophase stabilization for the "copolymeric" supramolecular structures of PmOBA with a mixture of trans-4-methoxy-4'-stilbazole (1OSz) and trans-4-cyano-4'-stilbazole (SzCN) or trans-4-nitro-4'-stilbazole (SzNO2). When a bifunctional molecule, 4,4'-bipyridine (BPy), is used as a component for "copolymeric" structures, supramolecular copolymeric networks based on PmOBA have been formed by self-assembly. The networks exhibit stable mesomorphic behavior and reversible phase transitions due to the dynamics of the hydrogen bonds.
The first use of ether protecting groups in the design of imaging systems based on substituted poly(hydroxystyrenes) is reported. Polymers containing 4-(2-cyclohexenyloxy) or 4-(1-phenylethyloxy) derivatives of 4-vinylphenol or 3,5-dimethyl-4-vinylphenol have been prepared from the corresponding monomers. Due to their design, which allows for facile elimination or rearrangement reactions, the ether protecting groups can be removed easily by acidolysis, or thermolysis, or a combination thereof. In some instances, the protecting groups can be split quantitatively from the polymers, while in others a thermal Claisen rearrangement or an acid-catalyzed alkylation occur with the formation of some alkylated phenolic moieties. Application of the design to imaging systems is achieved through the use of triarylsulfonium salts as photochemical triggers. Exposure of films of poly[4-(2-cyclohexenyloxy)-3,5-dimethyl-styrene] containing some of the onium salt to irradiation at 254 nm results in the formation of acid in the exposed areas which catalyzes the polymer deprotection and allows for the development of images in either positive or negative mode through a differential dissolution process.
This paper describes an 'environmentally friendly,' water castable, water developable photoresist system. The chemically amplified negative-tone resist system consists of three water-soluble components: a polymer, poly(methyl acrylamidoglycolate methyl ether), [poly(MAGME)]; a photoacid generator, dimethyl dihydroxyphenylsulfonium triflate and a crosslinker, butanediol. Poly(MAGME) was synthesized by solution free radical polymerization. In the three-component resist system, the acid generated by photolysis of the photoacid generator catalyzes the crosslinking of poly(MAGME) in the exposed regions during post-exposure baking, thus rendering the exposed regions insoluble in water. Negative tone relief images are obtained by developing with pure water. The resist is able to resolve 1 micrometer line/space features (1:1 aspect ratio) with an exposure dose of 100 mJ/cm<SUP>2</SUP> at 248 nm. The resist can be used to generate etched copper relief images on printed circuit boards using aqueous sodium persulfate as the etchant. The crosslinking mechanism has been investigated by model compound studies using <SUP>13</SUP>C NMR. These studies have revealed that the acid catalyzed reaction of the poly(MAGME) with butanediol proceeds via both transesterification and transacetalization (transaminalization) reactions at low temperatures, and also via transamidation at high temperatures.
Trypsin immobilization onto continuous "molded" rods of porous poly(glycidyl methacrylate-co-ethylene dimethacrylate) and some applications of the conjugate have been studied. The rods polymerized within a tubular mold (chromatographic column), were treated in situ with ethylenediamine, activated with glutaraldehyde and finally modified with trypsin. The performance of the trypsin-modified rods was evaluated and compared to that of poly(glycidyl methacrylate-co-ethylene dimethacrylate) beads, modified with the same enzyme. Overall the enzyme-modified rods performed substantially better than the corresponding beads. In particular, the performance of the molded supports as enzymatic reactors or as chromatographic media benefits greatly from the enhanced mass transfer that is characteristic of the molded rod at high flow rates. © 1996 John Wiley & Sons, Inc.
Attachment of drugs to high molecular weight polymers can significantly improve both tumor targeting and therapeutic efficacy due to the enhanced permeability and retention effect observed in tumor tissue. However, the commercial availability of well-defined water-soluble polymeric systems with narrow polydispersities that are biocompatible, nontoxic, and nonimmunogenic is rather limited. To address this need, we have investigated dendritic polymers as promising scaffolds for the preparation of new soluble polymeric drug carriers due to their well-defined molecular architecture and their multiplicity of surface sites. Herein we show the design and synthesis of dendritic polyester systems based on the monomer unit 2,2-bis(hydroxymethyl)propanoic acid as a possible versatile drug carrier. The potent anticancer drug doxorubicin was attached via a pH-sensitive linkage to one of the carriers presented, demonstrating the feasibility of using these polyester dendritic structures to prepare a viable polymer-drug conjugate.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHeterocyclic polymers as catalysts in organic synthesis - effect of macromolecular design and microenvironment on the catalytic activity of polymer-supported (dialkylamino)pyridine catalystsAndre Deratani, Graham D. Darling, Daniel Horak, and Jean M. J. FrechetCite this: Macromolecules 1987, 20, 4, 767–772Publication Date (Print):April 1, 1987Publication History Published online1 May 2002Published inissue 1 April 1987https://doi.org/10.1021/ma00170a011RIGHTS & PERMISSIONSArticle Views290Altmetric-Citations43LEARN 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 (819 KB) Get e-Alerts Get e-Alerts
The preparation and analysis of inorganic-organic polymer nanocomposites consisting of inorganic nanowires and multiwire “cables” in a random-coil organic polymer host is reported. Dissolution of inorganic (LiMo 3 Se 3 ) n wires in a strongly coordinating monomer, vinylene carbonate, and the use of a rapid polymerization in the presence of a cross-linking agent produce nanocomposites without phase separation. Polymerization of dilute solutions yields a material containing mostly (Mo 3 Se 3 − ) n mono- and biwires, 6 to 20 angstroms in diameter and 50 to 100 nanometers long. Polymerization of more concentrated liquid crystalline solutions yields a nanocomposite containing oriented multiwire cables, 20 to 40 angstroms in diameter and up to 1500 nanometers long, that display optical anisotropy and electrical conductivity.
ADVERTISEMENT RETURN TO ISSUEPREVArticleBase catalysis in imaging materials. 1. Design and synthesis of novel light-sensitive urethanes as photoprecursors of aminesJames F. Cameron and Jean M. J. FrechetCite this: J. Org. Chem. 1990, 55, 23, 5919–5922Publication Date (Print):November 1, 1990Publication History Published online1 May 2002Published inissue 1 November 1990https://pubs.acs.org/doi/10.1021/jo00310a028https://doi.org/10.1021/jo00310a028research-articleACS PublicationsRequest reuse permissionsArticle Views1006Altmetric-Citations65LEARN 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
The controlled functionalization of polystyrene using a process of metalation with a potassium superbase followed by reaction with electrophiles is described. The method is advantageous because metalation is extremely efficient, occurring rapidly even at room temperature, and the degree of functionalization can be controlled over a very broad range. Functionalization with trimethylsilyl groups allows effective monitoring and quantification of the metalation process. Other examples of modification include the introduction of small dendritic fragments by reaction with a dendron having an aldehydic focal point or the introduction of carboxylic acid pendant groups. This method, which has little effect on the polydispersity of the polymer, has broad applicability for the functionalization of a wide spectrum of polymers containing active hydrogens and may also be used to prepare randomly branched or star structures.
Read moreA novel non-contact method of forming groove servo patterns on optical disk substrates has been demonstrated. The servo forming layer consists of a copolymer of (p-t-butyloxycarbonyloxy)styrene and styrene formulated with an onium salt which photogenerates acidic species upon exposure to deep UV radiation. If the film is heated after exposure to light the photogenerated acid cleaves the p-t-butyloxycarbonyl ("t-BOC") group resulting in a thickness change in the regions exposed to radiation. Glass substrates coated with this formulation were exposed with an appropriate mask to deep CV light and the image developed by a post exposure bake of 2 minutes at 90°C. A magneto-optic trilayer consisting of 710 A Zr0<sub>2</sub>/800 A TbFeCo/710 A Zr0<sub>2</sub> was deposited onto the polymer surface. The complete structure has sufficient track error signal level to be trackable on a precision optical disk test stand with the TES servo loop closed and has a CNR of 53 dB, comparable to the same MO composition deposited on injection molded grooved polycarbonate substrates.
Read moreA molding process has been used for the preparation of separation media in different shapes such as rods and flat membrane-like disks. The polymerization is carried out using a mixture of monomers, porogenic solvent and free-radical initiator under conditions that afford macroporous materials with through-pores or channels large enough to provide the high flow characteristics required for applications in chromatography. In contrast to classical suspension polymerization, the solubility of monomers in water does not restrict their use. The versatility of the preparation technique is demonstrated in polymerizations involving both hydrophobic and hydrophilic monomers such as styrene, chloromethylstyrene, glycidyl methacrylate, alkyl methacrylates and acrylamide. Techniques have been developed that allow fine control of the porous properties of the polymers. These, in turn, determine the hydrodynamic properties of the separation devices that contain the molded media. Since all the mobile phase must flow through the separation medium, the mass transport within the molded media is accelerated considerably by convection. Therefore, the separations can be performed at much higher flow rates than in packed columns. This is particularly important for separations of large molecules such as proteins for which diffusion is a serious problem that significantly slows down the separation processes. The molded separation media have been used for the separation of biological compounds using gentle chromatographic modes such as hydrophobic interaction, ion-exchange and affinity chromatography during which the biological activity of the separated compounds is completely retained.
Read moreDendrimers possessing coumarin-2 dyes at the periphery, and either a coumarin-343 or a heptathiophene dye at the core, have been studied by femtosecond transient absorption spectroscopy in order to elucidate energy-transfer rate constants. These measurements indicated that energy transfer occurs with average correlation times of less than 6 ps in the first three generations, and slows to a correlation time of approximately 18 ps in the fourth. The transient spectral features arising from excitation of the peripheral donor chromophores at 330 nm are described. Additionally, these measurements provide a quantitative comparison between observed and theoretical energy-transfer rate constants (kET), indicating a close correlation of the experimental results with Förster theory.
Read moreADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTConvergent Dendrons and Dendrimers: from Synthesis to ApplicationsScott M. Grayson and Jean M. J. FréchetView Author Information Department of Chemistry, University of California, Berkeley, California 94720-1460 Cite this: Chem. Rev. 2001, 101, 12, 3819–3868Publication Date (Web):November 20, 2001Publication History Received5 March 2001Published online20 November 2001Published inissue 1 December 2001https://pubs.acs.org/doi/10.1021/cr990116hhttps://doi.org/10.1021/cr990116hresearch-articleACS PublicationsCopyright © 2001 American Chemical SocietyRequest reuse permissionsArticle Views11392Altmetric-Citations1488LEARN 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,Ethers,Molecules,Monomers Get e-Alerts
Read moreA comparison of the physical properties of hyperbranched and dendritic macromolecules with linear polymers and the linear analogs of these 3-dimensional polymers is presented. It is found that thermal properties, such as glass transition temperature and degradation, are the same regardless of the macromolecular architecture but are very sensitive to the number and nature of chain end functional groups. However, other properties, such as solubility, melt viscosity, chemical reactivity, intrinsic viscosity were found to be very dependent on the macromolecular architecture.
Read moreContibutors. Series Preface. A Brief Historical Perspective (D.A. Tomalia naad J.M.J. Frecht) B>I Introduction and Progress in the Control of Macromolecular Architecture Introduction to the Dendritic State (D.A. Tomalia and J.M. Frechet) Structure Control of Linear Macromolecules (C.J. Hawker) Progress in the Branched Architectural State (J. Roovers) Developments in the Accelerated Convergent Synthesis of Dendrimers (A.W. Freeman and J.M.J. Frechet) Formation, Structure and Properties of the Crosslinked State Relative to Precursor Architecture (K. Dusek and M. Duskova--Smrckova) Regioselectively--Crosslinked Nanostructures (C.G. Clark Jr and K. L. Wooley) Hybridization of Architectural States: Dendritic--linear Copolymer Hybrids (P.R.L. Malenfant and J.M.J. Frechet) Statistically Branched Dendritic Polymers (E. Malmstrom and A. Hult) Semi--Controlled Dendritic Structure Synthesis (R.A. Kee et al) II Characterization of Dendritic Polymers Gel Electrophoretic Characterization of Dendritic Polymers (C. Zhang and D.A. Tomalia) Characterization of Dendritically Branched Polymers by Small Angle Neutron Scattering (SANS), Small Angle X--ray Scattering (SAXS), and Transmission Electron Microscopy (TEM) (B.J. Bauer and E.J. Amis) Atomic Force Microscopy for the Characterization of Dendritic Polymers and Assemblies (J. Li and D.A. Tomalia) Characterization of Dendrimer Structures by Spectroscopic Techniques (N.J. Turro et al) Rheology and Solution Properties of Dendrimers (P. Dvornic and S. Uppuluri) III Properties and Applications of Dendritic Polymers Dendritic and Hyperbranched Glycoconjugates as Biomedical Anti--Adhesion Agents (R. Roy) Some Unique Features of Dendrimers based upon Self--assembly and Host--Guest Properties (J. Weener et al) Dendritic Polymers: Optical and Photchemical Properties (D.L. Jiang and T Aida) Bioapplications of PAMAM Dendrimers (J.D. Eichman et al) Dendrimer--Based Biological Reagents: Preparation And Applications in Diagnostics (P. Singh) Dendritic Polymer Applications: Catalysts (A.W. Kleij et al ) Optical Effects Manifested by PAMAM Dendrimer Metal Nano--Composites (T. Goodson III) Dendrimers in Nanobiological Devices (S.C. Lee) Antibodies to PAMAM dendrimers: Reagents for immune detection, patterning and assembly of Dendrimers (S.C. Lee et al) IV Laboratory Preparation of Dendrimers and Conclusion Preparation of a Frechet--typea Polyether Dendrons and Aliphatic Polyester Dendrimers by Convergent Growth: an experimental primer (J.M.J. Frechet et al) Laboratory Synthesis of Poly(amidoamine) (PAMAM) Dendrimers (R. Esfand and D.A. Tomalia) Synthesis and Characterization of Poly(Propylene imine) Dendrimers (M.H.P. van Genderen et al) Laboratory Synthesis and Characterization of Megamers: Core--shell Tecto(dendrimers) (D.A. Tomalia) Conclusion/Outlook -- Toward Higher Macromolecular Complexity in the Twenty--first Century (D.A. Tomalia and J.M.J. Frechet) Index
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