A novel divergent approach was developed for the synthesis of dendritic aliphatic polyester structures using an acetal-protected anhydride derivative of 2,2-bis(hydroxymethyl)propionic acid as the acylating agent. This divergent synthesis is remarkable, because unlike all others, it only requires a small excess of reagent to achieve quantitative growth, and it requires no means of purification other than a simple solvent extraction or precipitation. A monodisperse sixth generation dendrimer with molecular weight of 30 711 Dalton and 192 masked hydroxyl groups was prepared in high yield and purity using 1,1,1-tris(hydroxyphenyl)ethane as the core molecule. Linear and star-shaped poly(ethylene glycol) (PEG) derivatives of narrow polydispersity were also used as core molecules in the divergent synthesis of dendritic-linear copolymer hybrids up to the fourth generation without requiring any chromatographic purification.

With the goal of developing a pH-responsive micelle system, linear-dendritic block copolymers comprising poly(ethylene oxide) and either a polylysine or polyester dendron were prepared and hydrophobic groups were attached to the dendrimer periphery by highly acid-sensitive cyclic acetals. These copolymers were designed to form stable micelles in aqueous solution at neutral pH but to disintegrate into unimers at mildly acidic pH following loss of the hydrophobic groups upon acetal hydrolysis. Micelle formation was demonstrated by encapsulation of the fluorescent probe Nile Red, and the micelle sizes were determined by dynamic light scattering. The structure of the dendrimer block, its generation, and the synthetic method for linking the acetal groups to its periphery all had an influence on the critical micelle concentration and the micelle size. The rate of hydrolysis of the acetals at the micelle core was measured for each system at pH 7.4 and pH 5, and it was found that all systems were stable at neutral pH but underwent significant hydrolysis at pH 5 over several hours. The rate of hydrolysis at pH 5 was dependent on the structure of the copolymer, most notably the hydrophobicity of the core-forming block. To demonstrate the potential of these systems for controlled release, the release of Nile Red as a "model payload" was examined. At pH 7.4, the fluorescence of micelle-encapsulated Nile Red was relatively constant, indicating it was retained in the micelle, while at pH 5, the fluorescence decreased, consistent with its release into the aqueous environment. The rate of release was strongly correlated with the rate of acetal hydrolysis and was therefore controlled by the chemical structure of the copolymer. The mechanism of Nile Red release was investigated by monitoring the change in size of the micelles over time at acidic pH. Dynamic light scattering measurement showed a size decrease over time, eventually reaching the size of a unimer, thus providing evidence for the proposed micelle disintegration.

Microparticulate, monosized, and macroporous poly(2,3-dihydroxypropyl methacrylate- co -ethylene dimethacrylate) beads have been used as a stationary phase for HPLC separations of hydrophilic oligomers and polymers. Homogeneous coverage of the sorbent surface with a large number of chemically equivalent diol functionalities affords suitable retentivity in both normal-phase and hydrophilic-interaction chromatographic modes and enables the separations of water-soluble oligomers and polymers. Chromatographic properties of this stationary phase are demonstrated on a variety of separations of poly(oxyalkylene)s, polyvinylpyrrolidones, and polysaccharides.

Komponenten, die Klick machen: Eine Vielzahl unterschiedlicher Dendrimere (siehe Schema) wurde mit der im Titel beschriebenen Click-Chemie-Umwandlung nahezu quantitativ erhalten. In einigen Fällen war zur Reinigung der Produkte dieses hoch effizienten Aufbaus der Triazoleinheiten der Dendrimere nur eine Filtration oder Lösungsmittelextraktion erforderlich.

A novel stationary phase for capillary electrochromatography has been prepared via photoinitiated grafting of two layers of polymer chains onto the pore surface of a porous polymer monolith. To achieve the desired retention, the original monolith with optimized porous properties was grafted with an "interior" layer consisting of the ionizable monomer, 2-acrylamido-2-methyl-1-propanesulfonic acid, followed by a "covering" layer of hydrophobic polymer chains. This technique affords monolithic CEC columns that facilitate electroosmotic flow (EOF) while preventing ionized analytes from interacting with the charged surface functionalities. Grafting of the second layer does not adversely affect the EOF. Grafting times of 30 and 60 s for AMPS and butyl acrylate, respectively, enabled the preparation of a monolith with full shielding of the analytes from the ionizable functionalities and excellent chromatographic performance. This approach allows for the first time the independent optimization of both electroosmotic flow and retention properties in CEC columns. The efficient isocratic separations of mixtures of peptides, including some that are highly basic and would be affected by unshielded charges, were routinely achieved in 40-90 s using a simple MS compatible mobile phase consisting of 20 mmol/L ammonium acetate in a 1:1 water-acetonitrile mixture.

A new approach to two-photon excited photodynamic therapy has been developed. A dendritic array of eight donor chromophores capable of two-photon absorption (TPA) was covalently attached to a central porphyrin acceptor. Steady-state fluorescence measurements demonstrated that the donor chromophores transfer excited-state energy to the porphyrin with 97% efficiency. Two-photon excitation of the donor chromophores at 780 nm resulted in a dramatic increase in porphyrin fluorescence relative to a porphyrin model compound. Enhanced singlet oxygen luminescence was observed from oxygen-saturated solutions of the target compound under two-photon excitation conditions.

The oligothiophene derivative 4-(5' " '-decyl-[2,2';5',2' ';5' ',2' ";5' ",2' " '] pentathiophen-5-yl)-butyric acid (D5TBA) was synthesized by Stille cross-coupling methods using functionalized thiophene monomers. The structural and mechanical properties of D5TBA self-assembled monolayers on mica have been studied by atomic force microscopy (AFM). The self-assembled films were prepared by immersing the mica in dilute chloroform or tetrahydrofuran (THF) solutions. The films were predominantly of monolayer thickness with molecules packed in nearly upright orientations. In regions covered with multilayers, the molecules in each monolayer were oriented opposite to those in the neighboring ones, that is, with COOH-COOH and CH3-CH3 contact. The nature of the end group in contact with the substrate depended on the solvent used and the degree of hydration of the substrate, with hydrophobic chloroform solvent favoring the methyl end down and hydrophilic THF favoring the acid group end down. The orientation could also be controlled by dipping using the Langmuir-Blodgett technique.

A near-white light-emitting polymer, consisting of hole transport (HT), electron transport (ET), and phosphorescent Pt functionalities, was prepared and utilized as the emissive layer in solution-processed OLEDs. The air-stable devices had a maximum external quantum efficiency of 4.6%.

Capillary electrophoresis (CE) lends itself to miniaturization, because it uses electroosmotic flow rather than moving parts for flow generation. Its analytical figures of merit improve as channel dimensions decrease. However, solution flow in the small planar channels used in CE-on-a-chip is very sensitive to reservoir solution height. This adds a pressure driven flow components, which decreases resolution, sensitivity, and separation efficiency of the EOF-driven technique. We have observed that this contribution to parabolic flow from uneven solution heights can be minimized by using a porous polymer monolith (PPM) as a flow restriction plug in the reservoirs of a 75 micrometers wide X 15 micrometers deep microchannel etched in glass. Our results indicate an average PPM pore size of 1 micrometers is sufficient for flow restriction. Pore sizes below this result in charge trapping of even small dye molecules. Images of the flow profile on and off the monolith show the inverse-parabolic effect on the electroosmotic flow profile due to mismatched zeta potentials between the polymer and the fused silica wall surfaces depending on PPM surface charge and plug length.

We describe a cyclopolymerization approach to novel cyclic materials incorporating a) etch-stable adamantyl esters and b) t-butyl esters as functionalities suitable for chemical amplification. The synthesis of the monomers follows a highly convergent approach from the readily synthesized 1- adamantyl malonate ester. Two polymerizable side chains are then added, incorporating either a(t-butyl acrylate esters, or b) a terminal olefin functionality. These bifunctional, carbon-rich monomers undergo smooth and efficient free radical ring-closing cyclopolymerization to afford soluble, processable polymers that do not contain residual olefinic signals. In order to optimize the lithographic performance of the materials, these crystalline monomers can also be copolymerized with maleic anhydride, or other desirable monomers. These resists show excellent transparency at 193 nm and outstanding etch resistance. When used in combination with a photoacid generator, they ca be used to formulate deep UV, chemically amplified photoresists. Preliminary imaging experiments conducted with a 193 nm ArF laser stepper exposure unit demonstrate features below 0.18 (mu) .

The design and synthesis of a new dendrimer–poly(ethylene glycol) (PEG) conjugate that may be used as a model drug carrier are described. The starting material is a polyether dendrimer with two different types of chain end functionalities. The dendritic assembly is made water soluble through attachment of short PEG chains to the dendrimer via one type of functionality. The remaining chain end functionalities then were used to incorporate model drug molecules of varying polarity into the modified dendrimer. Cholesterol and two amino acid derivatives were selected as model drugs for attachment through their respective hydroxyl, carboxylic acid, and amino functional groups to the dendrimer via carbonate, ester, and carbamate linkages. The resulting water-soluble dendrimer-model drug conjugates were characterized by matrix-assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3492–3503, 1999

The design of novel alkylated norcamphor derivatives that undergo cyclopolymerization is explored; the resulting polymers incorporate suitable functional groups for chemical amplification and show excellent imaging characteristics under lithographic exposure at 193 nm.

ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTSignatures of the Order−Disorder Transition in Copolymers with Quenched Sequence DisorderH. B. Eitouni, T. J. Rappl, E. D. Gomez, N. P. Balsara, S. Qi, A. K. Chakraborty, J. M. J. Fréchet, and J. A. PopleView Author Information Department of Chemical Engineering, University of California, Berkeley, California 94720; Materials Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720; Department of Chemistry, University of California, Berkeley, California 94720; and Stanford Synchrotron Radiation Laboratory, SLAC, PO Box 4349, Stanford, California 94309 Cite this: Macromolecules 2004, 37, 23, 8487–8490Publication Date (Web):October 15, 2004Publication History Received13 July 2004Revised15 September 2004Published online15 October 2004Published inissue 1 November 2004https://pubs.acs.org/doi/10.1021/ma048583ahttps://doi.org/10.1021/ma048583arapid-communicationACS PublicationsCopyright © 2004 American Chemical SocietyRequest reuse permissionsArticle Views271Altmetric-Citations15LEARN 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:Copolymers,Diseases and disorders,Optical properties,Phase transitions,X-ray scattering Get e-Alerts