The feasibility of a chemically amplified fully water-soluble negative-tone resist based upon the cross-linking of a poly(vinyl alcohol) (PVA) matrix resin has been demonstrated. Two-component resists incorporating PVA and (2,4-dihydroxyphenyl)dimethylsulfonium triflate as a water-soluble photoacid generator were formulated in deionized water and spin-coated onto bare silicon wafers. Negative-tone images were obtained upon irradiation at 254 nm, postbaking, and subsequent development in pure water. The two-component resist suffered from swelling during development, but improved performance was obtained through the addition of a cross-linking agent, hexamethoxymethylmelamine (HMMM). The resulting three-component, water-soluble resist was able to resolve micron-sized images using a 248 nm stepper, at a dose of ca. 200 mJ/cm2. Model studies conducted using 13C NMR monitoring with 2,4-pentanediol as a model for PVA showed that under acidic catalysis HMMM reacts to form active electrophilic species that add to the diol, affording ether linkages with concomitant liberation of methanol.

S. M. Grayson, M. Jayaraman and J. M. J. Fréchet, Chem. Commun., 1999, 1329 DOI: 10.1039/A902340B

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOrdered Conducting Films of the Inorganic Polymer (LiMo3Se3)n Cast From SolutionJosh H. Golden, Francis J. DiSalvo, and Jean M. J. FrechetCite this: Chem. Mater. 1995, 7, 1, 232–235Publication Date (Print):January 1, 1995Publication History Published online1 May 2002Published inissue 1 January 1995https://pubs.acs.org/doi/10.1021/cm00049a036https://doi.org/10.1021/cm00049a036research-articleACS PublicationsRequest reuse permissionsArticle Views171Altmetric-Citations19LEARN 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

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The purpose of the present work was to investigate a liquid chromatographic method for the measurement of relative hydrogen bond basicities of dilute species. This type of determination cannot be done with conventional reversed-phase liquid chromatography due to the silanophilic interactions of basic solutes with the silica packing material. The studies were done on a polymeric stationary phase with pendant phenol groups that act as powerful hydrogen bond donors. Solute retention was evaluated in terms of two hydrogen bond basicity scales, beta 2H and beta 2C, and a steric hindrance parameter, Es. beta 2H and beta 2C are basicity scales based on the free energy of forming 1:1 hydrogen bond complexes and the retention on a strong hydrogen bond donor gas chromatographic phase, respectively. The Es parameter characterizes the steric effect experienced by the solute acceptor site. It is shown that retention correlates very strongly with beta 2H and less strongly with beta 2C. The log k' values need only two descriptive parameters, i.e., beta 2H and Es, to give a good fit. As a whole, retention on the phenolic polymeric phase provides an efficient method for the measurement of relative hydrogen bond basicities.

Previously described dendritic and hyperbranched polyesters and a new linear polyester obtained by polymerization of 3-hydroxy-5-(t-butyldimethylsilyloxy)benzoic acid, each based on the 3,5-dihydroxybenzoic acid building block, were used in the study of differences in chemical and physical properties between the three different polymer architectures. Comparison of the physical properties between the dendritic, hyperbranched and linear structures showed that thermal properties, such as glass transition temperature and thermogravimetric analysis, were independent of macromolecular architecture. However, the dendritic and hyperbranched materials demonstrated comparative solubilities which were much greater than that found for the linear polymer. Other differences were observed in chemical reactivities.

Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry was utilized to study simple poly(ethylene glycol)s (PEG) and a series of amphiphilic copolymers prepared from PEG and dendritic molecules. For the amphiphilic copolymers with branched dendritic structures, MALDI-TOF spectrometry affords more accurate molecular weight data than the conventional gel-permeation chromatography (GPC). For mass lower than 10 000, the molecular weight distribution of the polymer is well-resolved into individual peaks. Using MALDI-TOF in the linear mode, copolymers with molecular masses of up to 43 000 Da were analyzed. For various dendrons attached to the same PEG, a good correlation was observed between calculated and measured data for the expected incremental increase as a function of dendrimer generation. End-group analysis using MALDI-TOF mass spectrometry proved very useful for the analysis of polymers with relatively low molecular weights. The experimental results agree well with the calculated masses of selected oligomers. Such end-group analysis can differentiate between the AB dendritic−linear diblocks, ABA triblocks, and linear PEG. These analyses support our earlier finding that the Williamson ether synthesis utilized in the PEG−dendron coupling reaction indeed converts all of the PEG to the desired block copolymer products.

Printed organic electronics is promising for realizing low-cost flexible displays and RFID tags. We describe the state of the art in printed organic electronics, focusing on advanced materials currently being studied to realize devices with enhanced performance, including soluble oligomer semiconductor precursors, printable self-assembled monolayer dielectrics, and printable high-K dielectric precursors. These materials should enable the realization of devices with low operating voltages and carrier mobilities sufficiently high for the demonstration of high-quality displays and RFID tags on plastic.

Abstract Porous poly(butyl methacrylate‐ co ‐ethylene dimethacrylate), poly(benzyl methacrylate‐ co ‐ethylene dimethacrylate), and poly(styrene‐ co ‐divinylbenzene) monoliths have been prepared on the top of standard sample plates used for matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectrometry and the modified plates were used for laser desorption/ionization mass spectrometry (LDI‐MS). The hydrophobic porous surface of these monoliths enables the transfer of sufficient energy to the analyte to induce desorption and ionization prior to TOFMS analysis. Both UV and thermally initiated polymerization using a mask or circular openings in a thin gasket have been used to define spot locations matching those of the MALDI plates. The desorption/ionization ability of the monolithic materials depends on the applied laser power, the solvent used for sample preparation, and the pore size of the monoliths. The monolithic matrices are very stable and can be used even after long storage times in a typical laboratory environment without observing any deterioration of their properties. The performance of the monolithic material is demonstrated with the mass analysis of several small molecules including drugs, explosives, and acid labile compounds. The macroporous spots also enable the archiving of samples. Copyright © 2004 John Wiley & Sons, Ltd.

A series of small dendritic structures containing one of two efficient multiphoton absorbing dyes at the periphery and a nile red derivative at the core have been synthesized. These molecules display efficient (>96%) fluorescence resonance energy transfer (FRET) from the periphery to the core on selective excitation of the two-photon absorbing chromophore by either UV (linear absorption) or high-intensity IR (nonlinear absorption) radiation. In addition, a significant increase in core emission is observed on excitation of the peripheral chromophores, compared to direct excitation of the core. This "antenna effect" essentially doubles between increasing dendrimer generations within a series. The combination of the ability of the peripheral chromophores to absorb high-intensity IR radiation, coupled with a very efficient energy transfer process and a significant increase in the fluorescence of the acceptor chromophore, makes these molecules potentially useful for a variety of applications, including optical power limiting and biomedical imaging.

Photomechanical switching (photoisomerization) of molecules at a surface is found to strongly depend on molecule-molecule interactions and molecule-surface orientation. Scanning tunneling microscopy was used to image photoswitching behavior in the single-molecule limit of tetra-tert-butyl-azobenzene molecules adsorbed onto Au(111) at 30 K. Photoswitching behavior varied strongly with surface molecular island structure, and self-patterned stripes of switching and nonswitching regions were observed having approximately 10 nm pitch. These findings can be summarized into photoswitching selection rules that highlight the important role played by a molecule's nanoscale environment in determining its switching properties.

Plasmid DNA was directly encapsulated into biocompatible polymer microparticles via radical polymerization in an inverse emulsion system. Acrylamide-based microspheres 0.2-1 microm in diameter were prepared using an acid-cleavable difunctional monomer. Retention of the DNA payload at physiological pH with complete release under acidic conditions at lysosomal pH was demonstrated. By trapping the plasmid DNA within the cross-linked microparticle, enzymatic degradation was prevented when exposed to serum nucleases. For vaccine development, these delivery vehicles were also investigated for their ability to generate immune responses when delivered to phagocytic cells of the immune system. Encapsulated plasmid DNA demonstrated immunostimulatory activity in macrophages, leading to cytokine secretion of IL-6 with a response approximately 40-fold higher than that achieved with DNA alone.