A macroporous poly(styrene-co-divinylbenzene) rod has been prepared by a free-radical polymerization of a mixture containing monomers, initiator, and porogenic solvent in the confines of a chromatographic column and used for the first time in the very fast reversed-phase HPLC of proteins. Characterization of the pore structure of the continuous rod by mercury intrusion porosimetry revealed a large volume of pores with a diameter of about 1 micron to pores below 100 nm. Size exclusion chromatography and scanning electron microscopy confirmed the unusual pore size distribution. The presence of large pores make the rod easily permeable to eluents, and therefore, the back pressure of the rod column is modest even at high flow rates. The efficiency of the polymerized column is almost independent of the flow rate. The slope of the line showing capacity factor vs composition of the mobile phase was determined for several proteins, and a gradient for the separation of their mixtures was developed. Excellent separation was achieved even at a high flow rate of 25 mL/min as documented by the resolution data. Tripling the length of the column did not improve the column resolution in protein separation.
Abstract Die Methanolyse der Halogenide (Ia), (Ib) (bekannte Verbindungen), (Ic), (VIIc) und (VIId) unter verschiedenen Bedingungen [ a), b), c) bzw. d)] wird untersucht.
The ability of a dendritic shell to afford site isolation to a porphyrin core was evaluated using electron-transfer experiments with a series of porphyrin-core dendrimers. Cyclic voltammograms show that surrounding a porphyrin site with even a small generation (G ∼ 2) dendrimer can significantly lower the rate of interfacial electron transfer, ostensibly by decreasing the proximity of the porphyrin core to the electrode surface. This inhibition of electron transfer is more pronounced when larger generation dendrimers are employed. While a significant measure of site isolation is achieved with respect to an electrode surface, no hindrance to penetration of a small molecule is afforded by the dendritic shell surrounding the porphyrin core, an encouraging result if dendrimers are to be designed as macromolecular hosts with a functioning catalyst at the core. Stern−Volmer analysis was used to investigate the accessibility of a small molecule, benzylviologen, to the porphyrin core. For generations 1−3, the den...
We have previously shown that a copolymer of p-hydroxstyrene and p-acetoxymethylstyrene can be used as a sensitive deep UV resist. In that study we demonstrated that a formulation of this copolymer and an onium salt could be exposed, baked and developed in aqueous base to yield a high resolution negative tone relief image. In this paper we discuss a gas phase silylation process that converts this negative tone solvent-developable resist system into a positive tone dry-developable resist system. We have used an FT-IR microscope, coupled to a motorized X-Y stage, to study the silylation process as a function of UV exposure dose and silylation processing parameters. By altering the copolymer ratio, we found that resist contrast increased when the amount of acetoxymethylstyrene increased. This resist system and dry develop process were used to print 0.35 micrometers images at a DUV dose of approximately 25 mJ/cm<SUP>2</SUP>.
Abstract Als Oxidationsmittel für Alkohole (II) bzw. (IV) kann ein polymeres Polyvinylpyridinchlorchromat (I) eingesetzt werden, das aus einem schwach vernetzten Polyvinylpyridin mit HCl und Chromsäureanhydrid erhalten wird.
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Since their introduction in 1985 by Tomalia et al. (1) and Newkome et al. (2), dendrimers have attracted much attention because of their fascinating structure and unique properties (3, 4). Dendrimers are globular, size monodisperse macromolecules in which all bonds emerge radially from a central focal point or core with a regular branching pattern and with repeat units that each contribute a branch point. Not all regularly branched molecules are dendrimers because properties of the dendritic state (4), such as core encapsulation (5, 6) and unusually low intrinsic viscosity in solution (7), are reached only when globularity is achieved at a certain generation or size threshold. Therefore, many low-generation dendrons or the early cascade molecules of Vogtle and coworkers (8) are too small to exhibit the properties of dendrimers, but they are frequently used as branched oligomeric building blocks in their construction, and have a size relationship to dendrimers somewhat akin to that between oligomers and polymers.
Since the concept of chemical amplification was first introduced by us more that twelve years ago, a number of new resists based on acid-catalyzed thermolysis have been developed and commercialized. This report describes the first chemically amplified resist operating through photogenerated base. The concept is demonstrated with poly(2-cyano-2-(p-vinylphenyl)butanoic acid) which decarboxylates readily under basic conditions. A resist system consisting of this polymer and an amine photogenerator bis(2,6-dinitrobenzyloxy)carbonylhexan- 1,6-diamine has been formulated and tested in microlithography. The sensitivity of this resist is extremely high (1.4 mj/sq cm) with a very high contrast of 13. 7. This very high sensitivity confirms that chemical amplification is achieved as the photogenerated base is not consumed in the overall decarboxylation process. The mechanistic insights gained from the study of the decarboxylation process may be used in the designed of other resists involving more readily accessible polymers.
Insoluble polymers containing trityl chloride residues were used to block one primary alcohol functional group of several polyhydroxy alcohols. After protecting the remaining hydroxyl groups by benzoylation, the ether linkage between the polymer and the protected alcohol was cleaved in acidic medium. Depending on the reaction conditions and the nature of the starting alcohol, several alcohols or bromides in which only one of the two primary hydroxyls had been esterified, were obtained. In some cases benzoyl migrations were observed. The trityl chloride polymers could be regenerated in one step without degradation or appreciable loss of activity.
Abstract Crosslinked resins containing styrylboronic acid units were used in the protection of 1,2 and 1,3‐diol groupings with several acyclic triols. With 1,2,3‐propanetriol, a five‐membered ring boronate was formed almost exclusively while with 1, 2, 4‐butanetriol a six‐membered ring boronate predominated. The fully recyclable polymer could be used in a fast and efficient synthesis of monobenzoyl derivatives of triols. Macroreticular and 1% crosslinked solvent‐swellable resins were tested and the latter were found to perform better on repeated use.
Read moreMany chemically amplified resists that function on the basis of acid catalysis of thermolytic reactions have been described as well as systems that function on the basis of free radical chain reactions. But there have been very few reports on the use of base catalysis of chemical transformations in resist materials. We describe here our initial results on base catalyzed chemically amplified deep-UV photoresists. Photogenerated amines were used as catalysts for the decarboxylation of carboxylic acids. Two approaches to building resists around this chemistry were investigated. (1) Decarboxylation of a low molecular weight carboxylic acid led to base induced dissolution inhibition of a phenolic polymer giving negative tone images. (2) A carboxylic acid polymer was synthesized which also is susceptible towards base catalyzed decarboxylation. Wet development of this resist material gives negative tone images. Site specific gas-phase silylation of the carboxylic acid allows the use of this material in a positive tone dry develop process. A 0.5 micrometers line-space pattern obtained by this dry develop process illustrates the potential of base-catalyzed chemical amplification.
Read moreA series of new polyfunctional latent electrophiles capable of acting as crosslinkers in the photoimaging of aromatic polymers has been prepared and tested in chemically amplified photoresist formulations. Extremely high sensitivities have been achieved with a variety of modes of irradiations: deep-UV (DUV) (ca. 0.1 - 0.3 mJ/cm<SUP>2</SUP>), E-beam (< 1 (mu) C/cm<SUP>2</SUP>) and x ray (ca. 15 mJ/cm<SUP>2</SUP>). In some cases, the sensitivities of these materials are so high that they have surpassed the capabilities of many existing exposure tools, making it desirable to lower them. This can be achieved through the addition of an electron rich species to the resist formulations to partially capture the photogenerated acid. It was shown that there is a linear correlation between the amount of additive and the sensitivities of the resulting resists.
Read moreAn acid catalysed rearrangement that transforms a bicyclic lactone into a phenolic carboxylic acid has been tested for potential use in chemically amplified microlithographic imaging.
Read moreAbstract Crosslinked bead polymers containing vinylpyridine units were prepared by pearl copolymerization of monomer mixtures containing various percentagesof 4-vinylpyridine, styrene, and di-vinylbenzene. The polymers were functionalized by reaction with hydrogen bromide and bromine, and the resulting poly-(vinylpyridinium hydrobromide perbromide) resins, which were stable for long periods of time, were used to brominate a number of alkenes and ketones. In most cases, the brominated products were obtained in excellent yields and could be separated from the polymeric by-product by a simple filtration. The polymeric reagent could be fully regenerated after use without loss of activity.
Read moreAbstract Unlösliche Polymere (II) mit Trityl‐ (Tr)chloridresten werden zur Blockierung einer prim. Alkoholfunktion von Polyalkoholen wie (I) und (VII) eingesetzt; nach Schutz der restlichen OH‐Gruppen durch Benzoylierung [‐ (IIIa)‐(IIIc) bzw. (VIIIa) [ im Gemisch mit (VIIIb)], (VIIIc)] wird die Ätherbindung zwischen Polymer und geschütztem Alkohol in saurem Medium gespalten; Mit Trifluoressigsäure (TF A) entstehen dabei die Verbindungen (IV) [daneben die Trifluoracetate (V), die mit wäßrigem Bicarbonat in (IV) übergefuhrt werden können]; die Verbindungen (IVa) werden in guter Ausbeute auch aus (IIIa) mit HBr erhalten.
Read moreHigh molecular weight polymers (> 20 000 Da) have been widely used as soluble drug carriers to improve drug targeting and therapeutic efficacy. Dendritic polymers are exceptional candidates for the preparation of near monodisperse drug carriers due to their well-defined structure, multivalency, and flexibility for tailored functionalization. We evaluated various dendritic architectures composed of a polyester dendritic scaffold based on the monomer unit 2,2-bis(hydroxymethyl)propanoic acid for their suitability as drug carriers both in vitro and in vivo. These systems are both water soluble and nontoxic. In addition, the potent anticancer drug, doxorubicin, was covalently bound via a hydrazone linkage to a high molecular weight 3-arm poly(ethylene oxide)-dendrimer hybrid. Drug release was a function of pH, and the release rate was more rapid at pH < 6. The cytotoxicity of the DOX-polymer conjugate measured on multiple cancer lines in vitro was reduced but not eliminated, indicating that some active doxorubicin was released from the drug polymer conjugate under physiological conditions. Furthermore, biodistribution experiments show little accumulation of the DOX-polymer conjugate in vital organs, and the serum half-life of doxorubicin attached to an appropriate high molecular weight polymer has been significantly increased when compared to the free drug. Thus, this new macromolecular system exhibits promising characteristics for the development of new polymeric drug carriers.
Read moreAbstract Die Cinchona Alkaloide (IIa)‐(IId) lassen sich befriedigend über ihre Vinylgruppen mit den Thiolgruppen enthaltenden vernetzten Polymeren (I) verknüpfen; die so gebildeten Produkte (III)‐(VIII) werden dann eingesetzt, um die Michael‐Additionsreaktionen der Verbindungen (IXa), (IXb) bzw. (XIII) mit dem Enon (X) [= Reaktionen (1)‐(3) bzw. (l′)‐(3′)] bzw. (XV) mit Nitrostyrol (XVI) [= Reaktion (4) bzw. (4′)]‐ unter Bildung der Produkte (XI), (XII), (XIV) bzw. (XVII) zu katalysieren.
Read moreAbstract Aus handelsüblichem Polystyrol, vernetzt mit Divinylbenzol, wird nach Merrifield das Chlormethylderivat (Ia), in dem 10‐15% der Einheiten p‐chlormethyliert sind, dargestellt.
Read moreAbstract Size monodispersed poly(styrene-divinylbenzene) particles with a variety of pore size and pore size distribution were prepared by a multi-step swelling and polymerization method and utilized as packing materials in high performance liquid chromatography (HPLC). As an application of these packing materials, separation of carbon clusters C60 and C70 were examined in a mixture of hexane and benzene and an influence of the pore size and the pore size distribution of the polymer-based packing materials on the separation was investigated. Although carbon clusters are sterically bulky molecules, packing materials with smaller pores showed better separation than those with larger pores. Completely separated peaks and the good peak shape suggest possible isolation of carbon clusters on relatively cheap polymer-based packing materials.
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