Enzymatic microreactors have been prepared in capillaries and on microfluidic chips by immobilizing trypsin on porous polymer monoliths consisting of 2-vinyl-4,4-dimethylazlactone, ethylene dimethacrylate, and acrylamide or 2-hydroxyethyl methacrylate. The azlactone functionalities react readily with amine and thiol groups of the enzyme to form stable covalent bonds. The optimized porous properties of the monoliths lead to very low back pressures enabling the use of simple mechanical pumping to carry out both the immobilization of the enzyme from its solution and the subsequent analyses of substrate solutions. The Michealis-Menten kinetic characteristics of the reactors were probed using a low molecular weight substrate: N-alpha-benzoyl-L-arginine ethyl ester. The effects of immobilization variables such as the concentration of trypsin in solution and percentage of azlactone functionalities in the monolith, as well as the effect of reaction time on the enzymatic activity, and of process variables such as substrate flow velocity and residence time in the reactor, were studied in detail. The proteolytic activity of the enzymatic microreactor on chip was demonstrated at different flow rates with the cleavage of fluorescently labeled casein used as a substrate. The excellent performance of the monolithic microreactor was also demonstrated with the digestion of myoglobin at the fast flow rate of 0.5 microL/min, which affords a residence time of only 11.7 s. The digest was then characterized using MALDI-TOF MS, and 102 out of 153 possible peptide fragments were identified giving a sequence coverage of 67%.

A novel convergent approach for the synthesis of dendritic macromolecules is presented and its scope and versatility demonstrated with the synthesis of a series of monodisperse dendritic polyether macromolecules based on 3,5-dihydroxybenzyl alcohol as the monomer unit up to a molecular weight of 40 689.

The synthesis of functional aromatic bis(sulfonyl chlorides) containing an acetophenone and two sulfonyl chloride groups, i.e., 3,5-bis[4-(chlorosulfonyl)phenyl]-1-acetophenone (16), 3,5-bis(chlorosulfonyl)-1-acetophenone (17), and 3,5-bis(4-(chlorosulfonyl)phenyloxy)-1-acetophenone (18) via a sequence of reactions, involving in the last step the quantitative oxidative chlorination of S-(aryl)- N,N'-diethylthiocarbamate, alkyl- or benzyl thiophenyl groups as masked nonreactive precursors to sulfonyl chlorides is described. A related sequence of reactions was used for the synthesis of the aromatic trisulfonyl chloride 1,1,1-tris(4-chlorosulfonylphenyl)ethane (24). 4-(Chlorosulfonyl)phenoxyacetic acid, 2,2-bis[[[4-(chlorosulfonyl)phenoxyacetyl]oxy]methyl]-1,3-propanediyl ester (27), 5,11,17,23-tetrakis(chlorosulfonyl)-25,26,27,28-tetrakis(ethoxycarbonylmethoxy)calix[4]arene (38), 5,11,17,23,29,35-hexakis(chlorosulfonyl)-37,38,39,40,41,42-hexakis(ethoxycarbonylmethoxy)calix[6]arene (39), 5,11,17,23,29,35,41,47-octakis(chlorosulfonyl)-49,50,51,52,53,54,55,56-octakis(ethoxycarbonylmethoxy)calix[8]arene (40), 5,11,17,23-tetrakis(tert-butyl)-25,26,27,28-tetrakis(chlorosulfonyl phenoxyacetoxy)calix[4]arene (44), 5,11,17,23,29,35-hexakis(tert-butyl)-37,38,39,40,41,42-hexakis(chlorosulfonylphenoxyacetoxy)calix[6]arene (45), and 5,11,17,23,29,35,41,47-octakis(tert-butyl)-49,40,51,52,53,54,55,56-octakis(chlorosulfonylphenoxyacetoxy)calix[8]arene (46) were synthesized by two different multistep reaction procedures, the last step of both methods consisting of the chlorosulfonation of compounds containing suitable activated aromatic positions. 2,4,6-Tris(chlorosulfonyl)aniline (47) was obtained by the chlorosulfonation of aniline. The conformation of two series of multisulfonyl chlorides i.e., 38, 39, 40 and 44, 45, 46, was investigated by (1)H NMR spectroscopy. The masked nonreactive precursor states of the functional aromatic multisulfonyl chlorides and the aromatic multisulfonyl chlorides reported here represent the main starting building blocks required in a new synthetic strategy elaborated for the preparation of dendritic and other complex organic molecules.

Abstract A new approach to resist materials that exhibit chemical amplification is based on systems comprised of three structural units at least one of which is polymeric: (a) an aromatic moiety such as poly(4‐hydroxystyrene), Novolac, or other aromatic compounds which are susceptible to electrophilic aromatic substitution; (b) a latent electrophile which may be polyfunctional and, in the case of this study, is a carbocation precursor; (c) a material which generates strong acid upon irradiation. Exposure of a film containing these three structural components affords a latent image of acid dispersed in the polymer matrix. In a subsequent baking step, the photogenerated acid reacts with the latent electrophile releasing a very reactive carbocationic species which becomes bound to the aromatic moiety. As one of the components of the resist is polymeric and multifunctional, the result is a rapid increase in molecular weight due to branching and crosslinking of the chains. In terms of imaging, this process translates into the formation of a negative image of the mask although under some conditions a positive image may also be produced. The system shows a very high sensitivity and can provide high resolution images devoid of distortion due to the absence of swelling during development.

The accelerated synthesis of regular dendritic poly (ether-urethane) macromolecules through growth of two generations in a single synthetic operation has been explored. This procedure requires the use of two AB2 monomers such as 3,5-diisocyanatobenzyl chloride and 3.5-dihydroxybenzyl alcohol that can react pairwise in a one-pot sequential addition procedure. The two monomers are added stepwise to a previously formed first-generation dendrimer to produce a third-generation dendritic molecule without any need for intermediate purification or activation procedures. When 3,5-dihydroxybenzyl alcohol is used as the second monomer, some irregular growth is seen due to the occurrence of a side reaction involving transesterification of the carbamic ester moiety. The side reaction can be avoided if 3,5dihydroxybenzyl alcohol is replaced by methyl 3,5-dihydroxybenzoate.

Evaluation d'un adhesif a base de lessive residuaire sulfitique, d'une resine alcaline phenol-formaldehyde et d'un catalyseur acide

Abstract Newly designed hydrogen-bonded liquid crystals having the simplest mesogenic structure have been obtained by self-assembly of 4-alkoxybenzoic acid and 4-alkylpyridine. The complexes show nematic phases near room temperature. The nematic phase is broadened by mixing of several complexes within a homologous series.

Abstract 4‐Nitrophenyl methacrylate (1a), 4‐nitrophenyl esters of some N ‐methacryloyl‐ω‐amino acids (1b −d) and 4‐nitrophenyl esters of N ‐acetyl‐ and N ‐methacryloyltryptophane (2a and 2b) were prepared and characterized. Copolymers of 1 a −d and 2 b with N ‐2‐hydroxypropylmethacrylamide (HPMA), N ‐isopropylmethacrylamide (iPMA) and N ‐ethylmethacrylamide (EMA) were also prepared. The 4‐nitrophenyl ester content of the copolymers was determined spectrophotometrically from their UV absorption and from the UV absorption of the 4‐nitrophenolate ion which is released upon hydrolysis of the active esters with 0,1 M sodium hydroxide. The difference between these values depends on both the type of polymerizable active ester used and the comonomer. The proportion of non‐hydrolyzable structure is especially high in the case of copolymers containing 4‐nitrophenyl esters of the methacryloylated α‐amino acids 1b and 2b . The formation of non‐hydrolyzable structures is likely due to side reactions which occur during polymerization. The polymers prepared by copolymerization of the polymerizable 4‐nitrophenyl esters were not found to be suitable for the preparation of polymeric fluorescent probes by a chemical modification route. It was found that the rate of aminolysis of low‐molecular‐weight and polymeric activated esters increases with increasing the number of methylene groups in the N ‐(ω‐aminoalkyl)‐5‐dimethylamino‐1‐ naphthalenesulfonamides (dansylamines) 3a–f .

Abstract

Abstract Monodisperse polymer particle‐based separation media were prepared by a multi‐step swelling and polymerization method with two pairs of monomers and two porogenic solvents. Their chromatographic properties were compared to those of beads prepared by a corresponding suspension polymerization method without the use of seed polymer to ascertain the influence of the seed polymer on their porous structures. A large change in porous structure was observed when the swollen particle consisting of monomers and porogenic solvents contained at least one good solvent for the polystyrene seed polymer, allowing it to remain in the polymerizing medium. In contrast, when the polystyrene seed particle was excluded from the swollen oil droplets, due to its poor solubility in the monomers and the porogenic solvents, there was no difference in the chromatographic properties such as pore volume, pore size, pore size distribution, or retention selectivity between the multi‐step swelling and polymerization method and the suspension polymerization method. Since the only difference between the multi‐step swelling and polymerization method and the suspension method is the use of the seed polymer, it appears that a very small amount (< 1% v/v) of seed polymers in the enlarged swollen droplets plays an important role as a porogen and affects the porous structure as well as the chromatographic properties of the monodisperse polymer particle‐based separation media. © 1993 John Wiley & Sons, Inc.

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTHigh-Throughput Synthesis of Nanoscale Materials: Structural Optimization of Functionalized One-Step Star PolymersAnton W. Bosman, Andreas Heumann, Gerrit Klaerner, Didier Benoit, Jean M. J. Fréchet, and Craig J. HawkerView Author Information IBM Almaden Research Center, 650 Harry Road San Jose, California 95120 Symyx Technologies, 3100 Central Expressway Santa Clara, California 95051 Department of Chemistry, University of California, Berkeley Berkeley, California 94720 Cite this: J. Am. Chem. Soc. 2001, 123, 26, 6461–6462Publication Date (Web):June 7, 2001Publication History Received15 February 2001Published online7 June 2001Published inissue 1 July 2001https://pubs.acs.org/doi/10.1021/ja010405zhttps://doi.org/10.1021/ja010405zrapid-communicationACS PublicationsCopyright © 2001 American Chemical SocietyRequest reuse permissionsArticle Views2020Altmetric-Citations177LEARN 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-AlertscloseSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Aromatic compounds,Functionalization,Mixtures,Star polymers,Styrenes Get e-Alerts

The first use of polyether dendrons as macromolecular initiators for the controlled free radical polymerization of vinyl monomers has been demonstrated. Dendrons containing either a single benzylic TEMPO or halide functionality at their focal point have been used for the nitroxide mediated and atom transfer radical polymerizations, respectively. In both cases, hybrid dendritic-linear block copolymers with well-controlled molecular weights and low polydispersities can be obtained. The structure of the hybrid block copolymers is supported by SEC and spectral data. All the copolymers exhibit a single Tg, indicating that both blocks are miscible. Hybrid block copolymers difficult or impossible to prepare by previous techniques have been synthesized to demonstrate the versatility of this approach.

TEMPO-based stable radicals were attached to dendrimers of variable size and used to control radical polymerization of styrene, vinyl acetate, and (meth)acrylates. Thermal polymerization of styrene with [G-2]-TEMPO proceeded in a similar but not better controlled manner than with TEMPO alone. In the polymerization of styrene initiated with BPO, the kinetics and the molecular weight/conversion relations showed the same tendency as with TEMPO, though the polydispersity was higher than in the absence of dendrimers. This indicates that homolytic cleavage occurs at the reaction temperature, monomer can diffuse inside the cavity of the dendrimer, and polymer is at least partially compatible with the dendrimer. Model reactions indicate that the higher observed polydispersities could not be ascribed to transfer to benzyl hydrogen atoms. Therefore, the higher polydispersities could originate from the self-initiated polymerization of styrene outside of the dendrimers as well as the slow exchange of these chains with chains attached to dendrimers. To evaluate the effect of self-initiation, vinyl acetate, methyl methacrylate, and n-butyl acrylate were used; however, the resulting polymers were incompatibile with the dendrimers. The growing chains are easily released from the cavity of the dendrimers into solution, and their return into the cavities of the dendrimers was not fast enough to control the polymerization. The results of the polymerization in decalin solution indicate that polymerization of these monomers is better controlled but only at the early stages of the polymerizations. The subsequent precipitation of polymers attached to the dendrimers prevents further polymerization. These results suggest that the main reason for the higher observed polydispersities is not termination between growing chains but either decomposition of alkoxyamines or self-initiation occurring simultaneously with the slow propagation.

The design of new condensation polymers which undergo acid-catalyzed thermolysis is explored with polycarbonates. The polymers are prepared by phase-transfer catalyzed polycondensation using active esters or carbonates and diols. Polycarbonates containing tertiary, allylic or benzylic diol units susceptible to elimination decompose thermally near 200° to volatile materials. Self developing resist materials can be designed by combining the active polycarbonates with photoactive triarylsulfonium salts or other similar compounds which generate strong acids upon irradiation. Exposure of the resist material creates a latent image which can be developed thermally with evolution of volatile carbon dioxide, alkenes, and alcohols.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTFullerene-bound dendrimers: soluble, isolated carbon clustersK. L. Wooley, C. J. Hawker, J. M. J. Frechet, F. Wudl, G. Srdanov, S. Shi, C. Li, and M. KaoCite this: J. Am. Chem. Soc. 1993, 115, 21, 9836–9837Publication Date (Print):October 1, 1993Publication History Published online1 May 2002Published inissue 1 October 1993https://pubs.acs.org/doi/10.1021/ja00074a075https://doi.org/10.1021/ja00074a075research-articleACS PublicationsRequest reuse permissionsArticle Views743Altmetric-Citations159LEARN 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