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 .

Aliphatic small saturated carbocycles and azacycles are increasingly used as bioisosteres and structural cores in medicinally active compounds due to the beneficial pharmacological and physicochemical properties they can impart. Therefore, a need exists to modify these motifs and to install groups that enable their incorporation into organic structures; these goals can be accomplished by introducing functional groups at the position of the C-H bonds on the rings. However, functionalization of secondary C-H bonds in strained rings, such as cyclopropanes and cyclobutanes, confronts several challenges, including the greater strength of these bonds than those in unstrained rings. Although catalytic, undirected borylation has been reported to functionalize the C-H bonds of selected strained rings, the examples of such reactions in earlier studies are limited in scope, principally involving rings with a small number and size of substituents. We report the borylation of fused, spirocyclic, and polysubstituted cyclopropanes, cyclobutanes, azetidines, and β-lactams with high diastereoselectivity with the most recent generation of catalysts for the borylation of alkyl C-H bonds. Important for the formation of more complex structures, reactions occur, unlike reactions of larger rings, with steric hindrance on adjacent carbon atoms. The stoichiometry of the diboron reagent, the <i>s</i>-character of the C-H bond, and the disposition of substituents influence reactivity and product distribution in ways charted by our results. With these advances, the borylation of C-H bonds becomes a viable approach for the modification and incorporation of these ring systems into pharmaceutically active structures.

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.

Abstract Selective recognition between a benzoic acid derivative and nonmesogenic 4,4′-bibyridine through intermolecular hydrogen bonds results in a novel molecular structure with liquid crystalline properties, in which 4,4′-bipyridine functions as a core unit.

Supramolecular liquid-crystalline networks have been prepared by self-assembly of multifunctional H-bond donor and acceptor molecules through the formation of intermolecular hydrogen bonds. Two tricarboxylic acids, 1,3,5-tris(2-(2-(4-carboxyphenoxy)ethoxy)ethoxy)benzene (1) and 3,4-bis(2-(2-(4-carboxyphenoxy)ethoxy)ethoxy)benzoic acid (2), have been synthesized for the use as trifunctional H-bond donors. These trifunctional H-bond donors have been complexed with bifunctional H-bond acceptors, such as 4,4'-bipyridine (3), 1,2-bis(4-pyridyl)ethane (4), trans-1,2-bis(4-pyridyl)ethylene (5), and bis(2-(2-(4-(2-(4-pyridyl)ethenyl)phenoxy)ethoxy)ethyl) ether (6), maintaining a 1:1 donor/acceptor group stoichiometry. All individual components are nonmesogenic. Self-assembly of these multifunctional compounds results in the formation of liquid-crystalline network structures. For example, the H-bonded complex 1/5 shows a smectic A phase from 176 to 156 °C, while 2/5 exhibits a nematic phase between 200 and 87 °C on cooling. This behavior is attributed to the dynamics of the hydrogen bonds. These results suggest that the trifunctional H-bond donors adopt linear conformations that induce calamitic mesomorphic behavior with bifunctional H-bond acceptors.

We introduce here a novel approach to highly EUV transparent, carbon dense polymers for application as photoresist materials. The backbone of the prototype polymer consists of bicyclic hydrocarbons spiro-fused to cyclohexane moieties decorated with pendant t-butyl esters. This high polymer is formed through the free radical cyclopolymerization of functionalized norbornane derivatives. Imaging experiments conducted at 193 nm demonstrate features below 0.15 microns.

Several monolithic chiral stationary phases for reversed-phase electrochromatography have been prepared within the confines of untreated fused silica capillaries by the direct copolymerization of the chiral monomer 2-hydroxyethyl methacrylate (N-L-valine-3,5- dimethylanilide) carbamate with ethylene dimethacrylate, 2-acrylamido-2-methyl-1-propanesulfonic acid and butyl or glycidyl methacrylate in the presence of a porogenic solvent. The hydrophilicity of the stationary phase, which may be enhanced further by the hydrolysis of the epoxide functionalities of the glycidyl methacrylate moieties within the monolith, was found to have a pronounced effect on the enantioseparation. Using the most hydrophilic monolithic capillary column and optimized elution conditions, a separation of N-(3,5-dinitrobenzoyl)leucine diallylamide enantiomers with an efficiency of 61000 plates m–1 and a resolution of 2.0 was achieved.

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.

Supramolecular ferroelectric liquid crystalline complexes have been obtained from 4-alkoxybenzoic acids and optically active truns-4-substituted-4-stilbazolesC. hiral smectic C phases are induced by the formation of supramolecular mesogenic structure through the selective intermolecular hydrogen bond between the achiral benzoic acids and the chiral nonmesogenic stilbazoles.

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 (&lt; 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 &amp; Sons, Inc.

The photolysis of 9-hydroxy-10-methyl-9-phenyl-9,10-dihydroacridine 1 or its 9-methoxy derivative 2 occurs with heterolytic cleavage of a C–O bond and formation of the desired strong base together with a cation that stabilizes itself through aromatization.

The highly compact and globular shape, as well as the uniform size and plurifunctionality of dendrimers make them ideal molecular building blocks for a wide range of interfacial materials involving self-assembled monolayers, Langmuir films, multilayers, and other surface-confined assemblies. Moreover, the study of the behavior of dendrimers at surfaces and interfaces provides unique insight into their chemical and physical properties. Dendritic macromolecules play an increasingly important role in the materials and surface sciences, where applications utilizing polymer thin films can benefit from their distinctive chemical and physical properties. Recent investigations have highlighted the use of dendrimers as functional surfaces and as interfacial materials for applications in membranes, adhesion, microelectronics or in chemical and biological sensing.

Abstract Dendrimers and hyperbranched polymers are globular macromolecules that are characterized both by a highly branched structure, in which all bonds converge to a focal point or core, and a multiplicity of reactive chain-ends. Because of the obvious similarity of their building blocks, many assume that the properties of these two families of dendritic macromolecules are almost identical and that the terms “dendrimer” and “hyperbranched polymer” can be used interchangeably. This assumption is incorrect because only regular dendrimers have a precise end-group multiplicity and functionality and exhibit properties that are totally unlike those of all other families of macromolecules. For example, regular dendrimers display a maximum in the relationship between their intrinsic the applications that are contemplated for the dendritic polymers. Using living systems as a model, one must anticipate that the regular placement of reactive groups at a precise location, as opposed to throughout a structure, has great importance in terms of ultimate performance when surface and interfacial properties are involved. Therefore, just like Langmuir-Blodgett films, dendrimers belong to a special class of well-defined molecular architectures where exact structure and ultimate performance are intimately related. It is likely that regular dendrimers will continue to draw much attention in specialized applications that take advantage of their precise architecture: drug delivery, catalysis, nanoreactors, molecular devices, etc. In contrast, hyperbranched polymers will join other interesting functional polymers in applications that involve commodity materials: from coatings and adhesives to lubricants, compatibilizers, and carriers. Today, the frontiers in the chemistry of dendritic polymer are in the search for rapid methods of synthesis involving, for example, vinyl polymerizations [46, 50], the preparation of “engineered” dendritic structures, and the discovery of new properties and applications [1, 47].

Modes of attachment of functional groups to crosslinked polystyrene are discussed (1). Attention is drawn to improved stability and activity of polymer-bound reagents and catalysts incorporating dimethylene spacer between polystyrene aryl and functional group heteroatom, and the simplicity and versatility of their synthesis through high-conversion functional group modifications.