Analysis of polystyrene-b-polyisoprene copolymers by coupling of liquid chromatography at critical conditions to NMR at critical conditions of polystyrene and polyisoprene

For the investigation of the molecular heterogeneity of polystyrene-b-polyisoprene block copolymers, a chromatographic separation method, namely liquid chromatography at critical conditions was developed. This method was coupled on-line with (1)H-NMR(where NMR stands for nuclear magnetic resonance) for the comprehensive analysis of the polystyrene-b-polyisoprene copolymers. The copolymers were synthesized by two different methods: sequential living anionic polymerization and coupling of living precursor blocks. While (1)H-NMR allows just for the analysis of the bulk chemical composition of the block copolymers, the coupling with liquid chromatography at critical conditions provides selective molar mass information on the polystyrene and polyisoprene blocks within the copolymers. The polyisoprene block molar mass is determined by operating at chromatographic conditions corresponding to the critical point of adsorption of polystyrene and size exclusion chromatography mode for polyisoprene. The molar mass of the polystyrene block is determined by operating at the critical conditions of polyisoprene. In addition to the molar mass of each block of the copolymers, the chemical composition distribution of the block copolymers was determined. By using the coupling of liquid chromatography at critical conditions to (1)H-NMR, one can also detect the homopolymers formed during synthesis. Finally the microstructure of the polyisoprene block in the copolymers was evaluated as a function of molar mass.     

Microwave-Assisted Soluble Polymer-supported Synthesis of Peptoids

Libraries of peptide-like compounds are attractive sources of binding agents for proteomics applications. The synthesis of oligomeric combinatorial libraries of peptidomimetics is usually more straightforward than the creation of large libraries of more "drug-like" molecules. Herein we report synthesis of peptoids on soluble high loading Noncross-linked polystyrene. The synthesis route consists of: (a) preparation "soluble wang resin" from non-crosslinked polystyrene and 4-hydroxybenzyl alcohol via ether linkage, (b) an esterification step performed by the addition of bromoacetyl bromide to "soluble wang resin" and (c) a nucleophilic displacement of bromide with a primary amine.     

Ethylene glycol: properties, synthesis, and applications

Ethylene glycol (EG) is an important organic compound and chemical intermediate used in a large number of industrial processes (e.g. energy, plastics, automobiles, and chemicals). Indeed, owing to its unique properties and versatile commercial applications, a variety of chemical systems (e.g., catalytic and non-catalytic) have been explored for the synthesis of EG, particularly via reaction processes derived from fossil fuels (e.g., petroleum, natural gas, and coal) and biomass-based resources. This critical review describes a broad spectrum of properties of EG and significant advances in the prevalent synthesis and applications of EG, with emphases on the catalytic reactivity and reaction mechanisms of the main synthetic methodologies and applied strategies. We also provide an overview regarding the challenges and opportunities for future research associated with EG.     

Synthesis of a polypseudorotaxane, polyrotaxane, and polycatenane using ‘click’ chemistry

The synthesis of a polypseudorotaxane, polyrotaxane, and polycatenane containing the electron-deficient cyclophane cyclobis(paraquat-p-phenylene) (CBPQT⁴⁺) subunit in the side chain is described. These interlocked supramolecular polymers have been prepared from an azide-functionalized polystyrene derivative and an acetylene-functionalized [2]rotaxane, [2]catenane and their parent tetracationic cyclophane via Cu(I)-catalyzed 1,3 dipolar cycloadditions (‘click chemistry’). The synthesis and characterization of the polymers and intermediates has been described using IR, ¹H NMR, UV spectroscopies, and voltammetry. We have shown that the CBPQT⁴⁺ unit of the side chain polystyrene derivative has the ability to reversibly undergo complexation with a complementary dialkoxynaphthalene derivative.     

Oligonucleotide Synthesis on Polystyrene-Grafted Poly(tetrafluoroethylene) Support

Supports consisting of a thin layer (2–10%) of polystyrene (PS) grafted onto a poly(tetrafluoroethylene) (PTFE) core are an interesting alternative to controlled pore glass (CPG) carriers in oligonucleotide synthesis. The beads are mechanically stable, do not show significant swelling, and allow effective removal of substrates by short washing steps with organic solvents. PTFE-PS as an organic polymer has generally more hydrophobic properties than inorganic polymer supports and, therefore, is well compatible with organic solvents such as anhydrous MeCN. We found PTFE with a content of 2–3% PS graft to be a very good support for the synthesis of oligonucleotides of extended length. In comparison, PTFE with 5–10% grafted PS is especially useful for large-scale syntheses. Functionalization procedures minimized in the extent of side reactions are described as well as examples for the use of the supports in syntheses of oligonucleotides both on large scale and of extended chain length.     

A phosphorescent copper(I) complex: synthesis, characterization, photophysical property, and oxygen-sensing behavior

In this paper, we report the synthesis, crystal structure, photophysical properties, and electronic nature of a phosphorescent Cu(I) complex of [Cu(Phen-Np)(POP)]BF4, where Phen-Np and POP stand for 2-(naphthalen-1-yl)-1H-imidazo[4,5-f][1,10]phenanthroline and bis(2-(diphenylphosphanyl)phenyl) ether, respectively. [Cu(Phen-Np)(POP)]BF4 renders a yellow phosphorescence peaking at 545 nm, with a long excited state lifetime of 4.69 μs. Density functional calculation reveals that the emission comes from a triplet metal-to-ligand-charge-transfer excited state. We electrospun composite nanofibers of [Cu(Phen-Np)(POP)]BF4 and polystyrene (PS), hoping to explore the possibility of using the composite nanofibers as an oxygen sensing material. The finally obtained samples with average diameter of ～300 nm exhibit a maximum sensitivity of 7.2 towards molecular oxygen with short response time of 7s due to the large surface-area-to-volume ratio of nanofibrous membranes. No photobleaching is detected in these samples.     

Unconventional Route to Uniform Hollow Semiconducting Nanoparticles with Tailorable Dimensions,Compositions, Surface Chemistry,and Near‐Infrared Absorption

Despite impressive recent advances in the synthesis of lead chalcogenide solid nanoparticles, there are no examples of lead chalcogenide hollow nanoparticles (HNPs) with controlled diameter and shell thickness as current synthetic approaches for HNPs have inherent limitations associated with their complexity, inability to precisely control the dimensions, and limited possibilities with regard to applicable materials. Herein, we report on an unconventional strategy for crafting uniform lead chalcogenide (PbS and PbTe) HNPs with tailorable size, surface chemistry, and near‐IR absorption. Amphiphilic star‐like triblock copolymers [polystyrene‐block‐poly(acrylic acid)‐block‐polystyrene and polystyrene‐block‐poly(acrylic acid)‐block‐poly(3,4‐ethylenedioxythiophene)] were rationally synthesized and exploited as nanoreactors for the formation of uniform PbS and PbTe HNPs. Compared to their solid counterparts, the near‐IR absorption of the HNPs is blue‐shifted owing to the hollow interior. This strategy can be readily extended to other types of intriguing low‐band‐gap HNPs for diverse applications.     

Unconventional Route to Uniform Hollow Semiconducting Nanoparticles with Tailorable Dimensions,Compositions, Surface Chemistry,and Near‐Infrared Absorption

Despite impressive recent advances in the synthesis of lead chalcogenide solid nanoparticles, there are no examples of lead chalcogenide hollow nanoparticles (HNPs) with controlled diameter and shell thickness as current synthetic approaches for HNPs have inherent limitations associated with their complexity, inability to precisely control the dimensions, and limited possibilities with regard to applicable materials. Herein, we report on an unconventional strategy for crafting uniform lead chalcogenide (PbS and PbTe) HNPs with tailorable size, surface chemistry, and near‐IR absorption. Amphiphilic star‐like triblock copolymers [polystyrene‐block‐poly(acrylic acid)‐block‐polystyrene and polystyrene‐block‐poly(acrylic acid)‐block‐poly(3,4‐ethylenedioxythiophene)] were rationally synthesized and exploited as nanoreactors for the formation of uniform PbS and PbTe HNPs. Compared to their solid counterparts, the near‐IR absorption of the HNPs is blue‐shifted owing to the hollow interior. This strategy can be readily extended to other types of intriguing low‐band‐gap HNPs for diverse applications.     

Diversity-oriented synthesis of biaryl-containing medium rings using a one bead/one stock solution platform

Diversity-oriented synthesis of structurally complex and diverse small molecules can be used as the first step in a process to explore cellular and organismal pathways. The success of this process is likely going to be dependent on advances in the synthesis of small molecules having natural product-like structures in an efficient and stereoselective manner. The development, scope, and mechanism of the oxidation of organocuprates was investigated and exploited in the atropdiastereoselective synthesis of biaryl-containing medium rings (9-, 10-, and 11-membered rings). The methodology was performed on high-capacity, large polystyrene beads by metalating aryl bromides with i-PrBu(2)MgLi, followed by transmetalating with CuCN x 2LiBr and then oxidizing with 1,3-dinitrobenzene, and was used in a diversity-oriented synthesis of biaryl-containing medium rings (library total theoretical maximum 1412 members). The high capacity beads were arrayed into 384-well plates and, using a process optimized during the development of a one bead/one stock solution technology platform, converted into arrays of stock solutions, with each stock solution containing largely one compound. These stock solutions were used in numerous phenotypic and protein-binding assays. The process described outlines a pathway that we feel will contribute to a comprehensive and systematic chemical approach to exploring biology (chemical genetics).     

Cationic polymerization with boron halides. V. Synthesis of poly(isobutylene-b-styrene) and poly(styrene-b-isobutylene)

Block copolymers of isobutylene and styrene, PIB-b-PSt and PSt-b-PIB, have been prepared by a two-step synthesis involving (1) preparation of terminally chlorinated (telechelic) polyisobutylene or polystyrene “prepolymers” by using the H₂O/BCl₃ initiator system and (2) blocking from these telechelic prepolymers a second polymer segment by using an alkyaluminum, e.g., Et₂AlCl coinitiator. The telechelic polyisobutylene and polystyrene contain tertiary and benzylic chlorine termini, respectively. Block copolymer characterization included detailed selective solvent extraction procedures, coupled with GPC determinations, PMR, solubility, and intrinsic viscosity studies. The synthesis of PIB-b-PSt and PSt-b-PIB provides direct chemical evidence for the presence and position of active chlorine termini in BCl₃-coinitiated olefin polymerizations.     

Universal solid-phase approach for the immobilization, derivatization, and resin-to-resin transfer reactions of boronic acids.

Boronic acid-containing molecules are employed in a broad range of biological, medicinal, and synthetic applications. These compounds, however, tend to be difficult to handle by solution-phase methods. Herein, this problem is addressed with the development of the first general solid-phase approach for the derivatization of functionalized boronic acids. This approach is based on the use of a diethanolamine resin anchor that facilitates boronic acid immobilization by avoiding the need for exhaustive removal of water in the esterification process. The immobilization of a wide variety of boronic acids onto N,N-diethanolaminomethyl polystyrene (DEAM-PS, 1) can be performed within minutes by simple stirring in anhydrous solvents at room temperature. Evidence for the formation of a bicyclic diethanolamine boronate with putative N-B coordination was shown by (1)H NMR analysis of DEAM-PS-supported p-tolylboronic acid. The hydrolytic cleavage of the same model boronic acid from the DEAM-PS resin was studied by UV spectroscopy. Hydrolysis and attachment were shown to occur under a rapidly attained equilibrium, and a large excess of water (>32 equiv) is required to effect a practically quantitative release of boronic acids from DEAM-PS. Despite their relative sensitivity to water and alcohols, DEAM-PS-bound arylboronic acids functionalized with a formyl, a bromomethyl, a carboxyl, or an amino group can be transformed in good to excellent yields into a wide variety of amines, amides, anilides, and ureas, respectively. Ugi multicomponent reactions on DEAM-PS-supported aminobenzeneboronic acids, derivatization of multifunctional arylboronic acids, and sequential reactions can also be carried out efficiently. These new DEAM-PS-supported arylboronic acids can be employed directly into resin-to-resin transfer reactions (RRTR). This type of multiresin process helps eliminate time-consuming cleavage and transfer operations, thereby considerably simplifying the outlook of combinatorial library synthesis by manual or automated means. This concept was illustrated by a set of optimized procedures for the Suzuki cross-coupling and the borono-Mannich reactions.     

Monitoring solid phase synthesis reactions with electrochemical impedance spectroscopy (EIS)

This work describes the use of electrochemical impedance spectroscopy (EIS) as a means to monitor solid phase synthesis on resin beads. EIS was used to track changes during the swelling of beads in various solvents, during three typical reactions and throughout cleavage of the final product from the bead. The impedance response was investigated in a chemical reactor and was found to be faintly sensitive to the resin swelling and solvent flow. The position of the electrode within the reactor was found to be critical as polystyrene based beads float or sink dependent upon the solvent used. However, by choosing electrode position it was possible to monitor reaction progress on beads or within the bulk reactant/product mixture. Of the three typical chemical reactions studied impedance spectroscopy successfully followed two. Fitting of the impedance data to an equivalent electrical circuit provided an estimate as to the relative contribution of capacitive and resistive components to the overall response. Kinetic data from two reactions were also modelled, in both cases complex kinetics was observed, in close agreement with other studies.     

Synthesis of monodisperse hydroxyl-containing polystyrene via chemical modification

A facile synthesis of linear monodisperse hydroxyl-containing polystyrene, poly{styrene-co-[p-(1-hydroxyethyl)styrene]} and poly{styrene-co-[p-(2-hydroxypropan-2-yl)styrene]}, was carried out via chemical modification of polystyrene by a two-step procedure, i. e. monodisperse polystyrene was acetylated under mild conditions, followed by processes of reduction with LiAlH₄ and addition with CH₃MgBr, respectively. ¹H NMR and FTIR spectra showed that in both cases, the reaction of acetyl to hydroxyl is complete. Sizeexclusion chromatography demonstrated that both molecular weight and monodispersity of the final products were basically unchanged.     

Dmab/ivDde protected diaminodiacids for solid-phase synthesis of peptide disulfide-bond mimics

The use of pre-prepared diaminodiacids has been established as an effective approach for the chemical synthesis of peptide disulfide bond mimics. A technical problem often encountered in the implementation of the diaminodiacids strategy is the use of heavy metal reagents to remove the side-chain protecting groups. In the present work, we reported the development of diaminodiacid that carry 4-(N-[1-(4,4-dimethyl-2,6-dioxocyclo-hexylidene)-3-methylbutyl]amino)benzyl (Dmab) and 1-(4,4-dimethyl-2,6-dioxocyclohex-1-ylidene)-3-methylbutyl (ivDde) protecting groups. This pair of protecting groups can be readily removed by mild hydrazinolysis during the solid-phase synthesis on resin. We demonstrated the use of Dmab/ivDde protected diaminodiacids in the successful synthesis of a disulfide surrogate of oxytocin.     

Microporous polystyrene particles for selective carbon dioxide capture

This study presents the synthesis of microporous polystyrene particles and the potential use of these materials in CO(2) capture for biogas purification. Highly cross-linked polystyrene particles are synthesized by the emulsion copolymerization of styrene (St) and divinylbenzene (DVB) in water. The cross-link density of the polymer is varied by altering the St/DVB molar ratio. The size and the morphology of the particles are characterized by scanning and transmission electron microscopy. Following supercritical point drying with carbon dioxide or lyophilization from benzene, the polystyrene nanoparticles exhibit a significant surface area and permanent microporosity. The dried particles comprising 35 mol % St and 65 mol % DVB possess the largest surface area, ～205 m(2)/g measured by Brunauer-Emmett-Teller and ～185 m(2)/g measured by the Dubinin-Radushkevich method, and a total pore volume of 1.10 cm(3)/g. Low pressure measurements suggest that the microporous polystyrene particles exhibit a good separation performance of CO(2) over CH(4), with separation factors in the range of ～7-13 (268 K, CO(2)/CH(4) = 5/95 gas mixture), which renders them attractive candidates for use in gas separation processes.     

Production of micron-sized, monodispersed, multihollow polystyrene/poly(3,5-xylidine) composite particles by chemical oxidative seeded polymerization

 Micron-sized, monodispersed polystyrene/poly(3,5-xylidine) composite polymer particles were produced by chemical oxidative seeded polymerization of 3,5-xylidine with 1.37-μm-sized, monodispersed polystyrene seed particles. The chemical oxidative seeded polymerization was conducted in an aqueous medium at 25 °C in the presence of poly(vinyl alcohol) as a stabilizer using ammonium persulfate as an oxidant. The composite particles had a multihollow structure. Received: 30 June 1999/Accepted in revised form: 21 October 1999     

Production of porous suspension polymers using a continuous tubular reactor

The conventional method for the synthesis of porous cross-linked copolymer beads is by suspension polymerisation. Suspension polymerisation reactions are generally performed in a stirred tank, which generally results in a large size distribution. By careful control of the polymerisation conditions, polymer beads can be produced using a tubular poly(tetrafluoroethylene) continuous reactor. Such beads are produced with the same average pore size, but with a lower degree of polydispersity than analogous systems produced in a batch reactor (stirred tank). This is achieved by density-matching the droplet and continuous phases (by the use of a brominated monomer or a porogenic diluent) and increasing the viscosity of the monomer phase (with the addition of small amounts of polystyrene). Received: 26 June 1999/Accepted in revised form: 7 October 1999     

Synthesis of Dibenzo[hi,st]ovalene and Its Amplified Spontaneous Emission in a Polystyrene Matrix

A large number of graphene molecules, or large polycyclic aromatic hydrocarbons (PAHs), have been synthesized and display various optoelectronic properties. Nevertheless, their potential for application in photonics has remained largely unexplored. Herein, we describe the synthesis of a highly luminescent and stable graphene molecule, namely a substituted dibenzo[hi ,st ]ovalene (DBO 1 ), with zigzag edges and elucidate its promising optical‐gain properties by means of ultrafast transient absorption spectroscopy. Upon incorporation of DBO into an inert polystyrene matrix, amplified stimulated emission can be observed with a relatively low power threshold (ca. 60 μJ cm⁻²), thus highlighting its high potential for lasing applications.     

Facile design of degradable poly(β‐thioester)s with tunable structure and functionality

The synthesis of a range of linear biodegradable poly(β‐thioester)s, PBTs, via hexylamine‐catalyzed thiol‐ene Micheal additions between a variety of diacrylate and dithiol monomers is described. Molecular weights up to 12,000 g mol^?1 are obtained for this new class of polymer materials. PBTs featuring very different chemical and mechanical behavior are obtained on the basis of seven diacrylate and three dithiol monomers. Polar PBTs are synthesized based on ethylene glycol‐containing monomers in an environmentally friendly solvent. Furthermore, PBTs containing urethane units in the main chain are obtained, providing access to an isocyanate‐free polyurethane polymerization method. The thiol‐ene addition approach can also be used to couple polystyrene oligomers synthesized from a bifunctional trithiocarbonate reversible addition fragmentation transfer agent. In this way, PBTs featuring polystyrene segments as well as diacrylate segments are produced. In general for these step‐growth polymerizations, by tuning the stoichiometric monomer ratio, a desired end group functionality can be quantitatively introduced into the PBT, which is demonstrated via soft ionization mass spectrometry analysis. As an example, alkyne end groups have been built in, giving access to use these materials in modular polymer design strategies. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 178–187