Complex single-chain polymer topologies locked by positionable twin disulfide cyclic bridges (original) (raw)
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Macromolecular Symposia, 2014
The analysis of PS-b-PI copolymers, synthesized by sequential living anionic polymerization was conducted by on-line hyphenation of liquid chromatography at critical conditions (LCCC) and proton nuclear magnetic resonance spectroscopy ( 1 H-NMR). Critical conditions were established for polyisoprene using 1,4-dioxane as the mobile phase and varying the column oven temperature. At these critical conditions, the polyisoprene homopolymer formed during synthesis was separated from the copolymer. The molar mass of the PS block, the chemical composition of the block copolymers as well as the microstructure of PI were determined in a single experiment.
Journal of Applied Polymer Science, 2004
itaconimide with methyl methacrylate was carried out by taking varying mole fractions (0.1 to 0.5) of N-aryl substituted itaconimide monomers in the initial feed using azobisisobutyronitrile as an initiator and tetrahydrofuran as the solvent. The copolymer composition was determined by 1 H-NMR spectroscopy using the ratio of proton resonance signal intensity attributed to -OCH 3 of MMA (␦ ϭ 3.5-3.8 ppm) and the aromatic protons The comonomer reactivity ratios were determined using Kelen-Tü dos and nonlinear error in variable methods. The reactivity ratios obtained by nonlinear error in variable methods were r 1 (PI) ϭ 1.26/r 2 (MMA) ϭ 0.35; r 1 (MI) ϭ 1.21/r 2 (MMA) ϭ 0.34; and r 1 (OI) ϭ 0.78/r 2 (MMA) ϭ 0.34. The carbonyl carbon signals of MMA (M) as well as N-aryl itaconimide (I) copolymers were used for the determination of the sequence distribution of M-and I-centered triads. The sequence distribution of M-and I-centered triads determined from 13 C{ 1 H}-NMR spectra of the copolymers are in good agreement with the triad concentrations calculated using the Alfrey-Mayo statistical model and Monte Carlo simulation method.
Journal of Separation Science, 2012
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 polystyreneb-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.
Macromolecular Chemistry and Physics
has drawn great attention because it paves the way to various branched architectures, crosslinking reactions, reversible supramolecular noncovalent bonds, coupling with reactive groups of other polymer chains, and the initiation of polymers with different monomers. [1] One example of the benefits of chain functionalization is in the synthesis of macromonomers and indeed, the "macromonomer" approach has become widely adopted as a route to make a variety of complex branched and grafted architectures with a high compositional and molecular homogeneity. Macromonomers are (usually) linear macromolecules, synthesized by a living/controlled polymerization mechanism, with functional groups at one or both ends, such that they can undergo subsequent coupling reactions, leading to the construction of complex architectures. [2-22] In recent years, we have exploited and developed this concept for the synthesis of a variety of complex dendritically branched polymers including DendriMacs, [23-25] HyperMacs, [26-30] and more recently HyperBlocks. [31,32] One key advantage of this approach is that the coupling reactions need not to be carried out under the rigorously inert conditions required for anionic polymerization. [33] There are two main ways to introduce such functionalities at one end of a polymer chain. Traditionally, chain-end functionalization was achieved through a postpolymerization reaction of the living anionic chain-end with an electrophilic species carrying the desired functional group. Numerous functionalities may be introduced by the controlled termination of alkyllithium-initiated living polymers with special reagents. For example, a carboxylic acid group can be introduced by the addition of gaseous carbon dioxide to the living solution of the polymeric organolithium compound, [34,35] hydroxyl-terminated polymers can be obtained by reaction with ethylene oxide, [36,37] and amino groups can be added through protected α-halo-ωaminoalkanes. [38-40] Sulfonate end-capped polymers have been synthesized through the reaction of polymeric organolithium compounds directly with sultones. [41] However, many of these reactions are often affected by side reactions, usually leading to a lower degree of functionalization. [1] Alternatively, a (protected) functionalized initiator can be used for anionic polymerization of for example, styrene or dienes. Organolithium initiators with a silyl-protected hydroxy Anionic Functionalization The controlled functionalization of polymers via anionic polymerization draws great attention not only because of the importance of introducing functionality into otherwise unfunctionalized polymers, but also because of the possibility to use the resulting macromonomers to make a variety of complex architectures. The versatile family of 1,1-diphenylethylene (DPE) derivatives is widely used to produce many different functionalized (co)polymers. DPE can be added either as an end-capping agent or be activated by butyllithium to initiate the polymerization. However, each approach faces potential problems in gaining precise control over the number of DPE moieties per chain. In this work, for the first time, the effectiveness of each approach is compared by the characterization of 1,1-bis(4-tert-butyldimethylsiloxyphenyl)ethylene functionalized polystyrene, synthesized via both the procedures. A combination of NMR, size exclusion chromatography, matrix-assisted laser desorption ionization-time of flight (MALDI-ToF) mass spectrometry, and interaction chromatography is used. To overcome the limitations of DPE derivatives, the use of a novel (protected) bisphenol F potassium initiator is proposed.
A simple method for determining protic end-groups of synthetic polymers by 1H NMR spectroscopy
Polymer, 2006
A simple method for the determination of protic end-groups (–XH) in synthetic polymers involves in situ derivatization with trichloroacetyl isocyanate (TAI) in an NMR tube and observation of the imidic hydrogens of the derivatized products [–X–C(O)–NH–COCCl3] by 1H NMR spectroscopy. In this paper, we report that the method is effective for the quantitative determination of hydroxy, primary amino and carboxy end-groups of polymers with . It may also be applied to detect chain ends in higher molecular weight polymers. The signals for the imidic (and, in the case of amines, amidic) hydrogens appear in a region (δ 7.5–11) that is clear of other signals in the case of most aliphatic polymers and many aromatic polymers such as polystyrene and poly(ethylene terephthalate). The method has been applied in the characterization of polymers formed by conventional and living radical polymerization (RAFT, ATRP, NMP), to end functional poly(ethylene oxide) and to polyethylene-block-poly(ethylene oxide). The method appears less effective in the case of sulfanyl end-groups. The chemical shift of the imidic hydrogen shows remarkable sensitivity to the microenvironment of chain end. Thus, the imidic hydrogens of TAI derivatized polyethylene-block-poly(ethylene oxide) [PE-(EO)mOC(O)NHC(O)CCl3] are at least partially resolved for m=0, 1, 2, 3 and ≧4 in the 400 MHz 1H NMR spectrum. It is also sensitive to the chain end tacticity of, for example, amino-end-functional polystyrenes and thus to the relative configuration of groups removed from the chain-end by two or more monomer units. TAI derivatization also facilitates analysis of amine functional polymers by gel permeation chromatography (GPC) which is often rendered difficult by specific interactions between the amine group and the GPC column packing.
Sequence analysis of styrenic copolymers by tandem mass spectrometry
Analytical chemistry, 2014
Styrene and smaller molar amounts of either m-dimethylsilylstyrene (m-DMSS) or p-dimethylsilylstyrene (p-DMSS) were copolymerized under living anionic polymerization conditions, and the compositions, architectures, and sequences of the resulting copolymers were characterized by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and tandem mass spectrometry (MS(2)). MS analysis revealed that linear copolymer chains containing phenyl-Si(CH3)2H pendants were the major product for both DMSS comonomers. In addition, two-armed architectures with phenyl-Si(CH3)2-benzyl branches were detected as minor products. The comonomer sequence in the linear chains was established by MS(2) experiments on lithiated oligomers, based on the DMSS content of fragments generated by backbone C-C bond scissions and with the help of reference MS(2) spectra obtained from a polystyrene homopolymer and polystyrene end-capped with a p-DMSS block. The MS(2) data provided con...
Journal of Applied Polymer Science, 2007
Polyvinylpyrrolidone (PVP)-oximate-silicobenzoyl glycine (POSBG) copolymer has been prepared taking PVP and benzoyl glycine with tetraethylorthosilicate as binder. Average viscosity molecular weights (M v) each of PVP-oxime and POSBG were determined with dilute aqueous solutions. For molecular weights primarily a calibration curve between intrinsic viscosities [Z] and different molecular weights of polyvinyl alcohol (marker) has been obtained to determine M v of oxime as 42,042 g mol À1. Similarly the M v of POSBG as 80,297.13 g mol À1 was determined with [Z] of lysozyme (molecular weight ¼ 24,000 g mol À1) egg albumin (40,000 g mol À1) and BSA (65,000 g mol À1). For structural illustration, IR spectra of PVP-oxime and copolymer were recorded in Nujol, which do not depict band frequency of À ÀOH group of binder. The 1602, 1688, 1182, and 1127 cm À1 stretching vibration frequencies noted in spectra infer presence of À ÀC¼ ¼N, À ÀC¼ ¼O, À ÀSiÀ ÀOÀ ÀSiÀ À, and À ÀSiÀ ÀOÀ ÀCÀ À groups, respectively, in POSBG. Structures of PVP-oxime unit of POSBG are supported with Proton NMR. The work is aimed to develop new valuable biosensor and conducting copolymer molecule to serve as useful biochip and a biocompatible template.