Complex single-chain polymer topologies locked by positionable twin disulfide cyclic bridges (original) (raw)
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, 2003
Homopolymerization and copolymerization of N-(o-/m-/p-chlorophenyl) 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 (␦ ϭ 7.0-7.5 ppm) of N-(o-/m-/p-chlorophenyl) itaconimide. 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.
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.
Advanced Polymer Architectures with Stimuli-Responsive Properties Starting from Inimers
Macromolecules, 2008
Novel, well-defined, temperature-and/or pH-sensitive copolymer architectures were prepared by atom transfer radical (co)polymerization (ATRP) of a temperature-sensitive poly(methyl vinyl ether) (PMVE) macromonomer, obtained via living cationic polymerization of MVE initiated with inimer 3,3-diethoxypropyl acrylate. Temperature-sensitive comb architectures were obtained by ATRP homopolymerization (Me 6 TREN/ CuBr in toluene) of the PMVE macromonomer. ATRP copolymerization of the PMVE macromonomer with tert-butyl acrylate, a hydrolyzable precursor for pH-sensitive acrylic acid (AA), gives statistical graft copolymers. Palm-tree block copolymers containing a linear PtBA (PAA after hydrolysis) block and a branched block based on PMVE macromonomers were also prepared and fully characterized. Using turbidimetry, dynamic light scattering, FT-IR, and NMR, the temperature and/or pH responsiveness of those (co)polymer architectures are compared with the properties of previously synthesized linear block copolymers containing PMVE and PtBA or PAA.
Polymer architectures via mass spectrometry and hyphenated techniques: A review
Analytica chimica acta, 2016
This review covers the application of mass spectrometry (MS) and its hyphenated techniques to synthetic polymers of varying architectural complexities. The synthetic polymers are discussed as according to their architectural complexity from linear homopolymers and copolymers to stars, dendrimers, cyclic copolymers and other polymers. MS and tandem MS (MS/MS) has been extensively used for the analysis of synthetic polymers. However, the increase in structural or architectural complexity can result in analytical challenges that MS or MS/MS cannot overcome alone. Hyphenation to MS with different chromatographic techniques (2D × LC, SEC, HPLC etc.), utilization of other ionization methods (APCI, DESI etc.) and various mass analyzers (FT-ICR, quadrupole, time-of-flight, ion trap etc.) are applied to overcome these challenges and achieve more detailed structural characterizations of complex polymeric systems. In addition, computational methods (software: MassChrom2D, COCONUT, 2D maps etc....
Journal of Polymer Science: Polymer Chemistry Edition
The tripeptides Phe-Gly-Gly, 8-Ala-Gly-Gly, and c-Aca-Gly-Gly as well as the peptide derivatives 6-isothiocyanatovaleroyl-Gly-Gly and e-isothiocyanatocaproyl-Gly-Gly were synthesized by using known methods so that the peptide nitrogen between the two glycyl residues was isotopically enriched in 15N to a level of 0.8-0.9%. These monomer units were then used to produce the sequence polymers (Phe-Gly-Gly),, (0-Ala-Gly-Gly),, (6-Ava-Gly-Gly),, and (e-Aca-Gly-Gly),. The 18.24 MHz 15N-NMR spectra of the oligo-and polypeptides were obtained by using trifluoroacetic acid as solvent, since the solutions have relatively low,viscosity and exhibit a strong negative nuclear Overhauser enhancement of the 15N signals. For comparison, 15N-NMR spectra of the homopolymers (Gly),, (0-Ala),, (y-Abu),, (a-Ava),, and (e-Aca), were also recorded. The 15N signals from the w-aminoacyl residues in the sequence polymers appear up to 11 ppm upfield of the signals observed for the homopolyamides. The l5N signals from the two glycyl residues are separated by 3-7 ppm. Comparison with the 1%-NMR spectra of the same polymers indicates that 15N-NMR is better suited for the characterization and sequence analysis of these types of polymers.
Polymer, 2004
The sequence distribution and crystalline structure of a series of poly(ethylene-co-vinyl acetate) (EVA) copolymers with different VA contents were investigated with high-resolution nuclear magnetic resonance spectroscopy (NMR). It was found that most of the VA segments are isolated in the main chain, though three kinds of sequence distributions (VA -VA head to tail, VA -E -VA head to tail, and VA -E -E -VA head to tail) exist in the EVA copolymers with higher VA content. Furthermore, two kinds of alkyl-branching signals were detected in the high temperature 13 C NMR spectra of EVA copolymers. Solid-state 13 C NMR spectroscopic investigation indicated that only orthorhombic phase exists in the crystalline region of the EVA copolymers with lower VA content. For the EVA copolymers with higher VA content, however, besides the occurrence of orthorhombic crystalline phase, monoclinic phase was also detected. As a metastable state, monoclinic phase is mainly affected by VA content as well as the thermal treating history. q