Summary: Novel alternating polyketone‐based polymers bearing pendant saccharide units that are accessible by polymerization catalysis are presented. The materials were synthesized by polymerization of carbon monoxide and α‐olefins containing protected glucose or N‐acetyl glucosamine residues. The dicationic PdII bis(phoshine) complex [Pd(dppp)(NCCH3)2](BF4)2 was used as a catalyst precursor. An O‐deacetylation of the copolymers afforded materials with amphiphilic character.
Structure of the poly(1,4‐ketone) copolymers synthesized here. 相似文献
Functional polymers possess tremendous potential both in academia and in industry. In particular, oxiranes offer manifold possibilities for the introduction of single hydroxyl or multiple orthogonal functionalities in carbanionic polymerization. Here, we present a brief overview of the fascinating possibilities arising from the employment of common as well as individually designed epoxide derivatives for the synthesis of end‐functional polymers. Continuous flow techniques can be utilized for the rapid generation and screening of precisely defined hydroxyl‐modified polymers. The utilization of functionalized polymers as precursors for the formation of complex macromolecular architectures (e.g., miktoarm star polymers) is summarized and potential applications as well as future perspectives are discussed.
Highly efficient and well‐controlled ambient temperature reversible addition–fragmentation chain transfer (RAFT) polymerization is readily carried out under environmentally friendly mild solar radiation. This discovery has significantly extended studies from man‐made separated‐spectroscopic‐emission UV‐vis radiation (Macromolecules 2006 , 39, 3770) to natural continuous‐spectroscopic‐emission solar radiation for ambient temperature RAFT polymerization.
Nonlinear optical vinyl polymers with high glass transition temperature (Tg) were prepared by the functionalization of a fluorinated acrylate‐methyl vinyl isocyanate copolymer. A modified pathway to obtain a thiophene bridged chromophore was worked out. Poled films of the polymers show a fairly high and stable nonlinear optical response, even at elevated temperatures.
The thiophene‐bridged chromophore, based on a substituted dicyanomethylene‐dihydrofuran acceptor, synthesized here. 相似文献
The establishment of advanced living/controlled polymerization protocols allows for engineering synthetic polymers in a precise fashion. Combining advanced living/controlled polymerization techniques with highly efficient coupling chemistries facilitates quantitative, modular, and orthogonal functionalization of synthetic polymer strands at their chain termini as well as side‐chain functionalization. The review highlights the current status of selected post‐functionalization techniques of polymers via orthogonal ligation chemistries, major characteristics of the specific transformation chemistry, as well as the characterization of the products.
Water‐soluble single‐ and multi‐walled carbon nanotubes (CNTs) were prepared by grafting polyacrylamide chains from the graphitic surface via ceric ion‐induced redox radical polymerization. The reducing functionalities were covalently attached to the tubes by peroxide‐assisted radical reaction. The results showed that polymer chains were grafted onto CNTs by the redox process. The redox radical polymerization initiated by carbon nanotube‐bearing functionalities not only provides a powerful strategy for modifying the carbon nanostructures but also gives us the knowledge of their sidewall chemistry.
Summary: This paper presents the structural influence of the Si H functionality on the physicochemical properties of polysilanes. New low‐temperature restructuring processes were discovered using thermal analysis (TGA, DSC). Photoluminescent (FL) and X‐ray photoelectron spectroscopy (XPS) measurements revealed the optoelectronic properties‐chemical structure relationship of the synthesized polymers.
Highly reactive Si H groups lead to restructuring of the main polysilane chain. 相似文献
Poly(N‐isopropylacrylamide) (PNIPAM) oligomer containing one adamantyl (AD) and two β‐cyclodextrin (β‐CD) moieties at the chain terminals, AD‐PNIPAM‐(β‐CD)2, was synthesized by atom transfer radical polymerization (ATRP) and successive click reactions. In aqueous solution, AD‐PNIPAM‐(β‐CD)2 spontaneously forms supramolecular thermoresponsive hyperbranched polymers via molecular recognition between AD and β‐CD moieties. To the best of our knowledge, this work represents the first report of the construction of supramolecular thermoresponsive hyperbranched polymers from well‐defined polymeric AB2 building units.
A method for growing polymers directly from the surface of graphene oxide is demonstrated. The technique involves the covalent attachment of an initiator followed by the polymerization of styrene, methyl methacrylate, or butyl acrylate using atom transfer radical polymerization (ATRP). The resulting materials were characterized using a range of techniques and were found to significantly improve the solubility properties of graphene oxide. The surface‐grown polymers were saponified from the surface and also characterized. Based on these results, the ATRP reactions were determined to proceed in a controlled manner and were found to leave the structure of the graphene oxide largely intact.
Olefin isomerization side reactions that occur during ADMET polymerizations were studied by preparing polyesters via ADMET and subsequently degrading these polyesters via transesterification with methanol. The resulting diesters, representing the repeating units of the previously prepared polyesters, were then analyzed by GC‐MS. This strategy allowed quantification of the amount of olefin isomerization that took place during ADMET polymerization with second generation ruthenium metathesis catalysts. In a second step, it was shown that the addition of benzoquinone to the polymerization mixture prevented the olefin isomerization. Therefore, second generation ruthenium metathesis catalysts may now be used for the preparation of well‐defined polymers via ADMET with very little isomerization, which was not possible before.
The use of a bisaminooxy compound as initiator for nitroxide‐mediated radical polymerization (NMRP) of styrene or n‐butyl acrylate allows the synthesis of α,ω‐nitroxide‐capped polymers. At high temperatures and with the addition of acetic anhydride, it was found that these polymers could be applied as macroinitiators in the free‐radical polymerization of methyl methacrylate. This enables the synthesis of block copolymers with only minor contents of homopolymer.
The structure of bis‐TIPNO, the bisaminooxy compound used as an initiator for the nitroxide‐mediated radical polymerization of styrene or n‐butyl acrylate. 相似文献
Summary: Thermally curable benzoxazine ring‐containing polystyrene macromonomers were synthesized and characterized. 1,4‐Dibromo‐2,5‐bis(bromomethyl)benzene and 1,4‐dibromo‐2‐(bromomethyl)benzene were used as initiators in the atom transfer radical polymerization of styrene. The resulting polymers were used in combination with 3‐aminophenylboronic acid hemisulfate, for a Suzuki coupling. The obtained polymers, with amino groups in the middle or end of the chains, were reacted with formaldehyde and phenol to yield benzoxazine ring‐containing macromonomers. In addition to the glass transition temperature of the polystyrene segment observed at ca. 105 °C, differential scanning calorimetry thermograms exhibit an exotherm at ca. 276 °C corresponding to the oxazine thermal polymerization. Both macromonomers undergo thermal curing with the formation of thermosets having polystyrene segments.
Structure of the benzoxazine‐functionalized polystyrene. 相似文献
4‐Vinylbenzoyl azide was synthesized from p‐vinylbenzoic acid and polymerized by free radical polymerization. The obtained polymer contained acyl azide groups which were thermally transformed to the corresponding isocyanato groups. Reactions on these polymers with ethanol, hydroxyethyl methacrylate and 1‐pyrenebutanol proceeded quantitatively. Time‐resolved FT‐IR studies of the reactions with ethanol were carried out by varying the concentration and temperature. The effect of the solvent polarity on the Curtius rearrangement was investigated.
Poly(N‐isopropylacrylamide)‐block‐poly{6‐[4‐(4‐pyridyazo)phenoxy] hexylmethacrylate} (PNIPAM‐b‐PAzPy) was synthesized by successive reversible addition‐fragmentation chain transfer (RAFT) polymerization. In a water/tetrahydrofuran (H2O/THF) mixture, amphiphilic PNIPAM‐b‐PAzPy self‐assembles into giant micro‐vesicles. Upon alternate ultraviolet (UV) and visible light irradiation, obvious reversible swelling‐shrinking of the vesicles was observed directly under an optical microscope. The maximum percentage increase in volume, caused by the UV light, reached 17%. Moreover, the swelling could be adjusted using the UV light power density. The derivation of this effect is due to photoinduced reversible isomerization of azopyridine units in the vesicles.
A dextran‐based dual‐sensitive polymer is employed to endow gold nanoparticles with stability and pH‐ and temperature‐sensitivity. The dual‐sensitive polymer is prepared by RAFT polymerization of N‐isopropylacrylamide from trithiocarbonate groups linked to dextran and succinoylation of dextran after polymerization. The functionalized nanoparticles show excellent stability under various conditions and can be stored in powder‐form. UV and DLS measurements confirm that the temperature‐induced optical changes and aggregation behaviors of the particles are strongly dependent on pH.
Suitably activated, (Cp*){N(tBu)C(Me)N(Et)}ZrMe2 is known to initiate the ‘living’ and isotactic‐selective polymerization of alk‐1‐enes, and it can be used to synthesize block copolymers and stereoblock polymers. We report a full molecular kinetic investigation of propene, but‐1‐ene, and hex‐1‐ene polymerization with a MAO‐activated catalyst system. By combining NMR microstructural polymer analysis with QM modeling of the active species, the complicated regio‐ and stereochemistry of the polyinsertion process, as well as the active chain‐transfer pathways, are investigated. The perspectives and limitations of this catalyst for application in (stereo)block polymerizations are discussed.
The use of copper tubing as both the reactor and as a catalyst source is demonstrated for continuous controlled radical polymerization of methyl acrylate at ambient temperature and at low solvent content of 30%. The high surface area provided by the copper walls mediates the reaction via the single electron transfer–living radical polymerization (SET‐LRP) mechanism. The polymerizations proceeded quickly, reaching 67% conversion at a residence time of 16 min. Ligand concentration could also be reduced without a sharp drop in polymerization rate, demonstrating the potential for decreased raw material and post‐process purification costs. Chain extension experiments conducted using synthesized polymer showed high livingness. The combination of living polymer produced at high polymerization rates at ambient temperature and low volatile organic solvent content demonstrate the potential of a copper reactor for scale up of SET‐LRP.
Binary reactive/inert antifouling polymer brushes were grafted via a two step surface initiated polymerization from printed initiator monolayer and provided robust, effective polymeric surfaces for bioattachment with distinguishably reduced non‐specific adsorption. This synthetic strategy can be harnessed to build complex binary polymeric structures on substrate surfaces and the polymer brush surfaces reported in the present paper can be widely used for versatile biological study.
Summary: The first example of the synthesis of acrylonitrile copolymers with porphyrin pendants and the subsequent electrospinning of the resultant copolymers into nanofibers is presented in this communication. Vinyl porphyrin monomers have been synthesized and copolymerized with acrylonitrile through solution polymerization. FT‐IR, NMR, UV‐vis, and fluorescence spectroscopy are used to characterize the copolymers. Preliminary quantum chemical calculations have also been carried out to reveal the activity of the vinyl porphyrin monomers. Nanofibers with a diameter of around 330 nm are prepared by electrospinning the copolymer solutions. Their morphology and porphyrination are clearly observed by field‐emission scanning electron microscopy and fluorescence microscopy. It is speculated that this type of nanofiber may be a latent support of porphyrins for various purposes such as catalysis, molecular imprinting, sensors, and light/energy conversion.
The formation of luminescent nanofibers from porphyrinated polymers. 相似文献
A reactivity study of the most important elementary steps (propagation, intermolecular degradative transfer, and re‐initiation) in free‐radical polymerization of acrylfuranic systems, furfuryl acrylate (FA), and furfuryl methacrylate (FM), using the frontier molecular orbital theory is described. A qualitative explanation of reactivity trends of these steps for both systems is given based on absolute values of the SOMO/HOMO gap. The small difference between values of kp for FA and FM compared to that found for MA and MMA ( ) is justified semi‐quantitatively by applying a formulation for the change of energy in the transition state using second‐order perturbation theory.
