Summary: Conjugated three‐ and four‐arm star polymers were successfully prepared by palladium catalyzed one‐pot Suzuki polycondensation of the multifunctional cores and an AB‐type monomer. The molecular weight of the star polymers could be controlled by the feed ratios of the monomers. The bromo end groups could be completely modified by fluorene mono boronic acid or triphenylamine mono boronic ester. The investigation of the optical, electrochemical, and thermal properties of the star polymers was also reported. All polymers exhibited good thermal stabilities and all the TPA‐capped polymers showed good hole‐transport abilities.
Preparation of three‐ and four‐arm star polyfluorences. 相似文献
Summary: A new computational algorithm for dynamic lattice Monte Carlo simulations of the associative behavior of heteroarm copolymers in selective solvents was developed and optimized for efficient and relatively fast simulation studies. The algorithm is based on the Siepmann and Frenkel variant of the bias self‐avoiding walk procedure. Simultaneously, a new criterion for recognition of an associate was proposed. The first results on the micellization of heteroarm star copolymers are presented.
The preparation of novel highly water‐soluble electrostatic complexes from C60‐anchored multi‐armed poly(acrylic acid)s and cationic porphyrin derivatives was demonstrated. The UV‐vis absorption and photoluminescence (PL) of these complexes show that the absorption of soret band exhibits a remarkable red shift and the emission of the Q band indicates an apparent quenching effect in comparison with that of the parent cationic porphyrin. These results imply a remarkable ground state and excited state interaction between the porphyrin ring and the C60 moiety.
The synthesis of new star‐shaped polymers, prepared by atom transfer radical polymerization of methyl methacrylate with tris(dialkylaminostyryl‐2,2′‐bipyridine) zinc(II) and iron(II) metalloinitiators, is reported. Their thermal and optical (absorption and emission) properties are discussed.
The synthesis of poly(β‐alanine) by Candida antarctica lipase B immobilized as novozyme 435 catalyzed ring‐opening of 2‐azetidinone is reported. After removal of cyclic side products and low molecular weight species pure linear poly(β‐alanine) is obtained. The formation of the polymer is confirmed with 1H NMR spectroscopy and MALDI‐TOF mass spectrometry. The average degree of polymerization of the obtained polymer is limited to = 8 by its solubility in the reaction medium. Control experiments with β‐alanine as a substrate confirmed that the ring structure of the 2‐azetidinone is necessary to obtain the polymer.
Summary: A series of novel mesogen‐jacketed liquid crystal miktoarm star rod‐coil block copolymers were synthesized via atom transfer radical polymerization (ATRP). Their architectures {coil conformation of styrene segment and rigid rod conformation of {2,5‐bis[(4‐methoxyphenyl)oxycarbonyl]styrene} (MPCS) segment} were confirmed by GPC, 1H NMR, and MALDI‐TOF studies. The liquid crystalline behaviors of the synthesized copolymers are evidenced from POM observation. The liquid crystalline phase depends on the molecular weights of the rigid rod arm of miktoarm star copolymers.
Alternating copolymers comprised of (meth)acrylates and vinyl ethers with controlled molecular weights and polydispersities were synthesized for the first time by living radical polymerization using organotellurium, stibine, and bismuthine chain transfer agents. Combining living alternating copolymerization and living radical or living cationic polymerization afforded hitherto unavailable block copolymers with controlled macromolecular structures.
A new concept to build shape memory polymers (SMP) combining outstanding fixity and recovery ratios (both above 99% after only one training cycle) typical of chemically crosslinked SMPs with reprocessability restricted to physically crosslinked SMPs is demonstrated by covalently bonding, through thermoreversible Diels–Alder (DA) adducts, star‐shaped poly(ε‐caprolactones) (PCL) end‐functionalized by furan and maleimide moieties. A PCL network is easily prepared by melt‐blending complementary end‐functional star polymers in retro DA regime, then by curing at lower temperature to favour the DA cycloaddition. Such covalent network can be reprocessed when heated again at the retro DA temperature. The resulting SMP shows still excellent shape memory properties attesting for its good recyclability.
A series of donor‐acceptor alternated conjugated copolymers, composed of thiophene, bithiophene, thieno[3,2‐b]thiophene, and 2,1,3‐benzothiadiazole units and differing from each other by the nature and the number of 3‐alkylthiophene in the backbone, have been synthesized by Stille cross‐coupling polymerization. The material's optical and electrochemical properties, in solution and in thin films, have been investigated using UV‐Visible absorption and cyclic voltammetry. Bulk heterojunction solar cells using blends of the newly synthesized copolymers, as electron donor, and C60‐PCBM or C70‐PCBM, as electron transporting material, have been elaborated. A maximum power conversion efficiency of 1.8% is achieved with a 1:4 PPBzT2‐C12:C70‐PCBM weight ratio.
A novel type of supramolecular poly(azomethine) was synthesized by the polycondensation of an inclusion complex of β‐cyclodextrin/poly(oxypropylene)diamine with one of β‐cyclodextrin/terephthaldehyde and a subsequent reaction with [60]fullerene as the end capping agent. Molar mass determination by gel permeation chromatography showed that the polymers had a high molar mass (about 150 kg · mol−1) with a very narrow polydispersity. Isothermal titration calorimetric studies confirmed that each poly‐(oxypropylene)diamine unit could host seven cyclodextrin molecules, which was further supported by 1H NMR spectroscopy and molecular modeling studies. Additional characterization by 13C NMR and FT‐IR spectroscopy, as well as by thermogravimetric analysis, confirmed the structure of the cyclodextrin‐based polyrotaxane.
A water‐soluble polymeric photosensitizer that contains naphthalene chromophores and absorbs light in the near UV region was obtained by modification of hydroxyethylcellulose. The excitation energy migrates along the naphthalene chromophores covalently attached to the polymer chain and can be used to induce photochemical reactions such as photoinduced electron transfer.
UV‐vis absorption (○), fluorescence emission (□), and fluorescence excitation (×) spectra of HENC in water at cHENC = 0.232 g/L, and (+) emission spectrum of the lamps used for irradiations. 相似文献
The monomer 3‐ethyl‐1‐vinyl‐2‐pyrrolidone ( 3 ) and the homopolymer poly(3‐ethyl‐1‐vinyl‐2‐pyrrolidone) ( 5 ) have been synthesized. Polymer 5 is soluble in water and shows a critical temperature (Tc) of 27 °C. The presence of cyclodextrin causes a slight shift of the Tc. The lower critical solution temperature (LCST) could be varied between 27 and 40 °C by copolymerization with N‐vinyl‐2‐pyrrolidone. A linear correlation between the Tc and the copolymer composition is observed.
A photochemical approach toward the generation of enzyme‐containing redox polymer networks, which are the key material in enzymatic sensors and biofuel cells, is described. The approach is based on the incorporation of photo‐reactive benzophenone groups into the redox polymers. The obtained polymers are then deposited on the surface of glassy carbon electrodes and cross‐linked by illumination with UV light at 365 nm. If this step is done in the presence of the enzyme glucose oxidase, functional electrodes are obtained that yield electrical power upon addition of glucose. This work specifically addresses the question of electrode stability in buffer and demonstrates how slight variations in the chemistry of the redox polymer have a dramatic effect on the electrochemical performance of the electrodes. Different ferrocene‐containing redox polymer networks are synthesized and their properties in physiological buffer are studied.
Dynamic lattice Monte Carlo simulations on a simple cubic lattice were used to study the association behavior of heteroarm star copolymers with two types of chemically different arms (miktoarm star). The effect of architecture and composition (number and length of arms) on self‐assembly was investigated. Simulations revealed substantial differences between associates formed by linear diblock copolymers and by star copolymers. It was also observed that the length of arms considerably influences the association behavior. Apart from the structural characteristics of the whole associate, the properties of individual stars in associates were also studied. These results provide detailed information on the inner structure of associates.
The synthesis of branched macromolecules from renewable resources via olefin metathesis is described. We observed that it is possible to control the molecular weight during the acyclic triene metathesis (ATMET) of a triglyceride by the application of methyl acrylate as a chain stopper for this straightforward one step one pot polymerization. The resulting branched materials were characterized by GPC, NMR as well as ESI‐MS and the combination of these techniques provided valuable insights into the polymer structure as well as occurring side reactions during this olefin metathesis polymerization reaction.
The preparation, characterization, materials properties, crystallization behavior and biodegradability of a polylactide (PLA)/organically modified layered silicate nanocomposite is described. Wide‐angle X‐ray diffraction and high‐resolution TEM analyses confirmed that intercalated stacked and disordered/exfoliated mica layers coexist in the nanocomposite. The nanocomposite showed improved materials properties and crystallization behavior with a simultaneous improvement in biodegradability as compared to neat PLA.
Degree of biodegradation (i.e. CO2 evolution) of neat PLA and PLACN4 under compost conditions. 相似文献
A recently developed coarse‐grain model is used to investigate nonlinear rheological properties of model core–shell systems. The influence of several model parameters on the stresses and shear rates is investigated. Continuous planar elongational flow and superposition rheology are studied and compared to simple shear flow results. With particular values of the model parameters, an initially linear velocity profile splits into many bands with different shear rates and different densities, which finally merge into just two bands stacked along the gradient direction. With the box sizes used in our simulations, stick and Lees–Edwards boundary conditions lead to qualitatively similar results, with the stick boundary simulations showing better quantitative agreement with experiments.
Porous polymeric monoliths were prepared via electron beam triggered free radical polymerization of (meth)acrylates. Post‐synthesis functionalization of these supports was accomplished via electron beam initiated free radical graft polymerization of methacryloyl‐substituted NHC precursors. The grafted precursors were converted into the corresponding copper complexes. Cu‐loadings were between 1.3 mg · g−1 and 1.5 mg · g−1. These supported catalysts were used in selected CO hydrosilylation and cyanosilylation reactions using a continuous flow setup.
This communication details the successful synthesis of low polydispersity core cross‐linked star (CCS) polymers via DPE‐mediated polymerisation. We demonstrate the ability to produce poly(methyl methacrylate) and poly(acrylonitrile) CCS polymers that are currently inaccessible via the two most common non‐metal‐based controlled radical polymerisation techniques (NMP and RAFT polymerisations).
π‐Conjugated microporous networks have been prepared from the tetraarylated diketopyrrolo[3,4‐c]pyrrole unit as a tetrafunctional building block. The reactions are carried out using microwave‐assisted Yamamoto or Sonogashira cross‐coupling. Red insoluble powders are obtained, showing intense fluorescence. The polymer networks exhibit a high gas storage capability, with BET surface areas up to about 500 m2 · g−1.
