Poly(glycidyl methacrylate) (PGMA) was synthesized by the RAFT method in the presence of 2‐cyanoprop‐2‐yl dithiobenzoate (CPDB) chain transfer agent using different [GMA]/[CPDB] molar ratios. The living radical polymerization resulted in controlled molecular weights and narrow polydispersity indices (PDI) of ≈1.1. The polymerization of pentafluorostyrene (PFS) with PGMA as the macro‐RAFT agent yielded narrow PDIs of ≤1.2 at 60 °C and ≤1.5 at 80 °C. The epoxy groups of the PGMA block were hydrolyzed to obtain novel amphiphilic copolymer, poly(glyceryl methacrylate)‐block‐poly(pentafluorostyrene) [PGMA(OH)‐b‐PPFS]. The PGMA epoxy group hydrolysis was confirmed by 1H NMR and FTIR spectroscopy. DSC investigation revealed that the PGMA‐b‐PPFS polymer was amorphous while the PGMA(OH)‐b‐PPFS displayed a high degree of crystallinity.
The effects of temperature and solvent on the β‐phase formation and energy transfer in an Ir(III) complex‐containing polyfluorene were investigated. Efficient energy transfer from polyfluorenes host to Ir complexes guest can be realized at low temperature. The formation of β‐phase was observed both in THF solution at low temperature and as suspended nano‐particles at room temperature. In addition, phosphorescent polymer nanoparticles were prepared successfully and exhibited efficient phosphorescent emission.
A high molecular weight ladder polymer based on 5,5′,6,6′‐tetrahydroxy‐3,3,3′,3′‐tetramethylspirobisindane and 1,4‐dicyanotetraflurobenzene has been synthesized by polycondensation under high‐intensity mixing conditions at about 155 °C and cyclic‐free products were obtained in high yield with low molecular weight distribution (1.7–2.3). The reaction could be completed within a few minutes. The polymer properties were characterized by GPC, 1H NMR, 13C NMR, F NMR, FT‐IR, and MALDI‐TOF MS. In addition, the mechanical properties, apparent surface areas and gas permeability are also reported. This procedure can also be used for the synthesis of other ladder polymers by irreversible polycondensations of tetraphenols with activated tetrafluoro aromatics.
Summary: The polymerization of ε‐caprolactone (CL) in the presence of HCl · Et2O by an activated monomer mechanism was performed to synthesize diblock or triblock copolymers composed of poly(ethylene glycol) (PEG) and poly(ε‐caprolactone) (PCL). The obtained PCLs had molecular weights close to the theoretical values calculated from the CL to PEG molar ratios and exibited monomodal GPC curves. We successfully prepared PEG and PCL block copolymers by a metal‐free method.
The non‐metal catalyzed living ring‐opening polymerisation of ε‐caprolactone by PEG. 相似文献
A series of new copolymers with high molecular weight and low polydispersity, prepared from tetrahydroxydinaphthyl, tetrahydroxyspirobisindane, and tetrafluoroterephthalonitrile monomers, prevent efficient space packing of the stiff polymer chains and consequently show intrinsic microporosity. One copolymer, DNPIM‐33, has an excellent combination of properties with good film‐forming characteristics and gas transport performance, and exhibits higher selectivity than the corresponding spirobisindane‐based homopolymer PIM‐1 for gas pairs, such as O2/N2, with a corresponding small decrease in permeability. This work demonstrates that significant improvements in properties may be obtained through development of copolymers with intrinsic microporosity (CoPIMs) that extends the spectrum of high‐molecular‐weight ladder structures of poly(dibenzodioxane)s.
Summary: The coordinative polymerization/cyclization of a flexible monodisperse di‐terpyridine ligand with iron(II ) chloride is reported. Matrix‐assisted laser desorption ionization time‐of‐flight (MALDI‐TOF) investigations showed the preferred formation of a [2 + 2] macrocycle, but also larger aggregates (cycles or linear oligomers) with up to 10 monomer units were found. Because of its C16‐spacer, the solubility is sufficient for performing viscosity experiments in CHCl3/MeOH solution. A viscosity titration revealed a maximum in viscosity at the 1‐to‐1 ratio of iron(II ) ions to di‐terpyridine‐ligands, which indicates the formation of extended oligomers, polymers, catenanes and/or cycles at that ratio.
Schematic representation of intra‐ and intermolecular metallo‐macrocycles. 相似文献
We show that small quantities of 1,3:2,4‐di(4‐chlorobenzylidene) sorbitol dispersed in poly(ε‐caprolactone) provide a very effective self‐assembling nanoscale framework which, with a flow field, yields extremely high levels of polymer crystal orientation. During modest shear flow of the polymer melt, the additive forms highly extended nano‐particles which adopt a preferred alignment with respect to the flow field. On cooling, polymer crystallisation is directed by these particles. This chloro substituted dibenzylidene sorbitol is considerably more effective at directing the crystal growth of poly(ε‐caprolactone) than the unsubstituted compound.
Summary: New polymer gelators consisting of poly(propylene glycol) or poly(ethylene glycol) and L ‐lysine‐based low‐molecular‐weight gelators have been developed. These polymer gelators were synthesized according to a simple procedure with high reaction yield, and formed organogels in many organic solvents. The organogelation mechanism was proposed from the transmission electron microscopy and FTIR spectroscopy studies.
Structures of the polymer gelators synthesized here. 相似文献
Polymerizations of vinyl ethers are carried out with (α‐diimine)nickel(II ) catalysts in the presence of methylaluminoxane. Effects of structural variations of the ligand on the activities of catalysts and polymer microstructure are described. The catalysts prepared by changing the bulkiness of ligand substituents in the ortho aryl position result in no specific trends terms of the yield and molecular weight of polymer. Poly(vinyl ether)s are atactic regardless of the structure of the catalyst used.
The rheological properties of fractionated thermotropic nematic polyesters 4,4′-dioxy-2,2′-dimethyl azoxybenzenenonanediyl (n = 7) (AZA-9) and dodecanediyl (n = 10) (DDA-9) have been determined under oscillatory shear in the nematic and isotropic phase. A markedly more pronounced shear thinning characterizes the polydisperse DDA-9 polymer as compared to the fractionated polymer in the nematic state. This difference becomes less pronounced in the isotropic phase. In all cases, the elastic compliance J′ in the isotropic state is much lower than in the nematic state. The values of relaxation time λ, although lower in the isotropic state, are not very different in the nematic state. The loss tangent tan δ is significantly higher in the isotropic phase for lower molecular weights. For molecular weights of 13,000 and above, this difference becomes smaller and shifts to lower angular frequencies. For AZA-9 and DDA-9, η→0 the limit of the dynamic viscosity can be represented by η* = M with a value of α similar for both phases and approximately equal to 4. 相似文献
Summary: Semiconducting polymers with moderate HOMO–LUMO energy gaps between 1.5 and 2.0 eV are of increasing attraction as donor components of bulk heterojunction‐type organic solar cells. The synthesis and characterization of a novel cross‐conjugated, aromatic polymer, poly(diindenonaphthalene) PDIN, with a HOMO‐LUMO gap of ca. 1.6 eV (λmax: 724 nm) in comparison to poly(indenofluorene) PIF, a previously described, structurally related polymer, is presented. The replacement of the central benzene ring of PIF by a naphthalene moiety in PDIN leads to an increase of the optical bandgap energy of ca. 0.16 eV.
Summary: A multistep synthetic procedure for preparing novel C60‐anchored two‐armed poly(tert‐butyl acrylate) was developed. First, two‐armed poly(tert‐butyl acrylate) bearing a malonate ester core with well‐controlled molecular weight was synthesized through atom transfer radical polymerization. The effective Bingel reaction between C60 and the well‐defined polymer was then carried out to yield C60‐anchored polymer. GPC, 1H NMR, and UV‐vis spectroscopy indicated that the C60‐anchored polymer was a monosubstituted and ‘closed’ 6,6‐ring‐bridged methanofullerene derivative.
Schematic of a novel C60‐anchored two‐armed polymer. 相似文献
Summary: A pH‐sensitive block copolymer is synthesized by step polymerization and its pH‐sensitive micellization‐demicellization behavior is studied. This polymer has a hydrophilic MPEG (shell) and hydrophobic but pH‐sensitive poly(β‐amino ester) (core), which can form a self‐assembled micelle. As confirmed by fluorescence spectroscopy and dynamic light scattering (DLS), this polymer shows a sharp pH‐sensitive micellization‐demicellization behavior. It is confirmed that the pH sensitivity is affected by the molecular weight ratio between the MPEG and poly(β‐amino ester).
Plots of the intensity ratio I337/I334 (from pyrene excitation spectra): a) vs. pH for copolymer samples and b) vs. log (concentration) for M1. 相似文献
Disulfide‐functionalized hyperbranched poly(amido amine)s (HPAMAMs) were synthesized by Michael addition polymerization of N,N'‐cystaminebisacrylamide and 1‐(2‐aminoethyl)piperazine. The novel HPAMAMs displayed bright fluorescence, and the emissions bands cover nearly the whole visible wavelength range. When polymer solutions were excited at 330–385, 460–490, and 510–550 nm, blue, green, and red solutions were observed, respectively. The HPAMAMs are biodegradable and they can be easily cleaved by 2‐mercaptoethanol or glutathione, leading to a decrease in the fluorescence intensity. Studies of applications of the biocompatible and biodegradable HPAMAMs in fluorescence imaging technology and biological science are in progress.
New multifunctional copoly(2‐oxazoline) nanoparticles were prepared for cell studies. The polymer contains double‐bond side chains as potential reaction sites for “thio”‐click reactions as well as a fluorescein label covalently bound to the polymer backbone. Using the nanoprecipitation technique, spherical nanoparticles of 200–800 nm were obtained. Confocal laser scanning microscopy measurements revealed the cellular uptake of the nanoparticles.
Y not? A unique, three‐coordinate Y‐shaped bis(silyl)platinum(II) complex was isolated and characterized (see structure; C light gray, N blue, Si pink, Pt dark gray). DFT studies on a model system shed light on the nature of this unusual coordination mode for platinum(II).
