Summary: The growth of surface‐initiated poly([2‐(methacryloyloxy)ethyl]trimethylammonium chloride) (pMETAC) brushes by ATRP was monitored by the quartz crystal microbalance technique with dissipation (QCM‐D). The change in mass of the quartz crystals starting from the adsorption of a thiol initiator monolayer through to the growth of the polymer brushes was determined. The use of QCM‐D allowed determination of the kinetics of polymerization from the surface. The technique can be applied to other polymers synthesised from surfaces and allows the study of varying conditions on the polymerization kinetics.
Changes in frequency of a quartz crystal during polymerization. 相似文献
An atomic force microscope in the compression mode was used to probe the nanomechanical response of single dendrimeric molecules, as well as dendrimer aggregates adsorbed on silicon surface. The force‐compression behaviour of individual, generation 5 poly(amido amine) (PAMAM) dendrimers was described by a Hertzian model for the deformation of elastic bodies. The modulus values obtained ranged between 700 MPa (single dendrimers) and 150 MPa (dendrimer aggregates).
Summary: Fully linear polyethylene‐based latexes have been prepared by the hydrogenation of polybuta‐1,4‐diene dispersions. The latter were synthesized via dispersion ring‐opening metathesis polymerization of cycloocta‐1,5‐diene, and hydrogenated using RuCl2(PPh3)3 as catalyst, without any further treatment. A high hydrogenation efficiency was achieved as demonstrated by different techniques including DSC, and 1H NMR and FT‐IR spectroscopy. The hydrogenation process could be carried out without detrimental effect on particle size and colloidal stability as evidenced by optical microscopy and light scattering analysis.
Optical microscopy photograph of a polybutadiene‐based dispersion after hydrogenation. No change in size is observed. 相似文献
Poly(2,5‐thienylene vinylene) (PTV), an insoluble conjugated polymer, can be readily prepared in various shapes of different nanodimensions by the chemical vapor deposition polymerization of 2,5‐bis(chloromethyl)thiophene. The bischloromethyl monomer in the vapor phase is activated at 600 °C. The activated monomer vapor is deposited at room temperature on the surface of various substrates to prepare polymeric films, fibers, tubes etc., which are then thermally converted into PTV. PTV thin films can be carbonized thermally to produce graphitic compositions that contain sulfur atoms. Electrical conductivities of FeCl‐doped PTV and carbonized films are reported.
This feature article reviews the authors' work combined with highlighted specific aspects of polyaniline (PANI) macro/nanostructures, focusing on such issues as the following. 1) The new development of a hard‐template method. 2) Evaluation of a template‐free method in universality, controllability, and simplicity as well as the self‐assembly mechanism. 3) Multi‐functionality based on a template‐free method associated with other approaches. 4) Cooperation effect of a micelle soft‐template and molecular interactions as a new tool to complex 3D microstructures assembled from 2D or 1D nanostructures. 5) Electrical and transport properties of a single PANI nanotube, as measured by a four‐probe method. 6) Sensors guided by reversible switching wettability through a doping/de‐doping process. An outlook is also briefly given.
Bioconjugate amphiphiles comprising triterpene and poly(ethylene oxide) (PEO) were studied according to their thermoresponsive aggregation behavior (LCST) in water. Cholesteryl?PEO (CE) and betulinyl?PEO (BE) comprising <70 wt% PEO precipitated from water upon heating. CE, but not BE, solutions contained nanoscopic aggregates at room temperature causing different thermoprecipitation behaviors. Solutions containing 5 wt% solutions of BE with short PEO chains demonstrated dual thermoresponsive behavior, precipitating at high temperature and forming hydrogel at low temperature. A BE multiblock copolymer was found to form large aggregates, presumably vesicles, in water. Results suggest that the solution properties of triterpene–PEO amphiphiles can be controlled by the chemical composition and structure.
The importance of taking into account the principle of microscopic reversibility in the analysis of complex copolymerization systems is demonstrated. The analysis of a reversible copolymerization system in which segmental exchange is possible from the point of view of the reaction microreversibility proves that hetero‐reshuffling rate constants depend on homo‐reshuffling rate constants and copolymerization thermodynamics.
Commercially available 1,2‐PB was transformed into a well‐defined reactive intermediate by quantitative bromination. The brominated polymer was used as a polyfunctional macroinitiator for the cationic ring‐opening polymerization of 2‐ethyl‐2‐oxazoline to yield a water‐soluble brush polymer. Nucleophilic substitution of bromide by 1‐methyl imidazole resulted in the formation of polyelectrolyte copolymers consisting of mixed units of imidazolium, bromo, and double bond. These copolymers, which were soluble in water without forming aggregates, were used as stabilizers in the heterophase polymerization of styrene and were also studied for their ionic conducting properties.
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.
Summary: Using molecular dynamics simulations, we determine the linear and nonlinear viscoelastic properties of a model polymer melt in the unentangled regime. Several approaches are compared for the computation of linear moduli and viscosity, including Green‐Kubo and nonequilibrium molecular dynamics (NEMD). An alternative approach, based on the use of the Rouse modes, is also discussed. This approach could be used to assess local viscoelastic properties in inhomogeneous systems. We also focus on the contributions of different interactions to the viscoelastic moduli and explain the microscopic mechanisms involved in the mechanical response of the melt to external solicitation.
Novel poly(ethylene glycol) (PEG) derivatives having both carboxylic acid, and sugar side chains were synthesized. These polymers were used to coat DNA/poly(ethyleneimine) complexes, and effectively protected them against albumin-induced aggregation. They presented carbohydrate moieties on the DNA complex surfaces as a cell-binding ligand, and the galactose-bearing polymer remarkably enhanced the poly(ethyleneimine)-mediated gene transfection on HepG2 cells.
Synthesis of poly(ethylene glycol) derivatives having both carboxylic acid and sugar pendant groups. 相似文献
Summary: The synthesis of a series of polyferrocenylsilanes (PFSs) containing CC functionalities in the side‐group structure and their subsequent derivatization by hydrosilylation chemistry are described. Hydrosilylation is shown to be an effective postpolymerization functionalization method, particularly in the case of poly(ferrocenylmethylvinylsilane), which can be prepared by photolytic anionic ring‐opening polymerization of the corresponding ferrocenophane monomer.
Summary: Thermosensitive association of a diblock copolymer consisting of poly(3‐dimethyl(methacryloyloxyethyl) ammonium propane sulfonate) (PdMMAEAPS), as an upper critical solution temperature (UCST) block, and poly(N,N‐diethylacrylamide) (PdEA), as a lower critical solution temperature (LCST) block, has been investigated by using IR spectroscopy. The ν(CO) and ν(SO) bands of the PdMMAEAPS block and the amide I band of PdEA block critically changed at the UCST and LCST, respectively, indicating that the segmental interaction of each block is altered at each transition.
The double temperature responsiveness of a UCST block and LCST block containing diblock copolymer. Micelles form at temperatures both below the UCST and above the LCST of the blocks. 相似文献
Summary: Well‐defined pentablock copolymers of styrene–[1]dimethylsilaferrocenophane–methyl methacrylate (PMMA‐b‐PFS‐b‐PS‐b‐PFS‐b‐PMMA) are synthesized using lithium naphthalide as initiator and a 1,1‐dimethylsilacyclobutane‐mediated 1,1‐diphenylethylene (DPE) end‐capping technique. Annealing under various conditions followed by analysis by transmission electron microscopy revealed good phase separation by the copolymers and the presence of ordered microstructures, such as spheres‐on/in‐spheres, and spheres‐on/in‐lamellae micromorphologies.
Structure of the styrene–[1]dimethylsilaferrocenophane–methyl methacrylate pentablock copolymers. 相似文献
Novel tboc‐protected ionenes with exceeding 30 kDa were prepared from the step‐growth polymerization of tert‐butyl bis[3‐(dimethylamino)propyl]carbamate and 1,12‐dibromododecane. The protected ionenes yielded pH‐sensitive, protonatable ionenes with pKa ≈ 6.6 for the conjugate acid of the protonated secondary amine. Polyplexes of the protected and deprotected ionenes, whose cytotoxicity for endothelial cells was analyzed using the MTT assay, efficiently complex plasmid DNA. Polyplexes destabilized cellular membranes as revealed using the lactate dehydrogenase assay at high concentrations. The polyplexes were successfully transfected into HBMECs at mass ratios 2, 4, 8, 12, and 16 (polymer/DNA) at polyplex concentrations less than 10 µg · mL?1.
A novel pH‐responsive polymer vesicle obtained by the aqueous self‐assembly of carboxy‐terminated hyperbranched polyesters is reported. The synthesis is very simple, just a one‐step esterification of the commercially available hydroxy‐terminated hyperbranched polyester of Boltorn Hx (x = 20, 30, 40) with succinic anhydride. The vesicle size can be controlled from 200 nm to 10 µm by simply adjusting the solution pH as well as the degrees of branching (or generation).
Novel mesoporous polymers functionalized with carboxylic, sulfonic, and amino groups were synthesized by self‐organization of surfactant and functionalized phenolic building oligomers followed by surfactant removal. These materials have relatively large surface area, with a large number of functional groups on the pore walls, which may provide this new class of materials with enhanced adsorption capability and selectivity.
Amphiphilic star‐shaped oligo(ethylene glycol)s with a hydrophobic bile acid core and varying number of hydrophilic arms have been made. Their thermal behavior in aqueous solutions depends on the number rather than the length of the arms. The two‐armed lithocholate derivative showed the strongest tendency for association and exhibited the lowest cloud point (79 °C) of the oligomers made, as well as another phase separation at a lower temperature (31 °C). The “double thermosensitivity” arising both from the salt‐dependent LCST of the oligo(ethylene glycol) segments and the temperature‐responsive self‐assembly of amphiphilic bile acid derivative provides an interesting path in the design of bile acid‐based smart materials.
Summary: Hydrogenated acrylonitrile‐butadiene rubber is a high‐performance elastomer that has found important applications in the automobile industry and petroleum fields. A new catalytic process has been investigated for producing hydrogenated acrylonitrile‐butadiene rubber by direct hydrogenation of the rubber in latex form using RhCl(PPh3)3 as catalyst. The reactions were achieved without the addition of any organic solvents. This is the first time that the direct catalytic hydrogenation of an acrylonitrile‐butadiene rubber latex has been successfully realized in the absence of any organic solvent with a conversion of higher than 95% without cross‐linking of the polymer.
Effect of RhCl(PPh3)3/acrylonitrile‐butadiene rubber ratio on hydrogenation. 相似文献
