A novel chlorotitanium calix[4]arene complex was synthesized and tested, without activator, as catalyst for the polymerization of L ‐ and rac‐lactide under solvent‐free conditions. The catalyst displayed high activity, which depended on the monomer‐to‐catalyst molar ratio, and led to highly isotactic PLLA. Despite concomitant transesterification during the polymerization, polylactide formation was well‐controlled, the molar mass distribution indexes remaining in the restricted range of 1.2–1.4.
We report a new type of step‐growth radical addition‐coupling polymerization (RACP) involving consecutive addition of carbon‐centered radical derived from α,α′‐dibromo dibasic ester to NO double bond of C‐nitroso compound followed by cross‐coupling of carbon‐centered radical and in situ formed nitroxyl radical, which produces alternating copolymers with high molecular weight and unimodal molecular weight distribution from saturated and unsaturated monomers.
We report the use of a PTFE‐based microfluidic device for the encapsulation of living, therapeutically‐active cells within monodisperse alginate microspheres. We present a novel microfluidic platform and a flexible experimental method for the production of alginate microspheres. Cell lines HEK293, U‐2 OS and PC12 were separately encapsulated using this method, with minimal loss of cell viability.
A rod‐coil‐rod block copolymer, polyhexylisocyanate‐block‐polystyrene‐block‐polyhexylisocyanate, of controlled molecular weight was synthesized quantitatively via living anionic polymerization using potassium naphthalenide in the presence of sodium tetraphenylborate. The use of K+ as the counterion for the polymerization of styrene, and Na+ (NaBPh4) for the polymerization of isocyanate leads to the formation of a well‐controlled novel triblock copolymer.
This review covers the literature concerning the modification of polysaccharides through controlled radical polymerizations (NMP, ATRP and RAFT). The different routes to well‐defined polysaccharide‐based macromolecules (block and graft copolymers) and graft‐functionalized polysaccharide surfaces as well as the applications of these polysaccharide‐based hybrids are extensively discussed.
The synthesis of water soluble star‐block copolypeptides and their encapsulation properties are described. The star‐block copolypeptides, obtained by ring‐opening polymerization of amino acid N‐carboxyanhydrides, consist of a PEI core, a hydrophobic polyphenylalanine or polyleucine inner shell, and a negatively charged polyglutamate outer shell. The encapsulation study showed that these water soluble, amphiphilic star‐block copolypeptides could simultaneously encapsulate versatile compounds ranging from hydrophobic to anionic and cationic hydrophilic guest molecules.
Deposition of hole injection layers including a perfluorinated ionomer has been demonstrated using layer‐by‐layer spin self‐assembly for enhanced device efficiency and lifetime in PLEDs. We show that the LBL spin self‐assembled thin films enable to control work functions of indium‐tin oxide anodes by changing the PFI concentration and that a resulting green‐emitting device has an enhanced luminescence efficiency and 18 times longer half lifetime than a device using a conventional HIL. We also fabricate a gradient of energy levels by the LBL self‐assembly of the PFI that results in a work function of 5.74 eV, which can be used to improve carrier injection even for an emitting layer whose ionization potential is over 5.7 eV.
Low‐cost, responsive poly(N‐isopropylacrylamide)/polystyrene composite films were prepared by a facile electrospinning technique. The surface structures and wettabilities of the composite films are tunable by simply controlling the concentration of polymer. With a proper proportion of each polymer, the wettability of the surface can be switched between superhydrophilicity and superhydrophobicity when the temperature is changed from 20 °C to 50 °C. The combination of a stimuli‐responsive polymer with micro/nanostructures on the surface of the composite film contributes to this unique surface property.
Novel π‐conjugated coil–rod–coil triblock oligomers containing optoelectronic active oligoaniline segments were synthesized. The block oligomer can self‐assemble into diverse aggregating morphologies including spherical micelles and thin‐layer vesicles in THF, which is found associated with the removing of the protecting groups of oligoaniline segments. A possible mechanism was proposed to explain the self‐assembly behavior changes in which chain conformation variation of the aniline segments initiated from deprotection of the nitrogen atoms is pointed to be the key factor that dominates the transition process.
Oligomeric guanidines can be obtained by polycondensation of guanidine hydrochloride and 1,2‐bis(2‐aminoethoxy)ethane. A comparative MALDI‐TOF mass spectrometry/NMR spectroscopy study with a 13C‐labeled sample enabled the unambiguous analysis of a guanidine‐based polymer. Among the four major product series unprecedented macrocyclic compounds were detected. The minimum inhibition concentrations for four different microorganisms were determined, showing excellent biocidal activities.
Summary: Magnetic nanoparticles have been prepared by a co‐precipitation method and modified with methacryloxypropyltrimethoxysilane. Magnetic molecularly imprinted polymer particles have been prepared by suspension polymerization in silicone oil. The particles possess a high affinity to the template molecules and are rapidly separated under a magnetic field.
In this article, electrospinning technique has been demonstrated for the synthesis of ultra‐low dielectric constant polyimide fiber membranes. Poly(amic acid) fiber membranes have been prepared as precursor. After the treatment of thermal imidization, ultra‐low dielectric constant polyimide fibers membranes can be obtained. The morphologies and structures of precursors and products are characterized by scanning electron microscopy (SEM), Fourier transmission infrared (FTIR) spectra, and a radio frequency (RF) impedance/capacitance material analyzer. The DK of the as‐prepared polyimide membrane ranges from 1.53 to 1.56, which could be applied in the electronic packaging industry.
We have systematically studied the thin film morphologies of asymmetric polystyrene‐block‐poly(ethylene oxide) (PS‐b‐PEO) diblock copolymer subjected to solvent vapors of varying selectivity for the constituent blocks. Upon a short treatment in neutral or PS‐selective vapor, the film exhibited a highly ordered array of hexagonally packed, cylindrical microdomains. In the case of PEO selective vapor annealing, such ordered cylindrical microdomains were not obtained. Instead, fractal patterns on the microscale were observed and their growth processes investigated. Furthermore, hierarchical structures could be obtained if the fractal pattern was exposed to neutral or PS selective vapor.
Perfectly alternating copolymers can be synthesised by reacting diacrylates with terminal dienes using alternating diene metathesis polycondensation (ALTMET). This novel method is very versatile and allows preparation of diverse structures of polymers, including main‐chain liquid crystalline polymers.
Main‐chain liquid crystalline polymer obtained by ALTMET. 相似文献
Summary: Pulsed‐IR laser‐induced decomposition of poly(vinyl acetate) (PVAC) differs remarkably from its conventional pyrolysis, which results in the formation of acetic acid and non‐polar carbonaceous residue. In contrast, the products in the former case are (i) vinyl acetate (low energy channel), (ii) products of cleavage in the acetate group, and (iii) an ablatively deposited polar polymeric film containing roughly half of the acetoxy groups initially present.
Schematic of the different routes of poly(vinyl acetate) degradation. 相似文献
We report the formation of poly(propylene) spherical and ellipsoidal particles templated by carbon nanotubes via solution crystallization. With an increase in nanotube loading, the particle shape changes from sphere to ellipsoid. In the intermediate concentration range, both spherical and ellipsoidal shapes coexist. The particle size decreases with an increase in nanotube loading.
Summary: A novel kind of dendronized porphyrin polymers was synthesized by Sonogashira coupling of diethynyl‐functionalized porphyrin monomers and diiodo‐functionalized macromonomers bearing Fréchet‐type dendrons. The encapsulation of red‐light‐emitting porphyrin‐containing conjugated backbones into dendronized polymers can not only reduce the aggregation of polymer backbones and the self‐quenching of their fluorescence but also endow the porphyrin polymers with good solubility. We also report the optical and electrochemical properties of the porphyrin‐containing dendronized polymers.
Synthesis of a novel kind of dendronized porphyrin polymers by Sonogashira coupling of diethynyl‐functionalized porphyrin monomers and diiodo‐functionalized dendritic macromonomers. 相似文献
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.
This review article describes the preparation of polymer brushes by nitroxide‐mediated radical polymerization using either the ‘grafting to’ or the ‘grafting from’ approach. The use of TEMPO as a classical initiator is intensively described. More sophisticated nitroxides are also included in the discussion. Brush formation on flat surfaces such as wafers and also on particles is reported. Finally, some applications of polymer brushes are presented.
