The homogeneous conversion of cellulose in the ionic liquid 1‐ethyl‐3‐methylimidazolium acetate with 2‐furoyl chloride, p‐toluenesulfonyl chloride, and triphenylmethyl chloride yields surprisingly pure cellulose acetate samples in any case. From NMR spectroscopic studies, it may be concluded that during the homogeneous functionalization reactive intermediates including furane‐2‐carboxylic acid/acetic acid anhydride and acetic acid triphenylmethyl ester are formed leading to the cellulose acetates with DS values in the range from 0.55 to 1.86.
A simple and efficient Diels‐Alder (DA) reaction on carbon material has been demonstrated. The present work involves single and multiwall carbon nanotubes (CNTs), as well as Herringbone carbon nanofiber. The CNTs show a dual nature of reactivity in DA reaction, i.e., they behave both as dienophile and diene with furfuryl groups and maleic anhydride derivatives, respectively. Various functional groups, including alcohol, amine, epoxy, carboxylic and ester, have been introduced on the carbon materials. The results suggest that the reactivity of CNT in DA reaction may resemble the chemistry of small molecules.
Selectively dendronized cellulose at C‐6 was synthesized homogeneously (in DMSO) and heterogeneously (in methanol) by the conversion of 6‐azido‐6‐deoxy cellulose (degree of substitution, DS 0.75) with polyamidoamine (PAMAM) dendrons possessing an ethynyl focal moiety via the copper‐catalyzed Huisgen reaction (click reaction) under mild conditions. First to third generation of PAMAM‐triazolo cellulose derivatives with DS values of up to 0.69 could be prepared, which are soluble in organic solvents (DMSO, DMF) and in water. The novel biopolymer derivatives were characterized by elemental analysis, FTIR, and NMR spectroscopic methods, showing no impurities and no conversion at the secondary positions.
2,5‐Bis(chloromethyl)‐1,3,4‐oxadiazole was synthesized and dehydrohalogenation of this model compound was investigated under various base conditions. The formation of an intermediate with quinodimethane‐type structure is suggested for reaction in EtONa/EtOH. Polymerization of this intermediate proceeds via an anionic mechanism to form poly(1,3,4‐oxadiazole‐2,5‐diyl‐1,2‐vinylene). Polymerization at a toluene/water interface results in shorter polymerization times, milder conditions, higher molecular weights, higher yields and fewer defects in the polymer as compared to the corresponding polycondensation route.
While network‐like assemblies are formed by amphiphilic polyphosphazenes with poly(N‐isopropylacrylamide) and ethyl tryptophan as side groups in aqueous solution, a significant morphology transformation is observed when small molecules that exhibit hydrogen‐bonding interactions with amphiphilic copolymers are introduced during the preparation of polymeric assemblies through a dialysis procedure. Depending on copolymer composition and the content of small molecules introduced, aggregates ranging from general vesicles, high‐genus vesicles, to well‐defined nanospheres can be prepared successfully as clearly evidenced by TEM observation, which suggests this procedure should be a novel approach to prepare composite vesicles.
In this Communication, the copolymerization of ethylene with a sterically hindered α‐olefin comonomer, γ‐trisubstituted 3,3‐dimethyl‐1‐butene (DMB), using a chain‐walking Pd‐diimine catalyst, [(ArNC(Me) (Me)CNAr)Pd(CH3)(NCMe)]SbF6 (Ar2,6‐(iPr)2C6H3) ( 1 ) is reported. In spite of its high steric bulkiness in the close proximity of the double bond, appreciable DMB incorporations (up to 3 mol‐%) are successfully achieved in the copolymers. The chain microstructure of the copolymers is elucidated, and the effect of DMB incorporation on polymer topology and thermal properties are examined. This work thus demonstrates the high capability of the Pd‐diimine catalyst in incorporating sterically encumbered α‐olefins.
A cationic water‐soluble polyfluorene (P2) containing a high density of tetraalkylammonium side chains in polymer backbone was synthesized and characterized. The polymer shows excellent water solubility up to 100 mg · mL−1 as well as high photoluminescence (PL) quantum yield of 44% in water. The relatively high cationic density and appropriate side chain length of the polymer are the key factors to achieve such high water solubility. The reduction potential of P2 is decreased as compared with its neutral polymer, reflecting the enhanced electron injection abilities. The standard NPB/Alq3 device using such a polymer as the electron injection layer shows nearly three‐fold enhancement in the electroluminescence (EL) efficiency.
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.
Langmuir‐Blodgett films of a cellulose derivative containing porphyrins, porphyrin‐cellulose, were fabricated in order to construct a cellulose‐based molecular photocurrent generation system. On visible light illumination of the LB monolayer film deposited on an ITO electrode, anodic photocurrents were observed with a quantum yield of 1.6% at an applied potential of 0 V versus SCE, and 3.8–4.6% at 0.2–0.3 V versus SCE. These values indicate that the self‐quenching of the photoexcited porphyrins in the cellulose LB film was suppressed, while porphyrin moieties in the LB film had a densely packed structure. This is because the porphyrins are located at a distance of approximately 1.0 nm along the cellulose backbone.
POSS‐functionalized polyisobutylenes (PIBs) were synthesized by carbocationic polymerization using an epoxy‐POSS/TiCl4 initiating system in hexane/methyl chloride (60:40 v/v) solvent mixture at −80 °C. 1H NMR spectroscopy verified the incorporation of one epoxy‐POSS per polymer chain. Light scattering and TEM analysis demonstrated the formation of 50–100 nm sized aggregates and micron‐sized clusters.
Summary: The vapor‐based synthesis and characterization of a reactive polymer, poly[(4‐formyl‐p‐xylylene)‐co‐(p‐xylylene)] ( 1 ), have been reported. The reactive polymer coating enables the immobilization of oligosaccharides via the chemoselective aldehyde‐hydrazide coupling reaction.
3‐Bromopyridine‐4‐carbaldehyde is cyclized with carboxylic acids in acetonitrile at 100° under carbon monoxide pressure in the presence of a catalytic amount of a palladium catalyst along with a base to afford the corresponding 3‐oxo‐1,3‐dihydrofuro[3,4‐c]pyridine‐1‐yl alkanoates in moderate to good yields. 相似文献
Summary: A polymer‐iron oxide nanocomposite film has been successfully synthesized by using a microporous regenerated cellulose film as template and aqueous ferrous chloride as precursor. The nanocomposite film was investigated with XRD, XPS, SEM, TEM, and VSM. The nanoparticles synthesized in situ were disk‐shaped with a mean diameter of ≈24 and thicknesses of 2.5–3.5 nm. For the first time, the nanodisks were well aligned in the cellulose matrix to form an ordered multibilayer structure by the shrinkage of the hybrid film while drying. The nanocomposite film displayed anisotropic magnetic properties as a result of the alignment of magnetic nanodisks. This work provides a novel and facile method for template synthesis of nanoparticles and aligned nanocomposites.
TEM image of the air‐dried nanocomposite film; slice perpendicular to the film plane. 相似文献
Summary: We report a simple method for tuning catalytic property of a metallocene‐based catalyst, Cp2ZrCl2, for ethylene polymerization by the direct adsorption of Cp2ZrCl2 onto multi‐walled carbon nanotubes (MWCNTs). The direct interactions between MWCNTs and the Cp rings of Cp2ZrCl2 controlled the polymerization behaviors, and we could generate polyethylene with an extremely high molecular weight ( = 1 000 000) at 30 °C and under 1 atm of ethylene gas.
Microporous films consisting of two‐dimensionally ordered void structures ‐ so‐called honeycomb films ‐ were produced by evaporation of polymer solutions under high humidity. Two types of poly(vinyl cinnamate)s were used: A newly synthesized amphiphilic poly(vinyl cinnamate) and a mixture of a commercial poly(vinyl cinnamate) and an amphiphilic polyion complex. Photo‐crosslinking of the honeycomb structure could be achieved by UV irradiation while completely retaining the film morphology. The crosslinked films showed excellent stability against organic solvents.
