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.
Pseudopolyrotaxanes 4a and 5a are synthesized by two paths: a) directly from the pseudorotaxane, and b) by complexing with cucurbituril (CB[6]) in water at room temperature after the polymerization. Free radical copolymerization with CB[6] (un)complexed monomer and N‐isopropylacrylamide (NIPAAM) is carried out using a redox initiator in aqueous media at room temperature. The properties of pesudorotaxanes ( 4a and 5a ) and polymers ( 4 and 5 ) are investigated by TGA, DSC, and turbidity measurements. The lower critical solution temperatures of the NIPAAM‐containing copolymers and CB[6] are significantly higher than those of pure NIPAAM copolymers. The pseudopolyrotaxanes 4a and 5a have a higher thermal stability, as a result of threading of the CB[6] rings onto the polymer side groups.
A series of novel biodegradable random copolymers of 5‐benzyloxy‐1,3‐dioxan‐2‐one (5‐benzyloxy‐trimethylene carbonate, BTMC) and glycolide were synthesized by ring‐opening polymerization. The copolymers were characterized by nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC). The incorporation of BTMC units into the copolymer chains results in good solubility of the polymers in common solvents. The in vitro degradation rate can be tailored by adjusting the composition of the copolymers.
The in vitro degradation of the homopolymers and poly(BTMC‐co‐GA) copolymers. 相似文献
A Y‐shaped amphiphilic fluorinated monomer, 1‐(1H,1H,2H,2H‐perfluorodecyloxy)‐3‐(3,6,9‐trioxadecyloxy)‐propan‐2‐yl acrylate has been synthesized and its polymerization by reversible addition–fragmentation chain transfer (RAFT) homopolymerization has been investigated. The results show that the molecular weights of the polymers are controlled and all the molecular weight distributions are lower than 1.4. Well‐defined copolymers with 2‐(N,N‐dimethylamino)ethyl methacrylate have been prepared by RAFT polymerization, and the surface properties of the block and random copolymers have been examined by contact angle measurement for water and hexadecane. It has been found that the surfaces of the block copolymers simultaneously exhibit excellent anti‐fog and oil‐repellent properties.
Summary: A novel type of glycerol‐derived, water‐soluble polycarbonate with pendant, primary hydroxyl groups was prepared from 2‐(2‐benzyloxyethoxy)trimethylene carbonate (BETC). Ring‐opening polymerization of BETC and 2,2‐dimethyltrimethylene carbonate (DTC) gave narrow distribution of homopolymers or random copolymers with high molecular weights. The protecting benzyl groups were removed by catalyzed hydrogenation at atmosphere H2 pressure to give hydroxyl polycarbonates without observable changes on the polymer backbone and molecular weight distribution. The hydrophilicity of the copolymers increases with the increase in the hydrophilic glycerol‐derived carbonate content.
Synthesis of the glycerol‐derived polycarbonate. 相似文献
The large‐scale fabrication of nanofibers of coordination polymers (CPs) is reported for the first time from CP gel precursors by the electrospinning method. In the absence of organic polymeric additives, viscous solutions suitable for drawing fibers have been made by diluting the gel precursors, which are obtained by mixing Ni(OAc)2 and 4‐trifluoromethylbenzoic acid with 4,4′‐bis(pyridyl)ethylene (bpe) or 4,4′‐bipyridine (bpy) linear spacer ligands in organic solvents. One‐dimensional polymeric structures have been proposed for these gels and nanofibers based on the crystal structures of the compounds isolated. These fibers show some interesting field‐emission properties. The results described here may well be extended to other one‐dimensional polymers, thus opening the door for processing of the coordination polymers.
Summary: Nanowire lengths and length‐to‐width aspect ratios in regioregular poly(3‐hexylthiophene) (P3HT) were simply controlled through changes in the solvent vapor pressure during solidification. It is demonstrated that the nanowires grew by rod‐to‐rod association, in which the molecular long axis of the P3HT chains appeared to be well‐oriented parallel to the silicon substrate (Si/SiOx). The formation of the nanowires took place by one dimensional self‐assembly, governed by π‐π stacking of the P3HT units.
TEM high contrast images showing P3HT nanowires fabricated by spin‐coating under a solvent vapor pressure. 相似文献
Thermal field‐flow fractionation (ThFFF) is used as a novel fractionation technique to investigate the molecular heterogeneity of PB‐b‐PVP‐b‐PtBMA triblock copolymers. Such copolymers cause major problems in liquid chromatography due to very strong polar interactions with the stationary phase. ThFFF separates the copolymers with regard to size and/or chemical composition based on the normal and thermal diffusion coefficients. The separation mechanism in ThFFF and the chemical composition of the separated species is elucidated by online 1H NMR. Based on the compositional analysis and a calibration of the system with the respective homopolymers, the samples are quantified regarding their molar masses, chemical compositions, and microstructures providing comprehensive information on the complex structure of these block copolymers.
A trithiocarbonate RAFT agent was modified with a pyridyl disulfide group and used in the direct synthesis of endgroup pyridyl disulfide‐functionalized homo‐ and amphiphilic block copolymers of oligo(ethyleneglycol) acrylate (PEG‐A) and butyl acrylate (BA). Both the homo‐ and copolymerizations were found to be well controlled via the RAFT mechanism. The NMR analysis indicated that both the homopolymers of PEG‐A and the amphiphilic diblock copolymers of PEG‐A and BA possessed pyridyl disulfide terminal groups. A UV‐Vis absorption test revealed that the pyridyl disulfide endgroup of the polymer could be efficiently used to couple thiol‐bearing molecules to the polymer without the need for any post‐polymerization modification. This communication presents the first efficient direct synthesis of thiol‐reactive endgroup‐functionalized well‐defined polymers via the RAFT technique.
Well‐defined PEO‐b‐PMMA was prepared, initiated by macroinitiator PEO‐Br, by means of ATRP, where esterification of the terminal hydroxyl group of PEO with 2‐bromoisobutyryl bromide yielded a macroinitiator PEO‐Br. Highly ordered microporous films (hexagonal pattern) were constructed by emulsion micelles of such amphiphilic diblock copolymer formed from a solution with CHCl3/H2O/THF = 100:5:10 (v/v). We also constructed the microporous films using diblock copolymer by the current water‐assisted method.
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: PE‐block‐PS and P(E‐co‐P)‐block‐PS block copolymers were synthesised via sequential monomer addition during homogeneous polymerisation on various phenoxyimine catalysts. One phenoxyimine catalyst was tailored to produce high molecular weight block copolymers containing both, polyolefin and polystyrene segments. According to chromatographic analysis and TEM morphology studies, blends of block copolymers and PE homopolymers [or P(E‐co‐P), respectively] were formed. The direct olefin/styrene block copolymer synthesis on phenoxyimine catalysts represents an attractive, new one‐pot route to styrenic block copolymers which are commercially prepared by anionic styrene/diene block copolymerisation followed by hydrogenation.
Supramolecular poly(vinyl acetate) PVAc 3‐arms stars were successfully generated by Reversible Addition–Fragmentation chain Transfer (RAFT)‐polymerized chains bearing hydrogen‐bonding heterocomplementary associating units. Chain Transfer Agents (CTA) bearing thymine‐ and diaminopyridine‐based units were first synthesized and proved to mediate efficiently the polymerization of VAc. The binding ability of the chains in solution was then demonstrated by 1H NMR and GPC measurements, proving the formation of the supramolecular stars.
A new kind of chiral‐dendronized binaphthyl‐containing polyfluorene derivatives has been synthesized through “click chemistry” efficiently. The resulting copolymers exhibited desirable properties, such as excellent solubility, good thermal stability, and considerably high molecular weights. The photophysical properties of the copolymers were investigated in details, and the results indicated that the combination of chiral binaphthyl unit and bulky dendron could effectively suppress intermolecular packing and aggregation. In addition, the investigation of circular dichroism behavior of these chiral‐dendronized copolymers showed a strong Cotton effect at long wavelength (373–379 nm), indicating that the chirality of the binaphthyl units was transferred to the whole polyfluorene backbone.
A PTFE film surface was modified using a combined plasma/ozone‐activated process. The modified PTFE film was further reacted with 2‐bromoisobutyryl bromide to incorporate ATRP initiators in the film surface. Surface‐initiated ATRP on PTFE films was performed using sodium styrene sulfate as a monomer. The poly(sodium styrene sulfate) chain length grafted onto PTFE film surfaces increased with increasing reaction time. Analysis using X‐ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy and a contact angle analyzer gave evidence of the success of the PTFE surface modifications.
Summary: Fabrication of honeycomb‐patterned films from amphiphilic dendronized block copolymer (PEO113‐b‐PDMA82) by ‘on‐solid surface spreading’ and ‘on‐water spreading’ method is reported. Highly ordered honeycomb films with quasi‐horizontally paralleled double‐layered structure can be fabricated by the on‐solid surface spreading method. This work raises the possibility that such structures can be formed in amphiphilic dendronized block copolymers and extends the family of source materials.
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.
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
Interaction chromatography has been employed to validate that adsorption of poly[styrene‐co‐(4‐bromostyrene)] (PBrxS) random copolymers, where x denotes the mole fraction of 4‐bromostyrene (4–BrS) in PBrxS in solution depends on the average number of adsorptive segments, the type of adsorbing substrate, and on the co‐monomer sequence distribution in PBrxS.
Novel poly[(fluorene)‐co‐(2,8‐dioctyldibenzothiophene‐S,S‐dioxide‐3,7‐diyl)]s were synthesized. The octyl group on the 2,8‐dioctyldibenzothiophene‐S,S‐dioxide (DOSO) unit improved the solubility of the polymers and broadened the optical band gap from 2.95 to 3.20 eV as the content of DOSO unit increases. The electroluminescence (EL) spectra of polymers show CIE coordinates around (0.16, 0.07) independent of the ratio of DOSO units in the polymers, owing to the ICT and steric hindrance dual‐function. A high efficiency of 3.1 cd · A−1 (EQE = 3.9%) was obtained with the configuration of ITO/PEDOT:PSS/polymer/Ba/Al. The results indicate that PF‐3,7DOSOs could be a promising candidate for saturated blue‐emitting polymers with spectral stability and high efficiency.
