Photo‐crosslinkable side‐chain liquid‐crystalline polymers (LCPs) containing photoreactive benzophenone cores are synthesized in order to obtain their corresponding side‐chain liquid‐crystalline elastomers (LCEs). This strategic synthesis allows thin elastomeric films and their integration into microsystems for actuators and micromachines to be obtained. As an example of this principle, a gripper was developed. The position of its arms can be changed by applying voltages from 1.5 to 3.5 V at different rates. Small changes in the liquid‐crystalline elastomer film cause strains of up to 150% in the microdevice and the capacity to move up to 400 times its own mass due to the nematic‐to‐isotropic transformation.
Summary: Novel water‐soluble hydrophobically associative polymers, comprising sodium 2‐acrylamido‐2‐methylpropansulfonate , N,N‐dimethylacrylamide and different amounts of a hydrophobically associative macromonomer, were synthesized in an aqueous medium. Formation of a rotaxane‐like complex of this macromonomer, with randomly methylated β‐cyclodextrin, was studied. In addition, a side chain of polyrotaxane, comprising this complex and methyl methacrylate, was synthesized via ATRP. These polymers were characterized by dynamic light scattering and fluorescent‐probe technique. Effects of methylated β‐cyclodextrin on micelle formation of the polymers were also studied.
Summary: Biaxial side‐on cholesteric copolysiloxanes with laterally attached mesogenic groups were investigated in mixtures with a low molar mass liquid crystal. While mixtures with a low concentration of the polymer exhibit the conventional fingerprint texture, for concentrations above about 60 mol‐% characteristic irregularities appear in the cholesteric structure that are obviously due to phase biaxiality. Besides the absence of pseudo‐isotropic lines, irregular patterns perpendicular to the helix axis emerge and the periodic distance of regions with similar optical properties along the helix axis is strongly disturbed. This suggests that the photonic band gap width of a uniaxial cholesteric phase becomes strongly affected when a phase transformation into a biaxial cholesteric phase occurs.
Cholesteric fingerprint texture of a mixture of uniaxial nematic monomer and biaxial cholesteric polymer. 相似文献
A general approach to construct one‐dimensional face‐to‐face alignment of porphyrin/fullerene nanowires has been developed. This system uses extended trans‐dihydroxotin(IV) porphyrin and trans‐dicarboxylate‐substituted [60]fullerenoacetic diacid compounds. The nanowires are arranged in regular one‐dimensional linear arrays with lengths in the range 50–300 nm. In the nanowires, each fullerene unit is axially coordinated to the central metal ion of a Sn(IV) porphyrin unit via Sn‐carboxylate coordination and forms a face‐to‐face aligned structure. The synthesis and the hierarchical structure of nanowires have been investigated. They could have potential applications for photoelectronic devices, organic solar cells and so on.
This paper reports the preparation of inclusion complexes of amylose with synthetic polymers by means of enzymatic polymerization of α‐D ‐glucose 1‐phosphate monomer (Glc‐1‐P). The synthetic polymers, employed as the guests, are poly(ε‐caprolactone), poly(δ‐valerolactone), and poly(ester‐ether), containing ester groups in the main chains. The formation of the inclusion complexes was carried out by the enzymatic polymerization of Glc‐1‐P catalyzed by phosphorylase in the presence of the guest polymers.
Summary: After the condensation polymerization of benzoguanamine (BGA) and pyromellitic dianhydride (PMDA) under microwave irradiation, the resulting p‐π conjugate poly(amic acid) was grafted via the azo coupling reaction. The obtained side‐chain polymers were further grafted with TDI‐aliphatic alcohol derivatives and TDI‐aniline derivatives. The third‐order NLO coefficient and response time of PAA and graft polymers were measured by degenerated four wave mixing (DFWM) technique and their fluorescent properties were also investigated. All of the graft polymers have larger NLO coefficients and film‐formability than PAA. Their fluorescent properties were also changed by the different electronic effect of the side‐chains. The influences of the introduction of side‐chains, the side‐chain length and the electronic effect of the substituting groups on the azobenzol side‐chain to both optical properties of the polymers by varying the conjugation degree were investigated.
CROP has been used to synthesize well‐defined POXZ with a monofunctional (iodomethane) or a bifunctional (1,3‐diiodopropane) initiator. POXZ has been functionalized with an azido group at one (α‐azido‐POXZ, = 3.58 × 103 g · mol?1) or both ends (α,ω‐azido‐POXZ, = 6.21 × 103 g · mol?1) of the macromolecular chain. The Huisgen 1,3‐dipolar cycloaddition has been investigated between azido‐POXZ and a terminal alkyne on a small or larger molecule (PEG). In each case, the click reaction has been successful and quantitative. In this way, different telechelic polymers (polymers bearing different functions such as acrylate, epoxide, or carboxylic acid) and block copolymers of POXZ and PEG have been prepared. The polymers have been characterized by means of FTIR, 1H NMR, and SEC.
A novel stereo‐regular organo‐bridged ladder‐like polymethylsiloxane ( LPMS ) was synthesized by a stepwise coupling polymerization on the basis of an amido H‐bonding‐assisted self‐assembling template. The monomer N,N′‐bis{4‐[3‐(diethoxymethylsilyl)propoxy]‐phenyl}terephthalamide ( M ), prepared by hydrosilylation reaction at high temperature, was hydrolyzed in a dilute solution at a low temperature to form a ladder‐like supramolecular intermediate through amido H‐bonding interactions, which was further condensed to form the polymer LPMS . A combination of techniques including 1H NMR, 29Si NMR, and FT‐IR spectroscopies X‐ray diffraction (XRD), and differential scanning calorimetry (DSC) were used to characterize the titled polymer LPMS , and the results indicate that the polymer possesses an ordered ladder‐like structure.
Three new cyanobiphenyl polysiloxanes presenting long thioether spacers have been carried out. This type of spacer leads to very stable liquid‐crystalline polymers at room temperature and remove the crystallinity phenomenon. Dielectric analysis results show that the thioether spacer brings much more molecular flexibility to the system.
Example of an “interdigitated” structure observed by X‐ray analysis. 相似文献
D‐A‐D‐type polymers are of high interest in the field of photovoltaics and electrochromism. In this study we report the synthesis and electrochemical properties of PPyBT along with its photophysical properties and photovoltaic performance. PPyBT is soluble in common organic solvents and both n‐ and p‐type dopable, which is a desired property for conjugated polymers. During electrochemistry studies, the onset potentials of the polymer were determined as +0.2 V for oxidation and ?1.4 V for reduction. Using these values, HOMO and LUMO energy levels were calculated. The photovoltaic properties of PPyBT were also studied. PL studies showed that there is a charge transfer between PPyBT (donor) and PCBM (acceptor).
AAm was free‐radical polymerized at various temperatures in the presence of N,N'‐methylenebisacrylamide as a cross‐linker and dextran resulting in novel Dx/PAAm semi‐IPNs. The structure and morphology of networks were investigated by means of FTIR, DSC, and ESEM. In comparison to the PAAm network, the interior network structures of the novel semi‐IPNs prepared at ?18 °C exhibit a heterogeneous morphology consisting of pores of sizes about 80 µm, while those formed at +5 and +25 °C have pores with sizes about 3 µm. The Dx/PAAm semi‐IPNs exhibited higher swelling ratios, than those without Dx, irrespective of the gel preparation temperature. Moreover, Dx/PAAm semi‐IPN hydrogels formed at ?18 °C attain the equilibrium state in water within 15 s.
Novel water dispersible poly(benzimidazobenzophenanthroline) polymers functionalized with poly(ethylene oxide) (BBL:PEO) have been investigated by cyclic voltammetry, in situ UV‐vis spectroscopy and atomic force microscopy. The cyclic voltammograms recorded during n‐doping indicate that the drop coated BBL:PEO films retain their properties despite functionalization. A small influence of the PEO side chains on redox properties of the investigated polymers was found, diminishing however after annealing. During spectroscopic experiments structural changes connected with polymer charging were observed (in accordance with a two electron transfer process). The functionalization of BBL with PEO side chains provided an easy processing method to obtain smooth and reproducible polymer films.
Summary: A stereospecific polymerization of a novel aromatic acetylene containing an alkyl sulfide group, i.e., (p‐methylthiophenyl)acetylene (pMeSPA) was successfully performed to selectively give the corresponding polymer bearing a cis‐transoid structure as a main geometrical form and a very high molecular weight, = 1.7–5.8 × 106 in high yields. This was accomplished when a Rh complex catalyst, [Rh(norbornadiene)Cl]2, was used in the presence of triethylamine (TEA) solvent as a cocatalyst and its mixed solvents with TEA, together with a detailed characterization of the resulting polymers before and after compression at room temperature. Based on the data obtained before and after compression, it was concluded that compression of the PpMeSPA polymers induced a cis‐to‐trans isomerization at room temperature under vacuum even in the solid state (the Figure shows the radical generated by compression).
Summary: This study reports the synthesis, characterization, and electroluminescent device application of three new silicon‐containing polyquinolines: poly(2,2′‐(bis(p‐phenyl)diphenylsilane)‐6,6′‐bis(4‐phenyl quinoline)), poly(2,2′‐(bis(p‐phenyl)octylmethylsilane)‐6,6′‐bis(4‐phenyl quinoline)), and poly(2,2′‐(bis(p‐phenyl)diphenylsilane)‐6,6′‐bis(4‐hexylquinoline)). The polymers with alkyl side chains were soluble in organic solvents. The new polymers showed robust thermal properties with glass transitions of 161–339 °C. Cyclic voltammetry of the polymers revealed quasi‐reversible reductions with onsets of ?1.55 to ?1.71 V (vs SCE) and corresponding electron affinities of 2.69–2.85 eV. Organic light‐emitting devices using new polyquinolines as emissive materials showed blue (CIE coordinates = 0.21, 0.20) or blue‐green (0.23, 0.36) electroluminescence with a moderate brightness (≈140 cd · m?2) and efficiency (0.04%). The results demonstrate that silicon‐containing polyquinolines are promising n‐type wide band‐gap semiconductors for organic electronics.
Structures of new Si‐containing polyquinolines. 相似文献
Summary: Gas‐phase assisted surface polymerization (GASP) of methyl methacrylate (MMA) and styrene (St) was investigated with Fe‐based radical initiating systems, FeCl2/2,2′‐bipyridine (Bpy)/methyl α‐bromophenylacetate (MBPA), etc. GASP with these initiating systems proceeded to produce corresponding polymers on substrate surfaces. The resulting PMMA had very high PDI values, suggesting an uncontrolled reaction. In an attempt to control the GASP, polymerization with a simple initiating system, Fe(0)/MBPA, was examined on Fe(0)‐metal surfaces, resulting in significant polymerization activity to produce high‐molecular‐weight PMMA. The results of time‐course tests on GASP of MMA and St suggested that a change had taken place to produce physically controlled propagation sites on the Fe(0) powder surfaces.
GASP schemes with a simple initiating system Fe(0)/MBPA. 相似文献
Time‐resolved synchrotron X‐ray and DSC experiments were applied to investigate the phase behaviour of poly(diethylene glycol p,p′‐bibenzoate), PDEB. The DSC results are indicative of the formation of a smectic mesophase, previously identified as a SmCA type, which can be easily quenched down to room temperature. However, the synchrotron results show that the SmCA phase undergoes some kind of ordering or transformation at temperatures below 110 °C. Moreover, the annealing of PDEB at temperatures above Tg for sufficiently long times leads to the formation of a highly ordered structure, although very thin crystals and low crystallinities are obtained.
Scattering profiles corresponding to sample PDEB85 in a melting experiment. 相似文献
Summary: The synthesis and polymerization of macromonomers containing a polymerizable styrene head group and a tail of ethylene oxide derivatives of different character were investigated. The synthesis of macromonomers was based on living anionic polymerization of oxiranes. Two monomers were used: 1‐ethoxyethyl glycidyl ether (glycidol acetal), which after hydrolysis forms hydrophilic glycidol blocks and glycidyl phenyl ether forming hydrophobic blocks. Polymerizable double bonds were introduced by terminating the living chain with p‐(chloromethyl)styrene. The radical polymerization of the macromonomers was carried out in water with addition of a non‐polar solvent (benzene) and AIBN as initiator. Core‐shell polymers of different character and molar masses were obtained. The conversion of polymerized macromonomers was around 50%. However, the polymerization product could easily be separated from the reaction mixture.
Summary: A simple quantitative model for the analysis of EFM images of three‐ or more‐component polymer blends is applied to determine the dielectric constants of the blend constituents. The value of the dielectric constant of PIPA calculated from the EFM images of POMA‐PIPA‐APP blend is determined in good agreement with the literature value.
Summary: Stable free‐radical copolymerizations (SFRP) of styrene with N‐acryloyl morpholine (AMo), 2‐ethoxyethyl acrylate (EOEA) and isobornyl acrylate (iBoA), respectively, were carried out under control of the stable nitroxide radical 4‐hydroxy‐2,2,6,6‐tetramethylpiperidine‐N‐oxyl (OH‐TEMPO). The polymerizations were initiated by a polystyrene macroinitiator (PS‐MI). No accelerating agents were used. In contrast to the experiences made with methacrylates there was no decrease in the polymerization rates up to 50 mol‐% of AMo or EOEA in the monomer mixture. This behavior was ascribed to a compensation of the lack of thermal initiation by the high propagation rate constants of the acrylates. The produced AB diblock polymers were successfully employed in block extension reactions in styrene yielding ABA triblock polymers. Copolymerization reactivity ratios (r‐values) and glass transition temperatures have been estimated.
SCLCPs are synthesized using “click chemistry”. The resulting polymers, P1 and P2, have good solubilities and molecular‐weight distributions. Their and polydispersities are in the ranges of 26.7–8.4 × 103 g · mol?1 and 1.99–1.29, respectively. DSC and POM studies reveal that both polymers exhibit liquid‐crystalline behavior. P1 and P2 are found to display blue emission. DSSCs are fabricated using P1 and P2 as matrices for electrolytes. The maximum PCE of the P1‐ and P2‐based polymer electrolytes is 4.11% (at 1 sun). This synthesis route has again proven to be a useful synthetic methodology for fabricating SCLCPs that are promising materials for device applications.
