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1.
Polymer dispersed liquid crystal (PDLC) films were obtained by successive controlled living radical polymerizations: starting polystyrene (M1) was obtained by reversible addition‐fragmentation polymerization (RAFT), M1 was converted to P‐chloromethylated polystyrene (M2) which was grafted with polystyrene branches by atom transfer radical polymerization (ATRP) to yield RAFT‐initiating graft polymer containing trithiocarbonate moieties in the backbone (M3, RAFT‐active grafted polystyrene), and then PDLC films were prepared by photo‐induced RAFT copolymerization of methyl acrylate with M3 in the presence of a nematic liquid crystal. The electro‐optical properties of the films were investigated for the purpose to apply them to optical devices. Experimental results showed that preferable properties could be acquired by controlling the amount of M3 and the liquid crystal E7 in the polymer matrix of PDLC films. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers  相似文献   

2.
Two types of photoinitiators were synthesized: (1) a α,ω‐telechelic oligomeric photoinitiator, by the reaction of poly(propylene glycol) diglycidylether (PPGDGE) and 2‐hydroxy‐2‐methyl‐1‐phenyl‐propan‐1‐one (Darocur 1173), and (2) a polymeric photoinitiator, by copolymerization of a monomer that had a liquid crystalline property, 4‐[ω‐(2‐methylpropenoyloxy)decanoxy]‐4′‐cyanobiphenyl, with a vinyl monomer that had a photosensitive group. For comparison, low‐molecular‐weight (low‐MW) photoinitiator (Darocur 1173) also was used. Attention was directed to the structural effect of the photoinitiators on the electro‐optical properties of polymer‐dispersed liquid crystal (PDLC) film in which the LC phase occupied a major volume (80 wt % of the composite film). For the preparation of PDLC films by the polymerization‐induced phase separation method, the optimum UV‐curing temperature was observed at 50°C, a temperature slightly higher than the cloud temperature (Tcloud) of the low‐MW LC/matrix‐forming material mixture. It was found that the electro‐optical performance of the PDLC cell fabricated with the oligomeric or polymeric photoinitiator was better than that of the PDLC cell made with a low‐MW photoinitiator (Darocur 1173), exhibiting lower driving voltage (V90) and higher contrast ratio under identical formulation conditions. Oligomeric photoinitiators allowed premature phase separation between the LC and matrix phases, resulting in relatively pure LC‐rich phases. For the polymeric photoinitiator, incorporation of mesogenic moieties into the photoinitiator resulted in not only a well‐defined LC/matrix morphology but also in low driving voltage (V90) because of reduced friction at the LC/matrix interfaces. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 162–169, 2006  相似文献   

3.
A polydimethylsiloxane (PDMS) macroazoinitiator was synthesized from bis(hydroxyalkyl)‐terminated PDMS and 4,4′‐azobis‐4‐cyanopentanoic acid by a condensation reaction. The bifunctional macroinitiator was used for the block copolymerization of ethyl methacrylate (EMA) and 2‐(trimethylsilyloxy)ethyl methacrylate (TMSHEMA) monomers. The poly(DMS‐block‐EMA) and poly(DMS‐block‐TMSHEMA) copolymers thus obtained were characterized using Fourier transform infrared and 1H NMR spectroscopy and differential scanning calorimetry. After the deprotection of trimethylsilyl groups, poly(DMS‐block‐HEMA) and poly(DMS‐block‐EMA) copolymer film surfaces were analysed using scanning electron microscopy and X‐ray photoelectron spectroscopy. The effects of the PDMS concentration in the copolymers on both air and glass sides of films were examined. The PDMS segments oriented and moved to the glass side in poly(DMS‐block‐EMA) copolymer film while orientation to the air side became evident with increasing DMS content in poly(DMS‐block‐HEMA) copolymer film. The block copolymerization technique described here is a versatile and economic method and is also applicable to a wide range of monomers. The copolymers obtained have phase‐separated morphologies and the effects of DMS segments on copolymer film surfaces are different at the glass and air sides. Copyright © 2010 Society of Chemical Industry  相似文献   

4.
We prepared polymer-dispersed liquid crystal (PDLC) by using nematic liquid crystal 5CB and biphenyl methacrylate type monomer with alkoxy terminal group. Reverse mode properties were achieved by rubbing the glass substrates of the PDLC films in parallel directions so that polymer and liquid crystal molecules are plane-parallel aligned in the sample cell. The monomers with various carbon number (n ≤ 4) of alkoxy group were employed for the formation of the PDLC films. The films were cured by varying monomer concentration and UV curing time. The resulting liquid crystal/polymer composites showed significantly improved driving voltage and contrast ratio.  相似文献   

5.
Polymer‐dispersed liquid crystal (PDLC) composite films were fabricated by thermal polymerization with E7 liquid crystal, monomers, and novel azobenzene derivatives synthesized in this study. To investigate the effects of azocompounds on the optical switching of PDLC films, a series of novel azobenzene derivatives of 4‐alkyloxy‐4′‐methoxyazobenzene with carbon numbers of 3–6, chiral compounds of amyl‐4‐(4‐hexyloxyphenylazo)benzoate, and bornyl‐4‐(4‐hexyloxyphenylazo)benzoate were synthesized. The compounds synthesized in this investigation were identified using FTIR, NMR, and elemental analysis. The optical texture of the composite films was analyzed under crossed nicols with a polarizing microscope. The morphological observation of the solid polymer in the composite films was performed with a scanning electron microscope (SEM). The optical behavior of the composite films on UV irradiation and the effects of the curing time on the thermal stability of the composite films were investigated. Isomerization of the azobenzene derivatives due to UV irradiation was confirmed by a texture study and image recording method. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 789–799, 2004  相似文献   

6.
Pyrene end‐labeled star poly(?‐caprolactone)s (PCLs) with polyhedral oligomeric silsesquioxane (POSS) core were prepared by combination of copper(I)‐catalyzed azide–alkyne cycloaddition (CuAAC) click chemistry and ring‐opening polymerization techniques. First, ?‐caprolactone (?‐CL) is polymerized by using 1‐pyrene methanol as initiator and stannous octoate as catalyst to obtain α‐pyrene‐ω‐hydroxyl telechelic PCL with different chain lengths. Then, its hydroxyl group is converted to acetylene functionality by esterification reaction with propargyl chloroformate. Finally, the CuAAC click reaction of α‐pyrene‐ω‐acetylene telechelic PCL with POSS‐(N3)8 leads to corresponding pyrene end‐labeled star‐shaped PCLs. The successful synthesis of pyrene end‐labeled star polymers is clearly confirmed by 1H‐nuclear magnetic resonance, Fourier transform infrared, gel permeation chromatograph, differential scanning calorimeter, and thermogravimetric analysis. Furthermore, non‐covalent interactions of obtained star polymers with fullerene are investigated in liquid media. Based on Raman spectroscopy and visual investigations, the star polymer having shorter chain length exhibited better and more stable dispersion with fullerene. The amount of pyrene units present per polymer chains can directly influence the dispersion stability of fullerene. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46520.  相似文献   

7.
Poly(glycidyl methacrylate) grafted with double azo bond 4[4′‐(phenylazo)phenylazo]phenol was synthesized and characterized. Photo‐induced birefringence phenomenon of this polymer was studied by static absorption and dynamic pump‐probe techniques, and was compared with that of another polymer Poly{(methyl methacrylate)‐co‐4‐[(3‐methacryloyloxy)} [P(MMA‐co‐MAZ)] containing mono azobenzene chromophore. The results showed that former polymer carrying two azo bonds, with a larger birefringence ratio, had a relatively faster optical switching response than the latter polymer under the same pump beam power. Copyright © 2003 Society of Chemical Industry  相似文献   

8.
To develop conjugated polymers with low bandgap, deep HOMO level, and good solubility, a new conjugated alternating copolymer PC‐DODTBT based on N‐9′‐heptadecanyl‐2,7‐carbazole and 5, 6‐bis(octyloxy)‐4,7‐di(thiophen‐2‐yl)benzothiadiazole was synthesized by Suzuki cross‐coupling polymerization reaction. The polymer reveals excellent solubility and thermal stability with the decomposition temperature (5% weight loss) of 327°C. The HOMO level of PC‐DODTBT is ‐5.11 eV, indicating that the polymer has relatively deep HOMO level. The hole mobility of PC‐DODTBT as deduced from SCLC method was found to be 2.03 × 10?4 cm2/Versus Polymer solar cells (PSCs) based on the blends of PC‐DODTBT and [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM) with a weight ratio of 1:2.5 were fabricated. Under AM 1.5 (AM, air mass), 100 mW/cm?2 illumination, the devices were found to exhibit an open‐circuit voltage (Voc) of 0.73 V, short‐circuit current density (Jsc) of 5.63 mA/cm?2, and a power conversion efficiency (PCE) of 1.44%. This photovoltaic performance indicates that the copolymer is promising for polymer solar cells applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

9.
New hybrid poly(hydroxyethyl methacrylate‐co‐methyl methacrylate)‐g‐polyhedral oligosilsesquioxane [poly(HEMA‐co‐MMA)‐g‐POSS] nanocomposites were synthesized by the combination of reversible addition fragmentation chain transfer (RAFT) polymerization and click chemistry using a grafting to protocol. Initially, the random copolymer poly(HEMA‐co‐MMA) was prepared by RAFT polymerization of HEMA and MMA. Alkynyl side groups were introduced onto the polymeric backbones by esterification reaction between 4‐pentynoic acid and the hydroxyl groups on poly(HEMA‐co‐MMA). Azide‐substituted POSS (POSS? N3) was prepared by the reaction of chloropropyl‐heptaisobutyl‐substituted POSS with NaN3. The click reaction of poly(HEMA‐co‐MMA)‐alkyne and POSS? N3 using CuBr/PMDEATA as a catalyst afforded poly(HEMA‐co‐MMA)‐g‐POSS. The structure of the organic/inorganic hybrid material was investigated by Fourier transformed infrared, 1H‐NMR, and 29Si‐NMR. The elemental mapping analysis of the hybrid using X‐ray photoelectron spectroscopy and EDX also suggest the formation of poly(HEMA‐co‐MMA)‐anchored POSS nanocomposites. The XRD spectrum of the nanocomposites gives evidence that the incorporation of POSS moiety leads to a hybrid physical structure. The morphological feature of the hybrid nanocomposites as captured by field emission scanning electron microscopy and transmission electron microscopic analyses indicate that a thick layer of polymer brushes was immobilized on the POSS cubic nanostructures. The gel permeation chromatography analysis of poly(HEMA‐co‐MMA) and poly(HEMA‐co‐MMA)‐g‐POSS further suggests the preparation of nanocomposites by the combination of RAFT and click chemistry. The thermogravimetric analysis revealed that the thermal property of the poly(HEMA‐co‐MMA) copolymer was significantly improved by the inclusion of POSS in the copolymer matrix. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   

10.
The graft polymerization of methyl methacrylate and butyl acrylate onto poly(vinyl chloride‐co‐vinyl acetate) with atom transfer radical polymerization (ATRP) was successfully carried out with copper(I) thiocyanate/N,N,N,N,N″‐pentamethyldiethylenetriamine and copper(I) chloride/2,2′‐bipyridine as catalysts in the solvent N,N‐dimethylformamide. For methyl methacrylate, a kinetic plot of ln([M]0/[M]) (where [M]0 is the initial monomer concentration and [M] is the monomer concentration) versus time for the graft polymerization was almost linear, and the molecular weight of the graft copolymer increased with increasing conversion, this being typical for ATRP. The formation of the graft polymer was confirmed with gel permeation chromatography, 1H‐NMR, and Fourier transform infrared spectroscopy. The glass‐transition temperature of the copolymer increased with the concentration of methyl methacrylate. The graft copolymer was hydrolyzed, and its swelling capacity was measured. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 183–189, 2005  相似文献   

11.
The electro‐optic performance characteristic of polymer‐dispersed liquid crystal (PDLC) composite films out of poly(vinyl butyral) (PVB) and nematic liquid crystal (E7) have been studied for a wide range of PVB–E7 composite compositions (20–70 wt % of E7). Composites were prepared by solvent casting from chloroform at room temperature. A scanning electron microscopy study showed that a E7 phase is continuously embedded in chink‐like structure of PVB matrix. Optical transmittance of the composite films (of 60 and 70 wt % loading of E7) under an alternating current (ac) electric field (0–250, Vpp) and frequency (50 Hz to 1 KHz) were measured employing He Ne laser (λ = 632.8 nm). The results indicate that the (PVB–E7) composite exhibits a memory effect. In the memory state, higher transmittance is preserved without applying voltage. The memory state can be erased and changed to the scattering Off‐state by heating the film to the clearing temperature of the liquid crystal. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3485–3491, 1999  相似文献   

12.
In the present work, we study the thermal behavior of Polymer (Polystyrene) dispersed (4‐cyano‐4′‐pentylbiphenyl) 5CB liquid crystal film composite. A photopyroelectric device was used to study thermal conductivity at homeotropic and planar aligned of 4‐cyano‐4′‐pentylbiphenyl (5CB) liquid crystal. Thermal conductivity of polystyrene (PS) has been determined and calculated from experimental applied data reported in the literature. Thermal conductivity characteristics of the PDLC films were investigated with three prediction models as a function of both temperature and liquid crystal concentration in the polymer matrix. We particularly show the behavior of this thermal conductivity in the ON and OFF state. It was found that the difference in the film thermal conductivity ranges between 3 and 21%, depending on the ON and OFF state and the liquid crystal volume concentration. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 481–486, 2003  相似文献   

13.
High refractive index homogeneous hybrid materials were successfully prepared. The polymer matrix was the copolymer of methyl methacrylate, sulfur‐containing monomer 2,2′‐mercaptoethylsulfide dimethacrylate (MESDMA), and nanotitania was prepared by in situ solgel process of titanium n‐butoxide. The transmission electron microscope (TEM) study suggested that the hybrid was homogeneous without inorganic agglomerate, and the inorganic particles were 4–7 nm. The refractive index was ~ 1.75 when the inorganic content of the hybrid film reached to 70 wt %, and the transmittance maintained up to 85%. The sulfur‐containing monomer was used to improve the refractive index, also, it was a crosslinking reagent, which improved the film‐forming ability of the hybrid. After copolymerized with MESDMA, the film‐forming ability of the hybrid was better than the one without MESDMA. Even if the inorganic content exceeded 75 wt %, the films kept integrity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   

14.
A series of azobenzene monomers and related model compounds with various side‐chain lengths were synthesized. The electrooptical properties of a polymer‐dispersed liquid crystal (PDLC) were verified by side‐chain methoxy azobenzene in various chain lengths (n = 3, 6, 11). The properties under various voltages were measured and the effect of extra voltage on the transmittance of PDLC was researched as well. The experiment demonstrated the validity of employing these side chain methoxy azobenzene materials in electrooptical devices. The azobenzene model compound showed better electric–optical and thermal–optical properties, having a higher contrast ratio (CR = 689) and a lower saturation voltage (4.7 V/μm). All the azobenzene molecules can be photoisomerized through UV light irradiation, following the mechanism of isomerization. The reversible photo and heat isomerization property was studied. The cis‐azobenzene that was transformed from the trans‐azobenzene irradiated by UV light can decrease the clearing point of the liquid crystal phase. We used this unique characteristic to record image patterns and it worked successfully. We synthesized the azobenzene monomers can stabilize the PDLC and their relative model compounds with various alkyl chain lengths even got better electric–optical effects. We found that azobenzene monomer shows different behaviors in the electric–optical property from its relative model compound. The difference between the systems were explained using a proposed model. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 721–732, 2005  相似文献   

15.
p‐Chlorophenylmaleimide and p‐hydroxyphenylmaleimide with 2‐hydroxypropyl methacrylate were synthesized by radical polymerization, and the metal ion retention capacity and thermal behavior of the copolymers were evaluated. The copolymers were obtained by solution radical polymerization with a 0.50 : 0.50 feed monomer ratio. The maximum retention capacity (MRC) for the removal of two metal ions, Co(II) and Ni(II) in aqueous phase were determined using the liquid‐phase polymer based retention technique. Inorganic ion interactions with the hydrophilic polymer were determined as a function of pH. The metal ion retention capacity does not depend strongly on the pH. Metal ion retention increased with an increase of pH for a copolymer composition 0.50 : 0.50. At different pH, the MRC of the poly(p‐chlorophenylmaleimide‐co‐2‐hydroxypropylmethacrylate) for Co(II) and Ni(II) ions varied from 44.1 to 48.6 mg/g and from 41.5 mg/g to 46.0 mg/g, respectively; while the MRC of poly(p‐hydroxyphenylmaleimide‐co‐2‐hydroxypropyl methacrylate) for Co(II) and Ni(II) ions varied from 28.4 to 35.6 mg/g and from 27.2 to 30.8 mg/g, respectively. The copolymers and copolymer–metal complexes were characterized by elemental analysis, FT‐IR, 1H NMR spectroscopy, and thermal behavior. The thermal behavior of the copolymer and polymer–metal complexes were studied using differential scanning calorimetry and thermogravimetry techniques under nitrogen atmosphere. The thermal decomposition temperature and Tg were influenced by the binding‐metal ion on the copolymer. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007  相似文献   

16.
Polymer‐dispersed liquid crystal (PDLC) films were prepared by ultraviolet light‐induced polymerization of photopolymerizable monomers in nematic liquid crystal (LC)/monomers/SiO2 nanoparticles composites, and the effect of SiO2 nanoparticles on the electro‐optical properties of PDLC films was studied. The observed effect showed that by the adjustment of the SiO2 nanoparticles content, the refractive index ratio of the LC and polymer could be modulated, and the electro‐optical properties of the polymer matrix/LC/SiO2 nanoparticles composites could be optimized. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   

17.
Conventional polymer dispersed liquid crystals (PDLC) are devices with recognized applications. New PDLCs with permanent memory effect (PME) can be used as digital memory devices. The synthesis and characterization of a new monomer [pentaerythritoltetramethacrylate (PE4MA)] is here described. A PDLC was produced using the synthesized monomer (PE4MA) copolymerized with commercially available monomethacrylate oligomer poly(propyleneglycol) methacrylate (PPGMA) and 70% (w/w) liquid crystal (E7), showing 98% permanent memory effect, with 72% memory state contrast (MSC) and an electric field required to achieve 90% of the maximum transmittance (E90) of 3 V µm?1. The synthesized monomer (PE4MA) copolymerized with PPGMA seems to be a prospective material for preparation of PDLC with permanent memory effect with a view to application for digital memory devices based on write‐read‐erase cycles. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43482.  相似文献   

18.
Polymer‐dispersed liquid crystals (PDLCs ) with a well‐defined polymer matrix were successfully fabricated by the thiol‐ene click reaction based on poly(ethylene glycol) diacrylate (PEGDA ) and trimethylolpropanetris‐(3‐mercaptopropionate) (TMTP ). UV ?visible spectrophotometry, Fourier transform IR spectroscopy, SEM and polarized optical microscopy were employed to explore the PDLC films obtained. Electro‐optical properties were studied with a UV ?visible spectrophotometer. It was found that the PDLC films with optimal thiol content fabricated by the thiol‐ene click reaction showed high transmittance, low driving voltage and a low memory effect. It was concluded that the driving voltage change of PDLCs with different thiol concentrations was caused by the polymerization rate and the structure of the polymer matrix. © 2017 Society of Chemical Industry  相似文献   

19.
Copper‐catalysed alkyne–azide 1,3‐dipolar cycloaddition (CuAAC) is the predominantly used bioconjugation method in the field of activity‐based protein profiling (ABPP). Several limitations, however, including conversion efficiency, protein denaturation and buffer compatibility, restrict the scope of established procedures. We introduce an ABPP customised click methodology based on refined CuAAC conditions together with new accelerating copper ligands. A screen of several triazole compounds revealed the cationic quaternary {3‐[4‐({bis[(1‐tert‐butyl‐1H‐1,2,3‐triazol‐4‐yl)methyl]amino}methyl)‐1H‐1,2,3‐triazol‐1‐yl]propyl}trimethylammonium trifluoroacetate (TABTA) to be a superior ligand. TABTA exhibited excellent in vitro conjugation kinetics and optimal ABPP labelling activity while almost exclusively preserving the native protein fold. The application of this CuAAC‐promoting system is amenable to existing protocols with minimal perturbations and is even compatible with previously unusable buffer systems such as Tris ? HCl.  相似文献   

20.
Morphologies of polymer blends based on polystyrene‐b‐ polybutadiene‐b ‐poly(methyl methacrylate) (SBM) triblock copolymer were predicted, adopting the phase diagram proposed by Stadler and co‐workers for neat SBM block copolymer, and were experimentally proved using atomic force microscopy. All investigated polymer blends based on SBM triblock copolymer modified with polystyrene (PS) and/or poly(methyl methacrylate) (PMMA) homopolymers showed the expected nanostructures. For polymer blends of symmetric SBM‐1 triblock copolymer with PS homopolymer, the cylinders in cylinders core?shell morphology and the perforated lamellae morphology were obtained. Moreover, modifying the same SBM‐1 triblock copolymer with both PS and PMMA homopolymers the cylinders at cylinders morphology was reached. The predictions for morphologies of blends based on asymmetric SBM‐2 triblock copolymer were also confirmed experimentally, visualizing a spheres over spheres structure. This work presents an easy way of using PS and/or PMMA homopolymers for preparing nanostructured polymer blends based on SBM triblock copolymers with desired morphologies, similar to those of neat SBM block copolymers. © 2017 Society of Chemical Industry  相似文献   

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