CONSECUTIVE FORMATION OF SENSORY PHOTOSYSTEMS IN GROWING Halobacterium halobium

Abstract— The sensory photosystems PS 370 and PS 565 of Halobacierium halobium are actively degraded in the early growth phase and later resynthesized. Neither degradation nor resynthesis is correlated to the rate of cell division. The reappearance of photosensory activity requires de novo synthesis of proteins which are most likely directly involved in the sensory pathway. PS 370 appears earlier than PS 565 and thus may be studied independently of PS 565, before the latter is synthesized, or by blocking the synthesis of PS 565 with puromycin after PS 370 has appeared. The action spectrum of PS 370 alone shows the same maximum as the spectrum obtained when PS 565 is present. Carotenoids, which act as accessory pigments of PS 370, do not shift its activity peak. Also the maximum of PS 565 is not influenced by PS 370. We conclude that the maxima of the action spectra of PS 370 and PS 56.5 truely reflect the absorption maxima of the sensory retinal pigmentsP–370 andP–565.     

苯乙烯-氧乙烯-苯乙烯三嵌段聚合物的受限结晶行为的反气相分析

 采用反气相法研究了苯乙烯 氧乙烯 苯乙烯三嵌段结晶聚合物 (PS PEO PS)的结晶熔融相变 ,测定了PS PEO PS的结晶度、熔点以及熔程 ,探讨了正构烷烃探针分子的碳链长度对测定结果的影响。研究结果表明 :PS PEO PS的微相分离对PEO链段的结晶行为有较大的影响 ,其晶体结构中存在由多种不完善PEO结晶和PS非结晶构成的中间层 ;正构烷烃探针分子的碳链长度对测定PS PEO PS的熔点和熔程无影响 ,但对结晶度测定和PEO结晶熔融相变的检测影响较大 ,所测得PS PEO PS的结晶度随正构烷烃探针分子碳链的增长而降低。     

Synthesis and characterization of chiral liquid‐crystalline polysiloxanes containing fluorinated units and sulfonic acid groups

Chiral side‐chain liquid‐crystalline polysiloxanes ( PS‐1 , PS‐2 , PS‐3 , PS‐4 , PS‐5 , PS‐6 ) bearing fluorinated units and sulfonic acid groups were synthesized with poly(methylhydrogeno)siloxane, cholest‐5‐en‐3‐ol(3β)‐4‐(2‐propenyloxy)benzoate, and 3‐trifluoromethyl‐phenyl 3‐sulfo‐4‐undec‐10‐ enoyloxy‐benzoate. The effects of fluorinated units and sulfonic acid groups on characteristic of liquid‐crystalline properties were studied. PS‐1 , PS‐2 , and PS‐3 exhibited both smectic and cholesteric mesophases, while PS‐4 , PS‐5 , and PS‐6 exhibited only cholesteric mesophase. As the polymers contained more fluorinated units and sulfonic acid groups, segregation of the fluorinated segment to the surface and aggregation of hydrogen bonding should occur. Therefore, the highly ordered lamellar mesogen–siloxane matrix systems should be disturbed severely, suggesting that PS‐4 , PS‐5 , and PS‐6 show no smectic phase. The maximum reflection bands become broad and shifted slightly to long wavelength from PS‐1 to PS‐6 . Copyright © 2008 John Wiley & Sons, Ltd.     

Fabrication, morphology and thermal degradation behaviors of conductive polyaniline coated monodispersed polystyrene particles

This study describes the preparation of polyaniline (PANI) coated on the surface of monodispersed 400 nm polystyrene (PS) particles by in situ chemical oxidative polymerization. The monodispersed 400 nm PS particles served as cores were synthesized using the emulsion polymerization. Both images observed by field-emission scanning electron microscopy and transmission electron microscopy show the presence of a thin PANI layer uniformly coated on the surface of PS particle. The electrical conductivity of various amounts of PANI-coated PS particles is significantly increased about 13 orders of magnitude compared to that of the pristine PS particles. Differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA) were used to investigate the thermal stability and thermal degradation behavior of PS and PANI-coated PS particles. Both DSC and TGA curves revealed that the coating of a thin PANI layer on the surface of PS can drastically increase the thermal stability of PS matrix. TGA isothermal degradation data illustrate that the activation energy of the PANI-coated PS particle is larger than that of PS. This phenomenon can be attributed to the incorporation of PANI coating on the surface of PS particle caused a decrease in the degradation rate and an increase in the residual weight for the PANI-coated PS particle.     

Synthesis and characterization of polyethylene‐g‐polystyrene as the compatibilizer for polypropylene/ Polystyrene blends

Polyethylene‐g‐polystyrene (PE‐g‐PS) was synthesized as a compatibilizer for polypropylene/polystyrene­(PP/PS) blends by the living radical polymerization of styrene with polyethylene‐co‐glycidylmethacrylate (PE‐co‐GMA). The compatibilizer effect of PE‐g‐PS on the morphology and thermal properties of PP/PS blends was investigated. The crystalline temperature of PP in PP/PS blends decreased with increasing PE‐g‐PS contents. Morphologies of PP/PE‐g‐PS/PS blends showed much better dispersion of each domain for higher PE‐g‐PS contents. The molecular weight of PS segment in PP/PE‐g‐PS/PS blend was increased by addition of styrene monomer during the post melt blending process where post living radical polymerization reaction proceeded. Copyright © 2003 John Wiley & Sons, Ltd.     

新型sPS/PET/SsPS-Zn工程塑料合金的研究

熔融共混法制备了新型综合性能较好的间规聚苯乙烯 (sPS) 聚对苯二甲酸乙二醇酯 (PET) 磺化间规聚苯乙烯锌盐 (SsPS Zn)工程塑料合金 ,研究了合金结构与性能之间的关系 .加入SsPS Zn后 ,合金的力学性能先提高而后下降 ,当sPS PET SsPS Zn为 85 15 2 (质量比 )时 ,合金的综合力学性能较好 ,冲击强度达到 10 6kJ m2 ,为纯sPS的 2 5倍 ;加入SsPS Zn后 ,合金的耐热性提高 ;合金中sPS的熔点与纯sPS相同 ,而初始结晶温度和达到最大结晶速度时的温度均高于纯sPS ,且基本不受SsPS Zn用量的影响 .PET的熔点、初始结晶温度、达到最大结晶速率时的温度和结晶度均随SsPS Zn用量的增加而逐渐降低 ;DMA结果中所有合金均只呈现一个Tg,并且加入SsPS Zn后 ,Tg 和半峰宽都逐渐提高 ,常温下的储能模量在其用量为 2份时达到最大值 ;SEM观察到加入 2份SsPS Zn后 ,PET分散相的尺寸明显减小 ,继续增加其用量 ,PET分散相的尺寸反而有所增大和不均匀 ,并且合金的冲击断面由显著的层状结构转为相对平整     

Preparation of polystyrene/montmorillonite nanocomposites using a new radical initiator-montmorillonite hybrid via in situ intercalative polymerization

Polystyrene/montmorillonite (PS/MMT) nanocomposites were prepared by in situ free radical intercalative polymerization, using 1, 3 and 5 wt% of a new cationic radical initiator-MMT hybrid. The corresponding nanocomposites were designated as PS/MMT-1, PS/MMT-3 and PS/MMT-5, respectively. The silicate layers were well exfoliated and randomly dispersed in the PS/MMT-1 and PS/MMT-3, but were less exfoliated in the PS/MMT-5, due to the predominant extra-gallery polymerization over the intra-gallery polymerization. The unique properties of nanocomposites resulted from the strong interactions between the nano-sized silicate layer surfaces and the polymer chains. The onset temperature of thermal degradation, and the glass transition temperature, increased with increasing hybrid content, up to 3 wt%. The molecular weights of the PS in the PS/MMT-1 and PS/MMT-3 were less than those calculated theoretically, due to the predominant intra-gallery polymerization.     

Studies on partial compatibility of PP and PS

<正>Blends of polystyrene(PS) and polypropylene(PP) were prepared through melt compounding.With an increase of PS content up to 30 wt%,the tensile strength of PP/PS blends increased from 37.4 MPa to 42.2 MPa,although the blends were widely regarded as immiscible.The DSC results showed that there's slight decrease in melting temperature of PP, showing insufficient evidence for partial compatibility between PP and PS.Almost no variation of distinct characterization peaks were observed in FTIR spectra of PS/PP blends compared with those of neat PP and PS,indicating there is no chemical interactions between PP and PS.Since the morphology investigation showed a droplet structure as PS content was up to 30 wt%,the improvement of tensile strength could be simply considered as due to the reinforcing effect of dispersed rigid PS particles on the PP,combining with partial compatibility between them as evaluated by change of C_p at glass transition for both PS and PP.More interestingly,DSC and DMA results showed that the blending of PS and PP could lead to a substantial decrease of the glass transition temperature(T_g) of PP,and increase of T_g of PS.The annealing experiment was carried out to understand the change of T_g in PP/PS blends.It is believed that the compressive stress generated by the contracting PP should be the dominant mechanism for the T_g elevation of PS.On the other hand,the T_g decrease of PP is likely owing to the creation of a large amount free interface of PP and the dilatation of the PP phase resulting from the corresponding tension exerted by PS during cooling.     

PICOSECOND FLUORESCENCE STUDY OF PHOTOSYNTHETIC MUTANTS OF Chlamydomonas reinhardii: ORIGIN OF THE FLUORESCENCE DECAY KINETICS OF CHLOROPLASTS

Abstract— The fluorescence decay kinetics of photosynthetic mutants of Chlamydomonas reinhardii which lack photosystem II (PS II), photosystem I (PS I), and both PS II and PS I have been measured. The PS II mutant strain8–36C exhibits fluorescence decay lifetime components of 53, 424 and 2197 ps. The fluorescence decay of a PS I mutant strain12–7 contains two major fluorescence decay components with lifetimes of 152 and 424 ps. The fluorescence decay of mutant strain C2, which lacks both PS II and PS I, is nearly single exponential with a lifetime of 2561 ± 222 ps. In simulations in which it is assumed that wild-type decays are a simple sum of the major decay components of the isolated parts of the photosynthetic unit as measured in the mutants, curves are obtained that fit the wild-type C. reinhardii fluorescence decay data when the absorption cross-sections of PS II and PS I are weighted approximately equally. The 89 ps lifetime component in the wild-type is an average of 53 and 152 ps components arising from excitation transfer to and trapping in PS I and PS II. The single step transfer time in PS I is estimated to be between 100 and 700 fs depending on assumptions about array size. We find that between two and four visits to the PS I reaction center are required before final trapping.     

Effect of Nano-anatase TiO2 on Spectral Characterization of Photosystem Ⅱ Particles from Spinach

The photosystem I (PS Ⅱ) particles were purified by means of nano-anatase TiO2 treatment of spinach and studied by spectroscopy. The results show that the electron transport and the oxygen-evolving rate of PS I are accelerated after it has been treated with nano-anatase TiO2; the UV-Vis absorption spectrum of PS I particles is increased; the red shift of fluorescence emission peak of PS I is 2 nm; the peak intensity is decreased; the PS Ⅱ signal I s of low temperature electron paramagnetic resonanace(EPR) spectrum is intensified under light, and the PS I circular dichroism(CD) spectrum is similar to that of control. It is suggested that nano-anatase TiO2 might bind to the PS I reaction center complex and intensify the function of the PS I electron donor, however, nano-anatase TiO2 treatment does not change the configuration of the PS Ⅱ reaction center complex.     

Performance improvement of polysulfone ultrafiltration membrane by blending with polyaniline nanofibers

Polyaniline (PANI) nanofibers were used to improve hydrophilic property and permeability of polysulfone (PS) membrane. PS membrane and PS/PANI nanofibers blended membranes with different PANI–PS mass ratios (1, 5, 10, and 15 wt.%) were prepared by phase inversion process. The blended membranes showed similar bovine serum albumin (BSA) and albumin egg (AE) rejections to PS membrane. The blended membranes had larger porosity and better hydrophilic property than PS membrane, which caused the improvement of their permeability. Pure water fluxes of the blended membranes with PANI–PS mass ratios of 1 and 15 wt.% were 1.6 and 2.4 times that of PS membrane, respectively. During the filtration of BSA solution, the blended membranes had slower flux decline rate than PS membrane. Moreover, stable permeate fluxes of the blended membranes with PANI–PS mass ratios of 1 and 15 wt.% were 2.0 and 2.5 times that of PS membrane, respectively. Compared with PS membrane, mechanical property and thermal stability of the blended membranes with less PANI–PS mass ratio, e.g. 1 wt.%, had no obvious change. For the blended membrane with PANI–PS mass ratio of 15 wt.%, breaking strength increased 28% and elongation at break decreased 30.6%.     

乳液聚合法制备剥离型PS/MMT纳米复合材料

以阳离子表面活性剂十八烷基三甲基氯化铵(OTAC)和烯丙基十八烷基二甲基氯化铵(ATAC)为插层处理剂改性蒙脱土(MMT),原位乳液聚合分别制备了PS/C18MMT和PS/AC18MMT两种纳米复合材料.XRD和TEM分析表明,MMT均被剥离成单个或几个片层无规的分散在PS基体中,TGA分析表明,MMT的加入提高了材料的耐热性能,当PS基体与有机化处理的MMT片层发生一定的化学连接后,PS/AC18MMT纳米复合材料表现出更好的耐热性能.动态力学分析表明,MMT的加入提高了PS的玻璃态储能模量,降低了材料的动态损耗;PS/AC18MMT纳米复合材料的玻璃化温度较PS有所提高,而PS/C18MMT的玻璃化温度与PS相比略有降低.     

Phase structure and viscoelastic properties

The phase structure and dynamic mechanical properties of three polypropylene/polystyrene (PP/PS) systems of similar composition but various dispersion of the minor PS component have been examined. Two different PP/PS systems were prepared by polymerization of styrene (ST) molecularly dispersed in PP matrices (with the same initial structure) under the conditions leading to a linear or crosslinked PS component. The third PP/PS system has been prepared blending the homopolymers in the molten state. Studies of materials containingin situ polymerized PS revealed nanoscale phase separation of PS (atomic force microscopy) and pointed to the presence of physical entanglements between PS and non-crystalline phase of PP (DSC, dynamic mechanical analysis). The PS component in material prepared by melt mixing appeared to be completely phase-separated into micron-sized domains. Dynamic mechanical analysis revealed also the dependence of viscoelastic behavior of the PP/PS systems on dispersion of the PS inclusions and on the nature of the interface.     

The mechanism of ultrasonic improvement of weld line strength of injection molded polystyrene and polystyrene/polyethylene blend parts

The effect of ultrasonic oscillations and ultrasonic oscillation‐induced modes on weld line strength of polystyrene(PS) and polystyrene/polyethylene(PS/HDPE) blend was investigated. And the mechanism of ultrasonic improvement of weld line strength of PS and PS/HDPE blend was also studied. The presence of ultrasonic oscillations can enhance the weld line strength of PS and PS/HDPE blend. Compared with mode I(ultrasonic oscillations were induced into mold at the whole process of injection molding), the induced ultrasonic oscillations as mode II(ultrasonic oscillations were induced into mold after injection mold filling) is more effective to increase weld line strength of PS and PS/HDPE blend. The mechanism for ultrasonic improvement of weld line strength of PS and PS/HDPE blend is that the ultrasonic oscillations can improve the molecular diffusion across weld line of the melt at the core, and make against the fusion of melt at the skin. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1520–1530, 2006     

Surface phase separation, dewetting feature size, and crystal morphology in thin films of polystyrene/poly(ε-caprolactone) blend

Thin films of polystyrene (PS)/poly(ε-caprolactone) (PCL) blends were prepared by spin-coating and characterized by tapping mode force microscopy (AFM). Effects of the relative concentration of PS in polymer solution on the surface phase separation and dewetting feature size of the blend films were systematically studied. Due to the coupling of phase separation, dewetting, and crystallization of the blend films with the evaporation of solvent during spin-coating, different size of PS islands decorated with various PCL crystal structures including spherulite-like, flat-on individual lamellae, and flat-on dendritic crystal were obtained in the blend films by changing the film composition. The average distance of PS islands was shown to increase with the relative concentration of PS in casting solution. For a given ratio of PS/PCL, the feature size of PS appeared to increase linearly with the square of PS concentration while the PCL concentration only determined the crystal morphology of the blend films with no influence on the upper PS domain features. This is explained in terms of vertical phase separation and spinodal dewetting of the PS rich layer from the underlying PCL rich layer, leading to the upper PS dewetting process and the underlying PCL crystalline process to be mutually independent.     

膜乳化-液中干燥法制备单分散高分子微球

粒径可控的单分散高分子微球,在分析化学中可用作高效液相色谱填料^[1,2];在化学工业中可用作催化剂载体;在生物领域中用于药物释放、癌症与肝炎等临床诊断、细胞标记与识别等^[3].高分子微球的制备方法大致可分为两类,一是利用由单体出发的聚合反应或缩聚反应形成微球,二是高分子溶液经物理或物理化学手段处理后形成微球^[4]     

Surface modification of thin polystyrene films

 The sulfonation of polystyrene (PS) films with 50 and 96% sulfuric acid as a function of time is presented. In contrast to previous literature reports, we showed that the treatment of PS films even with dilute sulfuric acid yields sulfonated surfaces after reaction times of 30 s–1 h. The hydrophilicity of the modified PS increased considerably in comparison to the unreacted PS films. X-ray photoelectron spectroscopy yielded evidence for the sulfonation of PS at the surface. Unreacted spin-coated PS films were very smooth, while modified PS showed some clumps dispersed on a flat surface, as analyzed by atomic force microscopy. The surface morphology was identified as a phase-separated system composed of domains of unreacted PS and a matrix of sulfonated PS by fluorescence microscopy using the positively charged dye rhodamine B. The adsorption of the polycation diallyldimethylammonium chloride on the sulfonated PS surface could be detected. The thickness of the adsorbed polycation was 2.2 nm. Received: 3 November 1998 Accepted in revised form: 23 February 1999     

The influence of nano‐PS particle on structure evolution and electrical properties of PP/PS

The polypropylene‐g‐polystyrene (PP‐g‐PS) copolymers with different grafting ratios are used as compatibilizers to control the size of polystyrene (PS) particles at nanometer scale in polypropylene (PP) matrix. Then the PP/PS insulating nanocomposites (containing 10 wt % PS calculated from PS and PP‐g‐PS) are manufactured. With the increase in grafting ratio of PP‐g‐PS, the size of PS particle is reduced and the interfacial adhesion is enhanced. Meanwhile, the dielectric properties, DC breakdown strength and volume resistivity are increased with the decreasing of PS particle size. The spherulite size of PP is decreased and the boundary between crystals and amorphous regions is blurred or even disappears due to the presence of PS nanoparticles. This evolution of PP structure is attributed to the serious entanglements of PP and PS molecular chains. Finally, the correlation between morphological structure and electrical properties is ultimately established based on the in‐depth understanding of the molecular chain movement, crystal structure, and phase morphology. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 706–717     

Thin films of PS/PS‐b‐pnipam and ps/pnipam polymer blends with tunable wettability

We developed thin films of blends of polystyrene (PS) with the thermoresponsive polymer poly(N‐isopropylacrylamide) (PNIPAM) (PS/PNIPAM) and its diblock copolymer polystyrene‐b‐poly(N‐isopropylacrylamide) (PS/PS‐b‐PNIPAM) in different blend ratios, and we study their surface morphology and thermoresponsive wetting behavior. The blends of PS/PNIPAM and PS/PS‐b‐PNIPAM are spin‐casted on flat silicon surfaces with various drying conditions. The surface morphology of the films depends on the blend ratio and the drying conditions. The PS/PS‐b‐PNIPAM films do not show an increase in their water contact angles with temperature, as it is expected by the presence of the PNIPAM block. All PS/PNIPAM films show an increase in the water contact angle above the lower critical solution temperature of PNIPAM, which depends on the ratio of PNIPAM in the blend and is insensitive to the drying conditions of the films. The difference between the wetting behavior of PS/PS‐b‐PNIPAM and PS/PNIPAM films is due to the arrangement of the PNIPAM chains in the film. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 670–679     

Singlewall carbon nanotubes covered with polystyrene nanoparticles by in‐situ miniemulsion polymerization

This work is to make carbon nanotubes dispersible in both water and organic solvents without oxidation and cutting nanotube threads. Polystyrene‐singlewall carbon nanotube (PS‐SWNT) composites were prepared with three different methods: miniemulsion polymerization, conventional emulsion polymerization, and mixing SWNT with PS latex. The two factors, crosslinking and surface coverage of PS are important factors for the mechanical and electrical properties, including dispersion states of SWNT in various solvents. The PS‐SWNT composite prepared via a conventional emulsion polymerization showed SWNT bundles entirely covered with PS, whereas the PS‐SWNT composite prepared via a miniemulsion polymerization showed SWNT partially covered with crosslinked PS nanoparticles. The method of mixing SWNTs with PS latex did not show the well dispersed state of carbon nanotubes because PS was not crosslinked and was dissolved in a solvent, and nanotubes separated from PS precipitated. So the PS nanoparticle‐SWNT composite had lower electrical resistance, and higher mechanical strength than the other composites made by the latter two methods. As the amount of SWNT increases, the bare surface area of SWNT increases and the electrical conductivity increases in the composite made by the miniemulsion polymerization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 573–584, 2006