N+离子注入聚对苯乙炔衍生物的非线性光学性能

以对甲氧基苯酚和溴代异戊烷为原料,用脱氯化氢反应制备可溶性聚[2-甲氧基-5-(3'-甲基)丁氧基]对苯乙炔(MMB-PPV),通过核磁氢谱(1HNMR)和红外光谱(FTIR)对产物分子的结构进行表征.用能量为15keV、剂量为3.8×1015～9.6×1016ions/cm2的氮正离子(N+)对MMB-PPV薄膜进行注入改性.紫外-可见吸收光谱(UV-Vis)显示,注入离子在MMB-PPV薄膜内部引入杂质能级,破坏了分子的共轭结构.随着注入剂量增加,吸收边逐渐向长波方向移动,且分子激发态和基态间的光学带隙由2.12eV减小至1.81eV.用简并四波混频(DFWM)技术研究了离子注入MMB-PPV薄膜的三阶非线性光学性能.结果表明,未注入薄膜的三阶非线性极化率(χ(3))值为7.1×10-10esu,随着注入剂量的增加,χ(3)值逐渐增大,当注入剂量达到3.8×1016ions/cm2时,χ(3)值提高到9.3×10-9esu,继续增加注入剂量,χ(3)值开始下降,当注入剂量为9.6×1016ions/cm2时,χ(3)值降低到1.5×10-10esu.对离子注入MMB-PPV薄膜χ(3)值变化的机理进行了探讨.     

Poly(vinyl methyl ether) hydrogel formed by high energy irradiation

Poly(vinyl methyl ether) shows a lower critical solution temperature behavior in water. The dimension of the polymer molecules depends on the temperature. A thermo‐sensitive hydrogel was synthesized by irradiation of an aqueous solution of poly(vinyl methyl ether) with electron beam and γ‐rays. At high polymer concentration a bulk gel was formed. The structure of the gel in the dry, swollen and shrunken state was investigated by field emission scanning electron microscopy (FESEM). It could be shown, that the gel synthesized by electron beam has a sponge‐like structure consisting of cavities (≈1 μm) separated from each other by a polymer layer full of holes (≈10 nm). The macroscopic gel is characterized by several techniques, e.g. determination of the M_c‐value by NMR‐relaxation measurements.     

Ionic Conductivity in Solutions of Poly(ethylene oxide) and Lithium Perchlorate

Summary: Solution casting technique served to prepare solid solutions of lithium perchlorate and poly(ethylene oxide) (PEO) having different molecular masses. Salt concentrations of solutions were varied between around 2 and 13 wt%. Crystallinity and melting point depression served to determine composition and content of amorphous phase as well as thermodynamic behavior of the solutions. Conductivity as a function of salt concentration in the amorphous phase follows a power law at constant temperature (30 °C). It results that both exponent and mobility of charge carriers increase with ascending molecular mass of PEO. The mobility follows an increase with molecular mass proportional to M^2.8 indicating dependence of mobility on interstitial volume between chain molecules. Deviation of solution from perfect behavior can be evaluated by melting point depression. Accordingly, increase in conductivity is preferably related to approach to perfect solution behavior. Determination of dielectric function allows some conclusion about ion pair formation in the systems under discussion. It turns out that probability of ion pair formation decreases with increasing molecular mass of PEO in agreement with thermodynamic behavior of the solutions.     

Dynamics of Poly(methyl methacrylate) in Ionic Liquids with Different Concentration and Cationic Structures

The dynamic behavior of entangled poly(methyl methacrylate)(PMMA) chains in both the traditional monocationic ionic liquid(MIL)and synthetic dicationic ionic liquid(DIL) with the same anion bis[(trifluoromethyl)sulfonyl]imide([TFSI]-) has been examined over the wide composition range using differential scanning calorimetry and rheological measurements.PMMA/DIL and PMMA/MIL systems exhibit two glass transitions in the midrange of composition due to self-concentration effects.PMMA in DIL shows slo...     

Heat capacity of poly(vinyl methyl ether)

The heat capacity of poly(vinyl methyl ether) (PVME) has been measured using adiabatic calorimetry and temperature‐modulated differential scanning calorimetry (TMDSC). The heat capacity of the solid and liquid states of amorphous PVME is reported from 5 to 360 K. The amorphous PVME has a glass transition at 248 K (?25 °C). Below the glass transition, the low‐temperature, experimental heat capacity of solid PVME is linked to the vibrational molecular motion. It can be approximated by a group vibration spectrum and a skeletal vibration spectrum. The skeletal vibrations were described by a general Tarasov equation with three Debye temperatures Θ₁ = 647 K, Θ₂ = Θ₃ = 70 K, and nine skeletal modes. The calculated and experimental heat capacities agree to better than ±1.8% in the temperature range from 5 to 200 K. The experimental heat capacity of the liquid rubbery state of PVME is represented by C_p(liquid) = 72.36 + 0.136 T in J K^?1 mol^?1 and compared to estimated results from contributions of the same constituent groups of other polymers using the Advanced Thermal AnalysiS (ATHAS) Data Bank. The calculated solid and liquid heat capacities serve as baselines for the quantitative thermal analysis of amorphous PVME with different thermal histories. Also, knowing C_p of the solid and liquid, the integral thermodynamic functions of enthalpy, entropy, and free enthalpy of glassy and amorphous PVME are calculated with help of estimated parameters for the crystal. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2141–2153, 2005     

Interdiffusion in a polystyrene-poly(vinyl methyl ether) system

Interdiffusion in polystyrene-poly(vinyl methyl ether) systems is studied by optical-interferometry method in wide temperature and concentration ranges. For these systems, temperature-concentration dependences are constructed, activation energies are calculated, and dependences of the diffusion coefficient on the molecular mass of polystyrene are examined. The results are compared with the phase diagrams of the systems, and it is shown that the diffusion coefficient decreases as the binodal curve is approached, thereby leading to corresponding changes in the Arrhenius coordinates.     

Temperature-sensitive poly(vinyl methyl ether) hydrogel beads

Temperature-sensitive hydrogel beads were prepared by radiation crosslinking of poly(vinyl methyl ether) PVME spheres wrapped in Ca-alginate. The obtained gel beads have diameters in the sub-millimeter or millimeter range (depending on the PVME concentration). They were characterized by sol-gel analysis, swelling measurements, and differential scanning calorimetry. The gel content g increases with increasing radiation dose D. The swelling degree Q_v decreases with increasing PVME concentration c_p and increasing D. In comparison to PVME bulkgels the phase-transition temperature of the synthesized PVME gel beads is a little decreased.     

Dispersion Stability and Electrorheological Properties of Polyaniline Particle Suspensions Stabilized by Poly(vinyl methyl ether)

In the present article, a novel method of stabilization of a semi conductive polyaniline particle nonaqueous suspension of electrorheological (ER) materials was introduced. Using as the steric stabilizer poly(vinyl methyl ether) (PVME), a dispersion polymerization of aniline was performed and stable aqueous dispersions of the polyaniline were obtained. However, a stable colloidal suspension of polyaniline in silicone oil medium can be obtained only with a low concentration of PVME (0.75%), although the average size of the individual, redispersed particles in oil generally decreased with increasing concentration of PVME. At higher concentrations of PVME, formation of highly packed particle aggregates was investigated, as seen in the scanning electron microscopy images. The polyaniline suspension stabilized by 0.75% PVME content exhibited the best dispersing state and, therefore, showed the highest zero-field viscosity. Such a well-stabilized polyaniline suspension also showed the maximum ER property, namely the largest normalized yield stress in an electric field. Copyright 2001 Academic Press.     

离子交联聚氯乙烯的结构与性能

由氯乙烯/丙烯酸悬浮共聚合成了不同羧基含量的PVC树脂,采用溶液反应和熔融加工法制备离子交联PVC,对其结构和性能进行了研究.结果表明,共聚物中羧基主要以二聚体形式存在,用金属离子中和能形成部分络合结构;用Ca²⁺、Mg²⁺离子络合的羧基含量较高的VC/AA共聚物存在离子对聚集态结构;离子对含量、金属离子种类和增塑剂浓度影响离子聚集相的比例和稳定性,离子聚集具有热可逆性;离子交联使PVC的T_g、熔体粘度和回弹性提高.     

聚乙烯醇-碘复合物在水溶液中的形成

聚乙烯醇(PVA)在碘-碘化钾混合水溶液中能形成蓝色复合物,该复合材料在人们日常生活中已广泛应用.本文综述了在稀溶液条件下聚乙烯醇-碘复合物的形成,并对其复合物形成的可能影响因素,如:PVA的分子量、链结构的规整度、1,2-羟基结构、支链以及浓度、添加其它物质和反应时间等,进行了系统论述.从聚集模型观点看,在复合物中,碘主要是以线性多聚碘负离子形式存在的,如:T3-和I5-等;而PVA链通过分子间氢键作用形成链间聚集将多聚碘负离子包裹在内而形成复合物.     

聚甲基丙烯酸甲酯与聚醋酸乙烯酯共混的红外光谱研究

用红外光谱(FTIR)研究了聚甲基丙烯酸甲酯(PMMA)与聚醋酸乙烯酯(PVAc)共混体系相容性,在160℃以上共混体系发生相分离;分相体系与非分相体系的FTIR谱明显不同;共混体系的FTIR谱不能从两统组分红外光谱简单加和得到;结果表明大分子构象发生了变化,PMMA/PVAc体系相容可能是大分子构象熵变所致。     

Photooxidation of blends of polystyrene and poly (vinyl methyl ether)

Photooxidation of blends of polystyrene and poly (vinyl methyl ether) was studied at 30°C. The oxygen uptake by PS was negligible but PVME oxidized readily. The induction period of oxidation of PVME was prolonged by the presence of PS. The steady state rate of oxidation of the blend was strongly influenced by the segmental mobility of the blend which also governed the kinetics and morphology of phase separation. The molecular weight of PVME decreased more slowly in the blend as PS content increased. It was believed that the reaction between PVME radicals and PS resulted in less reactive PS radicals which retarded oxidation. The PS radicals eventually underwent chain scission reactions.     

Phase transformation in mixtures of polystyrene and poly(vinyl methyl ether)

Homogeneous films comprised of mixtures of polystyrene and poly(vinyl methyl ether) can be obtained by evaporation from a ternary solution containing toluene as the solvent. Heterogeneous films result when the solvent is trichloroethylene. The possibility that a heterogeneous film cast from trichloroethylene can be transformed to a homogeneous one by physical means is a logical expectation when the polymer-polymer interaction is favorable, though as yet no comprehensive report has appeared in the literature. We have accomplished the transformation by increasing the temperature. Optical microscopy and glass transition experiments were employed to observe the effects.     

Blends of poly(vinyl methyl ether) with styrenic copolymers

Blends of poly(vinyl methyl ether) (PVME) with styrene/acrylonitrile (SAN), with styrene/maleic anhydride (SMA), and with styrene/acrylic acid (SAA) copolymers were examined for glass transition and lower critical solution temperature behavior. These copolymers were found to be completely miscible with PVME at levels of 3% or less of AA; below 10–11% AN, and below 15% MA (w%). Small amounts of the comonomers raised the temperature at which blends with PVME undergo phase separation on heating. This effect was greatest in the order AA > AN > MA. An interpretation of these results is given in terms of recent theories for homopolymer-copolymer blends, and the extent to which solubility parameter theory can be useful is considered.     

Synthesis and characterization of amphiphilic diblock copolymers of methyl tri(ethylene glycol) vinyl ether and isobutyl vinyl ether

Water-soluble diblock copolymers of methyl tri(ethylene glycol) vinyl ether (hydrophilic block) and isobutyl vinyl ether (hydrophobic block) of different molecular weights and composition were synthesized by living cationic polymerization. The molecular weight and comonomer composition of these copolymers were determined by GPC and ¹H NMR spectroscopy, respectively. Aqueous solutions of the copolymers were characterized in terms of their micellar behavior using dynamic light scattering, aqueous GPC, and dye solubilization. All the copolymers formed aggregates with the exception of a diblock copolymer with only two hydrophobic monomer units. The micellar hydrodynamic size scaled with the 0.61 power of the number of hydrophobic units, in good agreement with a theoretical exponent of 0.73. An increase in the length of the hydrophobic block at constant hydrophilic block length or an increase in the overall polymer size at constant block length ratio both resulted in lower critical micelle concentrations (cmcs). The cloud points of 1% w/w aqueous solutions of the polymers were determined by turbidimetry. An increase in the length of the hydrophobic block at constant hydrophilic block length caused a decrease in the cloud points of the copolymers. However, an increase in the overall polymer size at constant block length ratio led to an increase in the cloud point. © 1996 John Wiley & Sons, Inc.     

Rheology and phase separation in polystyrene/poly(vinyl methyl ether) blends

Blends of monodisperse polystyrene and poly(vinyl-methyl-ether) of various compositions were prepared from solution in benzene. Dynamic rheological properties of these blends were studied at different temperatures below, near, and above T_s, the temperature of phase separation, and in a frequency range from 0.05 to 100 rad/s. A flattening in the storage modulus and an initial plateau for the complex viscosity were observed near and above T_s in the low-frequency region; in contrast, below T_s the behavior of the blends was similar to that of the homopolymers. The WLF superposition principle applies only at temperatures below T_s, i.e., in the miscible and homogeneous region. G″ versus G′ representations for the blends were found to be independent of temperature and to vary with composition in the miscible region but are temperature and composition-dependent in the immiscible region. It is also shown that the η″ versus η′ representation is a useful tool for characterizing phase separation of blends and is more sensitive than the classical frequency dependence of the material functions.     

Properties of Poly(methyl Methacrylate) Containing Metal Sulfoxide Complexes

The uniformity, light fastness, heat resistance, radiation hardness, and antistatic properties of poly(methylmethacrylate) prepared in the presence of metal sulfoxide complexes were studied.     

Radiation crosslinking and scission of poly(vinyl methyl ether) in aqueous solution

For a wide range of poly(vinyl methyl ether) (PMVE) concentrations (1–16 g dm⁻³), in anoxic conditions, polymer-derived radicals recombine in two major pathways: (i) crosslinking and (ii) disproportionation. Both these processes proceed inter- and intramolecularly. The radiation-chemical yields and kinetics of crosslinking have been studied by pulse radiolysis with light scattering intensity detection (LSI). In the absence of oxygen, G-values of intermolecular crosslinking were determined on the basis of LSI changes versus applied dose and compared with the results obtained previously for γ-irradiated samples. It has been found that the first half-life time of intermolecular crosslinking decreases with increasing dose per pulse. Addition of small amounts of macroradical scavenger (cysteamine hydrochloride) decreases, drastically, the increase of LSI signal. On increasing the PVME concentration, intermolecular crosslinking becomes more efficient.

In the presence of oxygen, for diluted PVME solution (0.1 g dm⁻³), decrease of LSI signal consisting of the kinetic of a first-order reaction was observed. The rate constant of LSI decrease was found to be 1.1×10³ s⁻¹ and it was attributed to the main-chain scission.     

Synthesis of perfluoro(methyl vinyl ether) polymer at high pressures

Polymer of perfluoro(methyl vinyl ether) was synthesized for the first time. Polymerization was carried out at pressures from 300 to 1500 MPa and temperatures from 80 to 200 °C. The polymer synthesized is elastic, transparent, and soluble in perfluorobenzene, perfluorodecalin, and other perfluorinated solvents. The intrinsic viscosity of the polymer reaches 2 dL g^s-1. The study of the thermal stability on a derivatograph showed that the weight loss of the polymer sample occurred at 372 °C, being 0.1%.