Investigation of the Dissociation and Dimerization of Cyclamic Acid in Aqueous Solutions by Means of a Conductometric Method

The electrical conductivity of aqueous cyclamic acid was studied in the concentration range (0.0004<c/mol⋅dm⁻³<0.14) at temperatures ranging from 278.15 to 303.15 K. Conductivities were measured by a precise method and examined by applying extended conductivity equations taking into account dimerization and incomplete electrolyte dissociation. Limiting molar electrolyte and ionic conductivities, dissociation and dimerization constants, and thermodynamic functions associated with dissociation and dimerization of cyclamic acid are discussed.     

Effect of random and block copolymer additives on a homopolymer blend studied by small-angle neutron scattering

Small-angle neutron scattering (SANS) has been employed to study a blend of polystyrene and polybutadiene modified by copolymer additives. SANS data from the one-phase region approaching the phase boundary has been acquired for blends modified by random and diblock copolymers that have equal amounts of styrene and butadiene monomers as well as a random copolymer with an unequal monomer composition. The binary blend is near the critical composition, and the copolymer concentrations are low at 2.5% (w/w). The data have been fitted with the random-phase approximation model (binary and multicomponent versions) to obtain Flory–Huggins interaction parameters (χ) for the various monomer interactions. These results are considered in the context of previous light scattering data for the same blend systems. The SANS cloud points are in good agreement with previous results from light scattering. The shifts in the phase boundary are due to the effects of the additives on the χ parameter at the spinodal. All the additives appear to lower the χ parameter between the homopolymers; this is in conflict with the predicted Flory–Huggins behavior. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3191–3203, 2004     

Ethylene‐based copolymers with tunable content of polymerizable hindered phenols as nonreleasing macromolecular additives

Four comonomers bearing a highly efficient phenolic antioxidant unit and different methylene spacers between the aromatic ring and the double bond have been prepared and tested in copolymerization with ethylene using metallocene‐based catalysts. The possibility of obtaining a “masterbatch” suitable for melt blending with commercial polyolefins has been evaluated by modifying: (i) the structure of the functionalized comonomer, (ii) the kind of catalyst, and (iii) the polymerization conditions. Characterization of monomers and copolymers was accomplished by using ¹H and ¹³C NMR, size exclusion chromatography (SEC), differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). Using the comonomer with the longest methylene spacer between the aromatic ring and the double bond, and rac‐(EBTHI)ZrCl₂ as catalyst, adjustable amounts of the antioxidant moiety can be incorporated into the polyethylene chains. TGA analysis carried out on some of the copolymers containing the antioxidant group showed no oxygen uptake before decomposition. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6393–6406, 2008     

New Physico-Chemical Properties of Extremely Dilute Solutions. A Conductivity Study at 25 °C in Relation to Ageing

The conductivity of extremely dilute solutions (EDS) was measured and studied in relation to the age of the solutions. The aim was to obtain information about the influence of succussive dilutions and succussions on the conductivity and structure of water. EDS are obtained by iteration of two processes: dilution 1:100 (mass basis) and succussion. The iteration is carried out until extreme dilutions are reached. We found significant increases in electrical conductivity with respect to the untreated demineralized water used as solvent, confirming the intriguing new behavior disclosed some time ago, namely the evolution of certain physico-chemical parameters with the age of the samples. We studied variations in electrical conductivity of samples up to two years old. Conductivities showed large variations reaching a pronounced maximum and, for several samples, then returning to their initial values. The latter fact suggests that the temporal evolution of this physico-chemical parameter does not stem from the slow attainment of an equilibrium condition, characterized by a minimum of energy, since that state, when reached, should be steady. These systems could be far from thermodynamic equilibrium, producing dissipative structures. In order to stay far from equilibrium, they need to dissipate energy. For reasons that are not yet clear, when modified environmental conditions prevent the necessary dissipation of energy, these systems return to their initial conditions. In the light of this interpretation, the succussion procedure may be the trigger for the formation of dissipative structures, the number and/or size of which increase with age, up to a certain point.     

Electron beam curing with glycerol methacrylate

Glycerol methacrylate and hydroxyethyl methacrylate in combination with glycerol dimethacrylate as crosslinker were applied with electron beam irradiation to consolidate the color painting of the terracotta army of the first Chinese Emperor Qin Shihuangdi. The described mixture allowed reducing the necessary irradiation dose for consolidation to 40 kGy. The formation of glossy spots could be suppressed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6660–6663, 2008     

Preparation and thermomechanical properties of epoxy resins modified by octafunctional cubic silsesquioxane epoxides

The thermomechanical properties of octafunctional cubic silsesquioxane‐modified epoxy resins associated with dicycloaliphatic hardener (4,4′‐dimethyldiaminodicyclo hexyl methane) were studied using thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. The structures of epoxy resin containing cubic silsesquioxane epoxides were characterized by Fourier transform infrared spectroscopy and wide‐angle X‐ray scattering techniques. In this work, octa(dimethylsiloxybutylepoxide) octasilsesquioxane (OB), and octa(glycidyldimethyl‐siloxyepoxide) octasilsesquioxane (OG), were synthesized and used as additives to improve the properties of a commercial epoxy resin by exploring the effects of varying the ratio of OB or OG. The commercial Ciba epoxy resin (Araldite LY5210/HY2954) was used as a standard. It was found, by thermogravimetric analysis and dynamic mechanical analysis, that the highest thermal stability was observed at N = 0.5 (N = number of amine groups/number of epoxy rings). No glass transition temperature was observed by adding 20 mol % OB to the Ciba epoxy resin, indicating the reduction of chain motion in the presence of octafunctional cubic silsesquioxane epoxide. The storage modulus of the OB‐modified epoxy resin also increased, especially at higher temperatures, compared with the Ciba epoxy resin under identical curing conditions. Fourier transform infrared data elucidated the preservation of cubic silsesquioxane structure after curing at high temperature. In contrast, the OG/Araldite LY5210/HY2954 systems gave poorer thermomechanical properties. The low viscosity of OB at room temperature (～ 350 cPs) makes it suitable for composite processing and, when used in conjunction with the Ciba epoxy, lowers the viscosity of this system as well. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3490–3503, 2004     

甘氨酸钠碳酸盐的合成及表征

在泡腾饮料、面食品和膨化食品中,过去一直用ＮａＨＣＯ3作ＣＯ2源[1],但它溶解度低、易残留、稳定性不高,加热至一百多度粉末会放出气体,水溶液中则会分解。甘氨酸钠碳酸盐溶解度大、不存在残留问题;且稳定性高,粉状品加热至385℃以上才会放出气体,加热至100℃水溶液中不分解;发生中和反应时不产生水,具有抗菌性防腐作用[3]和缓冲性故较宜用于复配发泡制品[2]。本文用超声合成法制备了甘氨酸钠碳酸盐,对其进行了ＩＲ及ＸＲＤ表征。1　实验部分1 1　合成超声合成法:取甘氨酸(ＡＲ)7 5ｇ(0 1ｍｏｌ)和碳酸钠(ＡＲ)5 3ｇ(0 05ｍｏｌ),加入…     

Quantum Chemistry Studies on the Difference of Structures and Electronic Properties of Polyacene,Polypyridinopyridine and Paracyanogen

IntroductionThestudiesonconductivepo1ymershavebeenofmuchinterestsbothinex-perimentalworkandtheorysincetheresultsonconductivityofdopedpolyacety-lenewerereported.Itwasreportedthatthehighestconductivityofdopedpoly-acetylenereachedupto1O5s/cmandjustfellintherangeofmetalconduction[1].Somepeoplehaveputforwardone-dimension(1D)graphitematerialfamilytobeconsistedofcondensedaromaticrings.Therearetwbkindsofimportantmolecularskeletonsforms,oneisanextended.versionfrompolyacene.Thepolyacenecanbeobtaintedb…     

Development of a miniature STM holder for study of electronic conductance of metal nanowires in UHV-TEM

A new miniature scanning tunneling microscope (STM) holder was developed in order to simultaneously investigate electronic conductance and structure of nanowires in an ultra high-vacuum electron microscope (UHV-TEM). A thin gold wire held between the STM tip and substrate stage of the specimen holder was stretched to form a suspended gold nanowire. The new TEM-STM system allowed us to measure electronic conductance at intervals of 20 ms, and to record high-resolution TEM images on videotape at 30 fps. Suspended gold nanowires formed from [1 1 0] oriented electrodes were well-elongated. In contrast, [1 0 0] and [1 1 1] electrodes produced nanowires with short necks. Electronic conductance was found to change as nanowire structure changed, with conductance quantization in units of 2e²/h, where e is the electron charge and h is Planck’s constant, only being exhibited for well-elongated nanowires.     

季铵盐型离子导电聚合物的研究

对聚苯胺呋喃季铵盐的物理性质及导电机制进行了分析讨论。结果表明，所制备的季铵盐最高电导率可达１０＾－４Ｓ·ｃｍ＾－１量级，其导电性随季铵化程度增加而增加，温度、湿度对其导电性有较大的影响；在环境温度、湿度基本恒定的条件下，季铵盐有较好的电导稳定性。此季铵盐是通过离散的阴离子而传导，通过链段运动传输电荷。