Temperature-modulated differential scanning calorimetry of reversible and irreversible first-order transitions

Temperature-modulated differential scanning calorimetry of first-order transitions has led to many new observations. Some of these involve non-linear processes or deal with transformations of practically instantaneous response. The latter may cause serious lags within the calorimeter due to limited thermal conductivity of the sample and the instrument. In both cases the “reversing heat capacity” or a “complex heat capacity” is not a precise representation of the transition since both are computed from abbreviated Fourier transforms, limited to the evaluation of the first harmonic component. One has in these cases to work in the time-domain with the raw output. But even from these analyses in the time-domain many interesting new insights about the transition and the calorimeter performance can be generated.     

Temperature dependence of the electrical conductivity of orthophosphoric acid in porous glass

Temperature dependence of the proton conductivity of a 85 wt % solution of orthophosphoric acid in a set of porous glasses with predominant channel radii of 4.5, 9, 19, and 74 nm was studied. A method for saturating a wide-pore glass with a dehydrated acid is suggested. This method provides a conductivity on the order of 10⁻⁴–10⁻³ ohm⁻¹ cm⁻¹ in the temperature range 373–473 K.     

Electromagnetic form factor ofD * →D transition in the time-like region

The internal conversion processD ^* De ⁺ e ^–, andD ^* -pair production ine ⁺ e ^–-collisions,e ⁺ e ^– D ^* , which are described by the same electromagnetic form factor with time-like momentum transfer, have been analyzed. After carrying out a general analysis of the kinematical aspects of the one-photon mechanism has been performed and the predictions of the vector-dominance model for theD ^* D transition form factor are discussed. It is shown that use of the asymptotic behaviour of the form factors ofD ^*+,0 D ^+,0* and the theoretical values of constants ofD ^*+,0 D^+,0 radiative decay enables one to determine part of the unknown parameters of these form factors. The coefficient of the internal conversion forD ^* De ⁺ e ^– is calculated and is shown to be model independent.     

Temperature dependence of the diffusion coefficient of copper(II) chloride in porous-glass membranes

Diffusion transport of a 0.5 M aqueous solution of CuCl₂ was studied in a set of porous-glass membranes with predominant pore radii of 4.5 to 70 nm in the temperature range 25–70°C. Raising the temperature causes a rise in diffusion coefficients and their gradual equalization, which eliminates their dimension dependence on the radius of membrane channels.     

Synthesis of expanded graphdiyne substructures

Graphdiyne (1) is a member of a novel family of interesting and potentially important allotropes of carbon. Reported herein are the synthesis and spectroscopic characterization of model substructures 2-6. The macrocycles were prepared by the intramolecular cyclization of suitable alpha,omega-polyynes. Key to the success of this approach was the development of an in situ protiodesilylation/alkynylation reaction utilizing reactive phenylbutadiyne synthons. This new method has allowed for the preparation of the largest, most complete substructures of the graphdiyne network to date (3-6).     

Relationship between the ratio of ligand to metal and the coordinating ability of anions. Synthesis and structural properties of AgX-bearing bis(4-pyridyl)dimethylsilane (X- = NO2-, NO3-, CF3SO3-, and PF6-)

Studies of the anion effects on the molecular construction of a series of AgX complexes with bis(4-pyridyl)dimethylsilane (L) (X- = NO2-, NO3-, CF3SO3-, and PF6-) have been carried out. Formation of the skeletal bonds appears to be primarily associated with a suitable combination of bidentate N-donors of L and a variety of coordination geometries of Ag(I) ions. The L:Ag(I) ratios of the products are dependent on the nature of the polyatomic anions. The 1:1 adduct Ag(I)-L for NO2-, 3:4 adduct for NO3-, 2:3 adduct for CF3SO3-, and 1:2 adduct for PF6- have been obtained. A linear relationship between the ratio of ligand to metal and the coordinating ability of anions was observed. [Ag(NO2)(L)] has a unique sheet structure consisting of double helices, and [Ag3(L)4](NO3)3 is a 2 nm thick interwoven sheet structure consisting of nanotubes. The compound [Ag2(L)3](CF3SO3)2 affords a characteristic ladder-type channel structure, and [Ag(L)2](PF6) is a simple 2D grid structure.     

Low-frequency glow discharge treatment of amorphous poly(ethylene terephthalate) films

The influence of treatment in a low-frequency glow discharge on the surface properties of an amorphous poly(ethylene terephthalate) (PET) film was studied. It was shown that, at identical external discharge parameters, changes in the wettability of plasma-treated PET films depended on its morphological structure—the amorphous film had higher values of the contact angle and lower values of the surface charge density than a biaxially oriented poly(ethylene terephthalate) of the PET-E brand.     

Discrete solitons in the bigraphene with adsorbed atomic hydrogen

The propagation of discrete solitons in the bigraphene waveguides was calculated according to the Anderson model. An effective equation analogous to the classical sine-Gordon formula was obtained. The dependence of energy distribution between the waveguides of the graphene bilayers with adsorbed atomic hydrogen on the initial pulse width was studied.     

Adsorption and luminescence properties of Tb3+-modified perfluorosulfonic acid membrane

After treatment of perfluorosulfonic acid membrane MF-4SK with an aqueous solution of TbCl₃, the protons in sulfo groups are completely replaced by the hydrated terbium cations. Specific features of the water adsorption and its influence on the luminescence of the modified membrane were examined.     

Polyimide-polysiloxane-segmented copolymers as high-temperature polymer electrolytes

Based on the fact that the flexibility of the polymer backbone will affect the ion transport and sometimes enhance the ionic conductivity, copolymer electrolytes of 1,2,4,5-benzene-tetracarboxylic dianhydride (PMDA), 4-aminophenyl ether (ODA), and aminopropyldimethyl-terminated polydimethylsiloxane (PSX), with or without doping of lithium triflate, have been prepared and investigated by infrared spectroscopy and electrical conductivity measurements. The PSX was found to be incorporated into PMDA-ODA polyimide to form block copolymers, and the best conductivity (10^-7 s/cm at 300°C) is observed in the lithium triflate-doped PMDA-ODA-PSX copolymer with a composition of 4PMDA: 3DA: 0.6PSX: 2LiCF₃SO₃. This conductivity is about 100 times better than the result of the lithium-doped PMDA, ODA, and 2,5-diaminobenzene sulfonic acid (DABSA) copolymer (4PMDA: 3DA:1DABSA:1LiCF₃SO₃) recently reported by this group. © 1994 John Wiley & Sons, Inc.