Inorganic-Organic Hybrid Polymers from the Polymerisation of Methacrylate-Substituted Oxotantalum Clusters with Methylmethacrylate: A Thermomechanical and Spectroscopic Study

New inorganic-organic hybrid materials were prepared by free-radical polymerization of methyl methacrylate (MMA) with methacrylate-substituted oxotantalum cluster [Ta₄O₄(OEt)₈(OMc)₄] and their properties evaluated. The cluster was prepared by the reaction of the parent alkoxide with methacrylic acid. Samples of the hybrid materials were produced with Ta-cluster to methyl methacrylate in the ratios of 1:50 and 1:100 and were characterized by thermal and spectroscopic techniques. The glass transition temperatures of the hybrid materials are shifted to higher temperatures than pure PMMA as a result of cross-linking of the polymer by the oxotantalum clusters. The increase in T_g is also observed from the dynamic mechanical analysis (DMA). Evidence of crosslinking between the Ta-cluster and PMMA is obtained from infrared spectroscopic study. Surface studies performed by X-ray photoelectron spectroscopy (XPS) provide information about the atomic concentrations of the surface and indicate tantalum bonded to oxygen.     

Metallation studies of organofunctional trisiloxanes

Summary The organofunctional trisiloxanes Me₃SiOSiMe(R)OSiMe₃ [R=(CH₂)₂PPh₂, (CH₂)₃C₅H₄N, (CH₂)₃CN, (CH₂)₂Ph, (CH₂)₂SPh, CH=CH₂ and CH₂CH=CH₂] have been reacted with metal halide and-carbonyl moieties in order to determine the coordination preferences of materials being used as models for metallated longchain linear functionalised polysiloxanes. The products [Me₃SiOSiMe(R)OSiMe₃]₃ML_n [R=(CH₂)₂PPh₂, ML_n=RhCl],cis-[Me₃SiOSiMe(R)OSiMe₃]₂ML_n [R=(CH₂)₂PPh₂ or (CH₂)₃C₅H₄N, ML_n=Mo(CO)₄],trans-[Me₃SiOSiMe(R)OSiMe₃]₂ML_n[R=(CH₂)₂PPh₂, ML_n=NiCl₂, PdCl₂, PtCl₂ and [Rh(CO)Cl] and [Me₃SiOSiMe(R)OSiMe₃]ML_n [R=(CH₂)₂PPh₂, ML_n=Mo(CO)₃(2,2-bipyridine); R=(CH₂)₂Ph, ML_n=Mo(CO)₃; R=(CH₂)₃C₅H₄N, (CH₂)₃CN, or (CH₂)₂SPh, ML_n=Rh(CO)₂Cl; R=CH=CH₂ or CH₂CH=CH₂, ML_n=Fe(CO)₄] have been isolated and characterised spectroscopically in the course of these studies.     

N-halogeno-compounds. Part 9 [1]. Azoxy- and azo-arenes derived from 4-(dichloroamino)tetrafluoropyridine; crystal structure of trans-2,3,5,6-tetrafluoro-4-(2,4,6-trimethylphenyl-onn-azoxy)pyridine

The nitrosoarenes ArNO (Ar = C₆H₅, 2-MeC₆H₄, 2,4,6- Me₃C₆H₂ and C₆F₅) have been condensed with 4-(dichloroamino)- tetrafluoropyridine to provide the azoxy-compounds py_FN$\text{N}\text{+}$($\text{N}\text{-}$)Ar (py_F = 2,3,5,6-tetrafluoro-4-pyridyl); de-oxygenation of the first three with triphenylphosphine or triethyl phosphite gave the corresponding azo-compounds, and the reverse reaction was achieved in the case of py_FNNC₆H₂Me₃-2,4,6 using peroxytrifluoroacetic acid. Thermolysis of 4-azidotetrafluoropyridine in the presence of pentafluoronitrosobenzene provided the perfluorinated azoxy-compound py_FN$\text{N}\text{+}$($\text{O}\text{-}$)C₆F₅. X-Ray methods have been used to determine the molecular geometry of py_FN$\text{N}\text{+}$($\text{O}\text{-}$)C₆H₂Me₃-2,4,6.     

Novel perturbation expansion for the Langevin equation

We discuss the randomly driven systemdx/dt= -W(x) +f(t), wheref(t) is a Gaussian random function or stirring force withf(t)f(t)=2(t–t), andW(x) is of the formgx ¹⁺². The parameter is a measure of the nonlinearity of the equation. We show how to obtain the correlation functionsx(t)f(t)···x(t( n)) _f as a power series in. We obtain three terms in the expansion and show how to use Padé approximants to analytically continue the answer in the variable. By using scaling relations, we show how to get a uniform approximation to the equal-time correlation functions valid for allg and.     

Evaluating the Frechet derivative of the matrix exponential

LetM _n denote the space ofn×n matrices. GivenX, ZM _n define

Energy dependence of the fast fragment of the target nucleus in high energy hadron-nucleus interaction

This paper presents an extensive study on the dependence of the mean number of the fast fragment of the target nucleus n _g on the incident beam energy in proton-nucleus interaction in emulsion in the range 6·2E ₀400 GeV/c. It has been observed that n _g decreases in the range 6·2E ₀200 GeV/c, then increases and attains an approximately steady value up to 400 GeV/c. It is very difficult to explain this behaviour with the help of the existing nuclear production models.The author would like to thank Prof A. J. Herz (CERN), Prof. K. D. Tolostov (Dubna, U.S.S.R.), Prof. P. L. Jain (State University of New York, U.S.A.), Prof. G. Giacomelly (Italy) for kindly supplying the exposed emulsion plates.     

A sensitive,specific method for the determination of tetraalkyllead compounds in air by gas chromatography/atomic absorption spectrometry

The development of a sensitive and specific method of determining individually the five tetraalkyllead compounds normally present in ambient air is described. The method is based on collection of the analytes on a porous polymer using a prefilter to destroy ozone and prevent decomposition of the sample during collection and storage. Two-stage thermal desorption, separation by gas chromatography and detection by modified flame atomic absorption spectrometry gives detection limits (3σ) of ca. 0.25 ng Pb m^?3 for tetramethyllead and 0.37 ng Pb m^?3 for tetraethyllead in an air sample of 80 dm³ collected over a 3–24 h period. Environmental sampling by this method in paralle with a wet chemical (iodine monochloride) method was used to validate the method. During the comparative study, higher organic lead levels were consistently found by the iodine monochloride method; it is postulated that this indicates the presence of vapour-phase tri-(or di)-alkyllead in excess of 1 ng Pb m^?3 in rural air. The versatility of the method is demonstrated by the results of atmospheric sampling at two locations, one rural and one at the kerbside in a city centre.