Thermal analysis (TGA and DTA) of samples of PAA, PVP, PAA-PVP complexes, containing different weight fractions of PAA and ternary polymer-metal-polymer complexes, were studied. The activation energy parameters for the thermal degradation were also calculated. The study of the effect of FeCl 3 , NiCl 2 , and Ni(NO 3 ) 2 on the TGA and DTA curves of the complexes showed that the decompositions are dependent on the concentrations and the nature of the metal ions. The DTA traces of PAA-PVP complex containing FeCl 3 , NiCl 2 , and Ni(NO 3 ) 2 showed that the treatment of the complex with these metal ions causes considerable changes in the thermal decomposition of PAA-PVP complex.

The FTIR spectroscopic technique was used in the study of ternary polymer-metal complexes containing two polyelectrolytes of opposite charge and metal ions. The structure of the ternary (PAA-Fe 3þ -PVP) complexes was examined by following the changes in their infrared spectra. It was found that the shapes of the absorption bands of the resultant compounds are influenced by the presence of Fe 3þ . According to this result it was suggested that two types of structure which differ in the composition are formed, one of which results from the coordination of Fe 3þ with PAA-PVP complex and the other is due to the formation of Fe 3þ polycarboxylate. Comparison between the spectrum of PAA-PVP complex and those of the compounds resulted from the reaction between the two opposite charged electrolytes, PAA and PVP and each of the divalent metal chlorides NiCl 2 , CoCl 2 , CuCl 2 , and ZnCl 2 ) led to the conclusion that a reaction took place between the divalent transition metal chlorides and the extent of reaction depends on the nature of metal ions and PAA-PVP complex. The FTIR spectra of the precipitate resulted from the mixtures of PAA-PVP and Ni(NO 3 ) 2 or Sr(NO 3 ) 2 were investigated. It was noted that the addition of Ni(NO 3 ) 2 or Sr(NO 3 ) 2 to the mixture of the electrolytes of PAA and PVP provoked appreciable changes in the characteristic spectral features of the complex resulting from the interaction of the metal ions with the polymer-polymer complex. The FTIR spectra of the precipitate resulted from the reaction between CeCl 3 , ErCl 3 , and LaCl 3 were also investigated. It was concluded that a reaction took place between the rare earth metals and the PPC. This means that ternary polymer-metal-polymer complexes were formed. The extent of changes in the spectral features differs from metal to metal according to the nature of metal ions.

No abstract

Objectives. To analyse the chemistry and bioactivity of NeoMTA Plus in comparison with the conventional root repair materials. Method and Materials. Unhydrated and hydrated (initial and final sets) materials were analysed by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). For bioactivity study, small holes of dentin discs were filled with either materials, immersed in PBS for 15 days, and analysed with FTIR and scanning electron microscope with energy dispersive X-ray (SEM/EDX). The calculation of crystallinity and carbonate/phosphate (CO 3 /PO 4 ) ratio of surface precipitates (from FTIR) and calcium/phosphate (Ca/P) ratio (from EDX) was statistically analysed using t-test or ANOVA, respectively, at 0.05 significance. Results. Both materials are tricalcium silicate-based that finally react to be calcium silicate hydrate. NeoMTA Plus has relatively high aluminium and sulfur content, with tantalum oxide as an opacifier instead of zirconium oxide in MTA Angelus. NeoMTA Plus showed better apatite formation, higher crystallinity and Ca/P but lower CO 3 /PO 4 ratio than MTA Angelus. SEM showed globular structure with a small particle size in NeoMTA Plus while spherical structure with large particle size in MTA Angelus. Conclusion. Due to fast setting, higher crystallinity, and better bioactivity of NeoMTA Plus, it can be used as a pulp and root repair material.

No abstract

The IR and UV spectra of poly (methyl methacrylate) (PMMA) doped with metal dithizonate were investigated. Films of the doped samples were heated in air at various temperatures from 25 to 14OoC for 2 h. Other films were also exposed to UV irradiation. The doped samples were treated with iodine. The experimental results provided strong evidence that certain weak reaction occurs between the dopants and the polymer, and the rate of reaction depends on the concentration of the dopant and the nature of the metal ions. It was found that heat treatment of the doped films induces considerable changes in the intensities of their IR bands. The magnitude of these changes depends also on the concentration and the nature of the metal ion. Moreover, the results proved that exposure of the doped films to UV irradiation has no effect on their absorption spectra. Furthermore, the treatment of the doped samples with iodine causes considerable changes in their UV absorption spectra. I NTRO DUCT10 NT h e studies of photoconductivity of charge transfer complexes performed hitherto fall into two groups. On the one hand there have been studies concerned with the mechanism of fluorescence quenching and dissociation process in solutions.'s2 On the other hand, there have been investigations connected with the search for polymeric materials of relatively high photoelectric sensitivity and low dark current. These materials doped with acceptors forming charge transfer complexes are employed in the production of photosensitive films in electrophotography. The influence of the polymeric matrices on the mechanism of fluorescence quenching of the organic dyes has been investigated by a number of researchers.3-Poly (methyl methacrylate) is among the polymeric materials that have been used as matrices for the organic dyes. It has also been accepted that metal dithizonates form a n interesting class of photochromic complexes, in addition ultraviolet, visible, and infrared spectroscopic technique were used for * To whom correspondence should be addressed. the characterization of the structural properties of metal d i t h i z~n a t e s .~,~ These techniques have also been used for the investigation of the structure of T h e present study is undertaken to apply ultraviolet and infrared spectroscopic techniques for the characterization of PMMA doped with metal dithizonates. The effect of heat, exposure to ultraviolet radiation, and doping with iodine on the spectral feature of the doped polymer will be investigated. PMMA.9-12 EXPERIMENTALThe metal dithizonate complexes were prepared by the methods cited in the literat~re.~,' Solution of concentration m / L of dithizone and its metal complexes in chloroform were prepared for UV measurements using a Beckman 5260 ultraviolet spectrophotometer. The solution of PMMA in chloroform at 10% ( w / w ) was homogenized for 1 h a t 110°C. Solutions of dithizone ( 1 , 3 , 6 , and 9 m L ) a t its metal complexes were then thoroughly mixed with 25 mL of the polymer solution. For the infrared measurements thin films of...

No abstract

No abstract