No abstract

Date de reception: 28 janvier 1975) R~S U M E :On a 6tudiC par diffraction des rayons X aux petits angles de Bragg la solubilisation d'une serie de polystyrenes de masse molCculaire variable dans la phase lamellaire d'un copolymkre biskquence polystyrkne, polyisopr5ne.On a d'abord montre que la solubilisation correspond B un &at d'Cquilibre veritable du systeme et non pas B un Ctat mktastable dii B I'insertion accidentelle de I'homopolymbe dans I'Cdifice.On a corrobore ensuite les conclusions 6noncCes prCcCdemment : l'homopolymere se solubilise tant que sa masse molCculaire ne depasse pas une masse comparable A celle des sequences parentes; il se localise 2 l'interieur des microdomaines de segregation qui contiennent les sequences de m&me nature; il s'y distribue enfin de manikre assez uniforme.On a observe, enfin, un phenomenede fractionnement, lie sans doute B la polydispersitC non negligeable des Cchantillons. SUMMARY:This is a low-angle X-ray diffraction study of the solubilization of a series of polystyrenes with varying molecular weight in the lamellar structure of a two-block polystyrene/polyisoprene copolymer.It has first been shown that the solubilization corresponds to a true equilibrium state, and not to a metastable one due to the accidental insertion of the homopolymer into the system. Previous conclusions in the field have then been confirmed. Homopolymer is solubilized only when its molecular weight does not exceed a value comparable to that of the *) De I'lkole Polytechnique de Lodz (Pologne), en stage post-doctoral au C.R.M. au

Sparingly water soluble complexes of lead(II), cadmium(II), and zinc(II) with Nphosphonomethylglycine (glyphosate, NPMG) of the general formulae C 3 H 6 O 5 NPPb, C 3 H 6 O 5 NPCd Á 2H 2 O, and C 3 H 6 O 5 NPZn were synthesized. The complexes were also precipited from a dilute Roundup solution, and their solubility in water was determined. Thermal, diffractometric, and IR spectrophotometric analyses were carried out. It was found that the metal is bonded to glyphosate through the oxygen atoms of the carboxylic and phosphonate groups; metal-nitrogen binding is absent in the above compounds. Studying the complexing behaviour in solution by UV spectrophotometry pointed out that a complex of the composition Pb(II) : NPMG 1:1 with an absorption band at 232 nm is formed. Its stability constant as determined by Job's method is logK 5.9AE0.1. Using potentiometric techniques, the dissociation constant of N-phosphonomethylglycine and the stability constants of its complexes with cadmium (II) and zinc (II) were determined.

No abstract