Showing papers in "Polymer Science U.s.s.r. in 1965"

Potentiometric titration of polyacrylic acid, polymethacrylic acid and poly-l-glutamic acid

Abstract: Potentiometric titration is a sensitive method of investigating the structure of polyelectrolytes. Despite the fact that the course of the titration curves is determined both by the mutual positioning of the charge groups on the polymer chain, and also by the ionic environment, and also that the interpretation of the titration curves may not always be carried out simply, the general course of the curves makes it possible to draw certain conclusions about the structure of the macromolecules. In the present work, a comparative investigation of a number of poly-acids has been carried out by the method of potentiometric titration at various ionic strengths; the poly-acid were: polyacrylic (PAA), polymethacrylic (PMAA) and poly- L -glutamic (PGA). The molecules of PAA and PMAA, despite their similar in chemical structure, differ markedly in a number of physical properties (see, for example, [1–4]), which the authors explain by the presence of intramolecular hydrogen bonds in PMMA and their absence in PAA. PGA represents a typical synthetic polypeptide, which has a helical configuration in the weakly ionized condition.

Flow birefringence of semirigid molecular chains in solution

Abstract: (1) A new method of introducing peroxide groups into a macropolymer, which is based on oxidation of different types of polymers in the presence of a redox system and creates free radical of the type H202-0xidant H202-reducing agent, has been worked out. (2) The peroxide group introduction by the above method was used to synthesize various graft copolymers of cellulose; polyvinyl alcohol and polycaproamide. (3) It was established that the graft copolymerization is initiated by peroxide groups which form in the polymer when treated with a redox system of the type H202-0xidant, H202-reducing agent. Translated by K. A. ALL~N

The synthesis of aromatic polyamides in amide solvents

Abstract: AMIDE solvents (dimethylformamide, dimethylacetamide etc.) are now widely used for carrying out various chemical reactions [1-3]. In view of their basic properties [4, 51 and high solvent power there is particular interest in their use in irreversible polycondensation reactions involving acid chlorides, especially in the preparation of certain aromatic polyamides. We have previously discussed a number of general interrelationships in the synthesis of poly-m-phenyleneisophthalamide in solution in dimcthylacctamide [61. The present communication reports further studies of the rcaction between acid chlorides and amines in solution in dimethylformamide (DMF) and dimethylacetamide (DMA), both in the synthesis of polyamides and with some model systems.

Effect of low plasticizer concentrations on the structural ordering of polyvinylchloride

Abstract: IN A number of references [1-5] it has been shown that relatively small concentrations of a plasticizer (up to 20 wt. ~ ) not only do not soften polyvinylchloride (PVC) but render it more rigid and brittle. Various authors have attempted to explain this phenomenon in different ways. The increase in brittleness with small plasticizer additions has been connected with an increase in the degree of crystallinity of the polymer [1-2]. In support of this statement, data are put forward from X-ray diffraction analysis of the crystalline copolymer of vinylidene chloride and vinylchloride, which point to the degree of crystallinity passing through a maximum in the region of small plasticizer additions. Data in reference [6] deal with the appearance of a new reflection in electron diffraction pictures of PVC films during their swelling in dibutyl phthalate vapour with annealing at the same time. However, there are also other explanations of this phenomenon. The anomaly in the properties of plasticized PVC has been connected [3] with solvation of the polymer by plasticizer molecules: the stronger the solvation, the less coiled is the shape which the macromolecule has, and the material thus becomes more brittle since the unwinding of the macromolecule, as a result of solvation, decreases its mobility. The increase in the strength of PVC on the addition of small quantities of plasticizer has also been explained by the fact that the first portions of plasticizer are introduced between the polymer bundles, that is plasticization takes place between the bundles [13]. We had previously [5] shown by the method of plasticization that the passage of the strength and modulus of elasticity of PVC through a maximum (and of the elongation at rupture through a minimum) with addition of 10-15 wt.~o of plasticizer (dioctyl phthalate) is connected with an increase in the degree of ordering of the polymer structure. The appearance of an increase in the rigidity of PVC when it is plasticized has acquired special significance in connection with the fact that in recent times