Yu.N. Panov

The degradation of poly (acid) amide based on pyromellitic dianhydride and bis-4-aminophenyl hydroquinone☆

Abstract The results of viscometric studies of the stability of solutions of poly(acid)amide (PAA) based on pyromellitic dianhydride and bis-4-aminophenyl hydroquinone have shown the dry polymer to have the greatest stability, while dilute solutions in dimethylformamide or dimethyl sulphoxide were the least stable. PAA decomposes as a result of first the hydrolytic cleavage of the amide bond, and secondly due to spontaneous imidization.

The antithixotropy of dilute solutions of copolymers of methyl methacrylate and methacrylic acid

Abstract Dilute solutions of methyl methacrylate-methacrylic acid copolymers (with low content of methacrylic acid) in ethylene dichloride exhibit the effect of antithixotropy which manifests itself in the time dependence on the shear stress (in rotatory viscometers) and in the upturn on the shear stress dependence of viscosity (in capillary viscometers). The upturn vanishes at infinite dilution. Conditions for the appearance of the effect (polymer concentration, temperature, addition of dimethylformamide) were investigated. The explanation of the effect is based on the assumption of strong intermolecular interaction brought about by hydrogen bonds.

The effect of the hydrogen bond networks on the sorption characteristics of methyl methacrylate-methacrylic acid copolymers

Abstract The sorption of dichloroethane vapours by random methyl methacrylate-methacrylic acid copolymers as untempered films was investigated. The partial specific thermodynamic potential of dichloroethane, the Flory-Huggins reaction parameter and the average efficiency of dichloroethane association were calculated from the sorption isotherm.

The molecular weight dependence for the chain conformation of diphilic copolymers

Abstract Viscosity measurements have been made for copolymers of methyl methacrylate (MMA) and methacrylic acid (MAA) in mixtures of the selective solvents ethylene dichloride (EDC) and N,N′-dimethyl formamide (DMF). The dependence of [η] on DP v and copolymer composition ( a ) has been established. The data for samples quite different in DP v and a can be represented by a single master curve using reduced co-ordinates [η] PMMA − [η]CP −c/a DP v a where c is the volume % DMF in the solvent. This means that the relative coil contraction due to intramolecular hydrogen bonds is proportional to the absolute MAA content in the copolymer chains. The location of the master curve depends only on the method of preparation for the copolymer (partial random hydrolysis of PMMA or direct radical copolymerization of monomers). This can be explained by the different types of distribution of the MAA units along copolymer chains. Analysis of the data suggests that, for the polymer series with fixed MAA content in selective solvents, it is impossible to obtain the Mark-Kuhn-Houwink type equations for [η] CP − M v . The proposed method for tracing a master curve allows formulation of equations for the [η] CP − M v relationships for MMA-MAA copolymers having a particular molar composition.

Complex-formation in aqueous solutions of mixtures of polyacrylic acid and polyvinylalcohol and its copolymers☆

Abstract The rheological behaviour of dilute solutions of a “polyelectrolytic” mixture of polyacrylic acid and PVA in water at a total polymer concentration of 0·5 wt.% has been studied. The relationship between relative viscosity and composition of the polymer mixture has been found, in a number of cases, to exhibit positive deviation from additivity with a maximum close to a composition of 20 wt.% of polyacrylic acid. In order for the effect to appear, the molecular mass of the polyacrylic acid sample should be above a critical value but the molecular mass of the PVA sample can be artitrary. The observed effects are explained by the supposition that non-stoichiometric polyelectrolytic complexes are formed. Application of model concepts, developed here for the supermolecular organization of the complexes, to the analysis of the experimental data has made it possible to conclude that the most probable organization is a randomly branched macromolecule with trifunctional branching nodes.

Features of the rheological behaviour of solutions of AB-type block copolymers of styrene and butadiene☆

Abstract Relations between viscosity and the rate of shear and elastic modulus G ′ and between the dynamic viscosity ν′ and frequency have been investigated for solutions of diblock copolymers of styrene and butadiene in decalin and tetralin at 25° in the concentration interval from 0·05 to 50 g/dl. The observed effects of pseudoplasticity and anomalous frequency dependences of G ′ are explained from the standpoint of formation of a macronetwork consisting of segregated domains of PS, the latter network being unstable with respect to the action of the velocity gradient field. In tetralin (a “good” solvent for both copolymer blocks) the effect is associated with thermodynamic incompatibility of the blocks. In decalin (φ-solvent for PS) at room temperature the effect is intensified on account of selective action of the solvent.

The vapour sorption kinetics for dimethylformamide by methyl methacrylate-methacrylic acid copolymers☆

Abstract The kinetics of vapour sorption for DMF by films of methyl methacrylate-methacrylic acid copolymers (up to 21 mole% of the second component) have been found to give a peak on the kinetic curves which becomes rapidly smaller as the acid content increases. One can explain this effect on the basis of porometry as due to the mechanism of sorption by pores (channels) in combination with the relaxation rearrangement of the supermolecular organization of the copolymers.

Kinetic investigation of dichloroethane sorption by copolymers of methyl methacrylate and methacrylic acid

Abstract A study has been made of the integral and differential kinetics of dichloroethane sorption by random copolymers of methyl methacrylate (MMA) and methacrylic acid (MAA) with variable MAA contents (0–21 mole %). Kinetic curves for the sorption were used as a basis for calculation of interdiffusion coefficients and unilateral coefficients of dichloroethane (DCE) diffusion for several consecutive concentration intervals, along with relaxation times for stresses caused by structural rearrangement occurring in the polymer under the action of the solvent. It was found that the coefficients of diffusion of DCE fall over the entire range of concentration, and that the average stress relaxation times grow longer as the MAA content of the copolymers is increased. The observed relationships are in agreement with the free volume theory of Fujita and are in keeping with the existence of a concrete H bond network in the system MMA-MAA copolymer-DCE.

Dependence of the process of the formation of interpolymeric complexes in aqueous solutions of blends of polyacrylic acid and copolymers of vinyl alcohol and vinyl acetate on the molecular parameters of the components and their total concentration

A quantitative investigation has been made into the influence of the molecular parameters of the components of the blend of PVAlc and polyacrylic acid (MM, degree of esterification and type of distribution of the vinyl acetate units in the PVAlc copolymers) and the total concentration of the polymer on the parameters of the interpolymeric complex formed in aqueous solution of this blend. As a measure of the efficacy of complexing the authors take the magnitude Δred 0 (ηrel − ηreladd)/ηreladd

Viscoelastic properties of a butadiene-styrene block copolymer. A mechanical model

The manifestations of microheterogeneous structure in the viscoelastic properties of a butadiene-styrene copolymer of AB type with lamellar superstructure were investigated. The temperature dependences of the shear elasticity components, G′ and loss G″, were measured at 0·5 Hz. A mechanical model for the calculation of G∗(T) is presented. An interpretation of the “maximum smearing” effect in the G″(T) dependence between the glass temperatures of polybutadiene and polystyrene is proposed.