Vladimír Petrus

Estimation of the characteristic ratio of poly[2-(triphenylmethoxy)ethyl methacrylate] from hydrodynamic properties of its dilute solutions

Abstract Properties of poly[2-(triphenylmethoxy)ethyl methacrylate] (PTEMA) molecules in solutions (under O-conditions and in “good” solvents) were investigated by the light scattering, sedimentation, viscometric and by phase equilibria methods. The O-temperature (47°) was determined for the system mesitylene-PTEMA. Unusual correlations of hydrodynamic data with molecular weight are discussed and slight branching of polymer chains is accepted as a probable explanation. Data for mesitylene solutions under O-conditions are used to estimate the characteristic ratio of PTEMA molecules ( R 0 2 /nl 2 = 19 ).

IONOMERS IN LOW-POLARITY SOLVENTS

Abstract A sedimentation and viscometric study was carried out with a neutralized copolymer of methacrylic acid and methyl methacrylate in tetrahydrofuran as a model ionomer in a low-polarity solvent. Viscosity measurements gave the usual result for ionomers in a low-polarity solvent. At a low concentration the reduced viscosity of the neutralized sample is lower than that of a non-neutralized one, while at a higher concentration this is the other way round. On the contrary, within the whole concentration range under study, the sedimentation coefficients of the neutralized copolymer are higher than those of the non-neutralized sample, and the plot of the reciprocal value of the sedimentation coefficient against concentration is linear in both cases as usual. The sedimentation and viscosity measurements can be made to comply, if one assumes that intermolecular association in non-polar solvents takes place already at low concentrations. Non-radiative energy transfer between donor and acceptor attached to the same ionomer molecule suggests that at a low concentration the individual ionomer molecules are contracted compared with the non-neutralized copolymer, and that, with increasing intermolecular association due to increasing concentration of the ionomer, the dimensions of the particular ionomer molecule also increase.

Solution properties of poly(methacrylamide)

Abstract Poly(methacrylamide) samples obtained by radical polymerization were fractionated by isothermal precipitation (formamide-methanol). Molecular weights were determined by light scattering and the Archibald approach-to-equilibrium method (in 0.4 M aqueous magnesium perchlorate), and the [η] M correlation was constructed. The characteristic ratio ( C 1 = 6.1). Its temperature coefficient (dln C 1 d T ≅ 0) and the interaction parameters of the polymer in aqueous solutions of urea (2–8 M) and magnesium perchlorate (0.4–1.2 M) at 10–50°C were determined using analysis of the viscometric data ([η], dln [ η ]/d T ). The data thus obtained are used to discuss the behaviour of the polymer in water.

Hydrodynamic properties of linear poly(dimethyl siloxanes) in bromocyclohexane at the theta temperature

Hydrodynamic quantities (sedimentation coefficients s°0,θ, and intrinsic viscosities [η]θ in bromocyclohexane at 310K) and weight-average molecular weights (by light scattering) have been measured for poly(dimethyl siloxane) fractions (45 ⩽ Mw × 10−3 ⩽ 300). The ratio [η]θs°0,θ was found to be invariant with respect to M, and the value of (〈R2〉0M)∞ (where 〈R2〉0 is the mean-square end-to-end distance) computed from [η]θs°0,θ was in good agreement with that found by other methods. It is concluded that the translational friction behaviour is similar to that of other flexible chain polymers and that anomalies indicated by some authors are due to inaccuracies in experimental data.

Effect of temperature on the solution properties in 2-ethoxyethanol of statistical copolymers of methacrylic acid and methyl methacrylate

SummaryThe temperature dependence of the second virial coefficient and intrinsic viscosity of statistical copolymers of methyl methacrylate and methacrylic acid in 2-ethoxyethanol was investigated. It was found that the θ-temperatures of copolymers are outside the temperature range given by the θ-values for poly(methacrylic acid) and poly(methyl methacrylate). Their dependence on the copolymer composition has a discontinuity. Simple theoretical considerations have shown that this behaviour may be expected with copolymers composed of monomer units dissolving, respectively, with absorption and evolution of heat.

A specific effect of alkali-metal iodides and thiocyanates on the viscosity of solutions of poly(methacrylic acid) in methanol

Abstract The solution properties of poly(methacrylic acid) (PMA) in methanol are specifically affected by thiocyanates and iodides of alkali metals. The relative decrease in the reduced specific viscosity of PMA in dilute methanolic solutions due to KSCN depends only on the ratio of concentrations of polymer and salt, and is independent of temperature and polymer molecular weight. With copolymers of methacrylic acid and 2-hydroxyethyl methacrylate, the effect is weaker.

The effect of branching on the Huggins coefficient of statistical styrene/butadiene copolymers†

The Huggins coefficient kH of solutions of statistical styrene/butadiene copolymers in cyclohexane (at 25 °C) and 2-pentanone (theta temperature 21 °C) is discussed. With an increase in branching the values of (i. e. kH at the theta temperature) increase from 0,5 to 0,73. Lower values in cyclohexane (good solvent) correlate with the viscosity expansion factor αη3, and the dependence is well fitted by the equation where is a function of the degree of branching, whereas C″0 only slightly exceeds the value found for linear polymers.