Jerzy Szafko

Light scattering characterization of organotin polymers: 1. Tributyltin acrylate copolymer Cutinox-1000

Abstract Laser light scattering including both elastic (integral) and quasielastic measurements, supplemented by intrinsic viscosity data, has been used to characterize a tributyltin acrylate copolymer commercially known as Cutinox-1000 in dilute solution. Four solvents differing in their thermodynamical quality and optical properties were used. Chemical composition heterogeneity of the investigated sample was estimated to be sufficiently small not to influence significantly results of light scattering measurements. Coupled integral and quasielastic light scattering methods were used to determine the molecular weight distribution function, from which the polydispersity of the investigated copolymer sample was estimated to be M¯w/M¯n= 2.1. Determined molecular properties were in reasonable agreement with some theoretical predictions. Conformational parameters, such as the steric factor σ, statistical segment length and R¯H/R¯G ratio, as compared with poly(methyl methacrylate) values suggest some small increase of the copolymer rigidity, probably due to steric hindrance caused by the large metalloorganic side groups.

Characterization by light scattering of simultaneous polymer chain scission and cross-linking processes

Abstract The results of investigations on the changes in molecular parameters, viz. the average molecular weights, M n , M w and M z ; the poly-dispersities M w / M n and M z / M w ; and the translational diffusion coefficient, D 0z , are presented for a polymer sample undergoing simultaneous chain scission and cross-linking. The calculations were carried out within the framework of the model of Saito and Inokuti. The values of D 0z were calculated by the use of the cascade substitution technique. The results of calculations were compared with the experimental results obtained by the light scattering method for polystyrene samples exposed to u.v. radiation with wavelength ⩾ 270 nm in degassed solutions containing CCl4 and CHCl3. Analysis of the results leads to conclusions about the usefulness of the measurement of individual molecular parameters for the detection and characterization of simultaneous chain scission and cross-linking.

Solvation effect in thermal decomposition of 2,2'-azoisobutyronitrile on the N,N-dimethylformamide/acrylonitrile system

The thermal decomposition rate constant of AIBN (kd) in N, N-dimethylformamide (DMF)/acrylonitrile (AN) mixtures of various compositions at 60°C is studied. The kd value is (6.45 ± 0.3) × 10−4 min−1 for pure DMF and (7.20 ± 0.3) × 10−4 min−1 for pure acrylonitrile. The kd values of DMF/AN mixtures were found to be dependent on the mixture composition. This dependence is not a linear function of the monomer mole fraction (xM), but has a minimum at ca. 70 mol % of AN. The relationship kd = f(xM) has been interpreted on the basis of the hypothesis of initiator solvation by monomer AN and solvent DMF.

Solvation effect in the thermal decomposition of 2,2′‐azoisobutyronitrile in the three‐component system

The thermal decomposition rate constant (kd ) of 2,2′-azoisobutyronitrile in acrylonitrile (AN; monomer A)–methyl methacrylate (MM; monomer B) comonomer mixtures in N,N-dimethylformamide (DMF) as a function of the comonomer mixture composition and its concentration in the solvent at 60 °C was studied. The dependences kd = f(xA ,C) [xA (mole fraction of A in the comonomer mixture) = A/(A + B) = A/C, where C is the comonomer mixture concentration] have a different course as a function of C: from a curve kd = f(xA ) approaching the straight line (C = 2 mol · dm−3) to a convex curve possessing a maximum at a point xA = 0.7 (C = 4 mol · dm−3) to a curve with a flattened wide maximum within the range of xA = 0.2–0.8 (C = 7 mol · dm−3) to a curve with the shape of a lying s (C = 9 mol · dm−3). All the courses of the experimental dependences kd = f(xA ,C) can be explained with a hypothesis of initiator solvation by the comonomers AN and MM and the solvent DMF. The existing solvated forms, their relative stability constants, the thermal decomposition rate constants, and the relative contents in the system were determined.