Konrad Witkowski

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.

Light scattering on chlorella vulgaris cells

Laboratory measurements of light scattering on the axenic cultures of unicellular alga Chlorella vulgaris monoculture confirm the thesis of multi-level light scattering by the cell i.e., both by outer cell membrane and the internal structure of the cell, as well as by its molecular structures. In the measurements, the technique of dynamic light scattering and analysis by the regulation method was used, indicate that the light scattering phenomenon is affected by particles of sizes corresponding either to overall dimensions of the cell or to the dimensions of its internal structures. A correlation was found between the suggested sizes and the stage of physiological evolution of the culture. The measurements of 10 functions constituting the elements of the scattering matrix for an alive Chlorella vulgaris culture and cultures with internal cell structures modified by chemical and mechanical agents evidence that the internal structures of cells play an important role in the interaction of phytoplankton and light.

Influence of diffusion and induced π-bonds on the ultra-violet radiation-initiated crosslinking of polystyrene in solution

Abstract An attempt has been undertaken to account for the mechanism of polystyrene crosslinking initiated by ultra-violet radiation with wavelengths of λ ⩾ 270 nm in outgassed solutions with CCl 4 and CHCl 3 . The investigations were carried out by the joint method of elastic and quasielastic light scattering, and by the use of absorption spectroscopy in the ultra-violet and visible spectral regions. From the experimental results obtained and the model and theoretical modifications introduced, the crosslinking of polystyrene macromolecules irradiated in solutions with CCl 4 and CHCl 3 is shown to be affected by both the diffusion properties of the macromolecules and the conjugated and isolated double 〉 CC 〈 bonds formed in polymer chains.

Interactions in macromolecular solutions manifested by the mobility of solvent molecules in the low-frequency raman range

Abstract The results of investigations on the effect of macromolecular interactions in dilute solutions upon the mobility of solvent molecules, observed in the low frequency Raman range ( 8 cm −1 v 50 cm −1 ), are reported. Both polarized (VV) and depolarized (VH) components of the scattered light were measured in order to detect the joint effect of the correlated anisotropy fluctuations and intermolecular vibrations. Three frequency ranges were observed in the spectra, characterized by different relaxation times attributed to different types of the solvent molecules mobility. The effect of the structure of polymer side groups on the increase in the relaxation time, τ1, measured in the range 8 v cm −1 was observed. These interactions are considerably weaker in solutions of polyetherester with a rigid backbone than those occurring in solutions of flexible macromolecules with mesogenic side groups.

Interactions in solutions of liquid-crystalline polymers—2. experimental evidence for intermacromolecular aggregation

Abstract The results of investigations carried out by the methods of elastic and quasi-elastic light scattering are reported for three liquid-crystalline polymer samples in solution in tetrachloroethane. In polyester solutions with mesogenic groups in the backbone chain and in polyolefinosulphone solutions with polar side-groups, strong effects of macromolecular aggregation were observed. The effect of the polarity of mesogenic groups on the aggregation and internal arrangement in the aggregates is discussed.

Quasielastic light scattering on swollen silicon networks

SummaryWe have measured cooperative diffusion coefficients Dc of different polymer networks (PDMS PDMSM) at equilibrium swelling by using the quasielastic light scattering technique. The model networks have been prepared by tetrafunctional endlinking of linear chains having different molecular masses. Dc is a function of the molecular mass of the network chains and the swelling degree at equilibrium, which can be described by scaling laws. The existence of a slow mode motion, similar to that in concentrated polymer solution, could be shown.