Dagmar Straková

Characterization of copolymers by the light scattering method from dilute solutions in mixed solvents

Abstract Conditions have been established suitable for the determination of the molecular characteristics and the parameters of composition heterogeneity for copolymers by the light scattering method in dilute solutions. These conditions are easiest to realize by using mixed solvents. A relationship has been derived describing the intensity of light scattered from the solution of a chemically heterogeneous copolymer in a mixed solvent. The method can also be applied to copolymers of components having equal refractive indices; it has been checked on mixtures of polyethyleneglycol methacrylate, polymethyl methacrylate and their copolymers in the system methylcellosolve-α-bromonaphthalene. Experimental results were in good agreement with the calculated values.

Light scattering characterization of thermodynamic interaction of polymers in dilute solution. Effect of experimental error and temperature

Abstract Interaction between non-identical polymer molecules in a dilute solution of a mixture of two polymers is quantitatively characterized by the interaction parameter A 24 , which is the second virial coefficient for interaction of unlike species. The value of A 24 may be experimentally obtained by light scattering. The determination of A 24 is very sensitive to experimental error in the input data, particularly for mixtures in which one polymer is greatly in excess, and for mixtures of polymers having molecular weights differing by orders of magnitude. A slight rise in A 24 with temperature has been observed for solutions of mixtures of polystyrene and poly(methyl methacrylate) in diethyl malonate in the range 25–100 C. This change in A 24 reflects the increased mutual miscibility of the polymers in solution at elevated temperatures.

Effect of polyethylene glycol on the rate of immune complex formation by non-precipitating antibody

A kinetic study formation of large size complexes of non-precipitating pig-Dnp anti-Dnp antibody and multivalent dinitrophenylated serum albumin was performed using light scattering and absorption spectroscopy of the Dnp-group. A very rapid phase of the process resulted in the formation of complexes having molecular weight of about 2 X 10(6). Further increase of the complex size was much slower. Addition of PEG affected positively the rate of complex growth even in concentrations below 1%. The spectroscopic kinetic curves also showed a rapid and a slow phase, sensitive to the presence of PEG. The character of the kinetic data does not support the simple view that polymers enhance precipitate-formation by the steric exclusion of complexes from the polymer domains. It can be assumed that the interaction of the polymer with the antigen-antibody system consists of a subtle temporary attachment of the polymer to the antibody molecule resulting in a change of the shape and/or flexibility of the antibody molecule, favouring its cross-linking capacity.