Formation of polyamidine-chromophore and polyamidine-(chromophore-poly(propylene oxide)-chromophore) complexes in methanol

Abstract

The kinetics of formation of nonstoichiometric ionic complexes of poly(octamethyleneacetamidine) with a low-molecular-mass chromophore (4-hydroxystyryl)-(4′-carboxystyryl)ketone and a block copolymer chromophore-poly(propylene oxide)-chromophore in dilute methanol solutions has been stud- ied by static and dynamic light scattering. The molecular masses of polyamidine and a poly(propylene oxide) spacer are 12000 and 2000, respectively. It has been shown that polyamidine-chromophore complexes have hydrodynamic radii comparable with those of polyamidine-(chromophore-poly(propylene oxide)-chromophore complexes (100–200 nm). The radii of gyration and the structural factors ρ of the complexes are estimated. In polyamidine-chromophore complexes, the chromophore is aggregated and the density of aggregates is high (ρ ≈ 1). The dependence of ρ for polyamidine-(chromophore-poly(propylene oxide)-chromophore) complexes on stoichiometry is related to a change in the ratio of dangling ends and the number of loops. With an increasing fraction of dangling ends, the complexes become less compact (ρ increases) and their aggregation proceeds at a higher rate. Moreover, a variation in the order of mixing of component solutions affects the size of complexes, the kinetics of structuring, and the change in their stoichiometry.