Dynamic light-scattering study of 3-indolbutyric acid polymeric derivative

Abstract

This paper describes the dynamics of new slow release formulations of plant growth regulator (PGR) 3-indolbutyric acid (IBA) in aqueous solution. The new PGR formulations are water-soluble copolymers derived from acrylamide and vinyl chloroethyl ether, containing side linkages of IBA, the latter being released after hydrolysis. From the observed photon correlation spectra of the polarized scattered light of the water-soluble PGRs, the distribution of relaxation times is computed by means of a direct Laplace transformation. The results of the light-scattering experiments suggest that the incorporation of the IBA groups does not affect the coil dimensions of the parent polymer. This behaviour is to be contrasted with a similar system containing hydrophobic side groups of 1-naphthylacetic acid that lead to the formation of interpolymeric micellar structures. The hydrodynamic radius R h which is 42 Å for the parent polymer (PF1), remains approximately the same for the different contents of the IBA polymeric ester considering the relative increase in size due to the increasing numbers of the IBA groups. In alkaline pH, the scattering intensities and apparent hydrodynamic radii display a systematic drop as a function of time due to the loss of the IBA linkages. However, such effects are negligible in neutral pH, in agreement with previous kinetic studies.