Adsorption of Polycomplexes at Solution/Air Interface
E.M. Shaikhutdinov, K.Zh. Abdiyev, M.B. Zhursumbayeva and S.Kh. Khussain
Department of Chemistry, K.Satpaev Kazakh National Technical University
22 Satpaev st., Almaty, 480013, KazNTU, Republic of Kazakhstan
The effect of complex formation of polyacids (polyacrylic (PAAc) and polymethacrylic (PMAAc)) with polyacrylamide (PAA) on their surface properties at solution/air interface has been studied by surface tension, electric conductivity and potentiometric measurements at 293±0.2 K. The relaxation time and surface activity of polycomplexes were calculated from kinetic data on the surface tension. It was found that during complex formation the relaxation time of a surface layer has a maximum and the surface activity of macromolecules is increased. Also the standard free energy of adsorption for PAA and polyacid-PAA polycomplexes were calculated. They are equal D adsGo293 = - 19.1±0.1 kJ/base-mol. for PAA, D adsGo293 = -21.2±0.1 kJ/base-mol. for PMAAc-PAA polycomplex and D adsGo293 = -23.0±0.1 kJ/base-mol. for PAAc-PAA polycomplex (calculation per base-mole of PAA monomer link).
It is shown that the surface activity and ability to decrease of the water surface tension is less for PMAAc-PAA than for PAAc-PAA. Such anomalous behaviour of PMAAc-PAA polycomplex probably is caused by an excessive strengthening of inner- and intermolecular hydrophobic interactions in macromolecules of PMAAc-PAA polycomplexes due to the presence of a -methyl groups in PMAAc macromolecules. Because of the rebuilding of macromolecule segments of complex by polarity at the interface is becoming a difficult one.