Kinetics and mechanism of interpolyelectrolyte exchange and addition reactions

Abstract

Transfer of relatively short polycation chains (guest polyelectrolyte, GPE) from their polyelectrolyte complex (PEC) with a relatively long polyanion (host poly electrolyte, HPE) to another polyanion of the same chemical structure and chain length but tagged with a fluorescent group has been investigated by the luminescence quenching technique. It has been shown that if only one polycation chain, on average, is transferred, the reaction follows irreversible second-order kinetics. The irreversibility of the reaction is due to additional selective nonelectrostatic interaction between the polycations and polyanion chains, carrying pyrenyl groups. The rate constant of the exchange reaction is independent of polyanion chain length and increases sharply with an increase of ionic strength of water-salt solution, a decrease of polycation chain length, and a decrease of the charge density. In accordance with the proposed mechanism, the rate-limiting step of the reaction is the transfer of a polycation chain from one polyanion to the other one in the united coil HPE-GPE-HPE*. The polyion addition reaction, i.e. the complexation between two oppositely charged polyanions, also has been studied by luminescence quenching and quasielastic light scattering techniques. The reaction can be considered as a multistage process, consisting first of the rapid coupling of the oppositely charged polyions with the formation of a nonequilibrium interpolyelectrolyte network followed by the slow relaxation process, leading finally to the formation of the individual PEC.

Polyelectrolyte Solutions: Phenomena and Interpretation

“…The kinetics of the interchange of one component of the IPEC complex was studied by mixing a solution of the PEPB-PMA complex with a solution of PMA* where the progress of the interchange could be monitored by the quenching of the pyrenyl fluorescence (49).…”

Modeling competitive substitution in a polyelectrolyte complex

“…The literature on this subject is extensive [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] and there are also several excellent reviews describing the phenomenology of solutions of oppositely charged polyelectrolytes. [1][2][3] There are also many simulation and theoretical investigations related to adsorption of polyelectrolytes to oppositely charged solid surfaces and inter-chain interactions.…”

“…Regarding the substitution reaction (second step) in Fig. 1, extensive kinetic studies were conducted some time ago by the Kabanov and Dautzenberg schools, [5][6][7][8][9][10][12][13][14] with many unexpected findings. For example, smaller polycations would complex first with a longer polyanion before these get displaced ultimately by longer polycations, demonstrating an interplay between kinetics and thermodynamics.…”

A Stopped-Flow Kinetic Study of the Assembly of Interpolymer Complexes via Hydrogen-Bonding Interactions

“…55 At PVPh-g-PS weight fractions higher than 0.6, the presence of excess of PVPh-g-PS may energetically favor the addition or/and substitution process due to less stretched PS chains at the shell of micellar complexes. 58 …”