Cooperative Interactions of Unlike Macromolecules: NMR Study of Ionic Coupling of Poly[2-(trimethylammonio)ethyl Methacrylate Chloride]-block-Poly(N-(2-hydroxypropyl) Methacrylamide) Polycation with Oligophosphates in D2O

Abstract

Cooperative effects in the interactions of poly[2-(trimethylammonio)ethyl methacrylate chloride]-block-poly(N-(2-hydroxypropyl) methacrylamide) polycation with oligophosphates (phosphate glasses) leading to micelle-like complexes were studied using NMR. 1H, 13C, 14N, 23Na, 31P,35Cl, and 79Br single- and double-quantum high-resolution and MAS NMR at 7.2 and 12 T of the complexes were studied at concentrations 0.1 and 0.02 mol/L of the ionic groups in D2O at 300−350 K. 1H, 13C, and 31P longitudinal and transverse relaxations and 23Na, 35Cl, and 79Br T11, T13, and T23 time evolutions were studied to reveal the ionization states, local and semilocal mobilities, and ion coupling conversions in the products of the same polycation with polyphosphates of Pn = 15, 25, 35, 45, 65, and 75. Pulsed gradient spin−echo (PGSE) was used to measure self-diffusion coefficients and thus the size of both reactants and products. The results show that the ionic coupling is almost complete with polyphosphates of Pn up to 35 but decreases steeply with higher values of Pn. In all cases, the products are aggregates of ionic complexes, but their size increases with higher Pn of the polyphosphate. The cooperativity in the products of self-assembling is discussed in terms of kinetic, thermodynamic (entropy), and microphase stabilization.