Ionization: constant: decrease with polymerization

The same phenomenon is responsible for the decrease in the ionization constant of a polymeric acid such as poly(acrylic acid) with increasing degree of ionization [Kawaguchi et al., 1990, 1992 Morawetz and Wang, 1987]. This effect is somewhat moderated for acrylic acid-ethylene copolymers, since charge density on the ionized polymer is decreased. The basicity... 

The authors concluded that polymerization of monomer involves a reaction between Si(OH) and bSiO ions, whether the latter are in solution as HSiOs or on a polymer as an ionized aSiO group. This is the mechanism suggested by Ashley and Innes (ISl). Marsh, Klein, and Vermeulen similarly e.xplained the autocatalytic effect on the basis that the ionization constant of SiOH groups on the polymer increased with the molecular size, and thus as more polymer formed and grew in size the total concentration of SiO ions in the system at a given pH also increased by orders of magnitude. Thus the rate increased until there was an offsetting decrease in the concentration of SifOH. ... 

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