Molecular distributions in polycondensations involving unlike reactants. VII. Treatment of reactants involving nonindependent groups

Abstract

Abstract The molecular distributions involving the use of reactants with nonindependent groups are considered in this paper. The distributions are shown to depend on the relative amounts of reactant in the unreacted state, the once‐reacted state, and the twice‐reacted state. The kinetic considerations determining these relative amounts are reviewed for several different types of reactants, including cyclic acid anhydrides and certain diisocyanates. The general linear distribution for a condensation polymerization of two reactants is derived. The calculations for nonindependent groups in other types of distributions are briefly indicated. The molecular distributions arising in polyurethane condensations, particularly those of chain extension, are slightly specialized forms of the general distribution. The methods of this paper are the only available tools to deal with these distributions. It is shown that a diacid or glycol can be treated as a reactant having nonindependent groups. The kinetic calculations for such a unit are seen to be the same as for a cyclic acid anhydride. Somewhat improved distributions for polymers of such units are thus made available.