Predicting and Measuring the Sequence Distribution of Condensation Polymers - Mathematical Approaches to Polymer Sequence Analysis and Related Problems - page 227

Chapter 11
Predicting and Measuring the Sequence
Distribution of Condensation Polymers

Maurizio S. Montaudo

Abstract The sequence of polycarbonates polyesters polyamides and other
condensation copolymers is discussed. The theory predicts that the sequence is
often radically different from addition polymers. One of the causes is the pres-
ence of a larger number of distinct monomers in the reaction vessel. Condensation
copolymers from symmetric and asymmetric monomers involve a different number
of parameters to be modeled, since asymmetric monomers require an additional
parameter. A peculiar reaction is discussed, namely the synthesis of copolymers
obtained by melt-mixing two different homopolymers. The sequence of copoly-
mer fractions collected at the exit of a liquid chromatographic device is discussed
as well. The measurement of condensation-polymer sequence distribution can be
performed using nuclear magnetic resonance (NMR) and mass spectrometry (MS).
Examples drawn from recent literature are discussed.

11.1 Introduction

Polymer science is a vast field and it is customary to classify polymerization
reactions into two groups, namely chain-growth polymerization and step-growth
polymerization [ 1 - 3 ]. In chain-growth polymerizations (also referred to as addi-
tion polymerizations), the chain grows in a well-defined manner, by adding one
monomer at a time. The monomer always contains a C D C bond (triple bonds are
very rare) and high masses are obtained at early reaction times. In step-growth
polymerization (commonly referred to as condensation polymerization), a small
molecule (water or methanol or chloridic acid) is often eliminated. The average
molar mass increases slowly. High masses can be obtained only at high conver-
sion [ 1 - 3 ]. Figure 11.1 reports two simple condensation polymerization reactions,