On the properties of polymers with random stereo‐sequences

Abstract

Abstract It is proposed that in most free radical polymerizations of polymers containing asymmetric carbon atoms in the principal chain, the relationships between the stereo‐positions of the substituents on adjacent units are governed by independent Bernoulli trials. An event in which a given substituent has the same stereo‐position as its immediate predecessor is called an “isotactic placement.” The probability, α, of this event may be a function of the temperature of polymerization. The methods of Flory's theory of the melting point of copolymers are used to derive an upper bound for the melting point of a homopolymer with “tacticity,” α. The notation and calculations are then extended to include polymers whose stereo‐sequences are governed by statistics of a more general type than Bernoulli trials. It can happen that the calculated upper bound for the melting point may lie near (or even below) the glass point for the amorphous polymer; when such is the case, the polymer cannot be crystallized by annealing.