relative amounts of specific units dyads triads within the polymer chain this is compared with values expected for a completely random copolymer containing the monomers in question the method can be demonstrated by referring to fig1 and the statistical analysis below fig1 a is a 1 h nmr spectrum showing the assignments for a copolymer synthesized from a mixture of caprolactam and cpeot as described below in control a which is random and thus not an example of this invention fig1 b is a 1 h nmr spectrum showing the assignments for a copolymer of caprolactam and cpeot synthesized by sequential addition of monomers according to a process as provided herein and as described below in example 1 peak assignments were made previously based on extensive 2d nmr analysis the relative amounts of various species were determined by calculating expected and observed probabilities using the following definitions y is the mole fraction of diethylene glycol derived moiety in the polymer chain diol t is the mole fraction of terephthalic acid derived moiety in the polymer chain diacid l is the mole fraction of caprolactam derived moiety in the polymer chain amine polymer end groups are disregarded we define a as the mole fraction of ty structures present b as the mole fraction of tl structures present c as the mole fraction of ll structures present and d as the mole fraction of ly structures present each diethylene glycol contributes two alcoholic oh groups each ring opened.