  We simulate the assembly of DNA copolymers from two types of short duplexes
(short double strands with a single-stranded overhang at each end), as
described by the oxDNA model. We find that the statistics of chain lengths can
be well reproduced by a simple theory that treats the association of particles
into ideal (i.e., non-interacting) clusters as a reversible chemical reaction.
The reaction constants can be predicted either from Santalucia's theory or from
Wertheim's thermodynamic perturbation theory of association for spherical
patchy particles. Our results suggest that theories incorporating very limited
molecular detail may be useful for predicting the broad equilibrium features of
copolymerisation.
