PolySMart is a python package which is designed to perform a reactive MD simulation in GROMACS MD package using MARTINI coarse-grain forcefield. It is specially designed to perform polymerization and crosslinking process in order to generate the topology of the resulting structure at any stage of the reaction. The algorithm utilized in this code package is based on exploring the system for the species that can react (with the conditions which had been defined by the user) and taking place the reaction by modifying related topology files followed by energy minimization and a short equilibration. These steps are iterated until a specified condition is satisfied. In addition to bond formation, the PolySMart also supports breakage of bonds and also the exchange of certain groups.
You can find the source code and more details here:
The package has been published and tested on several cases:
PolySMart: a general coarse-grained molecular dynamics polymerization scheme