  The first experience of virtual free-radical polymerization of a set of vinyl
monomers in the framework of the digital twins (DTs) concept (Polymers 2023,
15, 2999) is extended to methyl methacrylate, copolymerized with small
additives of stable radicals such as fullerene C60 and TEMPO. The
virtualization of chemical processes is based on the assumption of basic chain
reactions that lay the foundation of polymerization. In the current study, a
set of elementary reactions, covering the initial stage of the polymerization,
is considered. The reactions are the most suitable for quantum chemical
treatment. The calculations, covering about 30 DTs, were carried out using a
semi-empirical version of the unrestricted Hartree-Fock approximation. The main
energy and spin-density parameters of the ground state of DTs are determined.
The barrier profiles of three DTs were calculated, which led the foundation for
determining the activation energy of the studied processes. The decisive role
of spins in the formation of transition states of these processes is confirmed.
The two stable radicals behave quite differently with respect to the
polymerization of the studied monomer. The action of fullerene C60 concerns
mainly the capturing of the initiating free radicals, anchoring them to the
molecule body and thus slowing the main polarization process. In contrast,
TEMPO effectively capture monomer radicals manifesting itself as a killer of
the polymerization thus providing the appearance of the induction period in
practice. The obtained virtual kinetic data are in a full consent with
experimental reality.
