An acid-induced cyclohexanone/<i>tert</i>-butylhydroperoxide
initiation system for ambient temperature reversible addition–fragmentation
transfer (RAFT) polymerization of vinyl monomers is presented. The
reaction system is optimized for the synthesis of poly(<i>n</i>-butyl acrylate) of various chain length. The polymerization shows
typical living characteristics and polymers with dispersities close
to 1.1 are obtained. Analysis of the polymer end groups by means of
soft ionization mass spectrometry reveals the typical distribution
of polymer containing both <i>R</i> and <i>Z</i> RAFT end groups and a minor distribution of a RAFT polymer carrying
a cyclohexanone end group in α position. This observation demonstrates
that the polymerization is initiated solely by ketone radicals despite
a relatively complex initiation mechanism that involves several intermediates.
The room temperature-derived homopolymers are successfully chain extended
with <i>tert</i>-butyl acrylate resulting in well-defined
block copolymer structures. To demonstrate the versatility of the
approach, the room temperature RAFT polymerization is also applied
to synthesize styrene and <i>N</i>-isopropylacrylamide,
yielding best results for polystyrene. Finally, also a bisperoxide
structure is tested as an alternative for the ketone/peroxide mixture.
Polymerization proceeds substantially faster in this case and successful
controlled polymerization to full conversion is achieved even at 0
°C. In general the proposed room temperature RAFT technique is
very easy to carry out, in principle easily up scalable, metal free
and shows high potential toward the synthesis of well-defined temperature
sensitive materials
