Under can be controlled, but the possibility of some

Under normal
conditions, the ring opening polymerizations of 2-oxazolines can be controlled,
but the possibility of some side reactions should also be considered. For
example, by removing a proton from the R1-carbon atom of the species
propagating by the nitrogen atom of a monomer, a transfer reaction occurs. As a
result, in this mechanism highlighted by Litt et al., An unloaded polymer with
C = C double bond and a positively charged activated monomer are formed. And as
a result of these studies, it has been shown that carbon in the ring ?-position
in the ring is the main locus in chain transfer. It has been shown that higher
chain transfer occurs in POX containing active methylene groups, whereas in
polymers like poly (2-isobutyl-2-oxazoline) where the ?-methylene group is
protected, chain transfer is low. The stagnant ene-terminated POx chain can
behave as a nucleophilic species via a process called chain coupling, which
enhances the molecular weight once this chain transfer reaction has emerged. However,
the chain in the sleep state is less nucleophilic than the monomer, reacts more
softly, and most of the coupling reaction takes place throughout the final
stage of the polymerization reaction. It is proposed that polymerizations
should be applied under mild conditions and terminated before finish monomer
consumption to restrict any side reactions. Another factor which inhibits the
polymerization of 2-oxazolines is the very long reaction time. For instance,
the reactions may last several days at 85 °C. As a result, during the
polymerization, the reaction time can be reduced by optimizing the reaction
conditions. The polymerization proceeds in a controlled and living manner that
can be utilized in the design of clear systems and for block copolymer
synthesis in the polymerization mechanisms which the chain transfer and
coupling can be externalized. Some possible ways exist to analyze and light up
the transfer and coupling reactions such as size exclusion chromatography or
color changes in the reaction mediums.