The telomerization (chain transfer polymerization) kinetics of N-isopropylacrylamide were
investigated in various (hydro)organic solvents using 3-mercaptopropionic hydrazide as chain transfer
agent (telogen). Except for the dioxane/water system telogen consumption rates were similar for all cases,
while solvent effects could be observed for the monomer consumption rates. Chain transfer constants, as
defined by the ratio of the rate constants for chain transfer and chain propagation (C
T = k
tr,/k
p), were
highest in DMF (10.3), a solvent unable to form hydrogen bonds or dipole−dipole interactions with the
monomer, while a more promising value of C
T = 1.7 was found for the 6:4 methanol/water mixture. The
highest monomer consumption rates were observed for the 1:1 dioxane/water mixture. However, in this
particular case the telogen consumption was also found to increase, as we propose due to a “hydrophobic
effect” whereby polymer microaggregates serve to locally increase the concentration of telogen and/or
monomer once a certain water concentration has been passed. As a result a comparatively high C
T of 3.2
characterizes the dioxane/water system.
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