2 research outputs found
Kinetic Study for AB-Type Coupling Reaction of Tetra-Arm Polymers
The reaction rate for the polycondensation in the Tetra-PEG
gel
system, i.e., A–B type coupling reaction between mutually reactive
two four-arm polymers, has been studied by ATR-IR spectroscopy. It
was found that (1) the polycondensation kinetics of Tetra-PEG gel
can be simply treated as a chemical reaction between mutually reactive
end-groups in solution, (2) the reaction undergoes as a simple second-order
reaction from beginning to end regardless of gelation threshold, and
(3) the gelation mechanism was predicted from the thermodynamic enthalpy
and entropy at the transition state estimated by temperature dependence
of rate constants. The reson of smooth second-order kinetics is suspected
to be that the mean-field approximation can be applied to the reactivity
of terminal groups on Tetra-PEGs; i.e., the reactivity of terminal
groups on Tetra-PEGs is not affected by the steric hindrance, substitution
effet, and gelation threshold