Crosslink polymerization kinetics of poly(acrylic acid-co-2-acrylamido-2-methylpropane sulfonic acid)

AA/AMPS hydrogels

was investigated by using dilatometry in the presence of sodium persulfate as initiator and

N

N

'-methylene bis(acrylamide) as crosslinker.It was found that the reaction for the crosslink polymerization of AA/AMPS hydrogels had orders of 0.58

1.14

and 0.86 with respect to the initiator

AMPS

and AA

respectively.From the Arrhenius plots

the activation energy of the crosslink polymerization was found to be about 140 and 89 kJ·mol

-1

in the presence and absence of the crosslinker

respectively

in the temperature range from 45 to 65℃.It was noted that the crosslinker had effects on the reaction order of the initiator and the activation energy due to the formation of cross-linked networks

which was verified by Fourier transfer infrared (FTIR) spectrum.To further confirm the influences of the cross-linked network structure on kinetic parameters of the crosslink polymerization

a mechanism was proposed

which highlights the different termination routes between free radical polymerization and crosslink polymerization.These results suggest that dilatometry provides a convenient tool for crosslink polymeri-zation study

and confirm that the cross-linked networks are formed in the crosslink polymerization.