INVESTIGADORES
SOULE Ezequiel Rodolfo
congresos y reuniones científicas
Título:
Cinética de polimerización de isobronilmetacrilato en presencia de poliisobutilenos de diferentes masas molares y un monómero polifuncional
Autor/es:
E. R. SOULÉ; J. BORRAJO; R. J. J. WILLIAMS
Lugar:
Los Cocos, Argentina
Reunión:
Simposio; Archipol`05; 2005
Institución organizadora:
Sociedad Argentina de Polímeros
Resumen:
The scope of this study was to investigate the effect of a linear polymer dissolved in a reactive
monomer on the kinetics of free-radical polymerization before the start of phase separation. The selected
system was a solution of polyisobutylene (PIB) in isobornyl methacrylate (IBoMA), polymerized at 80 °C
in the presence of benzoyl peroxide (BPO). A ternary phase diagram of PIB, IBoMA, and poly(isobornyl
methacrylate) (PIBoMA) was built at 80 °C, both employing physical blends or determining the phase
separation conversion in the course of polymerization. Cloud-point curves (CPC) obtained by both methods
were coincident within experimental error. They were shifted to lower conversions when increasing the
molar mass of PIB. Different PIBs exhibiting CPC at advanced conversions were selected for the kinetic
study performed employing differential scanning calorimetry (DSC) at 80 °C. A simple kinetic model for
free-radical polymerizations describing the relevant termination rate constant in terms of the free-volume
theory provided a consistent fitting of the polymerization rates in the conversion range where the solution
remained homogeneous. Increasing the molar mass of PIB led to an increase in polymerization rate due
to the decrease in free volume and the corresponding decrease of the termination rate. Increasing the
amount of a particular PIB in the initial formulation led to a less marked gel effect, explained by the
smaller relative variation of free volume with conversion. The dimensionless free volume of PIB obtained
from the kinetic model was found to increase with the volume concentration of chain ends, as expected.
Under conditions where phase separation took place at very low conversions, the overall polymerization
rate exhibited the presence of two maxima (gel effects), representing the polymerization in two different
phases. The first maximum was associated with the polymerization taking place in the phase lean in
PIB, and the second maximum was associated with the polymerization of the monomer that was initially
fractionated with PIB.