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Publication
Molecular architecture of non-linear polymers: kinetic modeling and experimental characterization of the system methyl methacrylate + Ethylene Glycol Dimethacrylate
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Advisor(s)
Abstract(s)
A general kinetic approach allowing the prediction of the molecular architecture of non-linear polymers is applied to the study of the copolymerization of methyl methacrylate (MMA) with ethylene glycol dimethacrylate (EGDMA). Dynamic predictions of molecular weight distributions, sequence length distributions and mean square radius of gyration are possible before and after gelation. A set of experiments concerning the copolymerization of MMA and EGDMA was carried out in toluene solution at 60 8C for which classic radical kinetics is a good approximation.
The time evolution of key polymer properties was followed using a SEC system with a
refractive index detector coupled with MALLS allowing the determination of absolute
weight average molecular weight and apparent molecular size distributions as well as
z-average radius of gyration. Special focus was given to assess the influence of the
initial amount of cross-linker on the dynamics of the non-linear structure build-up of these products. A kinetic scheme comprising 23 different chemical species and 76 chemical reactions was used in the modeling studies of this chemical system. Most of the kinetic parameters used in the simulations have been collected from previous
studies. For experiments at low monomer conversion (up to about 0.5) a good
agreement between predictions and experimental measurements is observed for
molecular weights and z-average radius of gyration by fitting a small number of
parameters describing gel effect (with a conversion dependent but chain length
independent termination rate parameter) and the relative propagation on pendant
double bonds. However, predicted values of weight-average molecular weights and
z-average radius of gyration before gelation are too low at higher monomer
conversions with non-linear systems. The likely cause is the presence of intramolecular reactions which should not be neglected in these circumstances.
Description
Keywords
Crosslinking Kinetic Molecular weight Radius of gyration
Citation
Trigo, Ivone; Gonçalves, Miguel; Dias, Rolando; Costa, Mário (2008). Molecular architecture of non-linear polymers: kinetic modeling and experimental characterization of the system methyl methacrylate + Ethylene Glycol Dimethacrylate. Macromolecular Symposia. ISSN 1022-1360. 271:1, p.107-119
Publisher
Wiley