Inception and design of non-linear free radical polymerization processes in semi-batch reactor

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Publications

Time programmed feed of semi-batch reactors with non-linear radical copolymerizations: an experimental study of the system styrene + divinylbenzene using SEC/MALLS

Publication . Gonçalves, Miguel A.D.; Dias, Rolando; Costa, Mário Rui

The radical crosslinking copolymerization of mono and divinyl monomers was experimentally studied with a 2.5 dm3 semi-batch reactor using styrene + divinylbenzene as a model system. The analysis of products was carried out by SEC with a MALLS detector. The influence of the feed policy of divinylbenzene on the time evolution of the copolymer molecular weights and z-average mean square radius of gyration was assessed. A detailed kinetic model, in the absence of intramolecular reactions but taking into account the presence of the two isomers m- and p- in the commercial divinylbenzene and the different reactivities of the various radicals and double bonds was developed; most parameters have been collected from previous kinetic studies, and only two have been regressed using our measured molecular weights. These results can be used to improve the production of branched/crosslinked polymers with controlled molecular architecture.

2007Conference object

Open access

Molecular architecture of non-linear polymers: kinetic modeling and experimental characterization of the system methyl methacrylate + Ethylene Glycol Dimethacrylate

Publication . Trigo, Ivone; Gonçalves, Miguel A.D.; Dias, Rolando; Costa, Mário Rui

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.

2008Conference object

Open access

A general kinetic method to predict sequence length distributions for non-linear irreversible multicomponent polymerizations

Publication . Dias, Rolando; Costa, Mário Rui

A method to predict the sequence length distribution (SLD) for homogeneous non-linear irreversible multicomponent polymerizations is described. With more than two monomers, it also predicts chain length distributions of the sub-domains containing a prescribed sub-set of the repeating units, but in all possible orderings. Its goal is the analysis of polymerization systems involving complex kinetic schemes in an automated way. The radical terpolymerization of two vinyl monomers with a divinyl monomer and a radical copolymerization including branching by transfer to polymer and by propagation on terminal double bonds are considered as case studies showing the interest of our approach. Finally, the concept of gelation of sequences is presented and discussed in comparison with the related and better known gelation of the population of polymer molecules.

2006Journal article

Open access

SEC/MALLS measurement of the branched structure of methyl methacrylate + ethylene glycol dimethacrylate copolymers synthesized by atom transfer radical polymerization

Publication . Trigo, Ivone; Gonçalves, Miguel A.D.; Dias, Rolando; Costa, Mário Rui

In the last few years, atom transfer radical polymerization (ATRP) of acrylate and methacrylate monomers in the presence of a small amount of cross-linker has been investigated in order to produce branched polymers and gels with applications in microelectronics, coatings industries or biomedicine (Wang and Zhu, 2005; Gao et al., 2007). In this context, it is being explored the production by ATRP of branched/crosslinked polymers with a lower degree of heterogeneity than that obtained by conventional free radical polymerization (FRP). This work reports an experimental study on the ATRP of methyl methacrylate (MMA) + ethylene glycol dimethacrylate (EGDMA) initiated by MBPA (methyl -bromophenylacetate) and mediated by copper bromide (CuBr) ligated with HMTETA (1,1,4,7,10,10- hexamethyltriethylenetetramine). The synthesized copolymers were analyzed by size exclusion chromatography (SEC) with simultaneous detection of refractive index (RI) and multi-angle laser light scattering (MALLS) signals. Important details of the molecular architecture of these materials can therefore be measured, namely absolute molecular weights and z-average radius of gyration. Different experimental runs were performed in order to investigate the influence of the operating conditions (e.g. temperature and initial molar ratios MMA/EGDMA/MBPA/CuBr/HMTETA) on the structure of the products.

2008Conference object

Open access

Kinetic Modeling of Non-Linear Polymerization

Publication . Costa, Mário Rui; Dias, Rolando

Recent developments of a method based upon population balances of generating functions of polymer chain length distributions (CLD) are presented. The calculation of the CLD and how to take into account chain length dependent reactivity are discussed. Prediction of polymer properties is also possible but only easily done for the average molecular radius of gyration; some results are presented for a radical polymerization including transfer to polymer and propagation with terminal double bonds.

2006Conference object

Open access