Time Programmed Feed of Semi‐Batch Reactors with Non‐Linear Radical Copolymerizations: An Experimental Study of the System Styrene + Divinylbenzene Using SEC/MALLS

Abstract

Summary:The radical crosslinking copolymerization of mono and divinyl monomers was experimentally studied with a 2.5 dm 3 semi-batch reactor using styrene þ 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.

Gel Formation in Aqueous Suspension Nitroxide‐Mediated Radical Co‐Polymerization of Styrene/Divinylbenzene

“…Dissimilitudes between linear and non‐linear NMRP become clear when Figure 5 and 6 are compared. Formation of a polymer population with broad size distribution, formation of a low amount of a polymer cluster of very high size near gelation [see also Figure 7(a)], and the shift of the size distribution to lower values after gelation are general features associated with crosslinking processes, which are also observed with FRP mechanisms 61, 71, 72. In contrast to the linear case, no significant differences between CRP and FRP are observed concerning this aspect.…”

“…Owing to the crosslinking process, a very broad distribution of non‐linear species is formed and gelation (formation of a macroscopic insoluble network) is possible. With FRP of vinyl/divinyl monomers, this crosslinking mechanism was extensively theoretically and experimentally characterized in past works (see references 61, 71, 72 and the references therein) and these issues are here investigated for NMRP of S/DVB with gel formation. Figure 6(a) shows the RI signal of samples with different polymerization time from NMRP of S/DVB with conditions of run 10 in Table 1 (5 mol‐% of DVB in the monomer mixture).…”

“…Here, higher PVA concentrations were chosen in order to improve reactor sampling by decreasing average particle size. An atmospheric reactor61 with maximum capacity of 2.5 L was used to perform the polymerizations at T = 90 °C. A Parr 5100 pressurized glass reactor with 1 L maximum capacity was used to perform aqueous suspension experiments at T = 130 °C.…”

Styrene–dimethacrylate copolymerization kinetic modeling

“…Copolymers containing styrene as their main monomer unit are of great interest because they can be sulfonated at their aromatic rings, hence yielding organic catalysts. The literature contains plenty of kinetic data and model validations of the copolymerization of styrene with divinylbenzene (DVB) . However, DVB has been replaced with other divinyl monomers so as to evaluate their effects on copolymerization kinetics and resin properties.…”

“…Within the mathematical modeling framework, many tools for crosslinking copolymerization are available, such as generating functions, numerical fractionation and balance of sequences . Despite this diversity of available methods, modeling approaches for styrene–DMA copolymerization are scarce, and are generally focused on the prediction of copolymer composition .…”