Kinetic Modeling of the Suspension Copolymerization of Styrene/Divinylbenzene with Gel Formation

Abstract

Summary: Experimental and theoretical studies concerning the suspension copolymerization of styrene with divinylbenzene are reported. Experiments were carried out in a batch stirred reactor, at 1.2 dm3 scale, and extended beyond gelation in order to synthesize insoluble material. Looking for real time information concerning the building process of such materials, these polymerizations were In‐line monitored using a FTIR‐ATR immersion probe. Polymer samples collected before and after gelation were Off‐line characterized using a SEC/RI/MALLS system allowing the measurement of monomer conversion, average molecular weights, MWD and also the z‐average radius of gyration. The weight fraction of insoluble material (gel) was measured for samples with different reaction times. The experimental program has included the study of the influence of key polymerization parameters on the dynamics of gelation and some properties of the resulting networks, namely the initial mole fraction of crosslinker and the initial proportions between monomers and inert diluent. Variable n‐heptane/toluene mixtures were used within this purpose. These experimental observations were complemented with theoretical studies using a general kinetic approach allowing the prediction of MWD and z‐average radius of gyration before and also after gelation. Comparison of the experimental measurements with these predictions is being exploited to develop modeling tools useful for the design of operating conditions allowing the improvement of the performance of the final products.

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).…”

“…For comparison purposes, Figure 29 depicts SEM analysis of products of FRP aqueous suspension of S/DVB at 60 °C 72. Suspension gel beads with sizes up to 0.5 mm or lower can be observed in Figure 29(a).…”

“…Micro‐ and nano‐particles can also be observed in FRP S/DVB products synthesized at 60 °C, as shown in Figure 29(b). Note that with materials illustrated in Figure 29, the synthesis process includes a mixture of bad/good solvents ( n ‐heptane/toluene) in order to promote the formation of macropores in the gel beads; macroporous structures with diameter size in the range of 5 µm were thus identified 72. In the present research, only solvents with a good thermodynamic affinity with polymer (toluene and xylene) were used because the focus of this study is the effect of NMRP on the structural homogeneity of S/DVB products.…”

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.…”