Recent Advances in the Study of Multifunctional Initiators in Free Radical Polymerizations

Abstract

An overview of a systematic investigation of a tetrafunctional peroxide initiator's behaviour is presented. The study focuses on three main areas of research: kinetic experiments, polymer characterization and modelling efforts. The kinetic investigation compared the behaviour of the tetrafunctional initiator (JWEB50) to that of a monofunctional counterpart (TBEC) for a variety of monomers. Although higher rates of polymerization were generated with JWEB50 for all monomers investigated, switching from a mono‐ to a tetrafunctional initiator actually decreased the polymer molecular weight for methyl methacrylate. While chromatographic characterization methods were able to detect branching in polystyrene samples produced with JWEB50, this was not the case for poly(methyl methacrylate). However, evidence of branching was clearly observed for both polystyrene and PMMA when rheological methods were employed. In order to explain the experimental results, a mathematical model was developed. Through its use, the concentration and chain length of various polymer structures (i.e., linear, star or coupled stars) was found to depend upon monomer type and reaction conditions.

Modeling of ethylene copolymerization in nonisothermal high‐pressure reactors using bifunctional initiators

“…Their study revealed that the initiator effect on molecular weight distribution was dependent upon the monomer type. Characterization analysis revealed that the existence of chain branching affected rheological properties of polymer samples . Also, Galhardo et al studied the effect of bifunctional initiators on vinyl acetate polymerization to produce branched polymer at lower temperature, but no branching was recorded for polystyrene produced with the same initiator.…”

Mathematical model for the bulk polymerization of styrene chemically initiated by sequential and total decomposition of the trifunctional initiator diethyl ketone triperoxide

“…There are a limited number of works dealing with the use of multifunctional initiators (i.e. initiators containing more than two labile groups per molecule) . Cerna et al studied the particular case of the bulk polymerization of St using a cyclic trifunctional peroxide initiator, the diethyl ketone triperoxide (DEKTP).…”

Living free radical polymerization using cyclic trifunctional initiator

“…The authors prove that under specific experimental conditions narrow molecular weight distributions (MWDs) and polydispersities (PDIs) around 1.5 can be obtained. Scorah et al10 used a tetrafunctional initiator on conventional polymerization and proved that it is possible to produce polymers with different structures when compared to the ones produced using monofunctional initiator. Zhang and Zhang11 produced a star copolymer of styrene and butadiene using a multifunctional macromolecular initiator.…”