Emulsion polymerization of styrene using irreversible addition–fragmentation chain transfer agents: effect on the course of the polymerization and molecular weight

Abstract

The emulsion polymerization of styrene with three different chain transfer agents (CTAs) based on irreversible addition-fragmentation chain transfer (AFCT) mechanism was first reported in this work. The influences of these irreversible AFCT agents on the rate of polymerization, particle size, and molecular weight were investigated. It was found that the intrinsic activity and desorption behaviors of the CTAs determined the efficiency for molecular weight control, rate of polymerization, and particle size in the emulsion polymerization. It has been demonstrated that the rate of polymerization and particle size decreased dramatically in the presence of the irreversible AFCT agents with high chain transfer constant (ethyl α-ptoluenesulfonyl-methacrylate), meanwhile, the molecular weight of the polystyrene could not be controlled well, whereas the irreversible AFCT agents with low chain transfer constant (butyl(2-phenylallyl)sulfane and 2,3-dichloropropene) had a slight effect on the polymerization rate, particle size, and were fairly well for molecular weight control over the whole conversion range in the emulsion polymerization of styrene. The average number of radicals per particle and the number-average molecular weight were calculated by classical radical emulsion polymerization theory, and the experimental results were in good agreement with the results of model calculations, when the irreversible AFCT agents were used as CTAs. The effect of chain transfer agents on the kinetics and nucleation in the emulsion polymerization of styrene can be attributed to desorption of chain-transferred radicals from the polymer particles.The results of this work show that butyl(2-phenylallyl)sulfane as CTA in emulsion polymerization of styrene provides the best balance between the rate of polymerization and the efficiency for molecular weight control conflicting tendencies.

The Effect of Allylic Sulfide-Mediated IrreversibleAddition-Fragment Chain Transfer on the EmulsionPolymerization Kinetics of Styrene

“…Thus, a good balance between water solubility and monomer solubility of the CTA is required [20]. In our previous study [21], a similar conclusion was obtained in which ethyl α-p-toluenesulfonyl-methacrylate with a higher C tr significantly reduced the R p .…”

Exploring the benefits of β-allyl sulfones for more homogeneous dimethacrylate photopolymer networks

“…21 Alternative to thiol-ene chemistry, AFCT reagents 22,23 can also be used to modify the process of radical chain growth. However, AFCT reagents have been the focus of research mostly studying molecular weight regulation of linear polymers 24 or end-group functionalization. 25 Some studies were also done using AFCT chemistry for the acceleration of cationic photopolymerization.…”

β-Allyl Sulfones as Addition–Fragmentation Chain Transfer Reagents: A Tool for Adjusting Thermal and Mechanical Properties of Dimethacrylate Networks

“…The AFCT mechanism shows great potential in pushing an uncontrolled radical chain growth polymerization reaction toward a step growth-like manner (Figure ). , By adding AFCT reagents to a radical polymerizable cross-linking monomer mixture, the uncontrolled radical chain growth mechanism can be altered and would ultimately produce materials with a more homogeneous network structure and, consequently, improved mechanical properties. β-Allyl sulfones are promising AFCT reagents, and basic polymerization studies on such substances have already been performed. , However, hardly any AFCT reagents aside from β-allyl sulfides have been mentioned for the synthesis of photopolymerized cross-linked functional materials. Research on AFCT reagents thus far was mainly focused on molecular weight control of linear polymers (e.g., styrene and methyl methacrylate), for the synthesis of hyperbranched polymers or end-group functionalization. ,, In general, highly cross-linked polymers with AFCT reagents potentially pave the way for applications such as shape memory polymers , and covalent adaptable networks …”