High Solids Hydroxy‐TEMPO Mediated Radical Semibatch Emulsion Polymerization of Styrene

Abstract

Stable polystyrene latexes having controlled molecular weight distribution (MWD) with solids contents up to 40 wt% are obtained using potassium persulfate as initiator with the nitroxides 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (hydroxy-TEMPO) and 4-amino-2,2,6,6-tetramethylpiperidine-N-oxyl (amino-TEMPO). Using different concentrations of styrene (St) in the nucleation step, it is possible to create colloidal dispersions with particle size ranging from ≈57 to ≈390 nm, conversions up to ≈96%, nitroxide efficiencies (N Eff ) up to ≈0.76, and number average molecular weight (M n ) ranging from ≈10 000 to ≈85 000 g mol −1 . The effect of the monomer feed rate in the semibatch step is also studied. These polymerizations do not require a separate macroinitiator synthesis, since this is formed in situ during the heating ramp. A mathematical model is used to compare the mechanistic understanding of the system with the experimental results.

Toward Bio‐Sourced Elastomers with Reactive/Polar Groups. Myrcene – Glycidyl Methacrylate Copolymerization: Reactivity Ratios, Properties, and Preliminary RAFT Emulsion Polymerization

“…It should be remembered that some of the St-BD elastomers produced in industry via emulsion polymerization at relatively high temperatures (60-80 °C), in the so-called hot process, have a significant gel content. [39] The formulations and procedure used in the emulsion polymerizations, including the use of a St seed formed in situ, are based on previous experience of our group with NMP and RAFT emulsion processes, [19][20][21] particularly with the emulsion copolymerization of Is and GMA in emulsion via RAFT, recently published. [21] Figure 9 shows the evolution of global conversion with time for the polymerizations.…”

“…Additionally, preliminary results are presented showing the feasibility of preparing Myr‐GMA copolymers via emulsion polymerization with sequential addition of the monomers in semicontinuous mode. In these polymerizations a technique previously developed in our group was used: this technique, originally developed a few years back, [ 19 ] allowed the obtainment of nitroxide‐controlled polystyrene (PS) and has been successfully replicated for the copolymerization of St with acrylic monomers [ 20 ] and that of Is with GMA. [ 21 ]…”

Copolymerization of Styrene with 2-Ethylhexyl Acrylate and 2-Ethylhexyl Methacrylate by Semibatch Emulsion Polymerization Using BlocBuilderMA as Macroinitiator

“…To solve this problem, we applied strategies developed in our previous report, , whereby using different molar ratios of [Monomer]/[Nitroxide] it was possible to increase the N Eff up to 1.0, attributed to the effective formation of aqueous propagating chains of length j z and avoiding their termination or deactivation in the aqueous phase, consequently resulting in fast nucleation of particles.…”

“…In our previous reports, ,, we established general conditions for obtaining controlled and stable latexes of PS using TEMPO or derivatives as the controllers. The procedure in the present study was as follows: 0.55 g (1.44 mmol) of BB was dissolved in St (Table ) for ≈10 min and then added into a previously prepared solution of DI water, 5.27 g (15.12 mmol) of SDBS, and either 0.49 g (2.81 mmol) of potassium sulfate (for reaction R1) or 0.32 g (1.83 mmol) (for reactions R3–R6) (Table ).…”

“…An important step toward achieving industrial NMRP TEMPO-based emulsion polymerization processes is the process developed by González-Blanco et al − using the initiation systems TEMPO/KPS, hydroxy-TEMPO/KPS, and amino-TEMPO/KPS. They obtained controlled and stable latexes of PS with particle size ranging from ≈30 to ≈500 nm, solids contents up to 40 wt %, M n in the range of ≈17 000 to ≈70 000 g/mol, and N Eff up to ≈1.0.…”