Nucleation loci in the ring-opening polymerization of octamethyl- cyclo-tetrasiloxane in Winsor I system with dodecylbenzene sulfonic acid sodium salt and sulfuric acid

Abstract

The ring-opening polymerization of octamethylcyclotetrasiloxane (OTS) was carried out in an Winsor I system with dodecylbenzene sulfonic acid, sodium salt (DBSNa) as emulsifier and sulfuric acid as initiator, to clarify the mechanism of the polymerization, especially focusing on the nucleation loci, the rate of generation of nonvolatile molecules and the average diameter of generated polymer droplets.In the system where DBSNa concentration is higher than the critical micellar concentration (CMC), nonvolatile molecules were generated in the aqueous phase and their generation rate became higher with an increase in DBSNa concentration, while nonvolatile molecules were not generated at emulsifier concentrations lower than the CMC. These experimental results support that nucleation did not take place in the true aqueous phase, but originated from the micelles.

A New Interpretation of Apparent Induction Period in Ring‐Opening Polymerization of Octamethylcyclotetrasiloxane in Acid Emulsion

“…The shape and size of reaction vessel was reported in a former report. [ 10 ] Water (270g), DBSNa and one or two types of D i was charged in the reaction vessel, mixed by rotating the impeller in the reaction vessel with 600 rpm rotation speed, and heated to and kept at 75 °C. The amounts of charged cyclomethicones (D i 's) are summarized in Table 1 .…”

Preparation of free‐standing silicone particles in aqueous heterogeneous system

“…These results suggest that this polymerization proceeds under both ionic polymerization and polycondensation. Suzuki et al reported that the nucleation did not occur in the true aqueous phase but originated from the monomer swollen micelles, in which polymerization of D 4 did not proceed below CMC. On the basis of these results, we suggest the following formation mechanism: The initiation step occurs at the interface between the monomer droplets and DBSA, following which the ring‐opening reaction of D 4 and propagation by cationic polymerization proceeds.…”

“…The most common synthetic route to prepare silicone emulsion in an aqueous medium is via cationic‐anionic ring‐opening polymerization of cyclic siloxanes such as D 4 . However, the mechanism at work in miniemulsion systems is still debated . To the best our knowledge, most research in this area discusses the preparation of silicone oil (linear silicone).…”