Microemulsion and macroemulsion polymerization of octamethylcyclotetrasiloxane: A comparative study

GRAPHICAL ABSTRACT

ABSTRACT

Octamethylcyclotetrasiloxane (D4) was polymerized in a microemulsion system using novel formulations, in which acrylamide was involved as a co-emulsifier. Dodecylbenzene sulfonic acid was used as both a cationic initiator and emulsifier. The effect of emulsifiers, D4, feeding rate and temperature on conversion, polymerization rate (Rp), latex stability and particle sizes were investigated. A conventional (macroemulsion) system was also studied comparatively. Rp in the microemulsion was quickly increased to a maximum of 0.108 mol L⁻¹s⁻¹ at ∼30 min corresponding to a conversion of ∼38%, and then decreased with reaction progression over a period of 30–110 min. In the macroemulsion system, however, a constant rate was observed between conversion 30% and 50%, and its optimal sample contained an average particle diameter of 88 nm while that from microemulsion had smaller particles with diameter of 19 nm. Activation energies were also estimated to be 31.5 and 41.1 kJ/mol for the microemulsion and macroemulsion systems, respectively.

KEYWORDS:

• Octamethylcyclotetrasil-oxane
• micro-emulsion polymerization
• acrylamide
• particle size
• PDMS latex