Radical entry in emulsion polymerization: propagation at latex particles/water interfaces

Area of Science:

• Polymer Chemistry
• Chemical Engineering
• Physical Chemistry

Background:

• Emulsion polymerization involves initiator-derived radicals entering latex particles.
• Current models incorrectly define this propagation as a bulk reaction.

Purpose of the Study:

• To propose a new conceptual model for radical entry in emulsion polymerization.
• To express the rate of interfacial propagation of surface-active entry radicals.

Main Methods:

• Development of a new rate equation for interfacial propagation: Rate = k(I) * A * [M](P) * [R•](aq).
• Estimation of the interfacial radical propagation constant, k(I), using transition state theory.
• Application of the model to seeded styrene polymerization data.

Main Results:

• The proposed interfacial propagation model offers a more accurate description of radical entry.
• An estimated interfacial radical propagation constant (k(I)) was determined for seeded styrene polymerization.
• The new approach provides a means to simulate radical entry rates, particularly under rate-determining conditions.

Conclusions:

• The conceptualization of radical entry propagation as an interfacial reaction is crucial.
• This revised model is valuable for simulating radical entry in emulsion polymerization, especially under monomer-starved conditions.