Ali Darabi

Nitroxide-mediated surfactant-free emulsion copolymerization of methyl methacrylate and styrene using poly(2-(diethyl)aminoethyl methacrylate-co-styrene) as a stimuli-responsive macroalkoxyamine

The SG1-mediated copolymerization of 2-(diethyl)aminoethyl methacrylate (DEAEMA) and a small percentage of styrene (S) was performed with different initiating systems including a monocomponent initiating system using an alkoxyamine of n-hydroxysuccinimidyl BlocBuilder (NHS-BlocBuilder) at 80 °C and a bicomponent initiating system using 2,2′-azobis[2-(2-imidazolin-2-yl)propane] (VA-061) as the initiator and N-tertbutyl-N-(1-diethylphosphono-2,2-dimethylpropyl)nitroxide (SG1) as the nitroxide at 100 °C. The resultant macroalkoxyamines, poly(DEAEMA-co-S)-SG1, were used as pH-sensitive macroinitiators in the nitroxide-mediated surfactant-free emulsion copolymerization of methyl methacrylate (MMA) and styrene at 90 °C, which proceeded via a polymerization-induced self-assembly (PISA) process, leading to the in situ formation of pH-responsive amphiphilic block copolymers. The reaction was well-controlled with high initiation efficiency and exhibited excellent livingness as evidenced by evolution of the molar mass distribution. The final latex particles were pH-sensitive with excellent colloidal stability and monomodal size distribution.

Stimuli-Responsive Latexes Stabilized by Carbon Dioxide Switchable Groups

Preparation of stimuli-responsive latexes whose colloidal stability can be reversibly switched using only CO2 as a trigger is reviewed. By incorporating CO2-responsive moieties into the formulation of an emulsion polymerization, polymer particles can be made for which stabilization originates from functional groups that are readily switched “on” (charged) and “off” (neutral) simply by adding or removing CO2 at atmospheric pressure. The functional groups that provide colloidal stability, typically amidines or tertiary amines, can be added in various forms such as premanufactured surfactants, functional monomers, or functional, commercially available initiators. This review focuses on the preparation, behavior, and properties of these CO2-switchable emulsion polymers. Detailed discussion is provided on how the switching behavior and latex properties are influenced by the choice of CO2-switchable moieties and the method of their incorporation into latex particles.