Polymerizing systems are of great interest because they offer practical advantages in industrial applications. Most include monomer is carried in an emulsion or suspension in the liquid phase.

Hence, polymerizing systems are classified as homogeneous and heterogeneous.

Homogeneous Systems

Bulk polymerization is the most obvious method and mostly practised by the industries in producing condensation polymers (slightly exothermic reaction) and occurs when the mixture is less viscous.

This has advantages like avoids contamination and but has drawbacks complex when it comes to small particles, as requires agitation, material transfer, separation, and recycling.

small particle
Photo by ELEVATE

Solution polymerizing system, a solvent should be selected to prevent chain transfer and polymer should be utilized in solution, this helps in heat removal during the reaction.

Heterogeneous Systems

In these, the liquid or solid polymer is formed from the respective gaseous monomer. The practical application is polythene bags. Pressure conditions play an important role during polymerization.

Photo by Magda Ehlers

Emulsion (dispersion of liquid drops into another liquid which is immiscible) polymerization, consists of dispersing medium, monomer, emulsifier (a substance which stabilizes emulsion), the initiator.

Droplets are formed which stabilized by emulsifiers by the micellization process. This is more rapid than bulk polymerization.

Common emulsions include egg yolk, oil-water. The most common application is emulsive paints.

paints by polymerization
Photo by Sharon McCutcheon

Suspension polymerization system consists of a dispersing medium, monomers, stabilizing agents and a monomer soluble initiator.

The polymerization is carried out in the small droplets of liquid monomers. After the reaction, the polymer is freed of stabilizing agents and dried off.

Star shaped polymers from anionic polymerization - combined

For any question please comment below | Go to the next Chapter-4 Polymer Reactions

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