Table 1. Uncontrolled free-radical polymerization techniques for nanogel synthesis.
| Reaction | Details | Advantages//limitations | References |
|---|---|---|---|
| Miniemulsion | Nanodroplets formation through high shear stress (ultrasonication) of the mixture of monomers and surfactants | Narrow size distributions for diameters in the 50–500 nm range.Allows in situ encapsulation//Surfactant and co-stabilizer required.Special equipment necessary (ultrasonic device). | a |
| Microemulsion | Absence of high shear stressUse of a critical concentration of surfactantMonomer molecules are in micelles | Usually nanogel sizes between 10 and 150 nm can be achievedNo shear stress necessary//High surfactant concentration needed.Co-surfactant necessary. | b |
| Dispersion | Initially all the reaction ingredients are soluble in the reaction mediumPolymerization occurs in a homogeneous phaseThe polymers are insoluble and form a stable dispersion with an aid of colloidal stabilizers | Simple batch synthesis.Particle size adjusted by monomer and dispersant concentration in the range of 0.1–15 mmPreferably for core–shell particles synthesis//Preferably for vinylic functionalized monomers | c |
| Precipitation | Initiation of reaction occurs in homogeneous solution of the monomers in the reaction medium.Polymer is soluble in the reaction medium.Particles separation by crosslinking | Batch synthesisNo surfactant requiredParticle size adjusted by monomer concentration in the range of 100–600 nm//Frequently irregular shape and high polydispersity | d |