6.3.1　Monomer polymerization

Polymer NPs can be directly obtained by polymerization of monomers，at the meantime，drugs are loaded.Emulsion polymerization is a commonly used method for the preparation of NPs.Specifically，drug molecules are dissolved in a monomer as the oil phase，then emulsified by an aqueous phase containing surfactants，followed by polymerization reaction to produce nano-drug delivery system.This method is suitable for hydrophobic polymers and drugs，and typically used for spherical nano-drug carriers.It should be pointed out that in some polymerization reactions，high temperature may affect the activity of the drugs.Besides，residual monomer，catalyst，surfactant，and initiator，etc.that could bring side effects are hard to be removed completely.(https://www.daowen.com)