Phase inversion of medium-chain-length poly-3-hydroxyalkanoates (mcl-PHA)-incorporated nanoemulsion: effects of mcl-PHA molecular weight and amount on its mechanism

The study investigated the effects of molecular weight and amount of medium-chain-length poly-3-hydroxyalkanoates (mcl-PHA) on the formation of polymeric nanoparticle via phase inversion emulsification. Inversion from water-in-oil (W/O) to oil-in-water (O/W) emulsion through stepwise addition of water was affected by molecular weight and amount of incorporated mcl-PHA in the oil phase. The phase inversion mechanism depends upon molecular weight and amount of the incorporated mcl-PHA. It is hypothesized that at appropriate molecular weight and amount of mcl-PHA, the inversion occurs through the formation of bi-continuous/lamellar structure, in which the bulk composition of oil gradually decomposed into the desired nano-sized droplets. Otherwise, it will lead to an alternative phase inversion mechanism involving multiple emulsions resulting in larger nanoparticles with wider distribution.