Poly n-butyl cyanoacrylate nanoparticles: a mechanistic study of polymerisation and particle formation.

Poly n-butyl cyanoacrylate has been used in the synthesis of nanoparticles by dispersion polymerisation in aqueous media. Following establishment of a thermometric procedure for assessment of monomer reactivity, the relationships between monomer-polymer conversion reactions and particle development at various pH values was investigated. Particle size was measured during the synthesis process using a laser diffraction technique and final particle character was assessed by scanning electron microscopy. Optimum conditions for particle production were a dispersion medium of pH 2.5 at a temperature of 65 degrees C, with dextran 70 used as a steric stabiliser. In the presence of dextran, following a period of equilibration, colloidally stable particles form, but in the absence of dextran particles are colloidally unstable and rapidly coalesce. Measurement of molecular weight changes through the synthesis process show an upward shift consistent with the initial formation of oligomers, which then further polymerise through a re-initiation re-polymerisation process until an equilibrium molecular weight is reached.