Narrow-disperse poly (styrene-co-n-butyl acrylate) (P (St-co-nBA) ) microspheres were prepared by dispersion copolymerization in a mixture medium of ethanol with water initiated by 2

2′-azobisisobutyronitrile (AIBN) using poly (N-vinylpyrrolidone) (PVP) as a steric stabilizer.Products were characterized by 1H nuclear magnetic resonance (1H-NMR)

differential scanning calorimetry (DSC)

Fourier transfer infrared spectroscopy (FTIR)

scanning electron microscopy (SEM) and laser particle size analysis (LS) .The influences of comonomer ratio of nBA to St (nBA/St)

polymerization temperature

stabilizer content

media polarity and initiator concentration on particle size

size distribution and monomer conversion were examined.Results showed that with increasing molar ratio nBA/St

the particle size increased

but the size distribution broadened

and the monomer conversion decreased slightly

when the ratio nBA/St exceeded 20/80 it decreased rapidly.As the polymerization temperature increased from 60℃ to 75℃

the monomer conversion and the particle size all increased

but the size distribution broadened.When the temperature rised to 80℃ the particles had a tendency of merging with each other

at the same time the monomer conversion rate decreased.The content of stabilizer had no obvious effect on the monomer conversion rate

but the average size of particles decreased and the size distribution of particles narrowed with increasing the stabilizer content.The particle size and polydispersity initially decreased with the increase of EtOH/H2O ratio

passed through a minimum

and then increased.When EtOH/H2O mass ratio was 80/20 ～ 90/10

the size distribution of particles was narrow.With the increasing of initiator concentration

the monomer conversion rate and the particle size increased

while the size distribution broadened.At a well-controlled condition

the narrow-disperse particles in the size range of 0.7 ～ 2 μm were achieved.The SEM images indicated the copolymer particles were smooth on their spherical surface.The1H-NMR and FTIR spectra confirmed the polymerization between St and nBA.DSC experiments showed the glass transition temperature (Tg) of the copolymers in the range of 56.7 ～ 107.1℃.The copolymer’s composition and it’s Tg could be controlled by the ratio of the comonomers.