In view of the fact that the current polymer microsphere profile control agent has a single variety and high production cost

cross-linked poly (styrene-acrylamide) microspheres with the mean diameters lower than 1

µ

m

were developed by emulsion polymerization in the study. Styrene(St)

acrylamide (AAm)

and N

N′-methylenebisacrylamide(MBA)

were selected as the monomers. The factors which influence the mean diameter of the microspheres were investigated by particle size analysis

transmission electron microscopy(TEM)

and scanning electron microscopy(SEM). The SEM and TEM results show that the mass ratio of AAm to St and MBA addition is the key to prepare well-defined microspheres

the mass ratio of AAm to St must ≤3 : 17 and the MBA concentration must ≤ 18.5g/L. The results of particle size analysis show that the mass ratio of AAm to St and MBA concentration influence the particle size of the microspheres significantly; the mean diameter of the microspheres increased with the increase of the mass ratio of AAm to St. Increasing MBA concentration

the mean diameter of the microspheres increased firstly

and then decreased; The influence of AES concentration

APS addition and temperature on the mean diameter of the microspheres is insignificant. The results show that the optimum conditions for preparing well-defined microspheres are the mass ratio of AAm to St≤3 : 17

MBA concentration ≤6.25g/L

AES concentration ≤7g/L

APS concentration 1.25g/L

and temperature 70℃. Under the optimum conditions

the microspheres with mean diameters ranging from 58.5 to 559.8nm can be prepared.