Seed latex particles of polyvinyl acetate(PVAc) with narrow diameter distribution were first prepared by using ammonium persulfate as initiator

then unswelling and swelling seeded emulsion polymerization of methyl acrylate(MA) onto PVAc initiated by 2

2′-azobisisobutyronitrile(AIBN) were carried out at 60℃ in the absence of emulsifier. In order to investigate particle morphologies of various seeded latexes

a selective staining technique using phosphotungstic acid (PTA) was used under transmission electron microscopy(TEM) observation. Results showed that experimental particle size agree roughly with calculated particle size for all of seeded emulsion polymerizations

but particle mophologies are different. Under unswelling condition

taking into account the high water solublity of MA

its homonucleation in water was significant

and PMA secondary particles were formed and coagulated onto the PVAc particles

so initiation and polymerization loci of MA were both in PVAc seed particle and in water phase

and PMA domains were observed at the surface and inside of seeded latex particles when PVAc/MA weight ratios are 2 and 1. When PVAc/MA weight ratio decrease to 0.5

PMA-PVAc core-shell particle was observed. While under swelling condition

the inner of PVAc domains or core-shell structure were observed

and interpenetrating network structures were formed for different PVAc/MA ratios.