This reports on the preparation of polyvinylpyrrolidone(PVP)micro spheres in ethyl acetate by dispersion polymerization with N-vinylpyrrolidone(NVP)as initial monomer

P(NVP-co-VAc)as dispersant

and AIBN as initiator.The influences of monomer concentration

dispersant concentration and initiator concentration on the size of PVP micro spheres as well as the monomer conversion rate were studied.The structure and properties of PVP micro spheres were analyzed.The results show that the prepared PVP micro spheres have a mean diameter of 3～4 μm.As the concentration of NVP increased

the micro sphere size and the molecular weight of the PVP increased and the monomer conversion rate also increased.As the concentration of P(NVP-co-VAc)increased

the size of micro spheres decreased

and the molecular weight of the PVP and the monomer conversion rate increased.As the concentration of AIBN increased

the size of micro spheres and the monomer conversion increased

the molecular weight of the PVP is also increased.The PVP prepared by dispersion polymerization has crystal structure and its molecular weight is low as compared to those prepared by solution polymerization.