Preparation and dispersibility of poly(L‐lactide)‐grafted silica nanoparticle

To improve dispersibility of silica nanoparticle in organic solvents, the grafting of poly(L ‐lactide) (PLLA) onto silica nanoparticle surface by ring‐opening polymerization of L‐lactide (LA) was investigated in the presence of an amidine base catalyst. The ring‐opening polymerization of LA successfully initiated in the presence of silica having amino groups (silica‐NH₂) and an amidine base catalyst to give PLLA‐grafted silica, but not in the presence of untreated silica (silica‐OH). In the absence of the amidine base catalyst no ring‐opening polymerization of LA even in the presence of silica‐NH₂ and no grafting of PLLA onto silica were observed. It became apparent that the amidine base catalyst acts as an effective catalyst for the ring‐opening graft polymerization of LA from the surface of silica‐NH₂. In addition, it was found that the percentage of PLLA grafting onto silica could be controlled according to the reaction conditions. The average particle size of PLLA‐grafted silica was smaller than that of silica‐NH₂. Therefore, it was considered that the aggregation structure of silica nanoparticles was considerably destroyed by grafting of PLLA onto the surface. The PLLA‐grafted silica gave a stable dispersion in polar solvents, which are good solvents for PLLA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012