Unique size-change behavior of photo-crosslinked cinnamic acid derivative nanoparticles during hydrolytic degradation

A unique size change of photo-crosslinkable poly[(3,4-dihydroxycinnamic acid)-co-(4-hydroxycinnamic acid)] nanoparticles was observed during hydrolytic degradation depending on the crosslinking degree. The diameter of uncrosslinked nanoparticles decreased from 850 to 300 nm during hydrolysis, whereas that of 75% crosslinked nanoparticles increased from 700 to 950 nm. The diameter changes of crosslinked nanoparticles during hydrolysis might be induced by swelling of the crosslinked networks depending on the crosslinking degree. Moreover, the diameter of the uncrosslinked nanoparticle recovered by additional UV irradiation during hydrolysis. These results suggested that the diameter of the nanoparticles could be controlled even during hydrolysis by UV irradiation.