Interfacial Polycondensation Synthesis of Optically Sensitive Polyurea Microcapsule

TMPTA prepolymer resin and photoinitiators of ITX/TPO had been encapsulated in core-shell structured microcapsules as optical responding ingredients based on interfacial polycondensation method, and polyurea structured microcapsule shell had been formed on the sheared O/W interface. The synthesized microcapsule had regular core-shell structure with the diameter of about 0.455 mu m and shell thickness of about 40 nm. UV-visible absorption spectra indicated that the encapsulated ITX and TPO photoinitiators could efficiently absorb UV irradiation. Under exposure, the C=C bonds absorbance of the microencapsulated TMPTA decreased rapidly and then nearly unchanged during further exposure after 30 s. This implied that the optical response was achieved by C=C bond cleavage of TMPTA monomer initiated by the photoinitiator radicals, to form network polymers in microcapsules. The relative crosslinking rate was about 50%. Due to core polymer formation, the thermal phase change temperature of exposed microcapsules was narrowed and ranged from 105 to 205 degrees C, compared with that from 125 to 260 degrees C of unexposed microcapsules. Furthermore, the image density decrease at longer irradiation time had also verified the optical responding function of the synthesized microcapsules in macroscopic viewpoint.