dc.description.abstract | The size of monodisperse submicrospheres has been increased by using two-step method. Low or regular molecular weight of monodisperse seeds were prepared at the first step. Monomers were added in the seed latex and polymerized at the second step. On the other hands, in order to further shorten the reaction time, monomers were added when the seed conversion was 80% to 90%. The effect of monomer content and monomer species at two steps were also discussed.
The results indicated that low molecular weight and monodisperse PSt seed with diameter 469nm and 473nm were prepared by adding chain transfer agent at seed conversion 55% and 95%, respectively. The monodisperse PSt submicrospheres with 825 nm diameter were obtained when 0.7% to 2% of PVA were added at the second step.
The size of regular molecular weight of PSt and PMMA monodisperse seeds were 240nm and 316 nm, respectively. Using above seeds and monomers at the second step, the size of PSt and PMMA monodisperse submicrospheres became
375nm and 462nm, respectively. In addition, the reaction temperature was closed to Tg of seeds and chain transfer agent and stabilizer were not added.
To further reduce the total reaction time, monomers were added when the conversion of PSt or PMMA seed was 80% to 90%. The particle diameters of monodisperse submicrospheres were increased with increasing monomer amount at the first step (10g~25g) and with increasing monomers added at the second step (1~9) times, based on the first step monomer). The sizes of PSt, PMMA, and PMMA/PSt monodisperse submicrospheres were 420 nm, 560 nm and 582 nm, respectively. And the sizes of above seeds were 208 nm, 275 nm, and 402 nm respectively. In addition,
the monodisperse PSt submicrosphere with solvent resistant was obtained when more than 6 times of monomers and 20 wt.% of crosslinkers, EGDMA, were added at the second step. The PSt monodisperse submicrospheres with different hydrophilic functional group were also obtained by adding hydrophilic monomer at the third step. | en_US |