Sample Name(s): IP-01-15-CPT_1, IP-01-15-CPT_6

Description : Positive PS particles manufactured using surfactant-free emulsion polymerization.

Characteristics:
Diameter:     440 nm
ζ-potential:   +32.3 mV, +34.1 mV

Recipe: 

1. An alumina column stoppered with cotton was used to remove inhibitor from the packaged styrene monomer. The filtered styrene monomer was refrigerated at 4 ℃ until ready to use.
2. 350 mL of deionized water (by weight) was added into a 1000 mL triple-neck round-bottom flask.
3. The round-bottom flask was then submerged into a silicone oil bath placed above a heating plate, where a mechanical stirrer and a condenser were attached to the flask.
4. 35 mL of filtered styrene monomer were pipetted into the round-bottom flask, sealing the system with a rubber stopper.
5. Mechanical stirring was engaged at 330 rpm, and the system was purged with high-purity nitrogen for approximately 30 minutes while the heating plate raised the temperature of the flask to 60 ℃, where it would remain for the duration of the polymerization.
6. 350 mg of 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AIBA) were dissolved in 5 mL of deionized water, and added into the sealed system using a syringe.
7. After 30 minutes, 35 mL of the mixture was removed from the flask using a syringe.
8. The polymerization was allowed to proceed for 18-20 hours, at which point the system was opened and heated to 90 ℃ for 90 minutes to evaporate unreacted monomer, and then allowed to cool all while stirring.
9. The remaining radical initiator was cleaned out with three cycles of repeated centrifugation and resuspension in deionized water.