Mixed initiator approach to the surfactant‐free semicontinuous emulsion polymerization of large MMA/BA particles

Abstract

SYNOPSISThe emulsion polymerization of large monodisperse MMA/BA copolymer particles by surfactant-free means at high solids content is described. A series of sequential seeded growth reactions were used to obtain monodisperse particles with diameters of a t least 3 microns. A combination of an oil-soluble initiator, AIBN, and a water-soluble initiator, ammonium persulfate (AP), was used. The AIBN initiated the bulk of the polymerization and the AP provided the stabilization for the polymer particles through its charged endgroups. The amount of AP initiator to be used in each growth step was calculated empirically using a criterion of a constant ratio of moles of sulfate groups to the polymer particle surface area.

Preparation and Characterization of Macroporous α‐Alumina

“…Spheres with average diameters of 937 Ϯ 26 nm and 1580 Ϯ 55 nm were prepared by surfactant-free semicontinuous emulsion polymerization, using mixed initiators (potassium persulfate and azobisisobutyronitrile). 15 They were centrifuged, the supernatant liquid containing smaller particles was decanted, and the spheres collected at the bottom of the centrifuge tubes were redispersed in deionized water by sonication. This procedure was repeated eight times, and the spheres were allowed to sediment.…”

?Continuous? emulsifier-free emulsion polymerization for the synthesis of monodisperse polymeric latex particles

“…10,13,14 By varying the monomer feed composition in CEFEP, it should be possible to prepare multilayered composite particles rather than with a multistage batch seeding process which is currently used. 13, 14,44,45 Moreover, particles in CEFEP were crosslinked more uniformly than in batch copolymerization, 13 because monomer and crosslinker were fed into the reactor at a constant ratio.…”

Synthesis of large, high‐solid‐content latexes by miniemulsion polymerization

“…The methodology described here31 offers an alternative to conventional methods for obtaining large narrowly distributed particles when the specifications of the PSD broadness are not so stringent. Usually, standard techniques make use of several polymerization steps32 and, in some cases, constrain themselves to rather diluted systems 33, 34. Conventional techniques also make use of successive growth stages in seed polymerization.…”