S. Omi et al., Study of particle growth by seed emulsion polymerization with counter-charged monomer and initiator system, COLL SURF A, 153(1-3), 1999, pp. 165-172
Citations number
4
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
A two-step polymerization process was proposed to obtain composite latices
with an average size ranging from submicrons to 1 mu m. Negatively charged
PMMA Seed latex particles were prepared by using anionic sodium lauryl sulf
ate (SLS), and ammonium persulfate (APS). After the removal of unreacted mo
nomer and initiator by dialysis, seeded emulsion polymerization was carried
out by swelling the PMMA seeds with monomers consisting of hydrophilic dim
ethyl aminoethyl methacrylate (DMAEMA) and hydrophobic styrene. A cationic
initiator, 2,2'azobis(2-amidinopropane).2HCl (V-50), was used. A small amou
nt of non-ionic polyoxyethylene (23) nonylphenyl ether (POE23) solution was
added. The weight percent of DMAEMA in co-monomer, weight ratio of monomer
to polymer (M/P), and pH of the latex were changed to obtain controlled co
agulation and further growth of the seed particles. Incorporation of DMAEMA
was investigated by TEM observation of the particles stained with iodometh
ane, and by measuring the rate of quarternization of DMAEMA when iodomethan
e gradually diffused into the particles from the continuous phase. A maximu
m growth of the particles, from the initial average diameter of 0.21 mu m t
o a final 0.56 mu m, was attained when pH was set at 10.0 with a lower POE2
3 concentration. The final particles were stable aggregates of the several
seed particles with DMAEMA incorporated between the coagulated seeds as wel
l as deposited on the surface of the particles. The nucleation of DMAEMA-ri
ch secondary particles was enhanced when the pH was set at 9.0. Decreasing
the amount of POE23 normally promoted the growth unless the stability of th
e latex was affected. (C) 1999 Elsevier Science B.V. All rights reserved.