ISSN:
1435-1536
Keywords:
Key words Emulsion polymerization
;
styrene
;
N-isopropylacrylamide
;
cationic monomer
;
batch and shot process
;
particle size and morphology
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Cationic hydrophilic copolymer latexes were synthesized at 70 °C either by batch or two-step emulsifier-free emulsion poly-merization of styrene (St), N-iso-propylacrylamide (NIPAM), and aminoethylmethacrylate hydro-chloride (AEM) using 2,2′-azobis (2-amidinopropane) dihydrochloride as initiator. At first, batch polymerization kinetics were followed by gas chromatography (GC), revealing that NIPAM rapidly homopolymerized, before the polymerization of styrene had started. Particle size analysis by quasi-elastic light scattering (QELS) and transmission electron microscopy (TEM) showed that monodispersed particles were obtained with the formation of a poly[NIPAM] rich shell. Adding a small amount of the cationic monomer caused a strong decrease of the particle size without affecting the size monodispersity. When a shot process was used, a narrow particle size distribution was maintained, provided that the monomer addition was performed at a relatively high conversion of the first batch step. The poly[NIPAM] rich shell layer was larger with the shot process, but increasing the amino-containing monomer in the recipe resulted in a dramatic decrease of the thickness. Combination of transmission, scanning and atomic force microscopy techniques showed that these hydrophilic particles exhibited odd-shaped structures, the unevenness being dependent upon the performed process. Kinetic data and particle morphology information were inferred for discussion of the polymerization mechanism of this system.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s003960050232
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