Abstract
Monodisperse, cationic microgels were synthesized by surfactant-free emulsion copolymerization of 2-vinylpyridine and styrene, using the cationic initiator 2,2′-azobis(2-amidinopropane) dihydrochloride. Low levels of divinylbenzene were employed as a cross-linking agent. The particle morphologies and diameters were characterized by a combination of TEM and photon correlation spectroscopy. At styrene contents less than 40% by weight, the particles were spherical with diameters of approximately 200 nm. The diameter decreased with increasing styrene content and the morphology changed from spherical to irregular. The pH-dependent swelling of the microgel particles was studied in constant ionic strength acetate buffers, as a function of styrene content and cross-link density. Particle diameters increased sharply below pH 4.6 due to ionization of the 2-vinylpyridine residues. At higher styrene levels, the transition pH is shifted to lower values and the extent of swelling is reduced. The pH at which swelling occurred was identical for the three cross-linker levels (0.25, 0.50 and 1.5 wt%), but the extent of swelling decreased in this order as expected. The rate of swelling of the particles was investigated by stopped-flow spectrophotometry; as microgels swell the turbidity of the dispersions decreases and this was followed as a function of time. Higher styrene contents not only reduce the extent of swelling, but also the rate at which maximum swelling is reached, whereas the level of cross-linker employed in this study has no effect on the rate of swelling.
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References
Peppas NA (1991) J Bioactive Compat Polym 6:241–246
Quadrat O (1990) Chemicke Listy 84:496–504
Quadrat O, Snuparek (1990) J Progr Org Coatings 18:207–228
Sawai T, Shinohara H, Ikariyama Y, Aizawa M (1991) J Electronal Chem 297:399–407
Sawai T, Yamazaki S, Ikariyama Y, Aizawa M (1991) Macromolecules 24:2117–2118
Morris GE, Vincent B, Snowden MJ (1997) J Colloid Interface Sci 105:16–22
Kajiwara K, Rossmurphy SB (1992) Nature 355:208–209
Suzuki M, Hirasa O (1993) Adv Polym Sci 110:241–261
Siegel RA, Firestone BA (1988) Macromolecules 21:3254–3259
Rodriguez BE, Wolfe MS, Fryd M (1994) Macromolecules 27:6642–6647
Batich CD, Jun Y, Bucaria C, Elsabee M (1993) Macromolecules 26:4675–4680
Ricka J, Tanaka T (1984) Macromolecules 17:2916–2921
Hirotsu S (1993) Adv Polym Sci 110:1–26
Snowden MJ, Chowdhry BZ, Vincent B, Morris GE (1996) J Chem Soc Farad Trans 92:5013–5016
Flory PJ (1953) Principles of Polymer Chemistry. Cornell University Press, London
Tanaka T (1978) Phys Rev Lett 40:820
Nicoli D, Young C, Tanaka T, Pollak A, Whiteside G (1983) Macromolecules 16:887–890
Philippova OE, Sitnikova NL, Demidovich GB, Khokhlov AR (1996) Macromolecules 29:4642–4645
Tanaka K, Fillmore DJ (1979) J Chem Phys 70:1214–1218
Saunders BR, Vincent B (1996) J Chem Soc Farad Trans 92:3385–3389
Saunders BR, Crowther HM, Vincent B (1997) Macromolecules 30:482
Crowther HM, Vincent B (1997) Colloid Polym Sci, in press
Coutinho FMB, Siquerira MIN, Barbosa CR (1990) Eur Polym J 26:1189
Ma GH, Fukutomi T (1991) J Appl Polym Sci 43:1451–1457
Schild HG (1994) Macromol Rapid Comm 15:851–855
Johnson KL (1994) PhD thesis, University of Bristol, Bristol
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Loxley, A., Vincent, B. Equilibrium and kinetic aspects of the pH-dependent swelling of poly(2-vinylpyridine-co-styrene) microgels. Colloid Polym Sci 275, 1108–1114 (1997). https://doi.org/10.1007/s003960050190
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DOI: https://doi.org/10.1007/s003960050190