Swelling Kinetics for a pH-Induced Latex-to-Microgel Transition

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• 作者：Damien Dupin ; Julien Rosselgong ; Steven P. Armes ; Alexander F. Routh
• 刊名：Langmuir
• 出版年：2007
• 出版时间：March 27, 2007
• 年：2007
• 卷：23
• 期：7
• 页码：4035 - 4041
• 全文大小：169K
• 年卷期：v.23,no.7(March 27, 2007)
• ISSN：1520-5827

文摘

The kinetics of swelling of a series of six near-monodisperse, lightly cross-linked poly(2-vinylpyridine) latexes withmean diameters ranging from 380 to 1010 nm has been investigated by the pH jump method using a commercialstopped-flow instrument. These pH-responsive particles become substantially protonated at around pH 4.1, whichleads to a rapid latex-to-microgel transition within a time scale of tens of milliseconds. The characteristic swellingtime correlates linearly with the mean particle diameter, as predicted by the Tanaka equation. However, faster swellingis observed in the presence of added salt. This is contrary to the theory developed by Tanaka, which assumes thatthe relaxation of the polymer chains is the rate-limiting step. An alternative viewpoint, in which infusion of solventdetermines the characteristic swelling time, satisfactorily explains the experimental observations and collapses mostof the data, except for the largest microgels. This discrepancy is suggested to be due to the inaccurate sizing of thesemicrometer-sized swollen microgels by dynamic light scattering.