Materials Science

Colloidal Cores and Shells

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Science  24 May 2002:
Vol. 296, Issue 5572, pp. 1369
DOI: 10.1126/science.296.5572.1369b

A number of techniques have been used to create submicrometer colloidal particles that change size in response to external stimuli. Used in applications ranging from microfluidic valves and drug delivery capsules, the colloids typically are made from cross-linked polymer nanogels that undergo large swelling changes in response to changes in temperature or pH. Polymers based on N-isopropylacrylamide (PNIPAAm) collapse when heated above 35°C, and side chains based on 2-vinylpyridine (P2VP) swell below a pH of 4.8. By grafting P2VP onto a PNIPAAm backbone, Kuckling et al. create a polymer that shows both temperature and pH responses. The PNIPAAm chains were cross-linked to form the core, with the P2VP grafts forming the outer shell, producing two independent means for controlling the size of the nanogels. — MSL

Langmuir 10.1021/la015758q.

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