Nano Archive

Probing the morphology and nanoscale mechanics of single poly(N-isopropylacrylamide) microgels across the lower-critical-solution temperature by atomic force microscopy

Tagit, Oya and Tomczak, Nikodem and Vancso, G. Julius (2008) Probing the morphology and nanoscale mechanics of single poly(N-isopropylacrylamide) microgels across the lower-critical-solution temperature by atomic force microscopy. SMALL, 4 (1). pp. 119-126.

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Official URL: http://www3.interscience.wiley.com/journal/1178703...

Abstract

Submicrometer-sized particles of poly (N-isopropylacrylamide) (PNIPAM) are synthesized by surfactant-free radical polymerization. The morphology and nanomechanical properties of individual, isolated PNIPAM microgel particles at the silicon/air and silicon/water interfaces, below and above the PNIPAM volume-phase-transition temperature (VPTT), are probed by atomic force microscopy. In air, and in water below the VPTT, the PNIPAM spheres are flattened and adopt a pancakelike shape. Interestingly, above the VPTT the microgels adopt a more spherical form with increased height and decreased width, which is attributed to reduced interactions of the particles with the substrate. The elastic modulus calculated from force-indentation curves obtained for individual microgel spheres reveals that the stiffness of the particle's surface decreases by two orders of magnitude upon swelling in water. Additionally, the modulus of the PNIPAM spheres in water increases by one order of magnitude when crossing the VPTT from the swollen to the collapsed states, indicating a more compact chain packing at the particle surface.

Item Type:Article
Uncontrolled Keywords:atomic force microscopy; elastic modulus; microgels; nanoindentation
Subjects:Analytical Science > Microscopy and probe methods
Physical Science > Nano objects
Material Science > Nanochemistry
ID Code:2408
Deposited By:Anuj Seth
Deposited On:17 Dec 2008 10:55
Last Modified:20 Jan 2009 10:24

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