Open AccessInvestigation of conformation transition of poly(N-isopropylacrylamide) by surface stress detection using micro-cantilever
Author(s) -
Kai Li,
Hong Liu,
Qingchuan Zhang,
Yi Hou,
Guangzhao Zhang,
WU Xiao-ping
Publication year - 2006
Publication title -
wuli xuebao
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.199
H-Index - 47
ISSN - 1000-3290
DOI - 10.7498/aps.55.4111
Subject(s) - cantilever , materials science , poly(n isopropylacrylamide) , monolayer , deflection (physics) , aqueous solution , surface stress , nanotechnology , composite material , polymer , chemistry , optics , copolymer , surface energy , physics
A new method based on micro-cantilever sensors was presented and used to investigate conformation transition of macromolecules. Poly(N-isopropylacrylamide)(PNIPAM)were grafted onto one surface of a micro-cantilever by self assemble monolayer method. Then the micro-cantilever was immersed into distilled water in which the temperature can be adjusted in the range of 20—40℃. The deflection of the micro-cantilever induced by conformation transition of PNIPAM chains was measured using optical lever technique. The results show that the micro-cantilever deflects upon heating and opposite deflection occurs upon cooling, which indicates that the surface stress of the micro-cantilever changes when the conformation of PNIPAM changes upon heating and cooling. The surface stress changes continuously over the range of 20—40℃. However, a sharp change appears around the low critical solution temperature (32℃), at which a coil-globule transition occurs in free aqueous solution of PNIPAM. The whole process is irreversible and shows a clear hysteresis, which can be attributed to hydrogen bonding and the possible chain entanglement formed during the collapse process.