PNIPAM chain collapse depends on the molecular weight and grafting density

Langmuir : the ACS Journal of Surfaces and Colloids
Kyle N PlunkettDeborah E Leckband

Abstract

This study demonstrates that the thermally induced collapse of end-grafted poly(N-isopropylacrylamide) (PNIPAM) above the lower critical solution temperature (LCST) of 32 degrees C depends on the chain grafting density and molecular weight. The polymer was grafted from the surface of a self-assembled monolayer containing the initiator (BrC(CH3)2COO(CH2)11S)2, using surface-initiated atom transfer radical polymerization. Varying the reaction time and monomer concentration controlled the molecular weight, and diluting the initiator in the monolayer altered the grafting density. Surface force measurements of the polymer films showed that the chain collapse above the LCST decreases with decreasing grafting density and molecular weight. At T > LCST, the advancing water contact angle increases sharply on PNIPAM films of high molecular weight and grafting density, but the change is less pronounced with films of low-molecular-weight chains at lower densities. Below the LCST, the force-distance profiles exhibit nonideal polymer behavior and suggest that the brush architecture comprises dilute outer chains and much denser chains adjacent to the surface.

References

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Citations

Sep 18, 2013·ACS Applied Materials & Interfaces·Qian YuGabriel P López
Jul 19, 2012·Journal of the American Chemical Society·Christopher M Kolodziej, Heather D Maynard
Jun 15, 2011·Langmuir : the ACS Journal of Surfaces and Colloids·Changying XueDeborah E Leckband
May 25, 2011·Langmuir : the ACS Journal of Surfaces and Colloids·Roshan B VasaniNicolas H Voelcker
Jun 16, 2012·PloS One·Kalpana MandalLionel Bureau
Oct 16, 2014·Langmuir : the ACS Journal of Surfaces and Colloids·Gary J DunderdaleAtsushi Hozumi
Oct 3, 2014·Langmuir : the ACS Journal of Surfaces and Colloids·Stephanie ChristauRegine von Klitzing
Jan 7, 2014·Journal of Materials Science. Materials in Medicine·Andrzej DworakMarek Kawecki
Mar 13, 2014·Journal of Pharmaceutical Sciences·Hector Ivan Melendez-OrtizEmilio Bucio
Dec 15, 2015·Langmuir : the ACS Journal of Surfaces and Colloids·Steven James Peter McInnesNicolas H Voelcker
Nov 26, 2015·ACS Applied Materials & Interfaces·Harry C PappasDavid J Keller
Oct 16, 2012·Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy·Serkan DemirciTuncer Caykara
Jan 1, 2013·Materials Science & Engineering. C, Materials for Biological Applications·Serkan Demirci, Tuncer Caykara
Sep 13, 2014·Langmuir : the ACS Journal of Surfaces and Colloids·Ralitsa AleksandrovaJan K Krüger
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Mar 18, 2016·Langmuir : the ACS Journal of Surfaces and Colloids·Siddhartha VarmaDelphine Débarre

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