Work of adhesion as a dominant factor in formation of composition-gradient thermosensitive gel

Tokuyama Hideaki

Sasaki Masahiro

Sakohara Shuji

Chemical Engineering & Technology

By copolymerizing a thermosensitive primary component, N-isopropylacrylamide (NIPA), and an ionic secondary component, 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) between two substrates of hydrophilic glass and hydrophobic polytetrafluoroethylene (Teflon), a novel composition-gradient copolymer gel, in which the AMPS content decreases gradually towards Teflon, is prepared. The formation of the composition-gradience in NIPA-co-AMPS gels is discussed in terms of the work of adhesion between a solution and a substrate, i.e. the liquid-solid interfacial free energy. The work of adhesion is determined from the Young-Dupré equation on the basis of the contact angle, and the surface tension measured in the system consisting of an aqueous solution containing NIPA or AMPS monomers or polymers and glass or Teflon as the substrate. The values of the work of adhesion of AMPS monomer and polymer on Teflon were lower than those on glass. Thus, AMPS remains relatively stable at the glass interface and unstable at the Teflon interface. This repulsion of AMPS due to the hydrophobicity of the Teflon wall generates the composition-gradience.

Chemical technology [ 570 ]

eng

Wiley-VCH Verlag GmbH

Copyright (c) 2007 John Wiley & Sons, Inc.

[ISSN] 0930-7516

[DOI] 10.1002/ceat.200600249

[NCID] AA10695968

[DOI] http://dx.doi.org/10.1002/ceat.200600249