Competition between dewetting and cross-linking in poly(N-vinylpyrrolidone)/polystyrene bilayer films

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dc.contributor.authorTelford, AMen_AU
dc.contributor.authorThickett, SCen_AU
dc.contributor.authorJames, Men_AU
dc.contributor.authorNeto, Cen_AU
dc.date.accessioned2012-04-12T00:14:03Zen_AU
dc.date.available2012-04-12T00:14:03Zen_AU
dc.date.issued2011-12-06en_AU
dc.date.statistics2012-04-12en_AU
dc.description.abstractWe investigated the dewetting of metastable poly(N-vinylpyrrolidone) (PNVP) thin films (45 nm) on top of polystyrene (PS) thin films (58 nm) as a function of annealing temperature and molecular weight of PS (96 and 6850 kg/mol). We focused on the competition between dewetting, occurring as a result of unfavorable intermolecular interactions at the PNVP/PS interface, and spontaneous cross-linking of PNVP, occurring during thermal annealing, as we recently reported (Telford, A. M.; James, M.; Meagher, L.; Neto, C. ACS Appl. Mater. Interfaces2010, 2, 2399?2408). Using optical microscopy, we studied how the dewetting morphology and dynamics at different temperatures depended on the relative viscosity of the top PNVP film, which increased with cross-linking time, and of the bottom PS film. In the PNVP/PS96K system, cross-linking dominated over dewetting at temperatures below 180 °C, reducing drastically nucleated hole density and their maximum size, while above 180 °C the two processes reversed, with complete dewetting occurring at 200 °C. On the other hand, the PNVP/PS6850K system never achieved advanced dewetting stages as the dewetting was slower than cross-linking in the investigated temperature range. In both systems, dewetting of the PNVP films could be avoided altogether by thermally annealing the bilayers at temperatures where cross-linking dominated. The cross-linking was characterized quantitatively using neutron reflectometry, which indicated shrinkage and densification of the PNVP film, and qualitatively through selective removal of the bottom PS film. A simple model accounting for progressive cross-linking during the dewetting process predicted well the observed hole growth profiles and produced estimates of the PNVP cross-linking rate coefficients and of the activation energy of the process, in good agreement with literature values for similar systems.© 2011, American Chemical Societyen_AU
dc.identifier.citationTelford, A.M., Thickett, S.C., James, M., Neto, C., (2011). Competition between dewetting and cross-linking in poly(N-vinylpyrrolidone)/polystyrene bilayer films. Langmuir, 27(23), 14207-14217. doi:10.1021/la2029577en_AU
dc.identifier.govdoc3941en_AU
dc.identifier.issn0743-7463en_AU
dc.identifier.issue23en_AU
dc.identifier.journaltitleLangmuiren_AU
dc.identifier.pagination14207-14217en_AU
dc.identifier.urihttp;//dx.doi.org/10.1021/la2029577en_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/4118en_AU
dc.identifier.volume27en_AU
dc.language.isoenen_AU
dc.publisherAmerican Chemical Societyen_AU
dc.subjectPolystyreneen_AU
dc.subjectThin filmsen_AU
dc.subjectMolecular weighten_AU
dc.subjectCopolymersen_AU
dc.subjectRupturesen_AU
dc.subjectDynamicsen_AU
dc.titleCompetition between dewetting and cross-linking in poly(N-vinylpyrrolidone)/polystyrene bilayer filmsen_AU
dc.typeJournal Articleen_AU
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