Concentration dependent effects of urea binding to poly(N-isopropylacrylamide) brushes: a combined experimental and numerical study

dc.contributor.authorMicciulla, Samantha
dc.contributor.authorMichalowsky, Julian
dc.contributor.authorSchroer, Martin A.
dc.contributor.authorHolm, Christian
dc.contributor.authorKlitzing, Regine von
dc.contributor.authorSmiatek, Jens
dc.date.accessioned2017-10-24T06:17:20Z
dc.date.available2017-10-24T06:17:20Z
dc.date.issued2016
dc.description.abstractThe binding effects of osmolytes on the conformational behavior of grafted polymers are studied in this work. In particular, we focus on the interactions between urea and poly(N-isopropylacrylamide) (PNIPAM) brushes by monitoring the ellipsometric brush thickness for varying urea concentrations over a broad temperature range. The interpretation of the obtained data is supported by atomistic molecular dynamics simulations, which provide detailed insights into the experimentally observed concentration-dependent effects on PNIPAM-urea interaction. In particular, in the low concentration regime (c(u) <= 0.5 mol L-1) a preferential exclusion of urea from PNIPAM chains is observed, while in the high concentration regime (2 <= c(u) <= 7 mol L-1) a preferential binding of the osmolyte to the polymer surface is found. In both regimes, the volume phase transition temperature (T-tr) decreases with increasing urea concentration. This phenomenon derives from two different effects depending on urea concentration: (i) for c(u) <= 0.5 mol L-1, the decrease of T-tr is explained by a decrease of the chemical potential of bulk water in the surrounding aqueous phase; (ii) for c(u) >= 2 mol L-1, the lower T-tr is explained by the favorable replacement of water molecules by urea, which can be regarded as a cross-linker between adjacent PNIPAM chains. Significant effects of the concentration-dependent urea binding on the brush conformation are noticed: at c(u) <= 0.5 mol L-1, although urea is loosely embedded between the hydrated polymer chains, it enhances the brush swelling by excluded volume effects. Beyond 0.5 mol L-1, the stronger interaction between PNIPAM and urea reduces the chain hydration, which in combination with cross-linking of monomer units induces the shrinkage of the polymer brush.en
dc.description.sponsorshipDFG, EXC 310, Simulationstechniken
dc.description.sponsorshipDFG, SFB 716, Dynamische Simulation von Systemen mit großen Teilchenzahlenen
dc.description.sponsorshipDFG, GRK 1524, Self-Assembled Soft-Matter Nanostructures at Interfacesen
dc.identifier.eissn1463-9084
dc.identifier.issn1463-9076
dc.identifier.pmid26817960
dc.identifier.urihttps://depositonce.tu-berlin.de//handle/11303/6883
dc.identifier.urihttp://dx.doi.org/10.14279/depositonce-6222
dc.language.isoen
dc.rights.urihttps://creativecommons.org/licenses/by-nc/3.0/
dc.subject.ddc540 Chemie und zugeordnete Wissenschaftende
dc.titleConcentration dependent effects of urea binding to poly(N-isopropylacrylamide) brushes: a combined experimental and numerical studyen
dc.typeArticleen
dc.type.versionpublishedVersionen
dcterms.bibliographicCitation.doi10.1039/c5cp07544k
dcterms.bibliographicCitation.issue7
dcterms.bibliographicCitation.journaltitlePhysical chemistry, chemical physicsen
dcterms.bibliographicCitation.originalpublishernameRoyal Society of Chemistryde
dcterms.bibliographicCitation.originalpublisherplaceCambridgede
dcterms.bibliographicCitation.pageend5335
dcterms.bibliographicCitation.pagestart5324
dcterms.bibliographicCitation.volume18
tub.accessrights.dnbfree
tub.affiliationFak. 2 Mathematik und Naturwissenschaften>Inst. Chemiede
tub.affiliation.facultyFak. 2 Mathematik und Naturwissenschaftende
tub.affiliation.instituteInst. Chemiede
tub.publisher.universityorinstitutionTechnische Universität Berlin
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