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Tethered Poly(2-isopropyl-2-oxazoline) Chains: Temperature Effects on Layer Structure and Interactions Probed by AFM Experiments and Modeling
KTH, Skolan för kemivetenskap (CHE), Kemi.
KTH, Skolan för kemivetenskap (CHE), Kemi.
KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi. SP Technical Research Institute of Sweden, Sweden .ORCID-id: 0000-0002-2288-819X
Vise andre og tillknytning
2015 (engelsk)Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, nr 10, s. 3039-3048Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Thermoresponsive polymer layers on silica surfaces have been obtained by utilizing electrostatically driven adsorption of a cationic-nonionic diblock copolymer. The cationic block provides strong anchoring to the surface for the nonionic block of poly(2-isopropyl-2-oxazoline), referred to as PIPOZ. The PIPOZ chain interacts favorably with water at low temperatures, but above 46 degrees C aqueous solutions of PIPOZ phase separate as water becomes a poor solvent for the polymer. We explore how a change in solvent condition affects interactions between such adsorbed layers and report temperature effects on both normal forces and friction forces. To gain further insight, we utilize self-consistent lattice mean-field theory to follow how changes in temperature affect the polymer segment density distributions and to calculate surface force curves. We find that with worsening of the solvent condition an attraction develops between the adsorbed PIPOZ layers, and this observation is in good agreement with predictions of the mean-field theory. The modeling also demonstrates that the segment density profile and the degree of chain interpenetration under a given load between two PIPOZ-coated surfaces rise significantly with increasing temperature.

sted, utgiver, år, opplag, sider
2015. Vol. 31, nr 10, s. 3039-3048
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-165219DOI: 10.1021/la504653wISI: 000351327300013PubMedID: 25686020Scopus ID: 2-s2.0-84925004133OAI: oai:DiVA.org:kth-165219DiVA, id: diva2:810152
Merknad

QC 20150506

Tilgjengelig fra: 2015-05-06 Laget: 2015-04-24 Sist oppdatert: 2017-12-04bibliografisk kontrollert
Inngår i avhandling
1. Polymers in Aqueous Lubrication
Åpne denne publikasjonen i ny fane eller vindu >>Polymers in Aqueous Lubrication
2017 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

The main objective of this thesis work was to gain understanding of the layer properties and polymer structures that were able to aid lubrication in aqueous media. To this end, three types of polyelectrolytes: a diblock copolymer, a train-of-brushes and two brush-with-anchor mucins have been utilized. Their lubrication ability in the boundary lubrication regime has been examined by Atomic Force Microscopy with colloidal probe.

The interfacial behavior of the thermoresponsive diblock copolymer, PIPOZ60-b-PAMPTAM17,on silica was studied in the temperature interval 25-50 ˚C. The main finding is that adsorption hysteresis, due to the presence of trapped states, is important when the adsorbed layers are in contact with a dilute polymer solution. The importance of trapped states was also demonstrated in the measured friction forces, where significantly lower friction forces, at a given temperature, were encountered on cooling than on the preceding heating stage, which was attributed to increased adsorbed amount. On the heating stage the friction force decreased with increasing temperature despite the worsening of the solvent condition, and the opposite trend was observed when using pre-adsorbed layers (constant adsorbed amount) as a consequence of increased segment-segment attraction.

The second part of the studies was devoted to the interfacial properties of mucins on PMMA. The strong affinity provided by the anchoring group of C-PSLex and C-P55 together with their more extended layer structure contribute to the superior lubrication of PMMA compared to BSM up to pressures of 8-9 MPa. This is a result of minor bridging and lateral motion of molecules along the surface during shearing. We further studied the influence of glycosylation on interfacial properties of mucin by utilizing the highly purified mucins, C-P55 and C-PSLex. Our data suggest that the longer and more branched carbohydrate side chains on C-PSLex provide lower interpenetration and better hydration lubrication at low loads compared to the shorter carbohydrate chains on C-P55. However, the longer carbohydrates appear to counteract disentanglement less efficiently, giving rise to a higher friction force at high loads.

sted, utgiver, år, opplag, sider
Stockholm: KTH Royal Institute of Technology, 2017. s. 66
Serie
TRITA-CHE-Report, ISSN 1654-1081 ; 2017:15
Emneord
Lubrication, boundary lubrication, friction, surface forces, adsorption, adsorption hysteresis, non-equilibrium state, diblock copolymer, polyelectrolyte, thermoresponsive, mucin, QCM-D, ellipsometry, AFM
HSV kategori
Forskningsprogram
Kemi
Identifikatorer
urn:nbn:se:kth:diva-204931 (URN)978-91-7729-305-7 (ISBN)
Disputas
2017-03-31, Kollegiesalen, Brinellvägen 8, KTH-campus, Stockholm, 10:00 (engelsk)
Opponent
Veileder
Merknad

QC 20170407

Tilgjengelig fra: 2017-04-07 Laget: 2017-04-04 Sist oppdatert: 2017-04-07bibliografisk kontrollert

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