title: Temperature-dependent competition between adsorption and aggregation of a cellulose ether--simultaneous use of optical and acoustical techniques for investigating surface properties.
abstract: Adsorption of the temperature-responsive polymer hydroxypropylmethylcellulose (HPMC) from an aqueous solution onto hydrophobized silica was followed well above the bulk instability temperature (T(2)) in temperature cycle experiments. Two complementary techniques, QCM-D and ellipsometry, were utilized simultaneously to probe the same substrate immersed in polymer solution. The interfacial processes were correlated with changes in polymer aggregation and viscosity of polymer solutions, as monitored by light scattering and rheological measurements. The simultaneous use of ellipsometry and QCM-D, and the possibility to follow layer properties up to 80 °C, well above the T(2) temperature, are both novel developments. A moderate increase in adsorbed amount with temperature was found below T(2), whereas a significant increase in the adsorbed mass and changes in layer properties were observed around the T(2) temperature where the bulk viscosity increases significantly. Thus, there is a clear correlation between transition temperatures in the adsorbed layer and in bulk solution, and we discuss this in relation to a newly proposed model that considers competition between aggregation and adsorption/deposition. A much larger temperature response above the T(2) temperature was found for adsorbed layers of HPMC than for layers of methyl cellulose. Possible reasons for this are discussed.
authors.affiliation: Department of Chemistry, Surface and Corrosion Science, Royal Institute of Technology, Drottning Kristinas väg 51, SE-100 44 Stockholm, Sweden.
authors.forename: Rasmus
authors.initials: R
authors.lastname: Bodvik
authors.forename: Lubica
authors.initials: L
authors.lastname: Macakova
authors.forename: Leif
authors.initials: L
authors.lastname: Karlson
authors.forename: Esben
authors.initials: E
authors.lastname: Thormann
authors.forename: Per
authors.initials: P
authors.lastname: Claesson
mesh_terms: D000162:Acoustics; D000327:Adsorption; D057927:Hydrophobic and Hydrophilic Interactions; D065347:Hypromellose Derivatives; D007101:Immersion; D008027:Light; D008747:Methylcellulose / Q000031:analogs & derivatives* / Q000737:chemistry; D055620:Optical Phenomena; D011108:Polymers / Q000737:chemistry; D058525:Quartz Crystal Microbalance Techniques; D012212:Rheology; D012542:Scattering, Radiation; D012822:Silicon Dioxide / Q000737:chemistry; D012996:Solutions; D013499:Surface Properties; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D011108:Polymers; D012996:Solutions; D014867:Water; D065347:Hypromellose Derivatives; D012822:Silicon Dioxide; D008747:Methylcellulose