title: Study viscoelasticity of ultrathin poly(oligo(ethylene glycol) methacrylate) brushes by a quartz crystal microbalance with dissipation.
abstract: Ultrathin polymer brushes play important roles in natural and artificial systems. To better understand and utilize their unique behaviors, characterization is a fundamental, but not trivial, task. In this paper, we demonstrated that the quartz crystal microbalance with dissipation (QCM-D) could be applied to study ultrathin poly(oligo(ethylene glycol) methacrylate) brushes. First, we identified four linear relations between dissipation/frequency changes and thickness changes, which were measured by QCM-D and ellipsometry, respectively. Next, we derived a set of equations starting from the Voigt model to further extract viscoelasticity of poly(OEGMA) brushes (<or=30 nm) under high-frequency vibration in contact with water. The viscosity was approximately 10(-3) N s m(-2) and the elasticity was approximately 10(5) N m(-2). Both were frequency dependent. Also discussed were other quantities such as the density (both the dry and wet film) and the working range of linear relations. These equations and quantitative information are important in advancing our understanding of ultrathin polymer brushes, which consequently promote our ability in designing functional surface coatings (i.e., in biosensor applications) and studying related interfacial phenomena.
authors.affiliation: Department of Biomedical Engineering, College of Engineering, Peking University, Beijing 100871, The People's Republic of China.
authors.forename: Long
authors.initials: L
authors.lastname: Fu
authors.forename: Xinan
authors.initials: X
authors.lastname: Chen
authors.forename: Jianan
authors.initials: J
authors.lastname: He
authors.forename: Chunyang
authors.initials: C
authors.lastname: Xiong
authors.forename: Hongwei
authors.initials: H
authors.lastname: Ma
mesh_terms: D002627:Chemistry, Physical / Q000379:methods; D003460:Crystallization; D004548:Elasticity; D004867:Equipment Design; D007700:Kinetics; D008689:Methacrylates / Q000737:chemistry*; D015233:Models, Statistical; D011108:Polymers / Q000737:chemistry; D011791:Quartz / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013499:Surface Properties; D013816:Thermodynamics; D014783:Viscosity; D014867:Water / Q000737:chemistry
chemical_list: D008689:Methacrylates; D011108:Polymers; D013438:Sulfhydryl Compounds; D014867:Water; D011791:Quartz; C004919:ethylene dimethacrylate