title: Stick-slip phenomenon in measurements of dynamic contact angles and surface viscoelasticity of poly(styrene-b-isoprene-b-styrene) triblock copolymers.
abstract: In this paper, a series of poly(styrene-b-isoprene-b-styrene) triblock copolymers (SIS), with different chemical components, was synthesized by anionic polymerization. The relationships between surface structures of these block copolymers and their stick-slip phenomena were investigated. There is a transition from stick-slip to a closely smooth motion for the SIS films with increasing PS content; the patterns almost vanish and the three-phase line appears to move overall smoothly on the film surface. The results show that the observed stick-slip pattern is strongly dependent on surface viscoelasticity. The jumping angle Δθ, which is defined as θ(1) - θ(2) (when a higher limit to θ(1) is obtained, the triple line "jumps" from θ(1) to θ(2) with increases in drop volume), was employed to scale the stick-slip behavior on various SIS film surfaces. Scanning force microscopy/atomic force microscopy (AFM) and sum frequency generation methods were used to investigate the surface structures of the films and the contributions of various possible factors to the observed stick-slip behavior. It was found that there is a linear relationship between jumping angle Δθ and the slope of the approach curve obtained from AFM force measurement. This means that the stick-slip behavior may be attributed mainly to surface viscoelasticity for SIS block copolymers. The measurement of jumping angle Δθ may be a valuable method for studying surface structure relaxation of polymer films.
authors.affiliation: Department of Chemistry, Key Laboratory of Advanced Textile Materials and Manufacturing Technology of the Education Ministry, Zhejiang Sci-Tech University, Hangzhou, China.
authors.forename: Biao
authors.initials: B
authors.lastname: Zuo
authors.forename: Fan Fan
authors.initials: FF
authors.lastname: Zheng
authors.forename: Yu Rong
authors.initials: YR
authors.lastname: Zhao
authors.forename: TianYu
authors.initials: T
authors.lastname: Chen
authors.forename: Zhuo Hua
authors.initials: ZH
authors.lastname: Yan
authors.forename: Huagang
authors.initials: H
authors.lastname: Ni
authors.forename: Xinping
authors.initials: X
authors.lastname: Wang
mesh_terms: D002070:Butadienes / Q000737:chemistry*; D004548:Elasticity; D045782:Hemiterpenes / Q000737:chemistry*; D010420:Pentanes / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D020058:Styrene / Q000737:chemistry*; D013499:Surface Properties; D014783:Viscosity
chemical_list: D002070:Butadienes; D045782:Hemiterpenes; D010420:Pentanes; D011108:Polymers; C005059:isoprene; D020058:Styrene