Adsorption of a Nonionic Symmetric Triblock Copolymer on Surfaces with Different Hydrophobicity

Publication year: 2010
Authors: Xiaomeng Liu†, Dong Wu‡, Salomon Turgman-Cohen§, Jan Genzer§, Thomas W. Theyson∥ and Orlando J. Rojas*†⊥∥
Affiliations:
Department of Forest Biomaterials
§ Department of Chemical and Biomolecular Engineering
Department of Textile Engineering, Chemistry, and Science
North Carolina State University, Raleigh, Raleigh, North Carolina 27695
Department of Chemistry, Duke University, Durham, North Carolina 27708
Faculty of Chemistry and Materials Sciences, Department of Forest Products Technology, Aalto University, P.O. Box 16300, 00076, Aalto, Finland
Published in: Langmuir 2010, 26(12), 9565–9574
doi: 10.1021/la100156a

This study investigates the adsorption of a symmetric triblock nonionic polymer comprising ethylene oxide (EO) and propylene oxide (PO) blocks (Pluronic P-105, EO37PO56EO37) on a range of substrates including hydrophobic, i.e., polypropylene (PP), poly(ethylene terephthalate) (PET), nylon, and graphite, and hydrophilic, i.e., cellulose and silica. The adsorption process and the structure of the hydrated adsorbed layers are followed by quartz crystal microgravimetry (QCM), surface plasmon resonance (SPR), and atomic force microscopy. The unhydrated surfaces are characterized by ellipsometry and contact angle techniques. The adsorption kinetics and the extent of adsorption are determined by monitoring the changes in resonance frequency and refractive index of sensors coated with ultrathin films of the various substrates. Langmuirian-type adsorption kinetics is observed in all cases studied. The amount of adsorbed Pluronic on hydrophobic polymer surfaces (PP, PET, and nylon) exceeds that on the hydrophilic cellulose. The hydrophobic (graphite) mineral surface adsorbs relatively low polymer mass, typical of a monolayer, while micellar structures are observed on the hydrophilic silica surface. The amount of water coupled to the adsorbed polymer layers is quantified by combining data from QCM, and SPR are found to increase with increasing polarity of the substrate. On the basis of contact angle data, the nonhydrated adsorbed structures produce modest increases in hydrophilicity of all the substrates investigated. Overall, insights are provided into the structure and stability of both hydrated and nonhydrated adsorbed triblock copolymer.


MP-SPR keywords: AFM, cellulose, contact angle, ellipsometry, ethylene oxide (EO), graphite, hydration, hydrophilic, hydrophobic, nylon, poly(ethylene terephthalate) (PET), polypropylene (PP), propylene oxide (PO), QCM, silica, symmetric triblock nonionic polymer