Role of hydrophobic effect and hydrogen bonding in surface interactions of polymers

  • Author / Creator
    Faghihnejad, Ali
  • Polymers are widely used as coatings, adhesives, biomaterials and many other applications. These successful applications rely on the physical and chemical properties of the polymer molecules and surfaces. One type of important molecular and surface interaction is hydrophobic interaction which is believed to be responsible for many interfacial and colloidal phenomena such as micelle formation, protein folding and is widely used in industrial applications such as mineral floatation. Nevertheless, direct probing of hydrophobic interaction between polymer surfaces has received only limited attention. Using polystyrene (PS) as a model polymer, the surface interactions were measured in different electrolyte solutions by a surface forces apparatus (SFA) coupled with a top-view optical microscope. A long-range attraction was observed between two PS surfaces which was found to be due to the bridging of microscopic and sub-microscopic bubbles on the PS surfaces and depended on the type and concentration of the electrolyte solutions due to ion specificity. The interaction forces in asymmetric system (PS vs. mica) were also studied and long-range repulsion was observed associated with the deformation of bubbles on PS surface. The range of the surface interactions was significantly reduced to <20 nm after degassing the solutions which indicates the important role of dissolved gases on the measured forces. Another important type of intermolecular interaction widely used for the development of new polymers is hydrogen bonding through supramolecular chemistry where the reversible interaction is used for tuning polymer properties. In this work, the surface interactions of poly(butyl acrylate) (PBA) functionalized with a quadruple hydrogen bonding group called UPy were investigated. The adhesion and mechanical properties of PBA-UPy were found to be significantly enhanced by the UPy groups and strongly depend on temperature, relative humidity in air and contact time. The PBA-UPy polymer shows self-healing capability. Interesting surface patterns (e.g. fingers, stripes) were observed associated with the separation of two PBA-UPy films. Our results provide new insights into the fundamental understanding of the molecular interaction mechanisms of polymers containing hydrogen bonding and hydrophobic groups and the development of novel functional materials.

  • Subjects / Keywords
  • Graduation date
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
  • Language
  • Institution
    University of Alberta
  • Degree level
  • Department
    • Department of Chemical and Materials Engineering
  • Specialization
    • Chemical Engineering
  • Supervisor / co-supervisor and their department(s)
    • Zeng, Hongbo (Chemical & Materials Engineering)
  • Examining committee members and their departments
    • Zhang, Hao (Chemical & Materials Engineering)
    • Liu, Yang (Civil & Environmental Engineering)
    • Narain, Ravin (Chemical & Materials Engineering)
    • Song, Hau (Chemical & Petroleum Engineering, University of Calgary)