Poly (N-isopropylacrylamide) Microgel-Based Electroresponsive Optical Devices and Anisotropic Particles

• Author / Creator

  Wenwen,Xu

• Stimuli-responsive hydrogels, especially those with nanometer/micrometer-scale dimensions, have attracted intense research interest due to their many promising applications. Poly (N-isopropylacrylamide) (pNIPAm)-based hydrogel particles (nanogels and microgels) have been by far the most widely studied responsive materials, and their use in electroresponsive optical devices and as asymmetrically-modified particles are the focus of this dissertation. According to the different focuses of the projects, this dissertation is divided into three parts. Chapter 3, 4 and 5 focus on investigating pNIPAm microgel-based electroresponsive devices and their behavior. In Chapter 3, we demonstrate that electrical potential applied to a microgel coated electrode can induce localized solution pH changes that can be used to trigger a response from the microgel layer, and lead to the triggered release of small molecules. In Chapter 4, we show that poly (N-isopropylacrylamide-co-acrylic acid) (pNIPAm-co-AAc) microgels can be sandwiched between two Au layers to generate etalon devices discovered by our group. Etalons are optical devices which can present tunable color in response to different stimuli due to the light constructive/destructive interferences. The etalon was connected to a power supply and used as a working electrode, which yielded a shift in the optical properties of the devices in response to electrically-induced pH change. In Chapter 5, an external potential was directly applied to the two Au layers of the etalon device, which could interact with the charged microgel monolayer to make the microgel layer compress or elongate. Chapters 6 and 7 describe the generation of asymmetrically-modified pNIPAm-based microgels. Chapter 6 shows that asymmetric microgels could be synthesized through a self-assembly process to selectively coat one pole or both sides (poles) of microgels with Au nanoparticles. Chapter 7 describes that such asymmetric structures can also be obtained by selectively modifying only one side of the microgels with thiol groups. The last part of the thesis (Appendix A and B) describes a method to form hydrogel particles with complex patterns and the generation of dissolvable supramolecular hydrogel-based wound dressings (my project conducted at Tsinghua University in China), respectively.

• Subjects / Keywords

  • Janus particles
  • Electroresponsive Optical Devices
  • Poly (N-isopropylacrylamide) Microgel

• Graduation date

  Fall 2017

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R38W38G5F

• 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.