DFG-DST Project: Stimuli-Responsive Microgels with Permanent and Dynamic Ionic Crosslinks: Chemical Design and Behavior in Aqueous Solutions

• Applicant: Professor Dr. Andrij Pich
• Subject Area: Preparatory and Physical Chemistry of Polymers ; Polymer Materials
• Term: from 2017 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 323308141

In this project we propose to design a molecular toolbox of zwitterionic building blocks and to elaborate new synthesis protocols to obtain microgels with a controlled distribution and a high loading of zwitterionic groups. For these zwitterionic microgels a comprehensive picture to show the relationship between the molecular structure and the stimuli-responsive behavior in aqueous solutions is going to be developed.We aim to synthesize zwitterionic reactive building blocks with precisely controlled molecular architecture (chemical structure of zwitterionic group) and tunable size (monomers vs. macromonomers). Using different polymerisation approaches we will synthesize temperature-responsive microgels based on N-vinylcaprolactam (VCL), N-vinylpiperidone (VPP) and N-vinylpyrolidone (VPR) with tunable amount and controlled distribution of zwitterionic groups in the microgels (random vs. core-shell). The synthesized microgels will exhibit two unique features: They will have both, an upper critical solution temperature (UCST) (due to the presence of zwitterionic groups in polymer chains) and a lower critical solution temperature (LCST) (due to the presence of lactam groups in polymer chains). They will also have two types of crosslinks, ionic dynamic crosslinks generated by zwitterionic groups and covalent crosslinks generated by a crosslinker.To understand the properties of the synthesized zwitterionic microgels we will perform their characterization using different analytical methods to understand the internal structure and behavior in aquous solutions. Specifically, we will focus on following questions:-Which amount of zwitterionic groups in the microgels is required for the formation of ionic (dynamic) crosslinks?;-How do the structure of the zwitterionic building blocks (monomers vs. macromonomers) and the amphiphilic properties of the polymer chains (size of the lactam rings) influence the formation of ionic (dynamic) crosslinks?; -Can we tune the volume phase transition temperatures (UCST and LCST), swelling degree and colloidal stability of the microgels with high contents of zwitterionic groups?The scientific outcome of this project will be an elaborated synthesis to design a toolbox of temperature-responsive zwitterionic microgels with covalent and ionic (dynamic) crosslinks and an understanding of their behavior in aqueous solutions. Based on this knowledge new application perspectives for such microgels, as candidates for drug delivery vehicles and building blocks for self-healing and protein-repelling coatings, will be generated.

• DFG Programme: Research Grants
• International Connection: India
• Cooperation Partner: Dr. Nikhil K. Singha