Investigation of morphology and volume phase transition of supramacromolecular microgels by NMR spectroscopy and quartz crystal microbalance

Microgels have a wide range of applications, from catalysis to biomedical applications such as drug delivery in dispersion, or as surface-attached materials to improve the biocompatibility of implants or as anti-fouling coatings. The first aim of this work is to understand the morphology of the supramacromolecular, tannic acid (TA) crosslinked microgels using two-dimensional H-1 NMR spectroscopy, and relaxometry. The second aim is to study the volume phase transition (VPT) of TA-crosslinked microgels with different crosslinker densities in dispersion using NMR. In this context,H- 1 high-resolution NMR spectroscopy is used in combination with the two-state model and the Boltzmann sigmoidal function to determine thermodynamic quantities of the VPT, such as temperature (T-t), width of transition (Delta T-t), and change in entropy (Delta S). Third, surface-deposited microgels are characterized in terms of their VPT using a quartz crystal microbalance (QCM-D) to study the properties of these microgels for applications where they are used as coatings. Finally, the T-t of microgels supramolecular crosslinked with TA are compared with microgels covalently crosslinked with N,N'-methylenebisacrylamide (BIS) in dispersion, using NMR, and deposited on a surface, using QCM-D. For this purpose temperature-responsive poly(N-vinylcaprolactam) and poly(N-isopropylacrylamide) microgels crosslinked with the plant-derived polyphenol TA or BIS are used.