Thermodynamic Analysis of Polyethylene Glycol Thiol-ene Click Chemistry and Surface Modification of Bacterial Cellulose

Polyethylene glycol (PEG) has been one of the extensively studied polymers for medical applications. However, the use of PEG can require complicated and low efficiency reactions which can impose limits to potentially useful medical solutions. Click chemistry has recently emerged as a way to avoid these pitfalls by utilizing reactions that are highly efficient and require simple reaction conditions. One such reaction is known as the Michael-addition thiol-ene click reaction (TECC). The combination of PEG with TECC has received some study, but has not been thermodynamically characterized as a click reaction. In this work PEG-TECC reaction kinetics were studied by proton nuclear magnetic resonance (¹H-NMR) and quartz crystal microbalance with dissipation (QCM-D) in order to assess the components ability to form complex final products quickly and with minimal side products. From these kinetic studies, the energy of activation for PEG-TECC was determined. The reaction was concluded to follow the click chemistry philosophy and is viable for future applications. The energy of activation was determined to be 75 kJ/mol. Bacterial cellulose (BC) is a naturally produced polymer and has been shown to have great potential for bone, cartilage, and vascular tissue engineering applications. In order to incorporate PEG-TECC, BC was modified on the surface with acrylate functionalities to provide a Michael-addition TECC starting point. The surface of BC was modified with TECC components in a simple, straightforward manner, keeping in line with the philosophy of click chemistry. This modification allows BC to incorporate PEG to form a BC with PEG co-hydrogel and can be easily modified due to the variety allowed by incorporation of both TECC and PEG. This system allows for the combination of the strength of BC, the versatility of PEG, and speed and efficiency of TECC into one product without the need for complex reaction conditions. The surface modification of BC was confirmed with a colorimetric assay, Fourier transform infrared spectroscopy-attenuated total internal reflectance (FTIR-ATR), and titration.