Porozni polimeri, pripravljeni s polimerizacijo z odpiranjem obroča v emulziji : doktorska disertacija

slovenian

doktorska dela

2021

high internal phase emulsion (HIPE)   poly(%-caprolactone) (PCL)   ring-opening polymerization (ROP)   shape memory   synthetic polypeptides   tissue engineering

Univerza v Mariboru, Fakulteta za kemijo in kemijsko tehnologijo

In this doctoral thesis, ring-opening polymerization (ROP) of heterocyclic monomers in a continuous phase of high internal phase emulsions (HIPEs) was performed. ROP directly in HIPE enables the preparation of fully degradable polyester and synthetic polypeptide polyHIPEs with specific porous morphology. For the successful implementation of ROP in HIPE, anhydrous HIPEs were prepared and organic catalysts were used to enable ROP at relatively low temperatures and suitable polymerization rate. It has been shown that the rate of ROP in HIPEs is an extremely important parameter, as the continuous phase of the emulsion must gel within the time-frame of emulsion stability, while at the same time the HIPE viscosity must be suitable for adequate stirring and transfer of emulsions into the molds. %In the first part of the work, polyHIPEs based on a semi-crystalline polyester, poly(%-caprolactone) (PCL), are presented. The thermomechanical properties of the prepared PCL polyHIPEs were investigated and found to be strongly dependent on the degree of PCL crosslinking. PCL polyHIPEs exhibit shape memory behavior with excellent fixation of the temporary shape at low temperatures and excellent recovery of the original shape when heated above the melting temperature, as demonstrated by cyclic thermomechanical tests. Less crosslinked polyHIPE shows higher melting and crystallization temperatures and as a result, its temporary shape can be fixed even at room temperature. %The synthetic method was further extended to the polymerization of various types of %-amino acid N-carboxyanhydrides (NCAs) to prepare synthetic polypeptide polyHIPEs not previously reported. The polymerization rate has been shown to be an extremely important parameter for the successful preparation of polypeptide polyHIPEs, as it determines the rate of carbon dioxide release from HIPE during the ROP of NCA monomers. The synthetic process we developed allows the synthesis of polypeptide polyHIPE scaffolds with different chemical compositions. However, due to the different reactivity of NCA monomers, it is necessary to adjust the experimental conditions such as monomer concentration, catalyst amount, surfactant amount, type of crosslinker and type of solvent. Moreover, we have established relationships between the synthesis, structure and properties of the synthesized polyHIPE scaffolds and laid the foundation for the design and preparation of differently functionalized polypeptide polyHIPE scaffolds. We have shown that the morphology of the polyHIPEs, which plays an important role in the use of the material for cell culture, can be adjusted by the proportion of the internal phase in HIPE and the amount of surfactant. In the case of selected polypeptide polyHIPE, we have confirmed that the material is nontoxic to cells and that it allows good viability, migration and proliferation of cells throughout the polypeptide polyHIPE scaffold. Furthermore, the disclosed synthetic procedure is applicable for the preparation of polyHIPEs based on various polypeptides as well as copolypeptides. In addition, we have shown that we can prepare polyHIPE hydrogels by deprotecting the protected side groups of polypeptides. The unprotected functional groups allow further postpolymerization modifications of the polyHIPEs. The described approach to the preparation of polypeptide polyHIPEs promises the design and preparation of macroporous polypeptide scaffolds with different chemical compositions, whose functionality can be tuned simply by selecting the types of NCA monomers.

07.08.2023