Claudia Dworak

Imidazole-based ionic liquids for free radical photopolymerization

Ionic liquid (IL) monomers are receiving increased attention due to their versatile range of application, especially in the electrochemical and electromechanical fields. Within this study, imidazole-based ILs containing a polymerizable methacrylate (MA) group were synthesized to examine their influence on the viscosity and reactivity of typical (meth)acrylates. The IL-MAs were prepared from 1-butylimidazole and bromo methacrylates with different spacer lengths (C2–C6). The best results with respect to physicochemical properties and double bond conversions could be obtained for ILs with C3 and C6 spacers. Bulk polymerizations exhibited unusually high reactivity and double-bond conversion compared with typical mono-methacrylates. Addition of 10 wt% IL-MA to reactive diluents like hexane-1,6-diol diacrylate caused only minor reduction in reaction rate but increased final double bond conversion compared with the pure diacrylate.

Initiators Based on Benzaldoximes: Bimolecular and Covalently Bound Systems.

Typical bimolecular photoinitiators (PIs) for radical polymerization of acrylates show only poor photoreactivity because of the undesired effect of back electron transfer. To overcome this limitation, PIs consisting of a benzaldoxime ester and various sensitizers based on aromatic ketones were introduced. The core of the photoinduced reactivity was established by laser flash photolysis, photo-CIDNP, and EPR experiments at short time scales. According to these results, the primarily formed iminyl radicals are not particularly active. The polymerization is predominantly initiated by C-centered radicals. Photo-DSC experiments show reactivities comparable to that of classical monomolecular type I PIs like Darocur 1173.

Biocompatible Phosphorus-based Monomers for Radical Polymerization

Novel biocompatible and biodegradable monomers based on phosphorus-containing vinyl esters and vinyl carbamates for radical photopolymerization were prepared. By photo-Differential Scanning Calorimetry (photo-DSC) the reactivity of the mono-, di- and trifunctional monomers was investigated. Furthermore, their cytotoxicity, mechanical properties and hydrolytic degradation behavior were evaluated, aiming at a future application of our compounds in the biomedical area.