Embedding Nanofibers in a Polymer Matrix by Polymerization of Organogels Comprising Heterobifunctional Organogelators and Monomeric Solvents

We demonstrate the embedding of nanofibers in a polymer matrix through the polymerization of an organogel. A series of organogelators based on a biphenyl ester having two different polymerizable groups, namely, acryl and diacetylene groups, are prepared. The resulting heterobifunctional gelators show the ability to gelate various monomeric solvents. The photopolymerization of an organogel of a heterobifunctional gelator (1.5 or 10 wt %), formed in hexyl methacrylate (HMA), is carried out by UV irradiation in the presence of 2,2-dimethoxy-2-phenylacetophenone (photoinitiator, 4 wt %). The polymerization of HMA forms a polymer matrix, while the polymerization of the acryl and diacetylene groups of the gelator forms the nanofibers with a cross-linked structure. The copolymerization of a gelator and HMA at the interface will improve the adhesion between the nanofiber and the polymer matrix. The polymerized gels appear yellowish and exhibit strong fluorescence when irradiated with 365 nm UV light. This is due to the presence of polydiacetylene chains. The fluorescent polydiacetylene nanofibers embedded in the polymer matrix are visualized by using confocal laser scanning microscopy. The thermal and mechanical properties of the nanofibers embedded in polyHMA are investigated using differential scanning calorimetry, dynamic mechanical analysis, and a universal testing machine. The polymerized gels show improved thermal and physical properties in comparison to the matrix polymer (polyHMA).