Nucleobase-induced self-assembly of low-molecular weight macromonomers

The ability to control the organization of compounds through supramolecular interactions offers the researcher a way of tuning the properties of the resulting material. Nature utilizes this technique to allow access to a variety of complex architectures. This dissertation reports the investigations into using nucleobase-induced self-assembly as a method of controlling the formation of macromonomer architectures. In particular investigations have been carried out utilizing N-protected-nucleobases as the molecular recognition motifs. The use of such protected nucleobases, rather than the natural nucleobases, allows additional manipulation and control of self-assembly processes and their architectures. We have prepared a series of supramolecular telechelic macromonomers, which have derivatives of all four DNA nucleobase attached to either end. The attachment of nucleobase derivatives on the end of low molecular weight bis(3-aminopropyl) terminated poly(tetrahydrofuran) results in a marked change in the properties of the material. An increase of over 100°C in the melting is observed upon such derivatization as compared to either the starting material or the macromonomer derivatized with acetate group, where the material is an oil at room temperature. This indicates the marked change in properties of these materials is mainly on account of the presence of the nucleobase and not just the presence of the amide groups used to link the nucleobase to the core. All the materials were structural characterized by NMR, MALDI MS and FT-IR. Broad spectrum bands in the 3300–3500 cm −1 range indicated the presence of H-bonding in the material in solid state. The DSC thermograms showed only a melting points on the first heating for the guanine and adenine derivatives, while the cytosine and thymine derivatives show melting and crystallization point upon re-heating and re-cooling. Interestingly fibers could be pulled from adenine, cytosine, and guanine derivatived macromonomers indicating these nucleobase-terminated macromonomers are self-assembly into higher molecular weight supramolecular structures. Fiber could not be pulled from either the amine terminated poly(tetrahydrofuran) starting materials, nor the acetated poly(polytetrahydrofuran).; Simple addition of single nucleobase derivatives to low molecular weight macromonomer induces polymeric-like properties. These material, effectively display a ceiling temperature like many reversible polymers, above which no polymer-like properties are observed. Upon cooling these material to below the T_c the systems spontaneously re-polymerizes returning to their previous polymer-like state. This property opens the way for the development of self-healing and adaptive materials.; The preliminary results on synthesis of the PNA (peptide nucleic acid) repeat units are also reported in chapter 4 of this dissertation. The PNA monomer can be achieved by using a slight modification of the literature procedures.