Modern needs in materials science and bioapplications are manifold: From hydrophobic matrices for tissue engineering to water-soluble polymer therapeutics a great variety of polymers is necessary to fit each application. Our group seeks to establish a unique modular platform to fulfill the demands in these modern needs: the incorporation of phosphates within the polymer backbone is a unique handle to tune the materials properties both along the main chain but also at the side chains. These polyesters and –amides based on phosphoric acid allow tailoring the degradation and adhesion, for example via the pendant group. Also variation from hydrophobic semicrystalline or amorphous to highly water soluble, biodegradable PPEs is possible.
With the natural phosphate building block, biodegradable and biomimetic PPEs can be synthesized by different strategies.
We have developed a reliable protocol based on olefin metathesis (either acyclic diene metathesis or ring-opening metathesis polymerization (ROMP)) for the synthesis of smart PPEs with tunable hydrophilicity, adhesion properties and binding motifs. Novel 7-membered phosphates and phosphonates can be polymerized by ROMP and copolymers with commodity monomers are available. ADMET polycondensation gives access to semicrystalline PPEs which can be regarded as “defect polyethylene” and recently their crystallization behavior was studied together with the electron microscopy lab at MPIP.
Further, we develop the anionic ring-opening polymerization of five-membered cyclic phosphoesters. Recently, we were able to establish the first living polymerization of a cyclic phosphonate monomer up to very high conversions (above 90%) with low polydispersities. The resulting polymers are highly water-soluble and show no cell-toxicity. This phosphonate platform was extended to several novel monomers which allow a fast variation of the degradation kinetics and hydrophilicity of these novel poly(phosphonate)s.
Nanocarriers, coated with hydrophilic PPEs exhibit a “stealth” effect, similar to the well-known poly(ethylene glycol), rendering them as perfect biodegradable alternatives, especially for chronical diseases.
We believe that PPEs are the material that combines synthetic chemistry with biomedical and materials science needs for the future. In future, cell interactions and proliferation with various PPE-surfaces and the development of smart bone substituent materials purely based on PPEs will be studied and developed.