A powerful methodology for the synthesis of unsaturated polyphosphoesters (UPPEs) relying on acyclic diene metathesis (ADMET) polymerization is described. A facile two-step protocol gives fast access to structurally versatile and potentially degradable and biocompatible materials. For the first time this allows to control the microstructure of either backbone and/or side chains of polyphosphoesters. Four different monomers are polymerized under different conditions to yield UPPEs with molecular weights ranging from 7000 up to 50 000 g mol–1 with reasonable polydispersity. The unsaturated and saturated polyphosphoesters are characterized in detail with various techniques. A major benefit of the UPPEs is revealed by differential scanning calorimetry proving the control over thermal properties with tunable melting or glass transition temperatures for the different saturated and unsaturated PPEs which is an important feature for future applications. This unique combination of the benefits of metathesis polymerization and phosphorus chemistry is a highly versatile system for materials in many applications ranging from adhesives to biomaterials.

The energy stored in the triplet states of organic molecules, capable of energy transfer via an emissive process (phosphorescence) or a nonemissive process (triplet-triplet transfer), is actively dissipated in the presence of molecular oxygen. The reason is that photoexcited singlet oxygen is highly reactive, so the photoactive molecules in the system are quickly oxidized. Oxidation leads to further loss of efficiency and various undesirable side effects. In this work we have developed a structurally diverse library of hyperbranched unsaturated poly(phosphoester)s that allow efficient scavenging of singlet oxygen, but do not react with molecular oxygen in the ground state, i.e., triplet state. The triplet-triplet annihilation photon upconversion was chosen as a highly oxygen-sensitive process as proof for a long-term protection against singlet oxygen quenching, with comparable efficiencies of the photon upconversion under ambient conditions as in an oxygen-free environment in several unsaturated polyphosphates. The experimental results are further correlated to NMR spectroscopy and theoretical calculations evidencing the importance of the phosphate center. These results open a technological window toward efficient solar cells but also for sustainable solar upconversion devices, harvesting a broad-band sunlight excitation spectrum.

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While it has been shown that phosphates can target molecules and nanocarriers to bone we herein demonstrate the preparation of polyphosphate nanoparticles loaded with paclitaxel using a simple miniemulsion/solvent-evaporation technique as a model for chemotherapeutic delivery. Polyphosphates exhibit much higher structural versatility, relying on the pentavalence of the phosphorus center compared to conventional polyesters. This versatility allows for the development of new degradable polymeric carriers with inherent bone adhesion ability by the interaction of the nanoparticles with a calcium phosphate material used for bone regeneration. The novel polyphosphate nanoparticles were investigated in detail with respect to their size distribution, zeta-potential, thermal and morphological properties and were further proven to be efficiently loaded with a hydrophobic drug (up to 15 wt%). The in vitro cytotoxicity was assessed against human cancer cell lines (HeLa and Saos-2), and the paclitaxelloaded nanoparticles showed a similar cytotoxicity profile similar to the commercially available formulation Taxomedac® and the pure paclitaxel for loading ratios of 10 wt% but additionally proved efficient adhesion on calcium phosphate granules allowing drug delivery to bone. This first report demonstrates that polyphosphate nanoparticles are promising materials for the development of systemic or local bone cancer treatment, even by direct application or by formation of composites with calcium phosphate cements.