Polyphosphoester: eine neue Plattform für abbaubare Polymere

The Chemical Recycling of Polyesters for a Circular Plastics Economy: Challenges and Emerging Opportunities

Whilst plastics have played an instrumental role in human development, growing environmental concerns have led to increasing public scrutiny and demands for outright bans. This has stimulated considerable research into renewable alternatives, and more recently, the development of alternative waste management strategies. Herein, the aim was to highlight recent developments in the catalytic chemical recycling of two commercial polyesters, namely poly(lactic acid) (PLA) and poly(ethylene terephthalate) (PET). The concept of chemical recycling is first introduced, and associated opportunities/challenges are discussed within the context of the governing depolymerisation thermodynamics. Chemical recycling methods for PLA and PET are then discussed, with a particular focus on upcycling and the use of metal-based catalysts. Finally, the attention shifts to the emergence of new materials with the potential to modernise the plastics economy. Emerging opportunities and challenges are discussed within the context of industrial feasibility.

Stimuli-Responsive Phosphorus-Based Polymers

This microreview details recent developments in stimuli-responsive polymers with phosphorus in the main-chain, in particular polyphosphazenes and polyphosphoesters. The presence of phosphorus in the polymers endows unique properties onto the macromolecules, which can be utilized for the preparation of materials capable of physically responding to specific stimuli. Achieving the desired responsiveness has been much facilitated by recent developments in synthetic polymer chemistry, in particular controlled synthesis and backbone functionalization phosphorus-based polymers, in order to achieve the required properties and hence responsiveness of the materials. The development of phosphorus-based polymers which respond to the most important stimuli are discussed, namely, pH, oxidation, reduction, temperature and biological triggers. The polymers are placed in the context not just of each other but also with reference to state-of-the-art organic polymers.

Silica Mineralization of DNA-Inspired 1D and 2D Supramolecular Polymers

The preparation of hybrid materials from supramolecular polymers through the sol‐gel process is presented. Supramolecular polymers are assembled from phosphodiester‐linked pyrene oligomers and act as water‐soluble one‐ or two‐dimensional templates for silicification. The fibrillary and planar morphologies of the assemblies, as well as the excitonic interactions between the chromophores, remain unaffected by the silicification process.

Poly(phosphorodiamidate)s by Olefin Metathesis Polymerization with Precise Degradation

Degradable polymers are a currently growing field of research for biomedical and materials science applications. The majority of such compounds are based on polyesters and polyamides. In contrast, their phosphorus-containing counterparts are much less studied, in spite of their potential precise degradation profile and biocompatibility. Herein, the first library of poly(phosphorodiamidate)s (PPDAs) with two P-N bonds forming the polymer backbone and a pendant P-OR group is prepared through acyclic diene metathesis polymerization. They are designed to vary in their hydrophilicity and are compared with the structural analogues poly(phosphoester)s (PPEs) with respect to their thermal properties and degradation profiles. The degradation of PPDAs can be controlled precisely by the pH: under acidic conditions the P-N linkages in the polymer backbone are cleaved, whereas under basic conditions the pendant ester is cleaved selectively and almost no backbone degradation occurs. The PPDAs exhibit distinctively higher thermal stability (from thermogravimetric analysis (TGA)) and higher glass transition and/or melting temperatures (from differential scanning calorimetry (DSC)) compared with analogous PPEs. This renders this exotic class of phosphorus-containing polymers as highly promising for the development of future drug carriers or tissue engineering scaffolds.

Polyphosphazene Based Star-Branched and Dendritic Molecular Brushes

A new synthetic procedure is described for the preparation of poly(organo)phosphazenes with star-branched and star dendritic molecular brush type structures, thus describing the first time it has been possible to prepare controlled, highly branched architectures for this type of polymer. Furthermore, as a result of the extremely high-arm density generated by the phosphazene repeat unit, the second-generation structures represent quite unique architectures for any type of polymer. Using two relativity straight forward iterative syntheses it is possible to prepare globular highly branched polymers with up to 30 000 functional end groups, while keeping relatively narrow polydispersities (1.2-1.6). Phosphine mediated polymerization of chlorophosphoranimine is first used to prepare three-arm star polymers. Subsequent substitution with diphenylphosphine moieties gives poly(organo)phosphazenes to function as multifunctional macroinitiators for the growth of a second generation of polyphosphazene arms. Macrosubstitution with Jeffamine oligomers gives a series of large, water soluble branched macromolecules with high-arm density and hydrodynamic diameters between 10 and 70 nm.