Temperature-induced self-assembly of block copolymers allows the formation of smart nanodimensional structures. Mostly, nondegradable lower critical solution temperature (LCST) segments are applied to prepare such dynamic aggregates. However, degradable upper critical phase separation (UCST) block copolymers that would allow the swelling or disassembly at elevated temperatures with eventual backbone hydrolysis have not been reported to date. We present the first well-defined degradable poly(phosphonate)s with adjustable UCST. The organocatalytic anionic ring-opening copolymerization of 2-alkyl-2-oxo-1,3,2-dioxaphospholanes provided functional polymers with excellent control over molecular weight and copolymer composition. The prepolymers were turned into thermoresponsive polymers by thiol-ene modification to introduce pendant carboxylic acids. By this means, non cell-toxic, degradable polymers exhibiting UCST behavior in water between 43 and 71 °C were produced. Block copolymers with PEG as a nonresponsive water-soluble block can self-assemble into well-defined polymersomes with narrow size distribution. Depending on the responsive block, these structures either swell or disassemble completely upon an increased temperature.

Marine plastic pollution is a worldwide challenge making advances in the field of biodegradable polymer materials necessary. Polylactide (PLA) is a promising biodegradable polymer used in various applications; however, it has a very slow seawater degradability. Herein, we present the first library of PLA derivatives with incorporated “breaking points” to vary the speed of degradation in artificial seawater from years to weeks. Inspired by the fast hydrolysis of ribonucleic acid (RNA) by intramolecular transesterification, we installed phosphoester breaking points with similar hydroxyethoxy side groups into the PLA backbone to accelerate chain scission. Sequence-controlled anionic ring-opening copolymerization of lactide and a cyclic phosphate allowed PLA to be prepared with controlled distances of the breaking points along the backbone. This general concept could be translated to other slowly degrading polymers and thereby be able to prevent additional marine pollution in the future.

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Living organisms compartmentalize their catalytic reactions in membranes for increased efficiency and selectivity. To mimic the organelles of eukaryotic cells, we develop a mild approach for in situ encapsulating enzymes in aqueous-core silica nanocapsules. In order to confine the sol-gel reaction at the water/oil interface of miniemulsion, we introduce an aminosilane to the silica precursors, which serves as both catalyst and an amphiphilic anchor that electrostatically assembles with negatively charged hydrolyzed alkoxysilanes at the interface. The semi-permeable shell protects enzymes from proteolytic attack, and allows the transport of reactants and products. The enzyme-carrying nanocapsules, as synthetic nano-organelles, are able to perform cascade reactions when enveloped in a polymer vesicle, mimicking the hierarchically compartmentalized reactions in eukaryotic cells. This in situ encapsulation approach provides a versatile platform for the delivery of biomacromolecules.

Synthesis by ROP of star-like amphiphilic block copolymer surfactants composed of PCL hydrophobic segments and poly(phosphonate) as biodegradable segments.

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Imaging and tracing materials inside the body is essential to develop functional materials for personalized therapies, including drug delivering nanocarriers and artificial tissues. Magnetic Resonance Imaging (MRI) is a key whole-body imaging technology, where heteronuclear MRI agents enable background-free, quantitative labeling. However, many MRI agents raised concerns due to environmental pollution and organ accumulation. As a solution, we developed a biodegradable, biocompatible polymer platform for heteronuclear 31P magnetic resonance imaging (MRI). We introduce polyphosphoester colloids for heteronuclear MRI using 31P-nucleus. 31P MRI has been severely hampered by unfavorable magnetic resonance properties of 31P, including intrinsic background and low sensitivity. We overcame these fundamental challenges in imaging of 31P by tailoring molecular and structural features of polymeric colloids. We have synthesized gradient-type polyphosphonate copolymers that self-assemble into well-defined micelles. The gradient leads to favorable MRI characteristics compared with homo- and block copolymers. Background-free imaging and biodegradation were proven in vivo in Manduca sexta. Furthermore, we demonstrate by encapsulation of the potent drug PROTAC ARV-825 that these amphiphilic copolymers can simultaneously deliver hydrophobic drugs and thus enable theranostics. We present a unique platform of biocompatible, degradable polyphosphoesters that inherently act as background-free MRI agents and delivery vehicles.

Living organisms compartmentalize their catalytic reactions in membranes for increased efficiency and selectivity. To mimic the organelles of eukaryotic cells, we develop a mild approach for in situ encapsulating enzymes in aqueous‐core silica nanocapsules. In order to confine the sol‐gel reaction at the water/oil interface of miniemulsion, we introduce an aminosilane to the silica precursors, which serves as both catalyst and an amphiphilic anchor that electrostatically assembles with negatively charged hydrolyzed alkoxysilanes at the interface. The semi‐permeable shell protects enzymes from proteolytic attack, and allows the transport of reactants and products. The enzyme‐carrying nanocapsules, as synthetic nano‐organelles, are able to perform cascade reactions when enveloped in a polymer vesicle, mimicking the hierarchically compartmentalized reactions in eukaryotic cells. This in situ encapsulation approach provides a versatile platform for the delivery of biomacromolecules.