Antimicrobial Hyperbranched Polymer-Usnic Acid Complexes through a Combined ROP-RAFT Strategy.

Polymer-drug conjugates have received considerable attention over the last decades due to their potential for improving the clinical outcomes for a range of diseases. It is of importance to develop methods for their preparation that have simple synthesis and purification requirements but maintain high therapeutic efficacy and utilize macromolecules that can be cleared via natural excretory pathways upon breakdown. Herein, the combination of ring-opening polymerization (ROP) and reversible addition-fragmentation chain-transfer (RAFT) polymerization is described for the straightforward synthesis of amphiphilic, stimuli-responsive, biodegradable, and highly functionalizable hyperbranched polymers. These unimolecular nanoparticles demonstrate a versatile platform for the synthesis of polymer-drug conjugates owing to the inclusion of a Boc-protected polycarbonate moiety in either a block or random copolymer formation. A proof-of-concept study on the complexation of the poorly water-soluble antimicrobial drug usnic acid results in polymer-drug complexes with powerful antimicrobial properties against gram-positive bacteria. Therefore, this work highlights the potential of amphiphilic and biodegradable hyperbranched polymers for antimicrobial applications.

Catalytically Active N-Heterocyclic Carbene Release from Single-Chain Nanoparticles Following a Thermolysis-Driven Unfolding Strategy.

The need for efficient, tailor-made catalysts has inspired chemists to design synthetic macromolecular architectures for selective catalysis. To this purpose, herein the synthesis and in-depth characterization of Ag(I)-crosslinked single-chain nanoparticles (SCNPs) is reported and their application as catalysts is demonstrated. Specifically, a copolymer of styrenic benzimidazolium chloride is synthesized as a linear precursor via reversible addition-fragmentation chain-transfer polymerization. Metalation of the benzimidazolium moieties by Ag(I) resulted in the intramolecular cross-linking of single chains via the formation of silver-N-heterocyclic carbene (Ag-NHC) linkages under dilute conditions. The successful formation of well-defined, robust SCNPs is evidenced by size-exclusion chromatography, dynamic light scattering, nuclear magnetic resonance spectroscopy, and transmission electron microscopy. Finally, it is demonstrated that the Ag-SCNPs can be used as NHC pre-catalysts, by first indirectly evidencing the formation of the corresponding unfolded NHC-CS2 polybetaine and then organocatalysing a benzoin condensation reaction.

Tuning the Cloud-Point and Flocculation Temperature of Poly(2-(diethylamino)ethyl methacrylate)-Based Nanoparticles via a Postpolymerization Betainization Approach.

The ability to tune the behavior of temperature-responsive polymers and self-assembled nanostructures has attracted significant interest in recent years, particularly in regard to their use in biotechnological applications. Herein, well-defined poly(2-(diethylamino)ethyl methacrylate) (PDEAEMA)-based core-shell particles were prepared by RAFT-mediated emulsion polymerization, which displayed a lower-critical solution temperature (LCST) phase transition in aqueous media. The tertiary amine groups of PDEAEMA units were then utilized as functional handles to modify the core-forming block chemistry via a postpolymerization betainization approach for tuning both the cloud-point temperature (T CP) and flocculation temperature (T CFT) of these particles. In particular, four different sulfonate salts were explored aiming to investigate the effect of the carbon chain length and the presence of hydroxyl functionalities alongside the carbon spacer on the particle's thermoresponsiveness. In all cases, it was possible to regulate both T CP and T CFT of these nanoparticles upon varying the degree of betainization. Although T CP was found to be dependent on the type of betainization reagent utilized, it only significantly increased for particles betainized using sodium 3-chloro-2-hydroxy-1-propanesulfonate, while varying the aliphatic chain length of the sulfobetaine only provided limited temperature variation. In comparison, the onset of flocculation for betainized particles varied over a much broader temperature range when varying the degree of betainization with no real correlation identified between T CFT and the sulfobetaine structure. Moreover, experimental results were shown to partially correlate to computational oligomer hydrophobicity calculations. Overall, the innovative postpolymerization betainization approach utilizing various sulfonate salts reported herein provides a straightforward methodology for modifying the thermoresponsive behavior of soft polymeric particles with potential applications in drug delivery, sensing, and oil/lubricant viscosity modification.

Rapid Ring-Opening Metathesis Polymerization of Monomers Obtained from Biomass-Derived Furfuryl Amines and Maleic Anhydride.

Well-controlled and extremely rapid ring-opening metathesis polymerization of unusual oxanorbornene lactam esters by Grubbs third-generation catalyst is used to prepare a range of bio-based homo- and copolymers. Bio-derived oxanorbornene lactam monomers were prepared at room temperature from maleic anhydride and secondary furfuryl amines by using a 100 % atom economical, tandem Diels-Alder lactamization reaction, followed by esterification. Several of the resulting homo- and copolymers show good control over polymer molecular weight and have narrow molecular weight distributions.