RAFT Polymerization of N-Methyl-N-vinylacetamide and Related Double Hydrophilic Block Copolymers

Controlled Radical Copolymerization toward Tailored F/N Hybrid Polymers by Using Light-Driven Organocatalysis

Controlled radical copolymerizations present attractive avenues to obtain polymers with complicated compositions and sequences. In this work, we report the development of a visible-light-driven organocatalyzed controlled copolymerization of fluoroalkenes and acyclic N-vinylamides for the first time. The approach enables the on-demand synthesis of a broad scope of amide-functionalized main-chain fluoropolymers via novel fluorinated thiocarbamates, facilitating regulations over chemical compositions and alternating fractions by rationally selecting comonomer pairs and ratios. This method allows temporally controlled chain-growth by external light, and maintains high chain-end fidelity that promotes facile preparation of block sequences. Notably, the obtained F/N hybrid polymers, upon hydrolysis, afford free amino-substituted fluoropolymers versatile for post modifications toward various functionalities (e.g., amide, sulfonamide, carbamide, thiocarbamide). We further demonstrate the in situ formation of polymer networks with desirable properties as protective layers on lithium metal anodes, presenting a promising avenue for advancing lithium metal batteries.

Poly(N-methyl-N-vinylacetamide): A Strong Alternative to PEG for Lipid-Based Nanocarriers Delivering siRNA

Lipid-based nanocarriers have demonstrated high interest in delivering genetic material, exemplified by the success of Onpattro and COVID-19 vaccines. While PEGylation imparts stealth properties, it hampers cellular uptake and endosomal escape, and may trigger adverse reactions like accelerated blood clearance (ABC) and hypersensitivity reactions (HSR). This work highlights the great potential of amphiphilic poly(N-methyl-N-vinylacetamide) (PNMVA) derivatives as alternatives to lipid-PEG for siRNA delivery. PNMVA compounds with different degrees of polymerization and hydrophobic segments, are synthesized. Among them, DSPE (1,2-distearoyl-sn-glycero-3-phosphoethanolamine)-PNMVA efficiently integrates into lipoplexes and LNP membranes and prevents protein corona formation around these lipid carriers, exhibiting stealth properties comparable to DSPE-PEG. However, unlike DSPE-PEG, DSPE-PNMVA24 shows no adverse impact on lipoplexes cell uptake and endosomal escape. In in vivo study with mice, DSPE-PNMVA24 lipoplexes demonstrate no liver accumulation, indicating good stealth properties, extended circulation time after a second dose, reduced immunological reaction, and no systemic pro-inflammatory response. Safety of DSPE-PNMVA24 is confirmed at the cellular level and in animal models of zebrafish and mice. Overall, DSPE-PNMVA is an advantageous substitute to DSPE-PEG for siRNA delivery, offering comparable stealth and toxicity properties while improving efficacy of the lipid-based carriers by minimizing the dilemma effect and reducing immunological reactions, meaning no ABC or HSR effects.

Diversely substituted poly(N-vinyl amide) derivatives towards non-toxic, stealth and pH-responsive lipid nanocapsules

Surface modification of lipid nanocapsules (LNC) is necessary to impart stealth properties to these drug carriers and enhance their accumulation into the tumor microenvironment. While pegylation is commonly used to prolong the circulation time of LNC, the increased presence of anti-PEG antibodies in the human population and the internalization issues associated to the PEG shell are strong incentives to search alternatives. This work describes the development of amphiphilic poly(N-vinyl amide)-based (co)polymers, including pH-responsive ones, and their use as LNC modifiers towards improved drug delivery systems. RAFT polymerization gave access to a series of LNC modifiers composed of poly(N-methyl-N-vinyl acetamide), poly(N-vinyl pyrrolidone) or pH-responsive vinylimidazole-based sequence bearing a variety of lipophilic end-groups, namely octadecyl, dioctadecyl or phospholipid groups, for anchoring to the LNC. Decoration of the LNC with these families of poly(N-vinyl amide) derivatives was achieved via both post-insertion and per-formulation methods. This offered valuable and non-toxic LNC protection from opsonization by complement activation, emphasized the benefit of dioctadecyl in the per-formulation approach and highlighted the great potential of poly(N-methyl-N-vinyl acetamide) as PEG alternative. Moreover, incorporation of imidazole moieties in the shell of the carrier imparted pH-responsiveness to the LNC likely to increase the cellular uptake in the acidic tumor microenvironment, opening up new possibilities in the field of active targeting.

Tailor-Made Poly(vinylamine) via Purple LED-Activated RAFT Polymerization of N-vinylformamide

Photo-iniferter reversible addition-fragmentation chain transfer (PI-RAFT) polymerization of N-vinylformamide (NVF) is demonstrated by using purple light. PNVFs with predetermined molar masses and narrow molar mass distributions are obtained. High RAFT chain-end fidelity is confirmed by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) and electrospray-ionization time-of-flight mass spectrometry (ESI-TOF-MS), and chain extension experiment. To demonstrate the potential of this approach, an original poly(N-vinylpyrrolidone)-b-poly(N-vinylformamide) (PVP-b-PNVF) diblock copolymer is synthesized and characterized by aqueous size-exclusion chromatography (SEC), asymmetric flow field-flow fractionation (A4F), and ¹ H diffusion-ordered spectroscopy nuclear magnetic resonance (¹ H DOSY NMR). Finally, selective hydrolysis of PNVF block to corresponding pH-responsive poly(N-vinylpyrrolidone)-b-poly(N-vinylformamide) (PVP-b-PVAm) is performed.

RAFT polymerisation of N-vinylformamide and the corresponding double hydrophilic block copolymers

Polyvinylamine-based double hydrophilic block copolymers are synthesised from RAFT polymerisation of N-vinylformamide.