The purpose of this Viewpoint is to discuss the molecular design principles that guide development of synthetic antimicrobial polymers, especially those intended to mimic the structure of host ...defense peptides (HDPs). In particular, we focus on the principle of “amphiphilic balance” as it relates to some recently developed polyphosphoniums with somewhat atypical structure. We find that the fundamental concept of amphiphilic balance is still applicable to these new polymers, but that the method to achieve such balance is somewhat unique. We then briefly outline the future challenges and opportunities in this field.
The molecular design principles that guide development of synthetic antimicrobial polymers are discussed with a particular focus on the principle of “amphiphilic balance” as it relates to some recently developed polyphosphonium compounds with somewhat atypical structure. It is found that the fundamental concept of amphiphilic balance is still applicable to these new polymers.
New approaches to treat bacterial infections are badly needed to address the increasing problem of antibiotic resistance. This study explores phosphonium-functionalized block copolymer micelles as ...intrinsically antibacterial polymer assemblies. Phosphonium cations with varying alkyl lengths were conjugated to the terminus of a poly(ethylene oxide)–polycaprolactone block copolymer, and the phosphonium-functionalized block copolymers were self-assembled to form micelles in aqueous solution. The size, morphology, and ζ-potential of the assemblies were studied, and their abilities to kill Escherichia coli and Staphylococcus aureus were evaluated. It was found that the minimum bactericidal concentration depended on the phosphonium alkyl chain length, and different trends were observed for Gram-negative and Gram-positive bacteria. The most active assemblies exhibited no hemolysis of red blood cells above the bactericidal concentrations, indicating that they can selectively disrupt the membranes of bacteria. Furthermore, it was possible to encapsulate and release the antibiotic tetracycline using the assemblies, providing a potential multimechanistic approach to bacterial killing.
Ice accretion causes damage on power generation infrastructure, leading to mechanical failure. Icephobic materials are being researched so that ice buildup on these surfaces will be shed before the ...weight of the ice causes catastrophic damage. Lubricated materials have imposed the lowest-recorded forces of ice adhesion, and therefore lubricated materials are considered the state-of-the-art in this area. Slippery lubricant-infused porous surfaces (SLIPS) are one type of such materials. SLIPS are initially very effective at repelling ice, but the trapped fluid layer that affords their icephobic properties is easily depleted by repeated icing/deicing cycles, even after one deicing event. UV-cured siloxane resins were infused into SLIPS to observe effects on icephobicity and durability. These UV-cured polymer networks enhanced both the icephobicity and longevity of the SLIPS; values of ice adhesion below 10 kPa were recorded, and appreciable icephobicity was maintained up to 10 icing/deicing cycles.
There is currently an urgent need for the development of new antibacterial agents to combat the spread of antibiotic‐resistant bacteria. We explored the synthesis and antibacterial activities of ...novel, sugar‐functionalized phosphonium polymers. While these compounds exhibited antibacterial activity, we unexpectedly found that the control polymer poly(tris(hydroxypropyl)vinylbenzylphosphonium chloride) showed very high activity against both Gram‐negative Escherichia coli and Gram‐positive Staphylococcus aureus and very low haemolytic activity against red blood cells. These results challenge the conventional wisdom in the field that lipophilic alkyl substituents are required for high antibacterial activity and opens prospects for new classes of antibacterial polymers.
Sweet but deadly: Phosphonium‐based polymers appended with hydrophilic groups such as sugars or hydroxy groups can be employed as highly effective antibacterial agents against both Gram‐negative and Gram‐positive bacteria with minimal haemolysis of red blood cells. This challenges the conventional wisdom that hydrophobic appendages are necessary for this class of biocides.
The Front Cover shows the various “flavours” of α‐functionalized phosphine chalcogenides that can be generated from the hydrophosphorylation of C=O/N bonds. Even with multiple potential operative ...mechanisms such as a concerted 2+2 hydrophosphorylation, or a stepwise P(V)−P(III) tautomerization and subsequent nucleophilic attack, the resultant α‐functionalized phosphine chalcogenide remains the same. Additionally, the separation and organization of each α‐functionalized phosphine chalcogenide displays that each is distinctly unique and is treated as such throughout the course of the Review. More information can be found in the Review by J.‐W. Lamberink‐Ilupeju, P. J. Ragogna, and J. M. Blacquiere.
Synthesis and characterization of new P(III) and P(V) bis(azido)phosphines/phosphoranes supported by an N,N′-bis(2,6-diisopropylphenyl) imidazolin-2-iminato (IPrN) ligand and their reactivity ...with various secondary and tertiary phosphines result in the formation of chiral and/or asymmetric mono(phosphinimino)azidophosphines via the Staudinger reaction. The reaction of IPrNP(N3)2 (2) or IPrNP(S)(N3)2 (4S) with an excess of tertiary phosphine resulted in the chemoselective formation of IPrNP(N3)(NPMe3) (7) or IPrNP(S)N3(NPR3) (5 R ), respectively. The chemoselective Staudinger reactivity was also observed in reactions using a secondary phosphine (HPCy2) to produce IPrNP(S)N3NP(H)Cy2 (6a), which exists in equilibrium with a tautomeric IPrNP(S)N3N(H)PCy2 form (6b), as confirmed by 31P–31P nuclear Overhauser effect spectroscopy (NOESY). Density functional theory (DFT) calculations point to a combination of energetically unfavorable lowest unoccupied molecular orbitals (LUMOs) and the accumulation of increasing negative charge at the terminal azido-nitrogen upon a single azide-to-phosphinimine conversion that gave rise to the observed chemoselectivity.
Sequential reversible addition–fragmentation transfer (RAFT) polymerization of a mixed sandwich cobaltocene monomer (η5-cyclopentadienyl-cobalt-η4-cyclobutadiene (CpCoCb)) and a phosphonium salt ...functionalized styrene monomer resulted in the first example of a unique multifunctional block copolymer consisting of a metallopolymer block and a polyelectrolyte block. The polyelectrolyte block was decorated with a gold anion (AuCl4 –) via salt metathesis, resulting in a heterobimetallic block copolymer with distinct gold and cobalt sections. Solution self-assembly behavior of this unique metallopolymer-b-polyelectrolyte copolymer before and after salt metathesis was studied. Heterobimetallic micelles with a gold containing core and a cobalt-containing corona were obtained, and then the core was reduced to form gold nanoparticles (AuNPs). Studies on the solid-state self-assembly of this unique block copolymer showed that it phase separated into hexagonally packed cylinders. Salt metathesis of the phase-separated block copolymers was utilized as the first example of a nonstandard selective staining method to exclusively stain the polyelectrolyte domains with the AuCl4 – anion. Staining the metallopolymer domain by RuO4 provided the complementary pattern. Pyrolysis of the self-assembled block copolymers resulted in magnetic cobalt-phosphate nanoparticles with 17% char yield.
Four‐membered rings with a P2Ch2 core (Ch=S, Se) and phosphorus in the +3 oxidation state have been synthesized. The utility of these rings as a source of monomeric phosphinidene chalcogenides was ...probed by the addition of an N‐heterocyclic carbene, resulting in a base‐stabilized phosphinidene sulfide. Similarly, persistence of the phosphinidene selenide in solution was shown through cycloaddition chemistry with 2,3‐dimethylbutadiene at elevated temperatures. The observed reactivity was explained by detailed computational work that established the conditions upon which the P2Ch2 rings can liberate phosphinidene chalcogenides.
Four‐membered rings with a P2Ch2 core (Ch=S, Se) have been synthesized by the cyclocondensation of Ar*PCl2 and Ch(TMS)2, where phosphorus remains in the +3 oxidation state (Ar*=2,6‐Mes2C6H3, Mes=2,4,6‐(CH3)3C6H2). The utility of these rings as a source of monomeric phosphinidene chalcogenides was probed via the addition of an N‐heterocyclic carbene (NHC) and 2,3‐dimethylbutadiene.
Dimethyl 2-vinylcyclopropane-1,1-dicarboxylate underwent a hydrophosphination reaction with either a primary or secondary phosphine under photolytic conditions. Notably, a free radical initiator was ...not required. The resulting tertiary phosphines were derivatized using S
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to afford moisture and air stable yellow or colorless oils in a 27%-73% isolated yield. A series of control reactions were performed, and we propose that this UV induced hydrophosphination reaction proceeds through a radical mechanism.
The synthesis of new phosphine sulfides through the UV irradiation of dimethyl 2-vinylcyclopropane-1,1-dicarboxylate with either a primary or secondary phosphine.
Kraft lignin (KL) was converted to methacrylated lignin through an esterification reaction using methacrylic anhydride. It was determined that up to 70% of the hydroxyl functional groups contained ...within the structure of lignin were converted into corresponding methacrylate. The methacrylated lignin (ML) was incorporated into ultraviolet (UV)-curable formulations, where the formulations were applied to a surface and cured under UV light to give robust, lignin-rich coatings with loadings as high as 31 wt % of methacrylated lignin.
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