While topology effects by cyclic polymers in solution and melts are well-known, their translation into the interfacial properties of polymer “brushes” provides new opportunities to impart enhanced surface lubricity and biopassivity to inorganic surfaces, above and beyond that expected for linear analogues of identical composition. The impact of polymer topology on the nanotribological and protein-resistance properties of polymer brushes is revealed by studying linear and cyclic poly­(2-ethyl-2-oxazoline) (PEOXA) grafts presenting a broad range of surface densities and while shearing them alternatively against an identical brush or a bare inorganic surface. The intramolecular constraints introduced by the cyclization provide a valuable increment in both steric stabilization and load-bearing capacity for cyclic brushes. Moreover, the intrinsic absence of chain ends within cyclic adsorbates hinders interpenetration between opposing brushes, as they are slid over each other, leading to a reduction in the friction coefficient (μ) at higher pressures, a phenomenon not observed for linear grafts. The application of cyclic polymers for the modification of inorganic surfaces generates films that outperform both the nanotribological and biopassive properties of linear brushes, significantly expanding the design possibilities for synthetic biointerfaces.

The activation of C−Br bonds in various bromoalkanes by the biradical [⋅P(μ‐NTer)2P⋅] (1) (Ter=2,6‐bis‐(2,4,6‐trimethylphenyl)‐phenyl) is reported, yielding trans‐addition products of the type [Br−P(μ‐NTer)2P−R] (2), so‐called 1,3‐substituted cyclo‐1,3‐diphospha‐2,4‐diazanes. This addition reaction, which represents a new easy approach to asymmetrically substituted cyclo‐1,3‐diphospha‐2,4‐diazanes, was investigated mechanistically by different spectroscopic methods (NMR, EPR, IR, Raman); the results suggested a stepwise radical reaction mechanism, as evidenced by the in‐situ detection of the phosphorus‐centered monoradical [⋅P(μ‐NTer)2P‐R].< To provide further evidence for the radical mechanism, [⋅P(μ‐NTer)2P‐Et] (3Et⋅) was synthesized directly by reduction of the bromoethane addition product [Br‐P(μ‐NTer)2P‐Et] (2 a) with magnesium, resulting in the formation of the persistent phosphorus‐centered monoradical [⋅P(μ‐NTer)2P‐Et], which could be isolated and fully characterized, including single‐crystal X‐ray diffraction. Comparison of the EPR spectrum of the radical intermediate in the addition reaction with that of the synthesized new [⋅P(μ‐NTer)2P‐Et] radical clearly proves the existence of radicals over the course of the reaction of biradical [⋅P(μ‐NTer)2P⋅] (1) with bromoethane. Extensive DFT and coupled cluster calculations corroborate the experimental data for a radical mechanism in the reaction of biradical [⋅P(μ‐NTer)2P⋅] with EtBr. In the field of hetero‐cyclobutane‐1,3‐diyls, the demonstration of a stepwise radical reaction represents a new aspect and closes the gap between P‐centered biradicals and P‐centered monoradicals in terms of radical reactivity.

Zinc sulfide (ZnS) nanoparticles (NPs) are particularly interesting materials for their electronic and luminescent properties. Unfortunately, their robust and stable functionalization and stabilization, especially in aqueous media, has represented a challenging and not yet completely accomplished task. In this work, we report the synthesis of colloidally stable, photoluminescent and biocompatible core-polymer shell ZnS and ZnS:Tb NPs by employing a water-in-oil miniemulsion (ME) process combined with surface functionalization via catechol-bearing poly-2-methyl-2-oxazoline (PMOXA) of various molar masses. The strong binding of catechol anchors to the metal cations of the ZnS surface, coupled with the high stability of PMOXA against chemical degradation, enable the formation of suspensions presenting excellent colloidal stability. This feature, combined with the assessed photoluminescence and biocompatibility, make these hybrid NPs suitable for optical bioimaging.