Two novel supramolecular photoinitiators (supra-photoinitiators) based on the host−guest complexation of macrocycles (pillar[6]arene, P6; prism[5]arene, NP5) and diphenyl-iodonium salt (Iod) were fabricated. Under light irradiation, macrocycle P6 or NP5 could donate electrons to the guest molecule Iod, which generated highly active free radicals and cationic fragments to achieve efficient polymerization. Compared to a commercial activator, the electron transfer between macrocycles and Iod were under nondiffusion control, endowing a much higher photopolymerization rate and epoxy resin final conversion. In addition, the host−guest complexation of NP5 extended the initiating wavelength of Iod from ultrashort ultraviolet to near-ultraviolet, which could better match the environment-friendly LED light source. It is anticipated that a supra-photoinitiator may open a new route for designing novel photoinitiators with high performance.
In this work, a naphthalene-based macrocycle prism[5]arene (NP 5 OCH 3 ) is developed as a novel kind of photoinitiator. When NP 5 OCH 3 is irradiated under light, the bond between methylene and naphthalene can be quickly broken owning to the existence of ring tension. The macrocycle is cleaved to linear oligomer biradicals, which can effectively initiate the free radical photopolymerization of acrylate monomers. Compared with conventional photoinitiators, NP 5 OCH 3 has strong light absorption in the wavelength range of 365-405 nm, so it can well match the environment-friendly light-emitting diodes (LEDs) light source to realize highly efficient initiation. In addition, there is no small molecule fragment generated during NP 5 OCH 3 fracture, and the resulted linear oligomer biradicals can be immobilized in the polymer after initiating polymerization, so NP 5 OCH 3 photoinitiators show much lower migration rate and cytotoxicity. Cleavable macrocycle prismarene may provide a new idea for the design of safe and efficient photoinitiators matching long wavelength light.
The
controllable intermittent and stepwise release modes were achieved
in a dissipative system of supra-amphiphile. The supra-amphiphile
was constructed based on complexation of cationic amphiphile (Zn@DPA-14)
and biological energy currency, adenosine triphosphate (ATP). The
formation of supra-amphiphile and the competing hydrolysis of ATP
by enzyme drove the micelles assembled by Zn@DPA-14 away from the
thermodynamic equilibrium state, leading to the cargo release from
micelles during the process of micelles transformed to vesicles. Following
the time-dependent evolution, the intermittent release or stepwise
release modes of the loaded cargo realized through adjusting the polarity
of the cargo molecules. The strategy advancing from “traditional”
release modes under thermodynamic control toward the life-like controllable
modes in the far-from-equilibrium state shows unique potential applications
on transport vehicles and biomedical field.
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