Polyrotaxane‐Mediated Self‐Assembly of Gold Nanospheres into Fully Reversible Supercrystals

Abstract

The use of a thiol‐functionalized nonionic surfactant to stabilize spherical gold nanoparticles in water induces the spontaneous formation of polyrotaxanes at the nanoparticle surface in the presence of the macrocycle α‐cyclodextrin. Whereas using an excess of surfactant an amorphous gold nanocomposite is obtained, under controlled drying conditions the self‐assembly between the surface supramolecules provides large and homogenous supercrystals with hexagonal close packing of nanoparticles. Once formed, the self‐assembled supercrystals can be fully redispersed in water. The reversibility of the crystallization process may offer an excellent reusable material to prepare gold nanoparticle inks and optical sensors with the potential to be recovered after use.

Supramolecular Reinforcement of Polymer–Nanoparticle Hydrogels for Modular Materials Design

“…Our approach was motivated by evidence that αCD can thread onto PEGylated NPs, enhancing NP-NP interactions through polypseudorotoxane formation. [39][40][41][42][43][44][45][46][47] We leveraged this approach to engineer CD-PNP hydrogels through the inclusion of αCD in the formulation, which provided mechanical reinforcement and modular exchange of the hydrogel building blocks. As characterized via shear rheometry, αCD enhanced the viscoelastic properties of CD-PNP hydrogels by orders of magnitude while preserving the ability to shear-thin and self-heal.…”

“…[1] In the literature, αCD has been used to precipitate solidlike hydrogels via increased NP-NP interactions. [39][40][41][42][43][44] Based on these findings, we included αCD as a supramolecular motif in the PNP formulation to enhance the mechanical properties and enable modular design (Figure 1b). αCD increased the shear storage modulus of the hydrogels by several orders of magnitude (samples containing 1, 5, and 10 wt% αCD exhibited G′ ≈ 1.7 × 10 1 , ≈ 3.0 × 10 3 , and ≈ 6.5 × 10 4 Pa at ω = 10 rad s −1 , respectively; Figure 1c and Figure S1, Supporting Information).…”

“…[10,38] Polypseudorotaxanes have been exploited as supramolecular crosslinks to assemble hydrogels from polymeric and nanoparticulate building blocks, including for drug delivery applications. [39][40][41][42][43][44] Of note, Dreiss and co-workers demonstrated that αCD could precipitate PEGylated silica NPs into hydrogels and characterized the design space for gel formation. [42] Similar design principles have been applied to assemble colloidal hydrogels from block copolymer NPs, PEGylated inorganic NPs, and PEG-functionalized dendrimers or branched polymers.…”

Threading through Macrocycles Enhances the Performance of Carbon Nanotubes as Polymer Fillers

“…[23][24][25][26][27][28][29][30] The mechanical bond is also very relevant for polymer science: polyrotaxanes, polycatenanes, and supramolecular polymers including mechanically interlocked molecules have all been investigated. [31][32][33][34][35][36][37][38][39] The reinforcement effect of B/SiOx nanocomposites through the formation of interlocked "necklaces" has also been described. 40,41 The mechanical link was introduced by some of us as a tool for the chemical manipulation of SWNTs very recently.…”