Synthesis and Characterization of a Thermoresponsive Polyoxometalate–Polymer Hybrid

Abstract

We report the synthesis of the first organo-POM with thermoresponsive properties. Our concept will provide chemists with a new tool to design POMs whose solubility is reversibly controllable through an external stimulus. POM-polymer TBA(7)[POM]-poly(N,N-diethylacrylamide) (POM-PDEAAm), was prepared by grafting PDEAAm-NH(2) (obtained by RAFT polymerization) onto the activated Dawson acyl-POM, α(2)-[P(2)W(17)O(61)SnCH(2)CH(2)C(=O)](6-). Extensive MS analysis was used to monitor the chain-functionalization steps and to confirm the formation of the hybrid. Aqueous solutions of the (NH(4))(7)[POM-PDEAAm] exhibited a LCST of 38 °C. Thus, the solubility/aggregation of the hybrid was reversibly controlled by changing the temperature. Above 38 °C, the solution became cloudy, and cleared again upon cooling. Dynamic light scattering (DLS) revealed the formation of small aggregates in the range 100 nm. We assumed that the charged POM head units prevented the formation of the larger-scattering aggregates that are usually observed for PDEAAm, and promoted the formation of micelle-like structures. The conjugate exhibited a temperature transition, which was different from that of the polymer and depended on the counterions associated with the POM. This result demonstrates the potential for merging organic (in this case, polymer) and inorganic structures to afford materials that exhibit new properties.

Rational design of nanomaterials from assembly and reconfigurability of polymer-tethered nanoparticles

“…[35] Other materials, such as polyoxometalate anionic metal-oxygen nanocages, have been successfully attached to polymer tethers via covalent bonds. [36,37] As these studies demonstrate, a wide range of materials are amenable to this type of modification and are experimentally accessible, opening up an enormous design space for new functional materials.…”

Versatile Post‐functionalization of Polyoxometalate Platforms By Using An Unprecedented Range of Palladium‐Catalyzed Coupling Reactions

“…[2] Indeed, the covalent functionalization of POMs allows fine control of the interaction between the different components and may also facilitate the incorporation and the dispersion of POMs into polymers, [3] microdispersed media, [4] or onto surfaces, [5] while favoring long term stability. By using the covalent approach, POM-based hybrids were successfully developed for different applications such as artificial photosynthesis, [6] molecular electronics, [5a, 7] catalysis, [8] or autohealing.…”

“…[24] However, PdA Table 2, entries 1 and 2). Increasing the amount of (EtO) 3 SiA C H T U N G T R E N N U N G (vinyl) from 3 to 12 equivalents yielded a slightly better (38 %) conversion (Table 2, entry 3), which could be further increased (50 %) through pre-activation of (EtO) 3 Si-A C H T U N G T R E N N U N G (vinyl) with TBAF at room temperature for 1.5 h in a DMF/ THF mixture ( Table 2, Table 2, entry 5), although, in this case, POM by-products were observed (note that the POM-tin functionalization is retained in the undesired products). We then decided to test dimethyl-2-thienyl-vinylsilane, as thienyl silanes are known to be a very efficient and robust vinylating partners in cross-coupling reactions with aryl iodides.…”

Polyoxometalate-based phase transfer catalysis for liquid–solid organic reactions: a review

“…Several kinds of alcohols were efficiently oxidized in high yields. 77 The obtained material exhibited thermoresponsive properties with the lower critical solution temperature (LCST) of 38 °C. In the same year, they reported another temperature-controlled phase transfer catalyst of [(C 18 H 37 ) 2 (CH 3 ) 2 N] 7 [PW 11 O 39 ] that was used for the oxidation of pyridines and alcohols with H 2 O 2 in 1,4-dioxane ( Figure 15).…”