Chemical modification of materials by reaction with diaryl diazomethanes

Post‐Polymerization Modification of Materials using Diaryldiazomethanes: Changes to Surface Macroscopic Properties

“…However, for modified polystyrenes 4a and 5a , both of which possess a very high surface area, combustion analysis confirmed the presence of nitrogen at a level of 0.86 and 0.44% respectively, consistent with the formation of the expected diazo function, and indicated a loading level of 0.045–0.31 mmol g −1 , that is 3.6 × 10 12 to 3.3 × 10 13 molecules cm −2 , assuming a surface area of 750 m 2 g −1 (manufacturer's data). This is about 10 times better than the corresponding system 1 (R = OMe), and reflects the higher reactivity of the bis(dimethylamino) system 1 (R = NMe 2 ). More successful was XPS analysis (Table ), which confirmed the presence of low levels of N for polystyrenes 4a and 5a , PEs 4d and 5d , and PETs 4p and 5p ; the N/C loading levels are lower than that expected for a complete monolayer of surface coverage, as might be expected.…”

“…Thus, the presence of aromatic nitro groups in samples 5f,o,q,s,t was indicated in the FT‐IR analysis (at 1300–1390 and ∼1510–1520 cm −1 ), and of ether links in 5d,s,t (at 1060–1160 cm −1 ) (Table ). Combustion analysis, which had previously permitted good (upper) estimates of surface loading, was less successful for all the materials in this work, presumably as a result of their low surface loading density when compared to the bulk of the substrate, and nitrogen levels for 4c,f,q and 5c,f,q were all found to be < 0.1% (Table ). However, for modified polystyrenes 4a and 5a , both of which possess a very high surface area, combustion analysis confirmed the presence of nitrogen at a level of 0.86 and 0.44% respectively, consistent with the formation of the expected diazo function, and indicated a loading level of 0.045–0.31 mmol g −1 , that is 3.6 × 10 12 to 3.3 × 10 13 molecules cm −2 , assuming a surface area of 750 m 2 g −1 (manufacturer's data).…”

“…Polymers applicable for this sequence included polystyrene, polypropylene (PP), polyethylene (PE), poly(ethylene terephthalate) (PET), polyaramide (Kevlar), polyester, and nylon, all of which may be in powder, bead, pellet, film, and sheet form, as well as woven and non‐woven fabrics. These activated materials were then further treated with commercially available Fast Black K Salt, leading to diazo coupling, giving coloured materials 5a–t (Table and Scheme (Stage 2)); this gave direct visual indication of a successful surface modification sequence . This colour change was shown to be reversible with change of pH; thus, modified polystyrene 5a after treatment with 5% NaHCO 3 gave material with a reduction in colour intensity (Figure ) which could be restored to the original colour by washing with 5% HCl.…”

Antibacterial Drug Releasing Materials by Post-Polymerization Surface Modification

“…In one approach, by exploiting the well-known reactivity of carbenes with both and chemical bonds for insertion and addition processes respectively, the functionalization of both reactive (organic and inorganic polymers) and inert (diamond, nanotubes, hydrocarbon polymers) materials using diaryldiazomethanes 1 to introduce varied surface properties, [2][3][4] including chromophoric, 5 protein a±nity, 6,7 biocidal, 8 chelation, 9 biocompatibility, 10 payload delivery, 11 dispersability, 12 nano¯lling, 13 and wettability 14,15 e®ects has been achieved. Of interest, however, was whether the surface loading density which could be achieved using this approach, which was generally in the range 0.01-0.2 mmol/g, [2][3][4] was su±cient to permit the reversible binding of small molecules at a level which was both detectable and had the capacity for a therapeutic e®ect; that this might be possible which was suggested from earlier work in which the binding of hydrogen peroxide was shown to lead to bactericidal properties, a result which was considered likely to be a best case scenario, since the existence of an extensive hydrogen binding network appeared to support multiple hydrogen peroxide units per unit of introduced surface urea groups giving high overall surface loading. 8 The development of drug delivery systems, and in particular the surface delivery of bioactive agents, especially from nanoparticles, [16][17][18][19][20][21] is currently of interest for its obvious medical and hygiene applications [22][23][24] especially in the area of antibacterials 25 ; recent work is noteworthy in that regard.…”

“…In order to prepare the functional material, we used our published protocol involving an initial carbene insertion to introduce electron-rich surface functionality, 3 followed sequentially by a second diazonium coupling and then coupling with a reagent containing a spiropyran unit, to further elaborate the surface chemistry (Scheme 1); the coupling chemistry of the two earlier stages of this process has recently been scrutinized in detail in solution and on the surface, where the formation of products by para-azo coupling was clearly demonstrated. 34 Therefore, polystyrene XAD-4 was treated with diazomethanes 1a,b as reported previously to give materials 2a,b, which were reacted further with diazonium salt 3 to generate the azo derivatives 4a,b; detailed characterization of this material …”