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

Abstract

Diarylcarbenes have been shown to be suitable for the surface modification of a diverse range of polymers, including low surface energy materials, and this allows the modification of surface macroscopic effects, exemplified by changes in wetting behaviour, pH sensing, and bactericidal activity.

A comparative study of diaryl carbene insertion reactions at polymer surfaces

“…1d was made; this diazo compound was chosen for its known high level of reactivity and the ability to determine polymer surface loading levels using nitrogen as the reporter atom. 21,30,31 The materials were immersed in THF solutions at 10, 25, 50 and 100 %w/w relative to the mass of polymer. After the solvent was carefully removed, leading to physisorption of the diazo compound onto the surface, heating at 110 ˚C resulted in a colour change from the green diazo 1d to yellow modified polymer (Table 2, ESI); this colouration is consistent with the introduction of aromatic residues onto the surface, and the intensity of yellow colour broadly correlated with the surface loading (vide infra) of the modifying reagent (Table 2, ESI).…”

“…20 This value is consistent with the loading values in related polystyrene systems, previously estimated to be up to 10 13 molecules.cm -2 . 20,21,31 By way of elaborating this observation further, a key question was whether a more efficient azo-coupling step which would in turn improve the downstream surface modification could be achieved by harnessing the known superior activating properties of aromatic oxy-anion or hydroxy groups towards electrophilic aromatic substitution; 49, 50 of interest was whether this could be achieved with a protected diol system that could be revealed on the surface. To this end, THPderivatives 5b,d were prepared from phenols 5a,c respectively using the standard procedure (Scheme 2); these ketones were readily converted to diazo derivatives 6a,b.…”

“…19 A key advantage of this approach is that the diaryldiazo compounds may carry remote functional groups, and that the initially modified surface may be further reacted by a secondary diazonium coupling reaction to impart further new chemical functionality. 20 This breadth of reactivity allows for a flexible and efficient method of modification that can be applied to a wide range of materials, including organic and inorganic polymers 21,22 and which has been demonstrated to permit the introduction of visible 17 and fluorescent 23 chromophores, biocompatible and biocidal groups, 24 along with protein, cellular and interfacial adhesion, 20,25 and hydrophobicity 22,26 effects. Much of this work has focused on the change in macroscopic properties from the surface modification process, but this paper presents a more indepth investigation into the modification reaction itself, in which we seek to understand the interplay of the chemistry of diaryldiazo compounds and polymers in their reactions at the surface, by detailed analysis of the surface modification and its consequent effect on the macroscopic properties of the polymer.…”

Structure and Reactivity of Half-Sandwich Rh(+3) and Ir(+3) Carbene Complexes. Catalytic Metathesis of Azobenzene Derivatives

“…CCDC 1575834 (3), 1443595 (12), 1575835 (13), 1575836 (14a), 1575837 (15) and 1575838 (41) contain the crystallographic data of the complexes shown in the paper; CCDC 1575459 (4), 1575460 (8) and 1575461 (17) contain the crystallographic data of the complexes shown below (SI only): bis(4-methoxyphenyl)diazomethane (5a), 3 bis(4-(dimethylamino)phenyl)diazomethane (5b), 4 methyl 2-diazo-2-(4-methoxyphenyl)acetate (6a), 5 methyl 2-diazo-2-phenylacetate (6b), 5 methyl 4-(1-diazo-2-ethoxy-2-oxoethyl)benzoate (6c), 6 9-diazo-9H-fluorene, 7 (Z)-1,2-diphenyldiazene (Z-16), 8 (E)-1,2bis(4-methoxyphenyl)diazene, 9 (E)-1,2-bis(4-fluorophenyl)diazene, 9 (E)-1,2-bis(4-(trifluoromethyl)phenyl)diazene, 10 (E)-1,2-bis(3,5-dimethylphenyl)diazene, 9,11 (E)-1,2-di-p-tolyldiazene, 9 dioctyl 4,4'-(diazene-1,2-diyl)(E)-dibenzoate, 12 (E)-1,2-bis(2,6-dimethylphenyl)diazene, 13 (E)-1,2-bis(3methoxyphenyl)diazene, 9,10 (E)-1-(p-tolyl)-2-(4-(trifluoromethyl)phenyl)diazene, 14 (E)-1,2-di-o-tolyldiazene, 9 (E)-1,1'-(diazene-1,2-diylbis(3,1-phenylene))bis(ethan-1-one), 9,15 (E)-1,2-bis(4-azidophenyl)diazene 16 . matched the previously reported values.…”

Chemical functionalization of polyethylene surfaces by plasma-assisted carbene insertion

“…Due to the low chemical reactivity of many polymer surfaces, however, surface modification often requires strong acid or alkali conditions [18][19][20][21][22] and these harsh reaction conditions often damage the surface and internal structure of polymers, leading to deterioration of mechanical and bulk properties. An alternative direct surface modification under milder conditions by using highly reactive diarylcarbenes, generated by thermolysis or photolysis of precursor diaryldiazomethanes, [23] has been developed, and been shown to modify the macroscopic properties of material surfaces [24,25] for the introduction of a range of properties (e.g. visible [26] and fluorescent [27] chromophore, adhesion, [28,29] biocidal, [30] and hydrophobicity [31,32] effects) onto a variety of substrates.…”