Photochemical Coupling of Aryl Azides to Poly(ether urethane) Surfaces:  Studies with a Fluorescent Model Compound

Abstract

A fluorescent aryl azide [N-methyl-N-(2-hydroxyethyl)-5-(dimethylamino)naphthalene-1-sulfonamide 4-azidobenzoate] (2) was synthesized as a model compound for aryl azides that are used for the photochemical surface modification of poly(ether urethanes) (PEUs). We are using this method of surface modification in our search for artificial surfaces with optimized blood compatibility. As a part of this work, two pivotal questions are now addressed: (i) what is the surface density of coupled molecules that can be reached by this method and (ii) is binding to the surface really covalent? After the photochemical coupling of 2 to a PEU surface, the ester bonds of the coupled molecules were selectively hydrolyzed with 0.1 M NaOMe/MeOH and the concentration of fluorescent molecules in solution determined spectrofluorometrically. Since not all of the fluorescent molecules were removed by this procedure, an additional experiment was performed (in which the polymer was completely dissolved). It was found that 25 nmol/cm 2 had coupled to the outermost polymer layers and 7.7 nmol/cm 2 to polymer layers more within the material (unreachable for the NaOMe/MeOH reagent). In another experiment a modified PEU sheet was dissolved in THF, after which MeOH was added to precipitate it again. From the fact that no fluorescence was detected in solution it could be concluded that all of the fluorescent molecules were indeed covalently coupled to the polymer surface.

Block copolymers derived from photoreactive 2-oxazolines, 1. Synthesis and micellization behavior

“…This compound was prepared by reaction of 4-azidobenzoic acid in refluxing thionyl chloride for 3 hours and subsequent recrystallization from hexane according to a method described in the literature 14) .…”

“…Polymerization reactions of 2-oxazolines were performed using two types of initiators : methyl trifluoromethanesulfonic acid ester (15) and N-methyl-2-phenyl-oxazolinium trifluoromethane sulfonate (14).…”

A photochemical method for the surface modification of poly(etherurethanes) with phosphorylcholine-containing compounds to improve hemocompatibility

“…The maximum thrombin concoupled molecules. 24 Aryl azides have been used before centrations decrease as the clotting times increase exfor the surface modification of polymeric materials. cept for surface (d); a value of less than 56 nM would Copolymers made from p-azidostyrene and N,N-dibe expected, but 69 nM is found.…”

Adsorption of proteins onto poly(ether urethane) with a phosphorylcholine moiety and influence of preadsorbed phospholipid

“…We could further prove that this surface modification method indeed results in covalent coupling between the molecules and the polymer surface. 9 In our previous work we used this photochemical surface modification method to immobilize phosphorylcholine (PC) groups onto a PEU surface. 10 The photoreactive compound 1 ( Fig.…”