Polyglycidol-based metal adhesion promoters

Abstract

Hydrophilic adhesion promoters that facilitate intimate binding between metals and polymers are an important class of materials with a wide variety of applications in biomedical coatings. Currently, nonpoly(meth-)acrylate based hydrophilic polymeric adhesives are unavailable. Here, we report the preparation of such adhesion-promoters based on linear polyglycidol for biomedical applications. The adhesion promoting polymer is prepared from partly phosphonoethylated polyglycidol in three steps.First, the remaining hydroxyl groups of the polyglycidol backbone are reacted with acryloyl chloride; secondly, the phosphonate groups are chemoselectively dealkylated using bromotrimethylsilane. Finally, the bis(trimethylsilyl)phosphonate intermediate is converted to the phosphonic acid through ethanolysis.The reaction conditions of each synthetic step are optimized individually and the products are characterized by 1 H, 31 P NMR and SEC analysis. The optimized reaction conditions are applied to establish a straightforward one-pot reaction, resulting in an ethanolic formulation of the adhesion promoter, which can be used immediately for the coating application. Special attention is paid to the stability of the intermediates, the chemoselectivity of the reactions and the shelf-life of the product. 1 H NMR spectroscopy reveals hydrolytic instability of the product under ambient conditions; however, the polymers are sufficiently stable in dry ethanol for at least 14 days. The combination of this hydrophilic polymer with acrylate and phosphonic acid groups constitutes a versatile platform technology for the preparation of thin primer coatings on metal substrates for biomedical applications. The phosphonic acid residues assure strong binding to stainless steel wires and the acrylates can be addressed by UV light to enable crosslinking, thus improving mechanical stability and adhesion between the substrate and a biomedical hydrogel coating. The quality of the adhesion promotion to stainless steel wires is verified by using a lubricious, hydrogel top coat and by evaluating friction and wear resistance of this total coating system. Constant values for friction and wear are obtained, proving the applicability of phosphonic acidfunctionalized polyglycidols as metal adhesion promoters for biomedical applications.

The McKenna reaction – avoiding side reactions in phosphonate deprotection

“…HBr might form upon careless storage and/or use of BTMS, which exposes it to traces of water. As mentioned in the previous section, compounds having multiple bonds could undergo an addition reaction upon exposure to HBr [42]. We studied this problem using 1 H NMR spectroscopy with the model acrylamide 11 (Scheme 3), representing a Michael acceptor, as such is currently popular in the development of covalent inhibitors [43].…”

Homoserine Lactone as a Structural Key Element for the Synthesis of Multifunctional Polymers

“…Polyglycidol was functionalized in a Michael-type addition with diethylvinyl phosphonate and subsequent dealkylation of the pendant phosphonate groups [21]. Additionally, multifunctional polyglycidols carrying phosphonic acid and acrylate moieties were examined as UV-active adhesion promoters for a hydrogel coating on stainless steel wires [22].…”

Straightforward synthesis of phosphate functionalized linear polyglycidol

“…The phosphonate functionalized polyglycidols were used as macroinitiators in the graft-copolymerization of e-caprolactone, enhancing the hydrolytic degradability of the poly(caprolactone) formed [18,19]. Additionally, multifunctional polyglycidols carrying phosphonic acid and acrylate groups were prepared and examined as UV-active adhesion promoters for a hydrogel coating on stainless steel wires [20].…”