Graft Copolymers, for Erodible Resins, from α-Hydroxyacids Oligomers Macromonomers and Acrylic Monomers

Environmental concerns result in a progressive withdrawal of antifouling paints containing organotin derivatives. The nature of the binders is critical with regard to the erosion of the protecting film through factors such as bond cleavage, dissolution, and diffusion of the degradation products. The versatility of acrylic polymers, due to the possibility of varying their chemical structure had conducted, in the first stage, to combine different types of repeating units in the macromolecular backbone. Formulation and evaluation, in natural sites, of these binders, with a well-defined hydrophobic/hydrophilic balance and with hydrolyzable pendant groups, have shown the possibility to prepare new organotin free resins which can be formulated and which are erodible in seawater over a long period (more than 2 years). A further step has been engaged with the development of graft copolymers containing biocompatible and hydrolyzable oligomers of α-hydroxyacids. Their preparation requires the synthesis of α-methacryloyloxyoligo-α-hydroxyacid macromonomers. Copolymers prepared from a mixture of the macromonomer and of an alkyl ester of acrylic acid were formulated with a biocide and deposited on a plate. Their ability to release cuprous oxide, as a model molecule, has been checked and quantified by the inductively coupled plasma analytical method. The uptake of water in the paint, which is enhanced by the hydrolysis of α-hydroxyacid oligomers, as determined by the enzymatic measurement of liberated L-lactic acid, conducts to the polymer erosion and to a protecting bioactive surface.