6533b823fe1ef96bd127f0b9

RESEARCH PRODUCT

Crosslinking of polymers activated by electrogenerated hydroxyl radicals.

subject

description

Nanogels (NGs) are systems created by crosslinking of polymers taking nanosized dimensions and they have been proposed for biomedical and pharmaceutical applications due to their soft consistency, biocompatibility and good chemical properties that make them excellent drug delivery agents (1). Differently from typical hydrogels, nanogels are able to dissolve in solvents and to swell releasing the drug molecules loaded in the nano-vector. Furthermore, if properly functionalized with reactive groups, these materials can represent a very interestingly vector for different pharmacological treatments (2). Several methods have been investigated to prepare polymeric nanogels starting from preformed polymer chains, such those based on high energy ionizing radiations or accelerated electrons which induce generation of free radicals on the polymer backbone (3). These active centers can undergo inter and/or intramolecular combination thus leading to the generation of a 3D network. Other authors have studied more simple methods to generate hydroxyl radicals in aqueous environment such as those based on Fenton reactions. On the other hand, electro-oxidation processes are well known to allow the abatement of recalcitrant organic compounds by the action of electro generated hydroxyl radicals (4). In this contest, we have focused the attention on three different electrochemical processes, characterized by different nature and reactivity of electrogenerated hydroxyl radicals: - Electro-generation of phisisorbed hydroxyl radicals at Boron Doped Diamond (BDD) “non-active anodes”; - Electro-generation of chemisorbed hydroxyl radicals at DSA (Ti/IrO2-Ta2O5) “active anodes”; - Electro-generation of homogeneous hydroxyl radicals by electro-Fenton (EF) Clear evidences of intramolecular crosslinking of poly(vinylpyrrolidone) macromolecular chains were obtained when the electrogeneration of homogeneous hydroxyl radicals was carried out by an electro-Fenton process. This reaction was confirmed by a reduction of the average gyration diameter of the chains in solution detected by dynamic light scattering accompanied by narrowing of the molecular weight distribution of the polymer. This is the first indication that an electrochemical method can be used to generate hydroxyl radicals that can be used to modify the molecular architecture of preformed polymers. Work is in progress to evaluate the effect of many operating parameters, such as flow dynamic regime, current density, working potential and temperature.