An XPS study about the structure of plasma biocopolymers synthesized with resistive radio frequency glow discharges and random combinations of ethylene glycol, pyrrole, and iodine, as a dopant, is presented in this work. The collisions of molecules produced structures with a great variety of chemical states based in the monomers, their combinations, crosslinking, doping, fragmentation, and oxidation at different levels in the plasma environment. Iodine appears bonded in the copolymers only at high power of synthesis, mainly as C–I and N–I chemical bonds. Multiple bonds as C≡C, C≡N, C=O, and C=N were found in the copolymers, without belonging to the initial reagents, and were generated by dehydrogenation of intermediate compounds during the polymerization. The main chemical states on PEG/PPy/I indicate that all atoms in pyrrole rings participate in the polymerization resulting in crosslinked, partially fragmented, and highly oxidized structures. This kind of analysis can be used to modify the synthesis of polymers to increase the participation of the most important chemical states in their biofunctions. 1. Introduction Polymers formed with oxygenated and/or nitrogenated chemical groups, such as polyethylene glycol (PEG) and polypyrrole (PPy), are studied as biomaterials to be implanted in the central nervous system to reduce possible side effects in the spinal cord after a severe injury. PEG is an oxygenated polymer with the potential to influence or repair the membrane permeability caused by injuries or diseases [1, 2] and PPy is one of the most studied nitrogenated biocompatible polymers used as a biosensor, cell growth supporter for nerve cells, and substrate for junction between neurons and microelectrodes [3, 4]. The PPy potential for transferring electric charges is related to the alternated multiple-single chemical bonds in the rings of its structure. The chemical structure for random plasma combinations of ethylene glycol (EG) and pyrrole (Py) copolymers (PEG/PPy) is studied in this work to produce polymers capable of interacting with neuronal cells. Other components can be added to the mix, for example, iodine with the aim of increasing the conductive properties [5]. In the spinal cord, many polymers have caused rejection due to their noncompatible physicochemistry or to the residues of solvents, catalysts, or other reagents used in the synthesis which irritate the delicate tissues causing adverse reactions that destroy healthy nerve cells. The polymers of this work reduce this problem because the plasma synthesis only uses the monomers and
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