New Copolymer of Tautomerizable Monomer

GIUSSI, JUAN M.; ALLEGRETTI, PATRICIA E.; CORTIZO, M. SUSANA

Granada

Congreso; European Polymer Congress 2011; 2011

Although there are a lot of papers published on tautomeric studies of different organic compounds, no much works are related with tautomerics equilibria in polymers. For example, Czech studied metal chelate zirconium acetylacetonate (ZrACA) added into acrylic polymers with self-adhesive properties. These acrylic polymers, known as acrylic pressure-sensitive adhesives (PSA), were crosslinked with ZrACA to obtain acrylic self-adhesives and to study the crosslinking reaction between carboxylic groups of the polymer chain and metal chelate crosslinking agent. The tautomeric equilibrium in this reaction is very important because these reactions occur through tautomeric forms. We consider that tautomerics equilibria in polymers could be responsible for important properties and applications. That is why the aim of our work was the study of tautomerics equilibria in styrenic copolymer including a comonomer with tautomeric beta-ketonitriles form. 5-phenyl-3-oxo-4-pentenonitrile (CM3) was obtained through an adaptation of a literature method. The tautomerics equilibria in this monomer was study by mass spectra-gas chromatography (GC-MS) in gas phase, Nuclear Magnetic Resonance (NMR) in solution and Infrared (IR) spectroscopy in solid state. These experimental results were compared with DFT calculations. CM3 was copolymerized with styrene in thermal conditions at 60ºC using azobisisobutyronitrile (AIBN) as initiator. The polymerization reactions were carried out in closed reaction tubes in vacuum. The reactions was quenching by precipitation with cold methanol. The polymer isolated was purified by dissolving in chloroform and precipitation on methanol. We repeated this procedure until only the peak of the polymer was seen in the size-exclusion chromatography (SEC). The weight average molecular weight (Mw) and the polydispersity index (PI=Mw/Mn) were determined by SEC using a series of four Waters columns and Cl3CH as eluent. Polystyrene standard was used as calibrant. The tautomerisms present in this monomer are keto-enol and nitrile-ketenimine. The nitrile-ketenimine has been evidenced only by GC-MS, while the tautomerism keto-enol was seen by NMR and IR spectra only. We expected that this type of behavior can be observed in the corresponding copolymers. The polymers were characterized by IR spectroscopy. We could asignated picks for both monomers and also for tautomeric forms. Nitrile band at 2230 cm-1 and carbonyl band at 1685 cm-1. We assigned a band at 1620 cm -1 for double bound C=C for enolics forms in the polymers obtained. There is an increase of the reaction conversion when the content of CM3 decrease, which suggest a lower reactivity of this monomer. Accordingly, an increase in the Mw was observed. Actually, we are carrying out determinations by NMR spectroscopy in order to determinate the copolymer composition (F) and then the reactivity ratio. New copolymers styrene-5-phenyl-3-oxo-4-penteno-nitrile was synthetized and characterized whose tautomeric equilibria study is been conducted.