Size and charge distribution of oligomers and polymers synthesized from imidazole and diepoxy monomer

JUAN MANUEL LÁZARO MARTÍNEZ; CRISTINA VESCINA ; CAMPO DALL' ORTO, VIVIANA; TORRES, DIMAS IGNACIO

Mar del Plata

Simposio; XVI Simposio Latinoamericano de Polímeros (SLAP 2018); 2018

Instituto de Ciencia y Tecnología en Materiales (INTEMA)

INTRODUCTION The physico-chemical properties and therefore the applicability of statistical copolymers strongly depend on the molecular volume distribution of the chains in the mixture. In the case of highly functionalized macromolecules, the density of charged groups in the network and the cross-linking degree of the chains also determine their behaviour in operative processes of aggregation or adsorption. In this work we present the study of size and charge distribution of oligomers and polymers, all synthesized from imidazole (IM) and a diepoxy monomer named ethyleneglycol diglycidyl ether (EGDE). The mixtures and fractions were evaluated by size exclusion chromatography (SEC) and capillary zone electrophoresis (CZE). EXPERIMENTAL METHODS Synthesis: 80 milimols of IM were dissolved in 25 mL of acetonitrile, EGDE (in different proportions) was added and the solution was thermostatted at 60° C till the solvent resulted completely evaporated. The product mixture was dissolved or swelled in distilled water. SEC was performed with Ultrahydrogel 120 column in 0.01 M tetramethylammonium hydroxide (TMAH) pH 11 at 0.6 mL min-1 . CZE was made at 10 kV in a 75 µm x 51 cm capillary tube, injecting sample during 5 s at 30 mbar. RESULTS AND DISCUSSION The adducts EGDE:IM in the molar ratio range between 1:5 and 1:1, were water-soluble. SEC profiles indicated that the higher proportion of IM correlated with higher heterogeneity in the composition of the product mixture. The SEC record of the sample EGDE-IM 1:1.5 exhibited oligomers of 800 Da, and a minor fraction of product presented a retention time compatible with 3250 Da (Fig. 1). The electrophoretic behaviour of this sample indicated that the mixture was more complex: at least four species of high q/m ratio were partially resolved from a main population (Fig. 2). When the amount of IM was increased in the feed mixture, the product sample of EGDE:IM 1:4.6 presented at least three main components in SEC profile. One of them had a retention time equivalent to 830 Da, but the two main populations exhibited nonSEC behaviour at pH 11. Instead, the electrophoretic profile showed a main band at 8.5 min in which coexisted most of fractions collected from liquid chromatography. These species from EGDE:IM 1:4.6 had higher q/m ratio than those from EGDE:IM 1:1.5. The positive electric charge of these species, even at pH 11.0, can be attributed to the N,N disubstitution of IM residues, evidenced by NMR.CONCLUSION The heterogeneity in oligomer mixtures could be investigated by two complementary techniques: SEC and CZE, which brought information about molecular volumen and electric charge of the populations. ACKNOWLEDGMENTS Authors thank fellowship and funds from UBA, CONICET and ANPCyT (Argentina).