Investigação calorimetrica da interação entre poli (N-isopropilacrilamida) e surfatantes ionicos / Calorimetric investigation of the interaction of poly (N-isopropylacrylamide) and ionic surfactants

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

The interaction of poly(N-isopropylacrylamide), PNIPAM, with an anionic (SDS) and three cationic (dodecyl and hexadecyltrimethylammonium bromides, DTAB and CTAB, and dodecylammonium chloride, DAC) surfactants has been studied using isothermal titration calorimetry and within a temperature range between 17 and 29°C. The high sensitivity of this technique allows the precise determination of the parameters that characterize polymer-surfactant interactions. Based on these results, it is possible to conclude that the interaction of PNIPAM with ionic surfactants is significantly affected by temperature. This is attributed to changes in polymer hydration, which become more important near the lower critical solution temperature. The nature and the size of the headgroup, and the hydrophobicity of the hydrocarbon chain of the surfactants are important factors and interfere on the polymer-surfactant interaction. The interaction is more intense with the anionic than with the cationic surfactants. CTAB, which possesses the same headgroup and larger chain length than DTAB displays a more intense interaction than DTAB. DAC, which possesses the same chain length and smaller headgroup than DTAB, interacts more strongly with PNIPAM than DTAB. Thus, for the same degree of hydrophobicity, a smaller headgroup favors the interaction.

ASSUNTO(S)

calorimetria calorimetry ionic surfactants poli (n-isopropilacrilamida) poly (n-isopropylacrylamide) surfatantes ionicos

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