Document Type : Research Article
Chemistry Department, Faculty of Science, University of Benghazi, Benghazi, Qar Yunis, Libya
In the present work, the critical concentration for self-assembly of dansyl-polyacrylic acid (DANS-PAA) in aqueous solution has been characterized by a combination of spectrophotometric and tensiometric techniques, number average molar mass, degree of polymerization, and average number of bonds were also determined. The normalized absorbance value for DANS-PAA (10 -4 wt%) as a function of PAA concentration was at maximum below a critical self-assembly concentration (CAC) of 0.0005 g·mL −1 and decreased dramatically with PAA concentration above this CAC. This supposes that upon adding more polymer, assembly occurs in a short concentration range about 0.0005 g·mL −1 . Similarly, surface tension measurements for DANS-PAA decreased markedly with concentration after a threshold of around 0.0005 g·mL −1 , above which it remained constant at ca. 20 dyne·cm −1 . Consequently, the binary techniques produced an equivalent estimation of the CAC. Additionally, surface tension studies showed that the DANS-PAA polymer miscible with water caused surface tension to decrease by 49 % over a concentration range of 0 to 0.0014 g·mL −1 , whereas marked reduction in surface tension (33 %) upon adding PAA, and slight decreasing (7%) was recorded upon adding acrylic acid monomer (AA) to water. © VBRI Press.