Controlled one-pot synthesis of pH-sensitive self-assembled diblock copolymers and their aggregation behavior |
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Authors: | B.W. Mao Y.Y. Gan O.K. Tan |
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Affiliation: | a Natural Sciences and Science Education, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616, Singapore b Singapore-MIT alliance, School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore, Singapore c School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, Singapore |
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Abstract: | Diblock copolymers of t-butyl methacrylate (tBMA) and 2-(diethylamino)ethyl methacrylate (DEAEMA) were successfully synthesized by one-pot strategy via the atom transfer radical polymerization (ATRP). Kinetic results clearly demonstrated the controlled/‘living’ character of the polymerization. The zwitterionic block copolymers of poly(methacrylic acid-b-DEAEMA), obtained by hydrolysis of poly(tBMA-b-DEAEMA), showed pH-dependent reverse micellization behavior. Micellar aggregates formed from poly(MAA30-b-DEAEMA71), poly(MAA68-b-DEAEMA55) and poly(MAA64-b-DEAEMA44) had fairly low polydispersity index at both solutions of low pH of 2 and high pH of 12. Micelles formed at pH 2 were larger (Rh∼40-61 nm) with looser core due to hydration of the MAA. In the presence of simple electrolyte (0.3 mol dm−3 NaCl solution), the size of the micelles reduced by almost half while the aggregation number was little changed. This is attributed to the draining of the hydrated micellar core due to osmotic pressure. On the other hand, DEAEMA-core micelles formed at pH 12 were compact and much smaller (Rh∼14-22 nm). Addition of NaCl had only a small effect. The micellar size reduced only slightly due to the electrostatic screening effect and the aggregation number was almost unchanged. |
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Keywords: | One-pot ATRP Zwitterionic diblock copolymers Kinetics |
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