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ABA type tri-block amphiphilic polyelectrolyte consisting of poly(methyl methacrylate-block-methacrylic acid-block-methyl methacrylate) (P(MMA-b-MAA-b-MMA)) was synthesized by atom transfer radical polymerization technique (ATRP) and the self-assembly behavior of the polymers in aqueous solution was studied over the course of neutralization. Combination of potentiometric and conductometric titrations along with dynamic light scattering (DLS) techniques were used to investigate the size and shape of aggregates at various degrees of neutralization. The effect of hydrophobic-hydrophilic (MMA-MAA) ratio and polymer chain length on the aggregation behavior during neutralization was studied. P(MMA-b-MAA-b-MMA) with longer MMA segment self-assembles via the close association mechanism through stronger self-entanglement of MMA chains, whereas P(MMA-b-MAA-b-MMA) with shorter MMA chain self-assembles via the open association mechanism, as confirmed by transmission electron microscopy (TEM). Conductometric titration was used to determine the counterion condensation during the course of neutralization. When the charge density of micelle approaches a critical value as neutralization progresses, counterion condensation of Na+ ions on the polymer chains occurs. The effect of counterion condensation on the aggregation behavior during neutralization was elucidated., Singapore-MIT Alliance (SMA)

Atom transfer radical polymerisation (ATRP) technique was used to synthesize poly(methacrylic acid-block-methyl methacrylate) (P(MAA₁₀₂-b-MMA₁₀)) copolymer in order to study the aggregation behavior in aqueous solution over the course of neutralization. A combination of static and dynamic light scattering (SLS, DLS) and potentiometric titration techniques were used to investigate the size and shape of the micelle at various degrees of neutralization. The hydrodynamic radius (Rh) determined from dynamic light scattering increases from ~26nm (for unneutralized) to ~42nm (for completely neutralized sample). Both potentiometric and laser light scattering studies indicate the formation of a core shell micelle. The weighted average molecular weights of the polymer and micelle are 1.18x10⁴ and 2.25 x 10⁵ g/mol respectively, which suggests that the aggregation number of the micelle is ~20., Singapore-MIT Alliance (SMA)

Di-block copolymer of poly[methacrylic acid-block-2-(diethylamino)ethyl methacrylate] [P(MAA-b-DEA)] with narrow molecular weight distribution was synthesized using the atom transfer radical polymerization (ATRP) technique. The micellization behavior of the P(MAA-b-DEA) copolymer in aqueous solution at room temperature and different pH values were examined by potentiometric and conductivity titration, UV-Visible spectrophotometry, ¹H-NMR, static and dynamic laser light scattering. At low pH (< 4.2), core-shell micelles were formed with MAA core and protonated DEA shell. At moderate pH values, the polymer precipitated from water and formed a cloudy solution, where the polymer chains aggregated into larger particles resembling that of a hard sphere induced by electrostatic interactions. At high pH (> 9.5), core-shell like micelles consisting of hydrophobic DEA core and ionized MAA shell were re-established., Singapore-MIT Alliance (SMA)