Micellization of Non-Surface-Active Diblock Copolymers in Water. Special Characteristics of Poly(styrene)-block-Poly(styrenesulfonate)

Abstract

Strongly ionized amphiphilic diblock copolymers of poly(styrene)-b-poly(styrenesulfonate) with various hydrophilic and hydrophobic chain lengths were synthesized by living radical polymerization, and their properties and self-assembling behavior were systematically investigated by surface tension measurement, foam formation, hydrophobic dye solubilization, X-ray reflectivity, dynamic light scattering, small-angle neutron scattering, small-angle X-ray scattering, and atomic force microscope techniques. These copolymer solutions in pure water did not show a decrease of surface tension with increasing polymer concentration. The solutions also did not show foam formation, and no adsorption at the air/water interface was confirmed by reflectivity experiments. However, in 0.5 M NaCl aq solutions polymer adsorption and foam formation were observed. The critical micelle concentration (cmc) was observed by the dye solubilization experiment in both the solutions with and without added salt, and by dynamic light scattering we confirmed the existence of polymer micelles in solution, even though there was no adsorption of polymer molecules at the water surface in the solution without salt. By the small-angle scattering technique, we confirmed that the micelles have a well-defined core-shell structure and their sizes were 100-150 A depending on the hydrophobic and hydrophilic chain length ratio. The micelle size and shape were unaffected by addition of up to 0.5 M salt. The absence of polymer adsorption at the water surface with micelle formation in a bulk solution, which is now known as a universal characteristic for strongly ionized amphiphilic block copolymers, was attributed to the image charge effect at the air/water interface due to the many charges on the hydrophilic segment.

Hydrophobically-associating cationic polymers as micro-bubble surface modifiers in dissolved air flotation for cyanobacteria cell separation

“…However, highly cationic polymers (specifically LC10-h and HC10-h) had surface tensions similar to that of pure water at 72 mN m À1 (Table 1) despite the hydrophobic functionality. Similarly, in an investigation of polymers with low polydispersity at an airewater interface, Matsuoka et al (2004) also found that charged polymers exhibited 'non-surface activity' despite the presence of hydrophobic groups. Polymer accumulation at the air-liquid interface is theorised to occur as hydrogen bonding with OH À or H þ groups (Yang et al 2001), which translates to air-liquid surface adsorption without surface penetration.…”

Chemical analysis and aqueous solution properties of charged amphiphilic block copolymers PBA-b-PAA synthesized by MADIX®

“…To conclude this CMC discussion, one should note that the presence of free unimers in solution of amphiphilic diblocks with low CMC is not specific to radical polymerization samples. Free unimers have also been observed in solution of Poly(tertbutyl Styrene)-Poly(Styrene Sulfonate) [6] and Poly(Styrene)-Poly(Acrylic Acid) [34] diblocks in water, although these systems had been synthesized by anionic polymerization and form frozen core objects.…”

Why Ionic Amphiphilic “Block” Copolymer Can Be Non-surface Active? Comparison of Homopolymer, Block and Random Copolymers of Poly(styrenesulfonate)

“…Previously, 2 we studied the non-surface active nature of PS-b-PSS; the surface tension of the solution did not decrease and no foam was observed under a no salt condition, while it changed into surface active by salt additon. In this study, to make the origin of the non-surface activity clearer, we examined the nature of random copolymer of styrene and styrenesulfonate in additon to that of the PSS homopolymer.…”

“…2 The degree of polymerization was m:n = 57:59. Surface tension of the solutions of random, homo, and block copolymers, measured with FACE CBVP-Z Surface Tensiometer (Kyowa Interface Science, Tokyo) is shown in Figure 1 together with the observation of foam formation.…”

“…No adsorption of PSt-b-PSS block copolymer at the water surface had been already confirmed by XR in our previous study. 2 The XR profile for random polymer solution showed a Kiesigg fringe at the scattering vector q = 0.15 ¡ ¹1 (q = 4³ sin ª/, 2ª: scattering angle, : the wavelength of X-ray (1.5406 ¡)) although only slightly, indicating layer formaion on the water surface. By 1-Box model fitting of XR profile, the adsorbed layer with 25 ¡ thickness was confirmed.…”