Unimolecular Micelle Formation of Poly(methyl methacrylate)-graft-polystyrene in Mixed Selective Solvents of Acetonitrile/Acetoacetic Acid Ethyl Ether

Abstract

Unimolecular micelle formation is investigated by means of light scattering for poly(methyl methacrylate)-graft-polystyrene copolymers with low grafted chain densities in dilute solution of mixed selective solvents. Molecular weights of poly(methyl methacrylate) (PMMA) backbone and polystyrene (PS) branch are about 6 × 106 and 9 × 103 g mol-1, respectively, and the grafted chain density ranges from 6 to 17 wt % in terms of PS composition. The mixed solvents are marginally good solvents for PMMA and are nonsolvents for PS. From the results of static and dynamic light scattering measurements as a function of temperature and solvent composition, it is demonstrated that, at higher branch densities and lower temperatures, the rod like unimolecular micelles are formed, made of a few linearly connected flowers with small cores of associated PS branches and petals of PMMA backbone chain. The number of petals per flower increases with increasing branch density and decreasing solubility of solvents for PMMA. On the other hand, at the lowest branch density of 6 wt %, instead of unimolecular micelle formation, intermolecular associations take place, even at low copolymer concentration.

Folding and Formation of Mesoglobules in Dilute Copolymer Solutions

“…In most cases, interchain association often occurs with intrachain self-folding, which spoils the study and leads to multi-chain micelles coexisting with single-chain micelles [91,92]. To our knowledge, only Kikuchi and Nose [93] experimentally studied intrachain micelle formation. They used polystyrene-g-poly(methyl methacrylate) to observe the formation of thermodynamically stable singlechain multi-flower structures and revealed that the resultant structure was rigid and on average consisted of ca.…”

Micelle formation, gelation and phase separation of amphiphilic multiblock copolymers†

“…For the case of amphiphilic graft copolymers, the existence of intramolecular pearl-necklaces of micelles and cylindrical micelles was argued theoretically and directly observed in simulation studies 28,29 . Also, it was shown experimentally that amphiphilic graft copolymers in dilute solutions form either unimolecular rodlike chains of micelles or unimolecular rodlike micelles, depending on the quality of the solvent 30,31 .…”

Structure and dynamics of polymeric systems

“…Intramolecular structure formation of polymers carrying associative groups along the chain backbone have been the subject of experimental (McCormick, 2000;Glass, 2000;Kikuchi and Nose, 1996) and theoretical (Halperin, 1991;Borisov and Halperin, 1997;Koga, 2000, 2001;Koga and Tanaka, 2001) interest in recent years. Knowledge of the intramolecular structure formation of single polymer chains is absolutely essential for an understanding of the molecular mechanism of physical properties of many-chain associating systems, e.g., solution properties of associating polymers and the elasticity of networks whose subchains contain associative groups.…”