Self-assembly of gradient copolymers in a selective solvent. New structures and comparison with diblock and statistical copolymers. (19th November 2021)

• Record Type: Journal Article
• Authors: Kravchenko, Vitaly S.; Abetz, Volker; Potemkin, Igor I.
• Is Part Of: Polymer. Volume 235(2021)
• Publication Date: 2021-11-19
• Subjects: Gradient -- Diblock and statistical copolymers -- Self-assembly in selective solvents -- Dissipative particle dynamics -- Solutions; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2021.124288
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: We perform comparative studies of self-assembly of equivalent statistical, diblock and gradient AB copolymers in a selective solvent using dissipative particle dynamics simulations. Both effects of the fraction of soluble and insoluble groups, selectivity of the solvent and degree of immiscibility of A and B groups on self-assembled structures are studied. With a simplified model of the statistical copolymer we predict macroscopic phase segregation, when non-aggregated chains coexist with precipitate. The later can be dense or swollen (physical gel) depending on degree of immiscibility of the A and B groups. For the case of diblock copolymer solutions, we predict thermodynamic stability of few structures: spherical and worm-like micelles, rings, vesicles and precipitate. We develop a simple theory, which allows calculating free energies of worms and rings (closed worms) and explaining transition between the structures. A number of diagrams of states is constructed. In case of gradient copolymers, two scenarios of self-assembly are predicted. The spherical micelles of gradient copolymer can aggregate with each other forming worms, rings and vesicles through aggregation of coronae (so-called sticky corona), which contain insoluble groups, if the fraction of insoluble groups per chain is not high. Herewith, the core of the assembled structures remains multidomain despite a high interfacial tension. The second ("diblock-like") scenario is realized when the fraction of insoluble groups is high enough. In this case the core of worms, rings and vesicles is practically a monodomain, however, solvophilic groups can be intercalated into the core due to the primary structure of the copolymer. A new structure of a multi-compartment vesicle on the basis of gradient copolymers is predicted. Graphical abstract: Image 1 Highlights: Gradient copolymers can self-assemble into different morphologies in a selective solvent. The spherical micelles can aggregate with each other via sticking coronae forming worms, rings and vesicles. The core of the assembled structures remains multidomain despite a high interfacial tension. A new structure of a multi-compartment vesicle on the basis of gradient copolymers is predicted.