Computer simulations of comb-like macromolecules with responsive diblock copolymer side chains
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INVITED ARTICLE
Computer simulations of comb-like macromolecules with responsive diblock copolymer side chains Rustam A. Gumerov 1,2
&
Igor I. Potemkin 1,2,3
Received: 29 May 2020 / Revised: 8 September 2020 / Accepted: 11 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Comb-like macromolecules having diblock copolymer side chains with inner (grafted to the backbone) responsive block and outer soluble block were studied using dissipative particle dynamics simulations. Like for thermoresponsive polymers, responsiveness of the inner block means variation of its solubility upon changing of external conditions leading to variation of the solvent quality. The collapse of single copolymers (regime of infinite dilution) and their self-assembly in solution were examined. The effects of grafting density and the composition of the side chains were considered. The results reveal three distinct regimes which are characterized by the different balance of interactions between solvophilic and solvophobic groups and by the number of intramolecular clusters in the single macromolecules. The solvent quality, at which the transition between the regimes occurs, depends on the molecular architecture. In the case of macromolecular ensemble, the increase in the grafting density not only requires poorer solvent to induce intermolecular aggregation but also changes the shape of the aggregates (micelles). Namely, the grafted macromolecules can form the continuous or branched cluster, as well as cylindrical micelles. In turn, the change of the side chain composition strongly influences the stability of the solution: the longer the responsive block, the sooner the macromolecules precipitate upon the block collapse. Keywords Comb-like . Block copolymers . Collapse . Self-assembly . Computer simulations
Introduction Comb-like copolymers are well-known type of branched macromolecules consisting of multiple side chains grafted to a linear backbone polymer [1]. The conformation of such macromolecular objects is primarily determined by the amount of grafting chains (the grafting density) as well as their length in respect to the backbone length. In the regime of molecular bottlebrush (MB), which is characterized by high grafting density and long backbone, the macromolecules in a good solvent possess an increased (induced) persistence length due to the steric repulsion between the side chains [2]. This results in a cylindrical shape of * Igor I. Potemkin [email protected] 1
Physics Department, Lomonosov Moscow State University, Leninskie Gory 1-2, Moscow, Russian Federation 119991
2
DWI-Leibniz Institute for Interactive Materials, Forckenbeckstr. 50, D-52056 Aachen, Germany
3
National Research South Ural State University, Chelyabinsk, Russian Federation 454080
short macromolecules (shorter than the induced persistence length) or coiled worms otherwise [3, 4]. However, the local macromolecular shape is very sensitive to interactions between the monomer units and surroundings. In particular, the ad
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