Phase behavior of symmetric linear multiblock copolymers

TL;DR

This study uses molecular dynamics simulations to explore how symmetric linear multiblock copolymers behave under poor solvent conditions, identifying regimes of microphase separation based on block length, number, and temperature.

Contribution

It provides a detailed phase diagram of symmetric multiblock copolymers under poor solvent conditions, highlighting the regimes of microphase separation and their dependence on key parameters.

Findings

Full microphase separation occurs in certain regimes.

Probability of microphase separation varies with parameters.

Further investigation needed for very high block numbers and lengths.

Abstract

Molecular dynamics simulations are used to study the phase behavior of a single linear multiblock copolymer with blocks of A- and B-type monomers under poor solvent conditions, varying the block length $N$, number of blocks $n$, and the solvent quality (by variation of the temperature $T$). The fraction $f$ of A-type monomers is kept constant and equal to 0.5, and always the lengths of A and B blocks were equal ($N_{A}=N_{B}=N$), as well as the number of blocks ($n_{A}=n_{B}=n$). We identify the three following regimes where: (i) full microphase separation between blocks of different type occurs (all blocks of A-type monomers form a single cluster, while all blocks of B-type monomers form another), (ii) full microphase separation is observed with a certain probability, and (iii) full microphase separation can not take place. For very high number of blocks $n$ and very high $N$ (not accessible to our simulations) further investigation is needed.