Self-consistent field theoretic simulations of amphiphilic triblock copolymer solutions: Polymer concentration and chain length effects

Using the self-consistent field lattice model, polymer concentration $\bar{\phi}_{{P}}$ and chain length $N$ (keeping the length ratio of hydrophobic to hydrophilic blocks constant) the effects on temperature-dependent behavior of micelles are studied, in amphiphilic symmetric ABA triblock copolymer solutions. When chain length is increased, at fixed $\bar{\phi}_{{P}}$, micelles occur at higher temperature. The variations of average volume fraction of stickers $\bar{\phi}_\textrm{co}^\textrm{s}$ and the lattice site numbers $N_\textrm{co}^\textrm{ls}$ at the micellar cores with temperature are dependent on $N$ and $\bar{\phi}_{{P}}$, which demonstrates that the aggregation of micelles depends on $N$ and $\bar{\phi}_{{P}}$. Moreover, when $\bar{\phi}_{{P}}$ is increased, firstly a peak appears on the curve of specific heat $C_V$ for unimer-micelle transition, and then in addition a primary peak, the secondary peak, which results from the remicellization, is observed on the curve of $C_V$. For a long chain, in intermediate and high concentration regimes, the shape of specific heat peak markedly changes, and the peak tends to be a more broad peak. Finally, the aggregation behavior of micelles is explained by the aggregation way of amphiphilic triblock copolymer. The obtained results are helpful in understanding the micellar aggregation process.