Microstructural study of mechanical properties of the ABA triblock copolymer using self-consistent field and molecular dynamics

The molecular mechanism of the strain–stress behavior of the ABA triblock copolymer is studied by combining self-consistent field (SCF) calculation and molecular dynamics (MD) simulation. First, the equilibrium structure was obtained by the SCF calculation. The bridge fraction $φbridge$ was found to be about 0.4, 0.6, and 0.8 for lamellar, cylindrical, and spherical phases, respectively. From the segment distribution calculated by the SCF, the equilibrium chain configuration was generated by the method reported previously [Aoyagi et al., Comput. Phys. Comm. 145, 267 (2002)]. The loading and unloading behavior was then studied by the MD simulation. The loading curve shows a strain-softening, and then a yielding at a strain of about 350%, where the breakup of microdomains takes place. The strain–stress curve in the second elongation-compression cycle is different from that of the first cycle. Such hysteresis effect is seen also for small elongation where the domain breakup does not take place.