The microhardness H of the pure block copolymers
and the blends studied is plotted vs. the LN4 content
in Fig. 24a. Since LN4 is a rubber-phase-rich
block copolymer, its addition to the lamellar block
copolymer ST2 causes a decrease in H. In Section 4.2,
we concluded that the microhardness behavior of
the microphase-separated systems is mainly dictated
by their morphology [77]. Thus, the sharp decrease in
the microhardness at LN4 content of 20 wt%
correlates well with a transition of the microphaseseparated
morphology from well ordered lamellae to
disordered PS domains dispersed in a rubbery matrix
[117]. The stepwise variation of H for 20 wt% LN4
additionally suggests that the effective volume fraction
of the hard phase drastically decreases for this
composition [112]