Enlarged Stable Phase Region of Hybrid Lamella-sphere Phase Enabled by A_(1)B_(1)A_(2)(B_(2))m Branched Tetrablock Copolymer

Hybrid nanostructures possess a great potential for application in advanced nanotechnologies due to the anisotropic properties from different nanophases.Our previous work demonstrated that a linear A_(1)B_(1)A_(2)B_(2)tetrablock copolymer of symmetric overall volume fraction can self-assemble into a hybrid lamella-sphere(LS)structure by tuning the relative length of the two A-blocks through self-consistent field theory(SCFT),where the spherical and the lamellar domains are mainly composed of the long Ar and short A2-blocks,respectively.However,the phase region of LS is limited.In order to expand the stable region of LS,we change the linear A2B2 copolymer to a branched A_(1)B_(1)A_(2)B_(2)copolymer resulting in an increase of the local spontaneous curvature between A2-and B2-blocks.We examine the impact of the branching number m of 62-block on the stable region of LS in the phase diagram with respect to f_(A1)and for fixed f_(B)=0.5 and f_(B1)=0.26,and find that m=2 expands the LS region significantly in contrast to the linear architecture.On the other hand,the stability window of LS does not change notably when m=2 is increased to 3 in our calculated parameter space.