Self-assembly Of The Block Copolymers Containing Rigid Blocks

In recent years,the self-assembly of block copolymers with rigid blcok has attrac ted extensive attention in experiment and theory.The microphase separation of AB di block copolymer has been fully studied.Howerver,the phase behavior of triblock cop olymers with rigid blocks needs further study.Compared with diblock copolymers,th e complexity and kinds of structures for the self-assembly in triblock copolymers with rigid blocks increase remarkedly.In this paper,the self-assemblies in in the melts of ABC coil / rod / coil triblock copolymer and in the solutions of ABA coil / rod /coil tri block copolymer were studied.Firstly,the self-assembly in the ABC triblock copolymers under the asymmetric r od / coil block interaction was simulated by self-consistent field theory of lattice mod el.In addition to micelles,centrally symmetric lamellae(CSLM),perforated lamellae,strips,gyroid,the stable phases,i.e.,Noncentrally symmetric lamellae(NCSLM)and zigzag lamellae,were also observed.The phase diagram for the interaction between ro d / coil blocks VS the fraction of rod block was established given the interaction betw een coil blocks.The degenerate behavior with NCSLM and CSLM is observed when t he volume fraction of rod block is intermediate.The effect of the entropy of chain con formation on phase behavio was analysed.The mechanism of the degenerate behavior of block copolymers under nonconfinement was proposed.This result provides some new point of view on the study of degenerate behavior of block copolymers,which ca n provide theoretical reference for related experiments.Secondly,the effects of polymer concentration and hydrophobic block length(th e chain length remains unchanged)on micellar aggregation in the solutions of the AB A coil / rod /coil triblock copolymer were studied by self-consistent field theory of latt ice model.The average volume fraction of hydrophobic block and the heat capacity p eak for homogeneous solution / micelle transition were calculated.The simulated resu lts show that the adjustment of micelle structure caused by temperature is weak in theintermediate concentration,but at low and high concentrations this structural adjustme nt is remarkable,even demicellization emerges;the change in the length of the middle rigid block promotes the adjustment of micellar structure,and the two typical systems are the low concentration for the smallest middle block and high concentration for the longest one.The introduction of rigid blocks significantly increases the cooperativity of self-assembly,especially the three-stage cooperativity of nucleation,growth and sat uration appears in the low concentration system with the shortest length of intermediat e blocks.This research provides some insights for the effects of the rigidity of chain o n aggregation of block copolymers and for the cooperativity of self-assembly,which c an provide theoretical reference for related experiments.