Microphase-separated block copolymers alignment

The aligned microphase-separated block copolymer poly-XXVII-h-BA (Sect. 2.3) shows reversible contraction in one dimension - in other words, it acts like an actuator. 

Scheme 1 Different possible donor-acceptor active layer morphologies in OPV devices. The left drawing depicts a macrophase separated polymer blend morphology with undefined domains. In the middle and at the right, schematic active layer morphologies of disordered and vertically aligned microphase separated block copolymer thin films are shown. Dark and light grey domains correspond to the donor and the acceptor phase, respectively...

Block copolymers of sufficiently large and incompatible sequences of repeating units undergo microphase separation. Because of the geometric restriction caused by the needed alignment of the junctions between the different blocks, the phases... 

The homopolymer showed an enantiotropic nematic mesophase, whereas the diblock copolymer generated microphase-separated lamellae, in which the SCLCP block possessed a nematic-isotropization transition similar to the homopolymer (Table 17). Upon heating, the nematic microphase decreased continuously in the nematic phase from 38.5 nm to 27 nm and showed a constant value of about 26 nm after the nematic-isotropization transition. Therefore, materials in which these block copolymers are macroscopically aligned are expected to show reversible contraction in one dimension, making this polymer system an interesting candidates for an artificial muscle or actuator. 

The incorporation of rigid-rod polymers into block copolymers results in extremely rich self-assembly behaviors that differ markedly horn that of traditional block copolymers due to the interplay between microphase separation of the rod and coil components and liquid crystalline alignment. The combination of these effects results in novel stmctures in both solution and melts. 

Gurovich, E., On microphase separation of block copolymers in an electric field four universal classes. Macromolecules, 27, 7339-7362 (1994) Gurovich, E., Copolymers under a monomer orienting field. Macromolecules, 27, 7063-7066 (1994) Gurovich, E., Why does an electric field align structures in copolymers Phys. Rev, Lett., 74, 482-485 (1995). 

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