Structures formed by block copolymers containing amphiphilic repeating units

Block copolymers are composed of two or more chemically distinct and typically immiscible polymer blocks.  For a diblock copolymer (poly-A + poly-B) the immiscibility between A and B blocks drives a microphase separation in the melt, with alternating A-rich and B-rich microdomains. The melt phase behavior of linear diblock copolymers with random coil blocks is determined by the overall degree of polymerization N, the volume fraction of the A component f_A, and the A-B segment-segment interaction χ. With increasing f_A from 0 to 0.5, at a fixed high value of χN, one experimentally and theoretically obtains i) A-spheres arranged in a body-centered cubic lattice, ii) A-cylinders arranged in a hexagonal lattice, iii) a region of gyroid phase and iv) alternating A and B lamellae.

Very recently Khokhlov et al. reported computer simulation results for diblock copolymers where one of the blocks contains amphiphilic repeating units: One part of each amphiphilic unit interacts athermally (zero χ) with the other block, whereas the other part has a strongly repulsive interaction (strongly positive χ). The amphiphilic block is predicted to give a new morphological variation in the block copolymer phase separation, featuring thin channels and slits of amphiphilic units penetrating through the matrix of a major nonpolar components (See figure).

The project seeks first to test these new predictions by experimental structural studies of block copolymers containing one hydrophobic and one strongly amphiphilic block. In order to vary the volumes of the hydrophobic and amphiphilic microdomains, a hydrocarbon solvent and/or water will be added to the system. Experimental methods include SAXS and NMR.

People: Mehran Asad Ayobi, Lennart Piculell, Ulf Olsson

External collaboration: Alexei Khokhlov (Moscow State University/Russian Academy of Science)

OMM support: PhD project

Contact person: Lennart Piculell