The temperature behavior of self-assembling systems based on poly(methylacrylates) with bulky side groups and their macromonomers

The temperature behavior of self-assembling supramolecular structures based on poly(methacrylates) with highly tapered side chains and their molecular precursors with different chemical structures was studied by the methods o f differential scanning calorimetry, optical polarization microscopy, and w ide and small-angle X-ray diffraction. As was found, the above compounds ex ist at room temperature in the ordered columnar phase phi (0h) in which, du e to the van der Waals interaction, mesogenic groups are organized into cyl indrical pine-tree structures with a helical inner order. There is no corre lation between the neighboring cylinders packed into a two-dimensional hexa gonal lattice. As temperature is increased, the above materials usually exp erience two phase transitions. The first phase transition corresponds to st ructural disordering in a column and a transition to a disordered columnar phase phi (h), whereas the second transition is associated with the isotrop ization of the material. As was shown by the temperature X-ray studies of t he oriented samples, an order-disorder transition within the column constit utes a cooperative process which involves successive melting of aliphatic e nds and mesogenic groups and is accompanied by an abrupt change in the para meter of the two-dimensional hexagonal lattice. In the region of the existe nce of the disordered columnar phase, as material is heated, the diameter o f the column decreases with a temperature coefficient of similar to-(1-2) x 10(-3) K-1. This behavior may be explained by the untwisting of a polymer chain in the column upon heating and loss of helical conformation. In poly( methacrylates) with bulky side chains and their macromonomers, the stabilit y of the columnar phase is controlled by the energy interaction between rig id aromatic groups and an aliphatic matrix in which mesogenic cylinders are located.