Theory of T junctions and symmetric tilt grain boundaries in pure and mixed polymer systems

We apply self-consistent-field theory to T junctions and symmetric tilt grain boundaries in block copolymer systems with and without the addition of homopolymer. We find that, in the absence of homopolymer, T junctions have a larger free energy per unit area than that of the symmetric tilt junctions with which they compete except for a range of angles between about 100degrees and 130degrees. With the addition of homopolymer, this range increases. These results are quite consistent with experiment. As the angle between grains increases towards 180degrees, the T junction undergoes a morphological change somewhat similar to that which occurs in symmetric tilt grain boundaries. At the onset of this change, the free energy per unit area decreases markedly. (C) 2002 American Institute of Physics.