Possibility of twist-grain-boundary structure in nonchiral liquid crystals

Recent studies of highly chiral liquid crystals suggest that twist in smectic phases can be supported by the introduction of periodic twist grain boundaries that would produce a helical structure formed by smectic blocks that are twisted with respect to each other. Here, we examine the possibility of observing such a structure in nonchiral smectic liquid crystals. Experimental results suggest that such structures may be obtained by confining ordinary nonchiral liquid crystals in a cell in which the directors at the two surfaces are nonparallel.