title: Observation of a reentrant twist grain boundary phase.
abstract: We report the occurrence of a reentrant twist grain boundary phase, which we designate as Re- TGB(A). Microscopic observations on a nonsymmetric dimer showed the phase sequence Iso- N*- TGB(A)-Sm- A-Re- TGB(A)- TGB(C*). Here N* and Sm- A stand for the chiral nematic and smectic- A phases, TGB(A) is the twist grain boundary phase with smectic- A blocks, and TGB(C*) that with smectic- C* blocks and exhibiting features of both the smectic- C* and TGB phases. The reentrance of the TGB(A) phase is unambiguously demonstrated using x-ray diffraction, selective reflection, and optical rotation data.
authors.affiliation: Centre for Liquid Crystal Research, Jalahalli, Bangalore 560 013, India.
authors.forename: D S
authors.initials: DS
authors.lastname: Shankar Rao
authors.forename: S
authors.initials: S
authors.lastname: Krishna Prasad
authors.forename: V N
authors.initials: VN
authors.lastname: Raja
authors.forename: C V
authors.initials: CV
authors.lastname: Yelamaggad
authors.forename: S
authors.initials: S
authors.lastname: Anitha Nagamani