title: Vapor deposition of a smectic liquid crystal: highly anisotropic, homogeneous glasses with tunable molecular orientation.
abstract: Physical vapor deposition (PVD) has been used to prepare glasses of itraconazole, a smectic A liquid crystal. Glasses were deposited onto subtrates at a range of temperatures (Tsubstrate) near the glass transition temperature (Tg), with Tsubstrate/Tg ranging from 0.70 to 1.02. Infrared spectroscopy and spectroscopic ellipsometry were used to characterize the molecular orientation using the orientational order parameter, Sz, and the birefringence. We find that the molecules in glasses deposited at Tsubstrate = Tg are nearly perpendicular to the substrate (Sz = +0.66) while at lower Tsubstrate molecules are nearly parallel to the substrate (Sz = -0.45). The molecular orientation depends on the temperature of the substrate during preparation, allowing layered samples with differing orientations to be readily prepared. In addition, these vapor-deposited glasses are macroscopically homogeneous and molecularly flat. We interpret the combination of properties obtained for vapor-deposited glasses of itraconazole to result from a process where molecular orientation is determined by the structure and dynamics at the free surface of the glass during deposition. Vapor deposition of liquid crystals is likely a general approach for the preparation of highly anisotropic glasses with tunable molecular orientation for use in organic electronics and optoelectronics.
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA. ediger@chem.wisc.edu.
authors.forename: Jaritza
authors.initials: J
authors.lastname: Gómez
authors.affiliation: Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210093, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Jiang
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA. ediger@chem.wisc.edu.
authors.forename: Ankit
authors.initials: A
authors.lastname: Gujral
authors.affiliation: School of Pharmacy, University of Wisconsin-Madison, 777 Highland Avenue, Madison, WI 53705-2222, USA.
authors.forename: Chengbin
authors.initials: C
authors.lastname: Huang
authors.affiliation: School of Pharmacy, University of Wisconsin-Madison, 777 Highland Avenue, Madison, WI 53705-2222, USA.
authors.forename: Lian
authors.initials: L
authors.lastname: Yu
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA. ediger@chem.wisc.edu.
authors.forename: M D
authors.initials: MD
authors.lastname: Ediger
mesh_terms: D016880:Anisotropy; D005898:Glass / Q000737:chemistry*; D050866:Liquid Crystals / Q000737:chemistry*