Optical method for determining anisotropy of diamagnetic susceptibility of nematic and polar anchoring energy coefficient of nematic-substrate systems by using a cell of varying thickness

• Autorzy: Kędzierski J. , Raszewski Z. , Kojdecki M. , Zieliński J. , Miszczyk E. , Lipińska L.
• Konferencja: XV Liquid Crystal Conference: Chemistry, Physics and Applications ; (15 ; 12-17.10-2003 ; Zakopane, Poland)
• Języki publikacji: EN

Abstrakty

EN

A wedge cell of the wedge angle of the order of few milliradians was used to measure threshold magnetic fields for the magnetic Freedericksz transition [1-3]. A nematic liquid crystal filling the cell was of planar orientation enforced by the treatment of the flat boundary plates. A system of interference fringes appeared in the cell placed in normally incident light between analyser and polariser crossed. In the vicinity of each fringe, the cell could be considered as a flat-parallel one and hence it was equivalent to a system of flat cells of different precisely determined thickness, the same relates to any cell of slowly-varying thickness and flat cover plates. The threshold magnetic field magnitudes were interpreted as eigenvalues of the boundary eigenvalue problem for the operator of the second derivative; the interaction between the nematics and the substrate was described by the Rapini-Papoular formula [3] (i.e., weak coupling was considered). The resulting formulae were used to determine the polar anchoring energy coefficient and the anisotropy of diamagnetic susceptibility after the threshold fields measured. The method was applied to characterise the nematic liquid crystal 5CB and the coupling between it and the substrates made of poly(amic acid) MP2 [4, 5]. The estimates of material parameters agreed pretty well with those determined by the composite method [6].

Słowa kluczowe

EN

nematics elastic constants; magnetic susceptibility anisotropy; 4'-pentyl-4-cyanobipfenyl (5CB); pola

• Wydawca: Stowarzyszenie Elektryków Polskich ; Polska Akademia Nauk ; Wojskowa Akademia Techniczna im. Jarosława Dąbrowskiego
• Czasopismo: Opto-Electronics Review
• Rocznik: 2004
• Tom: Vol. 12, No. 3
• Strony: 299--303
• Opis fizyczny: Bibliogr. 6 poz.

Twórcy

autor

Kędzierski J.

• Institute of Applied Physics, Military University of Technology, 2 Kaliskiego Str., 00-908 Warsaw, Poland

autor

Raszewski Z.

• Institute of Applied Physics, Military University of Technology, 2 Kaliskiego Str., 00-908 Warsaw, Poland

autor

Kojdecki M.

• Institute of Mathematics and Cryptology, Military University of Technology, 2 Kaliskiego Str., 00-908 Warsaw, Poland

autor

Zieliński J.

• Institute of Applied Physics, Military University of Technology, 2 Kaliskiego Str., 00-908 Warsaw, Poland

autor

Miszczyk E.

• Institute of Physics, Radom University of Technology, 2 Malczewskiego Str., 26-600 Radom, Poland

autor

Lipińska L.

• 4Institute of Electronic Materials Technology, 133 Wólczyñska Str., 01-919 Warsaw, Poland

Bibliografia

• 1. D.F. Gu, S. Uran, and C.H. Rosenblatt, “A simple and reliable method for measuring the liquid crystal anchoring strength coefficient”, Liq. Cryst. 19, 427-431 (1995).
• 2. J. Kędzierski, Z. Raszewski, M.A. Kojdecki, E. Miszczyk, L. Lipińska, E. Białecka-Florjańczyk, and A. Orzeszko, „Determination of polar anchoring energy coefficient for nematics-substrate systems by wedge cell method”, Proc. SPIE 4759, 313-320 (2002).
• 3. A. Rapini and M. Papoular, “Distortion d'une lamelle nematique sous champ magnétic. Conditions d'anchrage aux parois”, J. Physique Colloq. 30, C4-C5 (1969). (in French)
• 4. M. Okulska-Bożek, T. Prot, J. Borycki, and J. Kędzierski, „Preparation and evaluation of polyimide layers as materials for nematic liquid crystal orientation”, Liq. Cryst. 20, 349-359 (1995).
• 5. J. Borycki, M. Okulska-Bożek, J. Kędzierski, and M.A. Kojdecki, “Correlation between surface free energy and anchoring energy of 6CHBT on polyimide surfaces”, Proc. SPIE 4759, 303-306 (2002).
• 6. J. Kędzierski, M.A. Kojdecki, Z. Raszewski, L. Lipińska, J. Rutkowska, E. Miszczyk, and J. Borycki, “Determination of nematic liquid crystal material parameters by use of wedge cells”, XV Conference on Liquid Crystals - Chemistry, Physics and Applications, 13-17 October 2003, Zakopane, Poland.