TY - JOUR
T1 - Surface anchoring of nematic liquid crystal on swollen polymer brush studied by surface forces measurement
AU - Yanagimachi, Takuya
AU - Li, Xiao
AU - Nealey, Paul F.
AU - Kurihara, K.
N1 - Funding Information:
This research was primarily supported by the World Premier International Research Center Initiative for AIMR of Tohoku University and its satellite at the University of Chicago . XL and PFN acknowledge the support from the U. S. Department of Energy , Office of Science , Basic Energy Sciences , Materials Sciences and Engineering Division (Synthesis of material and data analysis). We are grateful to Dr. Motohiro Kasuya for helpful discussions.
Funding Information:
This research was primarily supported by the World Premier International Research Center Initiative for AIMR of Tohoku University and its satellite at the University of Chicago. XL and PFN acknowledge the support from the U. S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division (Synthesis of material and data analysis). We are grateful to Dr. Motohiro Kasuya for helpful discussions.
Publisher Copyright:
© 2019 Elsevier B.V.
PY - 2019/10
Y1 - 2019/10
N2 - Surface anchoring plays a fundamental role in controlling the molecular alignment of a bulk liquid crystal (LC). It has been previously shown that the pretilt angle of a nematic liquid crystal (NLC) can be controlled by changing the grafting density of a liquid crystalline polymer, poly(6-(4-methoxy-azobenzene-4′-oxy) hexyl methacrylate) (PMMAZO). In this study, the thickness of the swollen PMMAZO brush was measured by employing the surface forces apparatus (SFA). NLC 4-cyano-4′-pentylbiphenyl (5CB) and toluene were used as the solvents. It was shown that both 5CB and toluene were good solvents for PMMAZO. The repulsive force in 5CB appeared at D0 = 98.2 ± 4.6 nm for high grafting density (HD) surfaces, and at 32.1 ± 4.5 nm for the low grafting density (LD) surfaces. These results indicated that the PMMAZO molecules extended nearly perpendicular to the HD surfaces, while they laid on the substrate for the LD surfaces. The interaction between 5CB and the mesogenic group of PMMAZO was stronger than that for toluene. These results could support the expected surface anchoring mechanism of 5CB by the PMMAZO brush.
AB - Surface anchoring plays a fundamental role in controlling the molecular alignment of a bulk liquid crystal (LC). It has been previously shown that the pretilt angle of a nematic liquid crystal (NLC) can be controlled by changing the grafting density of a liquid crystalline polymer, poly(6-(4-methoxy-azobenzene-4′-oxy) hexyl methacrylate) (PMMAZO). In this study, the thickness of the swollen PMMAZO brush was measured by employing the surface forces apparatus (SFA). NLC 4-cyano-4′-pentylbiphenyl (5CB) and toluene were used as the solvents. It was shown that both 5CB and toluene were good solvents for PMMAZO. The repulsive force in 5CB appeared at D0 = 98.2 ± 4.6 nm for high grafting density (HD) surfaces, and at 32.1 ± 4.5 nm for the low grafting density (LD) surfaces. These results indicated that the PMMAZO molecules extended nearly perpendicular to the HD surfaces, while they laid on the substrate for the LD surfaces. The interaction between 5CB and the mesogenic group of PMMAZO was stronger than that for toluene. These results could support the expected surface anchoring mechanism of 5CB by the PMMAZO brush.
KW - 5CB
KW - FECO
KW - Liquid crystalline polymer brush
KW - Surface anchoring
KW - Surface forces measurement
KW - Toluene
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U2 - 10.1016/j.cis.2019.101997
DO - 10.1016/j.cis.2019.101997
M3 - Letter
C2 - 31421457
AN - SCOPUS:85070595569
SN - 0001-8686
VL - 272
JO - Advances in Colloid and Interface Science
JF - Advances in Colloid and Interface Science
M1 - 101997
ER -