Synthesis and characterization of novel polyimides with 1‐octadecyl side chains for liquid crystal alignment layers

Lee, Yoon Jung; Kim, Yong Woon; Ha, Jae Du; Oh, Jae Min; Yi, Mi Hye

doi:10.1002/pat.862

Cited by 65 publications

(41 citation statements)

References 20 publications

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“…It has been known that the high pretilt angles of LC molecules required to produce homeotropic alignment are related to the low surface energy values of the alignment layer and/ or the steric repulsions between the LC molecules and the alignment layers. 36,[49][50][51][52][53][54][55][56] Therefore, polyimides having long alkyl side groups have been widely used to align LCs perpendicular to the surface of the alignment layer, because the long alkyl groups can produce low surface energy layers due to their steric effect. 51,56 We also found that the LC alignment behavior on the polystyrene derivatives in this study could be ascribed to the surface energy values.…”

Section: Resultsmentioning

confidence: 99%

The effect of phenoxymethyl side groups on the liquid crystal alignment behavior of polystyrene derivatives

2009

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Abstract:We synthesized a series of polystyrene derivatives containing various side chain terminal moieties, such as phenoxymethyl, 4-methoxyphenoxymethyl, 4-fluorophenoxymethyl, 4-methylphenoxymethyl, and 4-trifluoromethoxyphenoxymethyl groups, using polymer analogous reactions, in order to investigate the effect of the side group on their liquid crystal (LC) alignment behaviors. The polymers containing 4-fluorophenoxymethyl, 4-methylphenoxymethyl, or 4-trifluoromethoxyphenoxymethyl side groups had lower surface energy values and the LC cells fabricated using the unrubbed films of these polymers showed homeotropic LC alignment behavior. The LC cells fabricated using the rubbed films of the polymers containing phenoxymethyl or 4-fluorophenoxymethyl groups showed homogeneous planar LC alignment behavior in which the LCs were aligned perpendicular to the rubbing direction. This homogeneous planar and perpendicular alignment behavior was ascribed to the favorable anisotropic interactions between the LC molecules and the side groups preferentially oriented perpendicular to the rubbing direction.

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Section: Resultsmentioning

confidence: 99%

The effect of phenoxymethyl side groups on the liquid crystal alignment behavior of polystyrene derivatives

2009

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“…Besides the property of aligning, PI films need to induce LCM to certain pretilt angles for different display modes. For supertwisted nematic (STN) LCD, pretilt angles ranging from 5 to 20 are needed, particularly for vertical aligned nematic (VAN) LCD, where pretilt angles of 90 are a must (2). In order to raise the pretilt angles, side chains, mostly long and bulky, are incorporated into the PIs, which results in low molecular weight, and thus bad mechanical strength, of the resultant films.…”

Section: Introductionmentioning

confidence: 98%

Preparation of vertical alignment layers by blending polyimide precursors with and without side chains

Lai

Qin

et al. 2009

Liquid Crystals

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2009) Preparation of vertical alignment layers by blending polyimide precursors with and without side chains, Liquid Crystals, 36:2, 173-178, A series of polyimides (PIs) were prepared from the precursors, blends of a poly(amic acid) and a side-chain poly(amic acid), based on a diamine 4¢-(tert-butyldimethylsiloxy)biphenyl-4-yl 3,5-diaminobenzoate (DPA). The blended polyimide (bl-PI) films were relatively tough. The surface properties of the bl-PI films were characterised by surface energy measurement, X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance infrared spectroscopy (ATR-IR). The results showed that the non-polar side chains were highly enriched on the surface and 90 pretilt angles of liquid crystal molecules were generated regardless of side chain content. For comparison, the copolyimides (co-PI) with different DPA contents were synthesised. It was found that the enrichment of the side chain on the surface increased with increasing DPA content and the pretilt angles of liquid crystal molecules rose from 3 to above 20 when DPA content increased from 10% to 30%. For the polyimides based on a diamine without a non-polar end group, 4¢-biphenyl-4-yl 3,5-diaminobenzoate (DABBE), both bl-PIs and co-PIs could only generate the same low pretilt angles. In conclusion, by blending poly(amic acids) based on DPA, tough vertical alignment layers could be prepared.

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“…The pretilt angle is correlated with some parameters of a supertwisted nematic (STN) mode LCD, and a high value is preferable for a good performance [1,2]. However, different display modes need different pretilt angles, for example, STN mode (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) [3], in-place switch mode (0 ) [4], and multidomain vertical alignment mode (90 ). Therefore, controlling the pretilt angle has become a topic of considerable interest in recent decades.…”

Section: Introductionmentioning

confidence: 99%

Effect of the skeleton structures in the side chain of polyimides on their film surface properties and pretilt angles of liquid crystal molecules

Lai

Qin

et al. 2010

Liquid Crystals

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Polyimides (1c-4c, 1c'-4c') with side chains (1-4) containing four different skeletons were synthesised and characterised. Results showed that a similar high side chain abundance took place on the surface of the films, which was independent of the skeleton structures, while the pretilt angles of liquid crystal molecules were considerably affected by the skeleton structures. 1c, 1c' and 2c, 2c' achieved vertical alignment while 3c, 3c' and 4c, 4c' only obtained low pretilt angles. The main reason, based on surface testing results and molecular modelling, was the different interactions between liquid crystal molecules and the skeletons in the side chains.

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Synthesis and characterization of novel polyimides with 1‐octadecyl side chains for liquid crystal alignment layers

Cited by 65 publications

References 20 publications

The effect of phenoxymethyl side groups on the liquid crystal alignment behavior of polystyrene derivatives

The effect of phenoxymethyl side groups on the liquid crystal alignment behavior of polystyrene derivatives

Preparation of vertical alignment layers by blending polyimide precursors with and without side chains

Effect of the skeleton structures in the side chain of polyimides on their film surface properties and pretilt angles of liquid crystal molecules

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