Tải bản đầy đủ - 0 (trang)
Chapter 2. Monomeric Discotic Liquid Crystals

Chapter 2. Monomeric Discotic Liquid Crystals

Tải bản đầy đủ - 0trang

50



Chemistry of Discotic Liquid Crystals: From Monomers to Polymers



the phase behavior of benzene-based liquid crystals has also been reported. Furthermore, alignment and reorientation of columnar phases have been demonstrated, and photoconductivity, ionic

conductivity, and nonlinear optical properties have been evaluated. More interestingly, a display

device has been demonstrated with benzene multiynes [13,14]. To gain greater insight into the phase

behavior and useful physical properties, many theoretical and simulation studies have been accomplished on benzene-based discotic compounds [15–24]. The theoretical studies include molecular

interactions and dynamics in the mesophase, thermodynamic properties, pattern and texture formation, phase morphology and orientation dependence of viscosity, etc.

Chandrasekhar and coworkers prepared a series of hexaesters of hexahydroxybenzene, and from

optical, calorimetric, and x-ray studies, they established the columnar liquid crystalline nature of

these novel class of materials [1]. The synthetic route used to prepare these compounds is shown in

Scheme 2.1. Hexahydroxybenzene 3 is prepared from glyoxal 1 and treated with an acid chloride

to give the esters 4. Yields of the hexaesters are improved if an inert atmosphere is used. Typically,

no solvent is used for these reactions. The mesophase behavior of benzene hexaesters is summarized in Table 2.1 [25–28]. Almost all the mesomorphic derivatives exhibit a columnar hexagonal

O

CHO

CHO



HO



i



OH

ONa



NaO



ii



OH



OH



HO



O

2



1



HO



iii



OH



ROCO

ROCO



OH

3



OCOR

OCOR

OCOR

OCOR

4



Scheme 2.1  Synthesis of benzene hexaesters: (i) Na2SO3/O2; (ii) SnCl2/HCl; (iii) RCOCl.



Table 2.1

Transition Temperatures of Hexaesters of Benzene

Structure

4a

4b

4c

4d

4e

4f

4g

4h

4i

4j

4k

4l

4m

4n

4o

4p

4q

4r

4s

4t

4u



R



Phase Transition



Ref.



C6H13

C7H15

OC6H13

CH2OC5H11

C2H4OC4H9

C3H6OC3H7

C5H10OCH3

CH2OC3H7

CH2OC7H15

CH2SC5H11

C2H4SC4H9

C3H6SC3H7

C5H10SCH3

CH(Me)C6H13

CH2CH(Me)C5H11

C2H4CH(Me)C4H9

C3H6CH(Me)C3H7

C4H8CH(Me)C2H5

C5H10CH(Me)CH3

C4H8CH(Et)C2H5

C5H10CH(Me)C2H5



Cr 68 Colh 86 I

Cr 80 Colh 84 I

Liquid

Cr 68 Colh 94 I

Cr 30 Colh 32 I

Cr 43 Colh 44 I

Cr 16 Colh 25 I

Cr 110 Colh 112 I

Cr 74 Colh 94 I

Cr 66 Colh 67 I

Cr 101 I

? 53 Col 57 I

Cr 32 Col 37 I

Liquid

Cr 96 I

M 96 I

M 102 I

Cr 61 M 87 I

Cr 85 M 87 I

Cr 60 M1 86 M2 87 I

Cr 52 M 75 I



[1]

[1]

[25]

[25]

[25]

[25]

[25]

[25]

[25]

[25]

[27]

[27]

[27]

[28]

[28]

[28]

[28]

[28]

[28]

[28]

[28]



51



Monomeric Discotic Liquid Crystals



mesophase. The stability of the mesophase is sensitive to the presence of heteroatoms in the peripheral tails. Significant stabilization is observed for derivatives bearing a β-oxygen atom in the side

chain. However, when the position of this oxygen atom is moved toward or away from the core,

the mesophase stability is either reduced or the mesophase is suppressed. Branched side chains

stabilize the mesophase if the branch point is close to the middle, but destabilization is noticed as it

approaches the core. However, terminal branching points can have either an effect on the mesophase

stability depending on whether they exert steric effect or space filling effect, which contrast to each

other.

Being the first examples of liquid crystalline materials of its kind, the benzene hexaesters have

been studied for their physical properties to gain more insight into the mesophase structure and

molecular interactions involved in stabilizing discotic columnar phases [29–41]. Accordingly,

s­ olute–solvent interaction in the mesophase, heat capacity studies in the mesophase, infrared characterization of the relative orientation of molecular parts, phase transitions and molecular dynamics

by nuclear magnetic resonance, electric birefringence, Langmuir–Blodgett films, etc., have been

studied. The possible formation of lyotropic liquid crystalline phases has also been tested on some

of these hexaester derivatives.

Tetraesters of 2,3,5,6-tetrahydroxy-1,4-benzoquinone 6 and their corresponding hydroquinones

are also found to exhibit columnar mesomorphism, though over a very narrow range of temperature

[42–44]. The synthesis of these compounds is shown in Scheme 2.2 and their phase behavior is

shown in Table 2.2.

Phloroglucinol-derived C3 symmetric liquid crystals 9 have been reported by Lehmann et al.

These materials can be easily prepared via esterification of phlorogucinol with functionalized acid

chlorides (Scheme 2.3). Their thermal data are listed in Table 2.3 [45–47]. These compounds adopt

an E-shaped conformation in the columnar phase rather than a star-shaped conformation in order to

avoid the free space in the columnar phase of some of the derivatives. Interestingly, the columnar



O

HO



O

OH



HO



i



OH



ROCO



OH

OCOR



ROCO



ROCO



ii



OCOR



O

5



ROCO



O

6



Table 2.2

Transition Temperatures of

Benzene Tetraesters



6a

6b

7a

7b



OCOR

OH

7



Scheme 2.2  Synthesis of benzene tetraesters: (i) RCOCl/Pyridine; (ii) H+.



Structure



OCOR



R



Phase

Transition



Ref.



C6H13

C7H15

C6H13

C7H15



Cr 55 Col 57 I

Cr 68 Col 70 I

Cr 80 Col 85 I

Cr 79 Col 82 I



[42]

[42]

[44]

[44]



52



Chemistry of Discotic Liquid Crystals: From Monomers to Polymers

OH



OR1



RCOCl

HO



OH



R3O



8



e: R3 =



OR

R1 = R2 = R3 =

OR2



9



OC



OC



O

OR



n



O



c: n = 3

d: n = 4



a: n = 1

b: n = 2



OR

O



R1 = R 2 =



OR



O

R = C12H25

f: R3 =



OC



OR



OR



OC



O



OR΄

O



(CH2)4(CF2)8F



OC



OR



O

OR



R = C12H25



OR΄



O

R΄ =



g: R3 =



OR΄

R1 =



OR



OR



OC



O



O



OR



OR



O



O



OR

h: R3 =



OR



R = C12H25



OR



OC



R2 =



OR

OOC



O



OC



OR

R = C12H25



O



Table 2.3

Phase Transition Temperatures of

C3 Symmetrical and Unsymmetrical

Triesters of Benzene



9a

9b

9c

9d

9e

9f

9g

9h



OR

OR



OR



Scheme 2.3  Phloroglucinol-derived discotic liquid crystals.



Structure



OR



Phase Transition

Temperatures



Ref.



g 20 Colh 53 I

Col1 79 Col2 98 I

Col1170 Col2172 I

Col1 240 Col2 249 dec

Colh 65.1 I

Colr 151.9 SmA 190.9 I

Colh 43.2 I

Cub 60.6 I



[45]

[45]

[45]

[45]

[47]

[47]

[47]

[47]



R = C12H25



53



Monomeric Discotic Liquid Crystals



phase of some of the derivatives serve as templates for crystal growth, and it has been revealed

that the crystal growth is one dimensional in nature and preserves the orientation of the parent

mesophase. Non-symmetric mesogens containing naphthalene chromophore have also been studied. Structural investigations reveal a rich mesomorphism from columnar, lamellar, to cubic phases

depending on the type of oligobenzoate arms.

Diacetylene-armed C3-symmetric esters 12 and amides 13 derived from benzene tricarbonyl

chloride have been studied by Chang et al. These derivatives exhibit a rather ill-defined mesomorphism and undergo thermal polymerization [48,49]. The photopolymerization of these compounds

has also been carried out in the solid as well as liquid crystalline state. The chemical structures

of these compounds are shown in Scheme 2.4 and their phase transition temperatures are listed in

Table 2.4. It is interesting to note that the phloroglucinol analogue 14 is not mesomorphic, which

demonstrates the effect of changing the linkage to central benzene core that might act against the

π-stacking of the molecules.

Matsunaga and coworkers have replaced some of the ester linkages of the benzene hexaesters

with amide groups. The heavily substituted members of this class of compounds are prepared by

the total acylation of 3,6-diamino-1,2,4,5-tetrahydroxybenzene [50]. The synthetic route to prepare these compounds is shown in Scheme 2.5, and their mesophase behavior is summarized in

Table 2.5. It is very clear that the introduction of two amide groups stabilizes the columnar mesophase substantially with respect to the parent hexaesters indicating the role of hydrogen bonding

in the mesophase stability. The hydrogen bonding–induced phase stability of the above amides

has prompted them to synthesize a variety of mixed ester amides carrying even lesser number of



COCl

+

ClOC



COCl



COOR



(i)

ROH

11



ROOC



10

a: R =



b: R =



OC4H9



OC8H17



c: R =



OC6H13



d: R =



e: R =



OC12H25



f: R =



COR



ROC



COOR

12



COR



a: R =



HN



b: R =



HN



C6H13



OC8H17



C6H13



13

OCOR

R=

ROCO



OC8H17



OCOR

14



Scheme 2.4  Diacetylene-armed symmetric benzene esters: (i) NaH, THF, reflux.



54



Chemistry of Discotic Liquid Crystals: From Monomers to Polymers



Table 2.4

Phase Transition Temperatures

of Diacetylene-Armed Benzene

Derivatives

Structure

12a

12b

12c

12d

12e

12f

13a

13b

14



Phase Transition



Ref.



Cr 200 I > 250 poly

g120 M 135 poly

g 140 M

Cr (137 Colh) 146 I

Non LC

Non LC

Cr 190 ND 204 I

Cr 120 M >200 poly

Non LC



[49]

[49]

[49]

[48]

[49]

[49]

[48]

[48]

[49]



NH2

HO



OH



HO



i



OH



ROCO

ROCO



NHCOR

OCOR



NH2



OCOR

NHCOR



15



16



Scheme 2.5  Synthesis of benzene discotics with mixed ester–amide chains: (i) RCOCl/pyridine.



Table 2.5

Transition Temperatures of

Dialkanoyl Tetrakis(alkanoyloxy)1,4-Benzene Diamines

Structure

16a

16b

16c

16d

16e

16f

16g

16h

16i

16j



R



Phase Transition



C4H9

C5H11

C6H13

C7H15

C8H17

C9H19

C10H21

C11H23

C13H27

C15H31



Cr 134 Colh 208 I

Cr 71 Colh 209 I

Cr 64 Colh 208 I

Cr 75 Colh 205 I

Cr 77 Colh 200 I

Cr 77 Colh 199 I

Cr 81 Colh 198 I

Cr 89 Colh 197 I

Cr 92 Colh 189 I

Cr 94 Colh 190 I



Source: Data from Kobayashi, Y. and

Matsunaga, Y., Bull. Chem. Soc. Jpn.,

60, 3515, 1987.



55



Monomeric Discotic Liquid Crystals



peripheral alkyl chains [51–53]. The synthesis of such materials is shown in Schemes 2.6 through

2.8, and their thermal phase behavior properties are given in Tables 2.6 through 2.8. The C3 symmetric benzene tricarboxamides, which can be prepared from 1,3,5-benzene tricarbonyl chloride

and alkyl amines as shown in Scheme 2.9, also form mesophases [54]. However, their columnar

structure has not been confirmed unequivocally. The phase transition temperatures of these compounds are collected in Table 2.9.

The existence of both thermotropic and lyotropic mesomorphisms in disk-shaped compounds is

rather unusual. However, the latter can be stabilized by hydrogen bonding, as has been shown by Meijer

and coworkers [55–63]. They have prepared and studied mesomorphism of diamino-bipyridine-based



OH



NO2

i



OH



OH

18



17



NH2

OH



OH



ii



NO2



NHCOR

OCOR



iii



NHCOR

OCOR



NH2



OH

19



20



Scheme 2.6  Synthesis of tetrasubstituted benzene discotics with mixed ester-amide chains: (i) NaNO2,

(ii) SnCl2/HCl, (iii) RCOCl/pyridine.



CH3



CH3

i

H3C



O2N

H3C



CH3



CH3

NO2



ii



CH3

NH2



H3C



CH3



21



H2N



iii



ROCHN



CH3



NO2



NH2



22



23



NHCOR



H3C



CH3

NHCOR

24



Scheme 2.7  Synthesis of mesitylene-derived discotics: (i) HNO3/H2SO4; (ii) Sn/HCl; (iii) RCOCl/pyridine.



OH

O2N



OH

NO2

i



NH2



NO2



NH2



25



26



OH



28



i



HO

H2N



NO2



OAc

AcO



OAc



31



OCOR

ROCHN



ii



OH



29



ii



ROCO



NH2



ROCHN



OAc



ROCO



AcO

O2N



32



NO2



NHCOR

OCOR



30



OAc

iii



NHCOR



NHCOR

27



NH2



NO2

HO

O2N



H2N



i, ii



NHCOR



OCOR

OCOR



ROCHN



NHCOR

33



Scheme 2.8  Synthesis of mixed ester–amide derivatives of benzene: (i) Sn/HCl; (ii) RCOCl/pyridine;

(iii) HNO3.



56



Chemistry of Discotic Liquid Crystals: From Monomers to Polymers



Table 2.6

Transition Temperatures of Benzene

1,3-Diamide-2,4-Diesters

Structure

20a

20b

20c

20d

20e

20f

20g

20h



R

C6H13

C7H15

C8H17

C9H19

C10H21

C11H23

C13H27

C15H31



Phase Transition

Cr 89 Colh 124 I

Cr 87 Colh 122 I

Cr 90 Colh 121 I

Cr 93 Colh 122 I

Cr 95 Colh 120 I

Cr 97 Colh 117 I

Cr 101 Colh 114 I

Cr 103 Colh 114 I



Source: Data from Kawada, H. and Matsunaga, Y.,

Bull. Chem. Soc. Jpn., 61, 3083, 1988.



Table 2.7

Transition Temperatures of

1,3,5-Trimethyl Benzene Triamides

Structure

24a

24b

24c

24d

24e

24f

24g

24h

24i

24j

24k



R



Phase Transition



C3H7

C4H9

C5H11

C6H13

C7H15

C8H17

C9H19

C10H21

C11H23

C13H27

C15H31



Cr 380 Colh 410 I

Cr 315 Colh 380 I

Cr 300 Colh 357 I

Cr 257 Colh 357 I

Cr 239 Colh 346 I

Cr 200 Col 222 Colh 340 I

Cr 189 Col 206 Colh 342 I

Cr 185 Col 191 Colh 338 I

Cr 183 Col 189 Colh 342 I

Cr 118 Col 182 Colh 338 I

Cr 120 Col 175 Colh 328 I



Source: Data from Harada, Y. and Matsunaga, Y., Bull.

Chem. Soc. Jpn., 61, 2739, 1988.



C3 symmetric extended discotics stabilized by intramolecular hydrogen bonding. The synthesis

and chemical structures of the liquid crystalline compounds are shown in Scheme 2.10, and their

phase transition temperatures are collected in Table 2.10. The large core induces strong interactions

between molecules and hence leads to mesophases of enhanced thermal stability.

In dilute solutions, the compounds exhibit a columnar nematic phase owing to the hydrogen

bonding and π–π interactions. This mesophase adopts a uniaxial planar orientation in between two

glass plates. In an electric field, the columns can be switched to a homeotropic alignment and such

voltage-induced formation of large monodomains might be useful for one-dimensional ion and

charge transport. The chiral derivatives self-assemble into dynamic chiral helix in apolar solvents.

The chirality at the supramolecular level in the stacks can be tuned by temperature and solvent, as

has been revealed by circular dichroism spectroscopy.



57



Monomeric Discotic Liquid Crystals



Table 2.8

Transition Temperatures for Mixed Ester and Amide

Derivatives of Benzene

Phase Transition

Structure

A

B

C

D

E

F

G

H

I

J



R



Structure 27



Structure 30



Structure 33



C4H9

C5H11

C6H13

C7H15

C8H17

C9H19

C10H21

C11H23

C13H27

C15H31



Cr 144 Colh 222 I

Cr 133 Colh 225 I

Cr 129 Colh 229 I

Cr 123 Colh 227 I

Cr 109 Colh 226 I

Cr 111 Colh 227 I



Cr 107 Colh 225 I

Cr 112 Colh 225 I

Cr 113 Colh 218 I



Cr 100 Colh 241 I

Cr 55 Colh 238 I

Cr 63 Colh 241 I

Cr 49 Colh 242 I

Cr 73 Colh 227 I

Cr 65 Colh 225 I



Cr 78 Colh 224 I

Cr 84 Colh 224 I

Cr 66 Colh 225 I



Cr 113 Colh 196 I

Cr 67 Colh 208 I

Cr 88 Colh 208 I

Cr 77 Colh 208 I

Cr 93 Colh 206 I

Cr 92 Colh 203 I

Cr 96 Colh 202 I

Cr 101 Colh 203 I

Cr 103 Colh 198 I

Cr 103 Colh 193 I



Source: Data from Kawamata, J. and Matsunaga, Y., Mol. Cryst. Liq. Cryst., 231, 79,

1993.



CONHR



COCl

i

ClOC



COCl



RHNOC



10



CONHR

34



Scheme 2.9  Synthesis of benzene triamides: (i) RNH2/pyridine.



Table 2.9

Transition Temperatures

for N,N′,N″-1,3,5-Benzene

Tricarboxamides

Structure

34a

34b

34c

34d

34e

34f

34g

34h

34i

34j

34k

34l

34m

34n



R



Phase Transition



C5H11

C6H13

C7H15

C8H17

C9H19

C10H21

C11H23

C12H25

C13H27

C14H29

C15H31

C16H33

C17H35

C18H37



Cr 119 M 206 I

Cr 99 M 205 I

Cr 116 M 208 I

Cr 102 M 204 I

Cr 65 M 215 I

Cr 49 M 208 I

Cr 72 M 216 I

Cr 88 M 212 I

Cr 81 M 216 I

Cr 61 M 209 I

Cr 88 M 214 I

Cr 73 M 205 I

Cr 87 M 211 I

Cr 78 M 206 I



Source: Data from Matsunaga, Y. et al., Bull.

Chem. Soc. Jpn., 61, 207, 1988.



58



Chemistry of Discotic Liquid Crystals: From Monomers to Polymers

RO



COCl

RO

RO



OR



N



RO



OR

35



RO



O

H

N



N



NH2 N



Et3N



N



O



H N



NH2 N

ClOC



OR



O



N



COCl



10

Et3N



O



N H



d: R =

OR



OR

OR



RO



38

a: R = C6H13

b: R = C12H25

c: R = C18H37



N



COCl



NH



37



O



O

NH2



36



N



N



N

H N



N



OR



N H



O



H



OR



OR



e: R = (CH2CH2O)4Bn

f: R =



O



O



4



Scheme 2.10  Synthesis of intramolecular hydrogen bonded benzene-based discotic liquid crystals.



Table 2.10

Phase Transition Temperatures

of Intramolecularly Hydrogen

Bonded C3 Symmetric Benzene

Based Discotic Liquid Crystals

Structure



Phase Transition



Ref.



38a

38b

38c

38d

38e

38f



Colh 383 I

Cr 9 Colh 355 I

Cr 62 Colh 308 I

Colh 373 I

g −50 Colh 244 I

g −74 Colh 270 I



[55]

[55]

[55]

[60]

[58]

[59]



Recently, Nuckolls and coworkers designed and synthesized new benzene derivatives 43 forming

columnar phases that are held together by hydrogen bonding and π–π interactions [64–68]. These

hexa-substituted benzene derivatives contain three amides in the 1,3,5-positions that are flanked by

substituents other than hydrogen at each of the remaining positions. The first series of compounds

are substituted by amides and alkoxy groups alternatively (Scheme 2.11A), whereas the second

series of compounds are substituted by amides and ethynyl substituents (Scheme 2.11B). The key

to the synthesis of the first series of amides is the discovery that 1,3,5-tribromo-2,4,6-trialkoxy

benzene undergoes a triple lithium/halogen exchange reaction, as shown in Scheme 2.11A. These

compounds in the bulk state self-assemble to columnar superstructures. The phase transition temperatures of both the series of compounds are collected in Table 2.11. The key step in the synthesis

of the second series of compounds is the palladium-mediated coupling between an alkynyl subunit

and the trisbromotriester (Scheme 2.11B). Sonogashira coupling in this reaction was very sluggish

and produced a mixture of products even after an extended reaction time from which the desired

product could not be isolated. However, a modified Stille coupling furnished the desired product.



59



Monomeric Discotic Liquid Crystals

OR



OH

(i)

HO



Br



(ii)

RO



OH



RO



OR



Br

40



39



8



OR



OR

Br



MeO2C



(iii)



RO



OR



CO2Me



OR

CO2Me

41



(iv)

OR



a: R΄ = C12H25

b: R΄ = CH2CH2Ph

c: R΄ = Me

d: R΄ = GlyO-t-Bu



R΄HNOC



OR

CONHR΄

43



RO



(v)



COCl

42



SH

OEt



COCl

OR



O-tBu



O

g



O

f



e



ClOC

RO



OEt



Ph



OR



CONHR΄



O

h

O



Ph

(A)



O

j



i

COCl



Br



Br



ClOC



COCl



Br



(i)



l





COOMe

Br



MeOOC



Br

44



k



SnBu3







COOMe



(ii)



MeOOC



Br

45

(iii)







COOMe







COOMe

R΄ 46



a: R΄ = Ph, R = C12H25

RHNOC



b: R΄ = C10H21, R = Ph

c: R΄ = C10H21, R =

(B)



CONHR



Ph





CONHR

47







Scheme 2.11  (A) Synthesis of trialkoxy-triamides of benzene: (i) K 2CO3, C12H25I; (ii) Br2, FeCl3;

(iii) t-BuLi; ClCO2Me; (iv) NaOH; SOCl2; (v) RNH2, Et3N. (B) Synthesis of amide-alkyne-substituted ­benzene

discotics: (i) MeOH, pyridine; (ii) Pd(PPh3), AsPh3 (catalyst); (iii) KOH, i-PrOH; SOCl2; RNH2.



These compounds also exhibit columnar mesomorphism in the bulk state. The compounds of both

the series also exhibit lyotropic mesophases and hence they are amphotropic in nature. In solution,

depending on the solvent, concentration, temperature, and side chains, they form helical ­columnar

aggregates of various sizes that can be transferred to substrates. At lower concentrations, they

exhibit columnar nematic phase, but at higher concentrations, they exhibit chiral nematic phases of

helical columns, that is, the helical columns form a super-helix in solution, which reflects circularly

polarized light. Since the molecules possess dipole moment, on aggregation the columns possess

polar order and interestingly these polar aggregates can be directed by electric fields after transferring from solutions to substrates. Electric field–induced reorientation of the columns in these

amides is very promising from the device point of view.

Another class of discotic benzene derivatives consists of hexakis[(alkoxyphenoxy)methyl]

derivatives 49 [69]. These compounds are simply prepared from hexakis(bromomethyl)-benzene

48 and an excess of p-alkoxyphenoxide, as shown in Scheme 2.12. The thermal behavior of these

materials is summarized in Table 2.12. The mesophase of the compounds are ill characterized



60



Chemistry of Discotic Liquid Crystals: From Monomers to Polymers



Table 2.11

Phase Transition Temperatures

of 1,3,5-Trialkoxy Triamides and

1,3,5-Triethynyl Triamides of

Benzene

Structure

43a

43b

43c

43d

43e

43f

43g

43h

43i

43j

43k

43l

47a

47b

47c



Br



Phase Transition



Ref.



Cr 294 I

Cr 176 Colh 232 I

Cr 123 I

Cr 85 Colh 200 I

Cr 191 Colh 233 I

Cr 141 Colh 172 I

Cr 164 I

Cr 103 I

Cr 249 I

Cr 90 Colh 254 I

Cr 98 Colh 248 I

Cr 113 Colh 174 I

Cr 141 Colh 225 dec

Cr 96 Colh 225 dec

Cr 110 Colh 207 I



[64]

[64]

[64]

[64]

[65]

[65]

[65]

[65]

[65]

[65]

[65]

[65]

[67]

[67]

[67]



RO



Br



Br



RONa



OR



RO

OR



Br

Br



OR



Br

48



R=



OR

49



Scheme 2.12  Synthesis of hexakis[(alkoxyphenoxy) methyl] derivatives of benzene.



Table 2.12

Transition Temperatures for Hexakis

[(Alkoxyphenoxy) Methyl] Benzenes

Structure

49a

49b

49c



R



Phase

Transition



p-C5H11 OC6H4

p-C6H13 OC6H4

p-C7H15 OC6H4



Cr 68 Colr 97 I

Cr 76 Colr 83 I

Cr 67 Colr 71 I



Source: Data from Kok, D.M. et al., Mol. Cryst. Liq.

Cryst., 129, 53, 1985.



CnH2n+1



Tài liệu bạn tìm kiếm đã sẵn sàng tải về

Chapter 2. Monomeric Discotic Liquid Crystals

Tải bản đầy đủ ngay(0 tr)

×