Induced Crystal G Phase Through Intermolecular Hydrogen Bond Constructed by p-n-Alkoxy Benzoic Acids with Ortho-Toluamide (nOBA:TMD)

Induced Crystal G Phase Through Intermolecular Hydrogen Bond Constructed by p-n-Alkoxy Benzoic Acids with Ortho-Toluamide (nOBA:TMD)

T. Kalyani, L. N. V. H. Somasundar@, K. Mallika and S. Sreehari Sastry*

Department of Physics, Acharya Nagarjuna University, Nagarjunanagar -522510, India

@Department of Physics, DVR & Dr. H S MIC College of Technology, Kanchikacherla-521180 A.P. India

Abstract – A new series of supra molecular liquid crystals (nOBA:TMD n = 4 to 12) were synthesized with mesogenic p-n alkoxy benzoic acids (nOBAS) and non-mesogenic ortho toluamide (TMD) moieties. Intermolecular interaction between the proton donor (COOH) of nOBA and proton acceptor (OH) of TMD results the hydrogen bond. Newly formed complexes are characterized by polarizing optical microscope and differential scanning calorimetry, along with the conformational studies of hydrogen bonding through vibrational spectroscopy (FTIR). The IR spectral study confirms that the formation of hydrogen bond between proton donor (- COOH) of nOBA and proton acceptor (OH) of TMD. The formation of hydrogen bond is attributed to the quenching of the nematic and Smectic phase and inducement of crystal G phase in liquid crystal complex. A comparative study of phase abundance is presented with respect to the pure p-n alkyloxy benzoic acids (nOBA) and other hydrogen bonded liquid crystal complexes of nBAs.

Key words–Supra molecular liquid crystals,ntermolecular interactions, hydrogen bond,Differential Scanning Calorimetry, Fourier Transform Infrared Spectroscopy.

1. INTRODUCTION

   Unique materials that have large number of applications in the field of Engineering, technology and medicine are liquid crystals [1-5]. As these materials possess good number of applications, there is always vigorous research in developing novel liquid crystalline materials with different molecular structures and phases. Preparing novel liquid crystals involve various techniques like synthesizing using organic compounds and mixing two different compounds, metals and halogenated compounds etc [6-9]. In most of the cases chemists keep keen observation on the synthesis of hydrogen bond [10-21], as well as p-n Alkoxy Benzoic acids [19]. Among these novel liquid crystals, Hydrogen bonded liquid crystals have distinctive nature to show mesomorphic behavior due to their strong and directional nature in different types of interactions [22]. The alkoxy benzoic acids exhibit liquid crystalline nature. The same nature was observed in the in all hydrogen bonded liquid crystals obtained from the combinations of mesogen and mesogen, non mesogen and non mesogen, mesogen and non mesogen materials. The non-covalent interactions exhibit superficial effects on physical and thermal properties i.e., mesomorphic behavior and transition temperatures [15]. In the

   present article, a novel homologous series of liquid crystal complexes are prepared through the development of hydrogen

   bond between COOH of liquid crystal compounds p,n- alkoxy benzoic acids when n = 4 to12 and OH of non liquid crystalline compound Ortho-Toluamide (TMD). Fourier Transform Infrared (FTIR) spectroscopy is used to confirm the formation of hydrogen bonding and the prepared complexes mesomorphism is characterized by polarizing optical microscope (POM), Differential Scanning Calorimetry (DSC).

2. EXPERIMENTAL

   The p-n-alkoxy benzoic acid (99% purity) and o-TMD supplied by M/s. frinton, Inc., USA. Solvent pyridine from M/s. Qualigens, India. The transition temperatures and phase variant of p-n-alkoxy benzoic acid and corresponding hydrogen bonded complexes were found from textural observations carried out using thermal optical polarizing microscope (Meopta, DRU-3) with a hot stage and HD Canon camera attachment. Methodology for sample cell preparation and observation of mesophase of the samples as a function of temperature has been given in [ 9],[16], and [19 ]. Phase transition temperatures were compared with temperatures of Perkin-Elmer Diamond Differential Scanning Calorimeter (DSC) at a scan rate of 2oC/min and confirmed. The IR spectrum in solid state was recorded on FTIR (FTIR 5300) Spectrometer (JASCO, Japan).

   Preparation of p-n alkoxy benzoic acid (nOBA):ortho toluamide (TMD) complexes (where n=4 to 12):

   Supra molecular Hydrogen bonded liquid crystalline complexes namely, nOBA: TMD (where n=4 to 12) are prepared by the following procedure given in scheme 1. Required amount of samples for synthesis are weighed on a single pan electronic balance Dhona make, ER- 180A with an accuracy of 0.01mg.Equimolar (1:1) ratio of nOBA and TMD are used for the preparation of liquid crystal complexes 4OBA: TMD to 12OBA:TMD. Compounds are taken individually and mixed in the pyridine solvent (20ml). Thus the naturally

   existing dimeric forms of nOBA compounds with complementary hydrogen bond are converted into the monomeric form. Now the two solutions are mixed and kept under constant stirring at 800C for 4hrs. Then most of the pyridine is removed by vacuum distillation process. It means the resultant homogeneous mixture was reduced to almost dryness by removing the excess pyridine under a controlled vaccum filtration. The white crystalline product was dried and re- crystallized from hot dichloromethane solution. The yielding is at about 85%. The entire process involved in synthesis of given liquid crystal complexes are shown in the form of chemical reaction as follows.

   ortho toluamide (TMD) p,n – alkoxy benzoic acids (nOBA)

   hydrogen bond is formed between nOBA and TMD [23-26]. Crystal G phase [27] consisting of molecules packed in different layers with long axis tilted with respect to normal layer planes characterized by C centered monoclinic cell with tilt molecules having pseudo hexagonal close packing [27]. Thermal span of all the Crystal G phases induced in complexes range is around 100C 200C which is a remarkable feature of these samples. Thermal span of the nematic phase was reduced from the pure mesogens (nOBA).

   Pyridine, 4 hrs reflux (at 800C) And after distillation

   Liquid crystal complex – nOBA : TMD ,Where R= CnH2n+1, and

   n = 4 to 12.

   Newly synthesized nOBA : TMD complexes are characterized by different thermal analysis techniques: POM and DSC. Structural characterization is done by the FTIR studies. Complexation of mesogenic nOBA and non mesogenic TMD influences the thermal and phase behavior of pure mesogens. The resultant nOBA:TMD complexes shows the interesting and completely novel phases which are not present in the pure samples.

3. RESULTS AND DISCUSSION

   Characterization of novel homologous series of liquid crystal complexes nOBA:TMD are explained in the preceding section.

   In detail, all the pure series of samples possess nematic phase and samples with n=7 12 additionally exhibit Smectic C phase. It was observed that phase transition temperatures of all the complex samples were decreased compared to their pure counterparts. Astonishingly, nematic phase was quenched in the complexes n= 4-6 and Crystal G phase was induced in whole series of the samples and nematic phase also observed in complexes with n = 7to12. As a representative case nematic droplets and Crystal G phases of 8OBA :TMD was shown in Figs 1 and 2. Quenching of old phases, inducement of new phases and change in transition temperatures in the prepared complexes were identified which has helped us to conclude that certainlyintermolecular

   Fig 1..Nematic phase in 8OBA:TMD

   Figure3. Smectic-G phase in 8OBA:TMD

   The Phase Transition temperatures recorded using thermal microscope was in good agreeent with the recordings using DSC thermo grams given in Table

   1. As a representative case DSC thermo gram of 8OBA: TMD was shown in Fig 3.

      TABLE 1. Observed Phase Transition temperatures of

      Compound nOBA:TMD	Phase	Isotropic (I)0C	I N (0C)	I-G (0C)	N/G- Cr (0C)
      n =4 (TM) (DSC)	SG	116.1 112.4			97.8
      n =5 (TM) (DSC)	SG	110.7 105.1			94
      n =6 (TM) (DSC)	SG	112		99.6 103.7	85.4
      n =7 (TM) (DSC)	N,SG	103	92.6 94.6	86 96.1	73
      n =8 (TM) (DSC)	N,SG	108	90.2 89.5	86.8 76.8	72.1
      n =9 (TM) (DSC)	N,SG	103	101 100.1	95.2 95.8	84.2
      n =10 (TM) (DSC)	N,SG	106	100.3 102.3	91.6 95.4	78.2
      n =11 (TM)	N,SG	105.8	94.2	94.5	75.3

      Compound nOBA:TMD	Phase	Isotropic (I)0C	I N (0C)	I-G (0C)	N/G- Cr (0C)
      n =4 (TM) (DSC)	SG	116.1 112.4			97.8
      n =5 (TM) (DSC)	SG	110.7 105.1			94
      n =6 (TM) (DSC)	SG	112		99.6 103.7	85.4
      n =7 (TM) (DSC)	N,SG	103	92.6 94.6	86 96.1	73
      n =8 (TM) (DSC)	N,SG	108	90.2 89.5	86.8 76.8	72.1
      n =9 (TM) (DSC)	N,SG	103	101 100.1	95.2 95.8	84.2
      n =10 (TM) (DSC)	N,SG	106	100.3 102.3	91.6 95.4	78.2
      n =11 (TM)	N,SG	105.8	94.2	94.5	75.3

      nOBA:TMD using DSC and POM

      (DSC)			96.0	87.5				:TMD
      n =12 (TM) (DSC)	N,SG	110	103.5 104.6	89.5 94.2	70.9		8	11OBA :TMD	1668	1662	3365	3182	696	2918
      							9	12OBA :TMD	1669	1667	3365	3183	698	2916

      100

      33775379..3937345272

      33775379..3937345272

      361326.4617.26307461

      361326.4617.26307461

      3355263.69.348608738

      3446.79419

      3355263.69.348608738

      3446.79419

      2011979.524.41656493

      2011979.524.41656493

      95

      394389.6218.67385806

      394389.6218.67385806

      386338.49128.3455069

      386338.49128.3455069

      2320.36565

      2320.36565

      2065.76194

      2065.76194

      1923.02955

      1923.02955

      1869.0227

      1780.29717

      1869.0227

      1780.29717

      644.22454 692.44494

      549.7510275.627861

      644.22454 692.44494

      549.7510275.627861

      90

      Transmittance %

      Transmittance %

      2671.41016

      2555.6812

      2671.41016

      2555.6812

      2374.3725

      2374.3725

      1066.63525

      1066.63525

      1016.48603

      1016.48603

      85

      933.54694

      933.54694

      80

      2926.01387

      2848.86123

      2926.01387

      2848.86123

      1516.04938

      1427.32384

      1516.04938

      1427.32384

      1296.16435

      1296.16435

      846.75022

      769.59758

      846.75022

      769.59758

      75

      1170.79131

      1170.79131

      70

      1689.64282

      1608.63254

      1689.64282

      1608.63254

      1253.7304

      1253.7304

      65

      60

      Fig 3. DSC Graph of 8OBA:TMD

      1. Fourier Transform Infrared spectroscopy (FTIR):

   The IR Spectra of the p-n-alkoxy benzoic acids (nOBA), ortho toluamide (TMD) and their inter molecular H- bonded complexes were recorded both in solid (KBr) and dissolved (in chloroform) states at room temperature and was shown in Fig 4. The summaries of infrared frequencies along with their assignments were shown in Table 2. The IR spectra of TMD exhibit the strong characteristic absorptions bands at 3369.0 cm-1 for N-H stretching along with (out plane bend) OPB modes of NH at 618.02 cm-1 [28,29] nOBA : TMD complexes show the absorption bands in the range of 620 698 cm-1 for (NH) OPB modes, strong intense bands due to C- H mode of benzoic acid moiety in the range of 2954-2916 cm- 1which supports the existence of nOBA moieties in monomeric form upon complexation. The stretching, bending vibrations involving the proton donating groups (NH2) and proton acceptor groups (O-H) showed shifts in their absorption frequencies, confirms the formation of hydrogen bonding in liquid crystal complexes. TMD with proton accepting substituents O-H, the intra molecular H-bond in

   4000 3500 3000 2500 2000 1500 1000 500

   wavenumber(cm-1)

   (a)

   3365.78392

   3184.47522

   2974.23427

   2783.28149

   1957.74824

   1654.92413

   1492.90358

   1394.53397

   1139.93026

   1037.70301

   945.11984

   746.45179

   682.80086

   536.21085

   3365.78392

   3184.47522

   2974.23427

   2783.28149

   1957.74824

   1654.92413

   1492.90358

   1394.53397

   1139.93026

   1037.70301

   945.11984

   746.45179

   682.80086

   536.21085

   100

   Transmittance %

   Transmittance %

   80

   60

   40

   20

   0

   4000 3500 3000 2500 2000 1500 1000 500

   wavenumber(cm-1)

   (b)

   3948.28635

   3863.41845

   3797.8387

   3377349.79.678492429

   361346.4630.15138342

   33552636.9.348608738

   3365.78392

   3184.47522

   2926.01387

   2848.86123

   2673.33898

   2551.82357

   2374.3725

   2320.36565

   2065.76194

   2017.54154

   1923.02955

   1867.09389

   1778.36835

   1687.714

   1608.63254

   1514.12056

   11348287..7342735824

   1255.65922 1296.16435

   1170.79131

   1066.63525

   1018.41485

   933.54694

   848.67904

   769.59758

   692.44494

   644.22454

   549.71255607.27861

   3948.28635

   3863.41845

   3797.8387

   3377349.79.678492429

   361346.4630.15138342

   33552636.9.348608738

   3365.78392

   3184.47522

   2926.01387

   2848.86123

   2673.33898

   2551.82357

   2374.3725

   2320.36565

   2065.76194

   2017.54154

   1923.02955

   1867.09389

   1778.36835

   1687.714

   1608.63254

   1514.1206

   11348287..7342735824

   1255.65922 1296.16435

   1170.79131

   1066.63525

   1018.41485

   933.54694

   848.67904

   769.59758

   692.44494

   644.22454

   549.71255607.27861

   80

   75

   Transmittance %

   Transmittance %

   70

   65

   60

   55

   50

   45

   40

   35

   TMD disturbs the symmetry of the amino group. Therefore,

   4000 3500 3000 2500 2000

   1500 1000 500

   -1

   the formation of intermolecular H-bond with acceptor substituent is formed by the free N-H group. Stability of the hydrogen bonding is observed by IR peak shift of the in plane bend (IPB) mode of N-H and C-H towards the higher frequency side.

   TABLE 2. IR spectral data (cm-1) for TMD and nOBA:TMD

   wavenumber(cm )

   (c|)

   Fig 4. (a) FTIR Spectrum of 8OBA;( b). FTIR Spectrum of TMD; b).

   FTIR Spectrum of TMD;(c) FTIR spectrum of 8OBA:TMD.

   As a comparative study between the nBA:TMD [16] and nOBA:TMD (n= 4 to 12) , the data given in Table 3 reveals that in case of NH (IPB) there is a increased shift of 74cm-1 for nBA:TMD and 513cm-

   Sam ple No.	Compo und nOBA: TMD	(C=O)		(NH) AMIDE		(NH ) OPB	(CH )ACID
   		Acid	Amide	(NH ) ASY	(NH) SY
   0	TMD		1654	3365 .	3184	618
   1	4OBA: TMD	1669	1729	3365	3181	620	2954
   2	5OBA: TMD	1662	1729	3367	3184	686	2953
   3	6OBA: TMD	1669	1663	3365	3165	698	2931
   4	7OBA: TMD	1668	1562	3365	3184	751	2931
   5	8OBA: TMD	1689	1687	3365	3184	693	2931
   6	9OBA: TMD	1662	1668	3365	3180	682	2918
   7	10OBA	1669	1662	3365	3184	694	2918

   Sam ple No.	Compo und nOBA: TMD	(C=O)		(NH) AMIDE		(NH ) OPB	(CH )ACID
   		Acid	Amide	(NH ) ASY	(NH) SY
   0	TMD		1654	3365 .	3184	618
   1	4OBA: TMD	1669	1729	3365	3181	620	2954
   2	5OBA: TMD	1662	1729	3367	3184	686	2953
   3	6OBA: TMD	1669	1663	3365	3165	698	2931
   4	7OBA: TMD	1668	1562	3365	3184	751	2931
   5	8OBA: TMD	1689	1687	3365	3184	693	2931
   6	9OBA: TMD	1662	1668	3365	3180	682	2918
   7	10OBA	1669	1662	3365	3184	694	2918

   1

   for nOBA:9HB. And also by comparing the FTIR Spectra of nBA:TMD and nOBA:TMD, the below table shows that nBA:TMD exhibits the 12cm-1 hypochromic shift in (NH) bond stretch and nOBA:TMD shows 25cm-1 bathochromic shift with respect to the (NH) bond stretch respectively.

   TABLE 3. FTIR data of nBA:TMD and nOBA:TMD

   Compound	(c=o)		(NH) amide		(NH)opb	(CH)acid
   	Acid	Amide	(NH)asy	(NH)sy
   TMD	–	1655	3367	3185	682	–
   8BA	1644	–	–	–	–	2926
   8OBA	1684	–	–	–	946	2928
   4BA:	N.A.	N.A.	N.A.	N.A.	N.A.	N.A.

   TMD 4OBA: TMD	1679	1616	3361	3182	685	2954
   5BA: TMD 5OBA: TMD	1655 1678	1617 1617	3367 3367	3184 3184	686 686	2863 2953
   6BA: TMD 6OBA: TMD	1657 1691	1607 1607	3375 3375	3165 3165	696 682	2855 2931
   7BA: TMD 7OBA: TMD	1658 1678	1612 1612	3366 3366	3184 3184	694 696	2851 2931
   8BA: TMD 8OBA: TMD	1658 1689	1612 1687	3367 3365	3185 3184	693 694	2852 2931
   9BA: TMD 9OBA: TMD	1662 1681	1617 1612	3369 3369	3180 3180	682 693	2853 2918
   10BA: TMD 10OBA: TMD	1658 1681	1610 1612	3366 3362	3184 3184	694 682	2851 2918

   TMD 4OBA: TMD	1679	1616	3361	3182	685	2954
   5BA: TMD 5OBA: TMD	1655 1678	1617 1617	3367 3367	3184 3184	686 686	2863 2953
   6BA: TMD 6OBA: TMD	1657 1691	1607 1607	3375 3375	3165 3165	696 682	2855 2931
   7BA: TMD 7OBA: TMD	1658 1678	1612 1612	3366 3366	3184 3184	694 696	2851 2931
   8BA: TMD 8OBA: TMD	1658 1689	1612 1687	3367 3365	3185 3184	693 694	2852 2931
   9BA: TMD 9OBA: TMD	1662 1681	1617 1612	3369 3369	3180 3180	682 693	2853 2918
   10BA: TMD 10OBA: TMD	1658 1681	1610 1612	3366 3362	3184 3184	694 682	2851 2918

4. CONCLUSION

A new series supra molecular hydrogen bonded liquid crystal complexes have been synthesized from p- n-alkoxy Benzoic acid (nOBA) where n=4 to 12 and TMD. (The Crystal G phase induced in all the complexes, and threaded nematic phase is induced in 12OBA:TMD compound.) Hydrogen bond is established between the OH group of the p-n-Alkoxy Benzoic acid and NH group of TMD, leads to an orthorhombic arrangement of the molecules. Hence, the molecular packing was influenced by the intermolecular Hydrogen Bonding, due to this influence in each layer of the molecule of nOBA an arrangement was created like headtotail and TMD as an adjacent molecule, a condition which induce crystal G mesomorphism.

From the below Table 4 it is observed that, the thermal span for alkoxy complexes is more than alkyl complexes further that thermal stability is comparatively more in nOBA:TMD complexes and is around 50oC. crystal G phase is dominant in nBA:TMD complex and nOBA:TMD series. Further, theremal stability for nBA:TMD complexes lie in between 25oC. Hence, nOBA:TMD complexes are thermally and texturally more stable than nBA:TMD.

TABLE 4. Comparison of transition temperatures obtained from POM for nOBA:TMD and nBA:TMD

*NA represents Not Available

ACKNOWLEDGEMENTS:

One of the author (SSS) is grateful to University Grants Commission for providing BSR Faculty fellowship No.:F.18-1/2011(BSR) dated: 04/01/2017. The authors also gratefully acknowledge University Grants Commission Departmental Special Assistance program at Level I program No. F.530/1/DSA- 1/2015 (SAP-1), dated 12th May 2015.

REFERENCES

1. Frederic J. Kahn, Electric Field Induced Orientational Deformation of Nematic Liquid Crystals: Tunable Birefringence, Applied Physics Letters 20, 199 (1972); doi: 10.1063/1.1654107

2. G. Singh, G. Vijaya Prakash, S. Kaur, A. Choudhary, A.M. BiradarMolecular relaxation in homeotropically aligned ferroelectric liquid crystalsPhysica B 403 (2008) 3316 3319

3. Faten Al-Hazmi, Ahmed A. Al-Ghamdi, Noruh Al-Senany, Fowzia Alnowaiser, Fahrettin Yakuphanoglu Dielectric anisotropy and electrical properties of the copper phthalocyanine (CuPc): 440-n-Heptylcyanobiphenyl (7CB) composite liquid crystals, Composites: Part B 56 (2014) 1519

4. Chih-Hsin Chena, Kun-Lin Yang A liquid crystal biosensor for detecting organophosphates through the localized pH changes induced by their hydrolytic products, Sensors and Actuators B 181 (2013) 368 374

5. Mashooq Khan and Soo-Young ParkLiquid Crystal-Based Proton Sensitive Glucose Biosensordx.doi.org /10.1021/ ac402916v | Anal. Chem. 2014, 86, 14931501

6. Alicia Gamble Synthesis of Liquid Crystals Filling Forms with Function University of Colorado Boulder Liquid Crystals Materials Research Center

7. Synthesis and mesogenic properties of liquid crystals with bent core-tail substitution geometry Thesis written by Richard Davis B.S., Westminster College, 2008 M.S., Kent State University, 2013

8. S. Salma Begum, T. Vindhya Kumari, C. Ravi Shankar Kumar,

   S. Sreehari Sastry, Liquid crystalline G phase of self assembled donoracceptor molecules by intermolecular hydrogen bonding Journal of Non-Crystalline Solids 357 (2011) 17451749

9. K. Vijayalakshmi and S. Sreehari Sastry Induced Smectic A Phase through Intermolecular Hydrogen Bonding: Part XVIII: Influence of p-n-Alkyl Benzoic Acids on Thermal and Phase Behavior of Hydrogen-Bonded Liquid Crystals Acta Physica Polonica A Vol. 115 (2008) xxxx

10. Vijayakumar VN, Madhu Mohan MLN. Synthesis and characterization of double hydrogen bonded ferroelectric liquid crystals exhibiting reentrant smectic ordering. Ferroelectrics. 2009; 392:8197.

11. Chitravel T, Madhu Mohan MLN. Occurrence of ambient temperature and re-entrant smectic ordering in an inter-molecular hydrogen bonding between alkyl aniline and alkoxy benzoic acids. Mol. Cryst. Liq. Cryst. 2010; 524:131143.

12. Vijayakumar VN, Madhu Mohan MLN. Design, synthesis and characterization of hydrogen bonded ferroelectric liquid crystals. Mol. Cryst. Liq. Cryst. 2010; 524:5467.

13. Subhapriya P, Vijayakumar VN, Madhu Mohan MLN, Vijay anand PS. Study and characterization of double hydrogen bonded liquid crystals comprising of p-n alkoxy benzoic acids with azelaic and dodecane dicarboxlic acid. Mol. Cryst. Liq. Cryst. 2010; 53:3650.

14. Kumar PA, Pisipati VGKM, Rajeswaria AV, Sreehari Sastry S. Induced smectic-G phase through intermolecular hydrogen bonding, part XII: thermal and phase behaviour of p-aminobenzonitrile: p-n-alkoxybenzoic acids. Liquid Crystals Today Z. Naturforsch. 2002; 57a:184188.

15. Swathi P, Kumar PA, Pisipati VGKM, Rajeswaria AV, Sreehari Sastry

    S. Induced smectic-G phase through intermolecular hydrogen bonding, part XV: thermal and phase behaviour of p-alkyl anilines: p- n- alkoxybenzoic acids, Z. Induced smectic-G phase through intermolecular hydrogen bonding, part XV: thermal and phase behaviour of p-alkyl anilines: p-n- alkoxybenzoic acids, Naturforsch. 2002;57a:797802.

16. Swathi P, Kumar PA, Pisipati VGKM. Induced smectic-G phase through intermolecular hydrogen bonding, part III: inuence of alkyl chain length of p-n-alkoxybenzoic acids on thermal and phase behaviour. Mol. Cryst. Liq. Cryst.2001;365:523533.

17. Paleos CM, Tsiourvas D. Thermo tropic liquid crystals formed by intermolecular hydrogen bonding interaction. Angew. Chem. Int. Ed. Engl. 1995; 34:16961711.

18. Gray GW. Molecular structure and the properties of liquid crystals. London: London Academic Press; 1962. p. 163.

19. Kelker H, Hatz R. Handbook of liquid crystals. Weinheim: Verlag Chemie; 1980. p.59.

20. Vijayakumar VN, Madhu Mohan MLN. Study of inter molecular hydrogen bonding in p-n-alkoxybenzoic acids and alkyl aniline homologous seriespart-I Mol.Cryst. Liq. Cryst. 2009;515:3948.

21. Swathi P, Kuar PA, Pisipati VGKM. Induced smectic-B phase through intermolecular hydrogen bonding part IX: comparative thermal and phase behaviour studies on two distinct structural isomers possessing linear and bow shapes. Z. Naturforsch. 2001; 56a:692696.

22. K. Vijayalakshmi and S. Sreehari Sastry, Induced smectic phase trhough intermolecular hydrogen bnonding Part XVIII: Influence of p-n-alkyl benzoic acid on thermal and phase behavior of hydrogen bonded liquid crystals. Acta Physica Polonica A Vol. 115 (2009) 690-693-

23. S. Salma Begum, T. Vindhya Kumari, C. Ravi Shankar Kumar, S. Sreehari Sastry Liquid crystalline G phase of self assembled donor- acceptor molecules by intermoleculrar hydrogen bonding Journal of Non-Crystalline Solids 357 (2011) 17451749,

24. S. Sreehari Sastry, S. Salma Begum, K. Mallika, K.B. Mahalakshmi, Ha Sie Tiong Image analysis to detect phase transition temperatures of p-n- alkyl bnenzoic acids International Journal of Innovative Research in Science, Engineering and Technology Vol. 2, Issue 9, September 2013, 4641-4647

25. S. Sreehari Sastry, S. Salma Begum, T. Vindhya Kumari,V.R.K. Murthy, and Sie Tiong Ha, Effect of mage\netitel nano particles on p-n- alky benzoic acid mesogens, E-Journal of Chemistry, 2012, 9(4), 2462- 2471,

26. Ch. Hemalakshmi and S. Sreehari Sastry Study of Supramolecule through Intermolecular Hydrogen Bond in 5OBA:TMD Liquid Crystals, IJERT, 2017, 6, 225-228

27. Robert M. Silverstein, Francis X. Webster, Spectrometric Identification of Organic Compounds, 6th Ed., 1997.

28. H. Williams, Ian Fleming, Spectroscopic Methods in Organic Chemistry, TMH, 2004.

29. William K. Organic Spectroscopy. Haryana: Replika Press; rr 2008.