Investigation of squaric acid derivates

Polymer Testing 20 (2001) 205–208 www.elsevier.nl/locate/polytest

Test Method

Investigation of squaric acid derivates Z. Glavcheva a

a,*

, Ts. Kolev a, I. Glavchev

b

Bulgarian Academy of Science, Institute of Organic Chemistry, build. 9, Acad. G. Bonchev Str., 1113 Sofia, Bulgaria b University of Chemical Technology and Metallurgy, 8 Kl. Ohridski Bul., 1156 Sofia, Bulgaria Received 10 June 1999; accepted 3 March 2000

Abstract The aims of the present work are to prove the possibility of employing IR spectra to investigate the compounds obtained by interaction of Squaric acid (H2Sq) and phenyl- or alkyl glycidyl ethers (PhGE or AlkGE), to establish the most suitable absorbances for quantitative analyses and to evaluate the formation of H-bonds. Indication of H-bond formation could be taken as the shift of some characteristic absorption bands ⌬n for (C–O–C) groups and decreasing of the value ⌬h1/2, where ⌬h1/2 is the peak width at half height. The interactions of H2Sq and glycidyl ethers were made in the medium of the ethers.  2000 Elsevier Science Ltd. All rights reserved. Keywords: IR spectroscopy; Squaric acid; Glycidyl ethers

1. Introduction

2. Experimental

As a result of interaction of H2Sq by AlkGE or PhGE its epoxy ring was opened and an OH group was formed. This reaction may be a usual condensation or catalytic one by obtaining oligomers. In [1] was described the interaction of super acids in ring opening reaction with epoxy resin. The H2Sq is a very strong acid. The ring open reaction with dicarboxylic organic acids or their anhydrides was made by heating at 140°C. In the literature there are many works using different acids but we have not found any information for H2Sq because of its bad solubility in organic solvents. For example, in water it is possible to produce 苲1% solution by stirring and heating [2]. Interaction with alcohols was also produced by heating and stirring [3]. The aim of the present work is to investigate the compounds obtained by the interaction of H2Sq and AlkGE or PhGE and the formation of H-bonds by IR spectroscopy.

H2Sq is a product of Hu¨ls (Marl), Germany, AlkGE (Cardura E-10) is a product of Shell, UK, PhGE is a product of Fluka, Switzerland. The sample No I is AlkGE; No II is a mixture of AlkGE: H2Sq=10:1 (mol/mol); No III is a mixture of AlkGE: H2Sq: H2O=10:1:6 (mol/mol/mol); No IV is a mixture of AlkGE: H2Sq: C2H5OH=10:1:1.9; No V is PhGE; No VI is a mixture of PhGE: H2Sq=16:1 (mol/mol); No VII is a mixture of PhGE: H2Sq: H2O=16:1:6 (mol/mol/mol) and No VIII is a mixture of PhGE: H2Sq: C2H5OH=16:1:1.9 (mol/mol/mol). The interactions of the compounds were made in ampoules by heating and stirring at 100°C for long times. GPC on the obtained compounds was made using Waters apparatus (USA). The IR spectra were obtained using Perkin Elmer apparatus (USA) in thin layer. The shift of the absorption bands was taken into account. The ratio A⬘ was calculated from the absorbances for (C–O–C) groups (1250, 1080, 1040 and 910 cm⫺1) and internal standards (CH2) groups (No 1—2980, No 2—1465, No 3—1355, No 4—1142 and No 5—845 cm⫺1) or in phenyl ring (No 6—1600, No 7—1500, No 8—1175 and No 9—753 cm⫺1). The ⌬h⬘1/2 was calculated from the relation: peak width at half height for absorption bands of (C–O–C) and

* Corresponding author. E-mail address: [email protected] (Z. Glavcheva).

0142-9418/01/$ - see front matter  2000 Elsevier Science Ltd. All rights reserved. PII: S 0 1 4 2 - 9 4 1 8 ( 0 0 ) 0 0 0 2 4 - 6

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for the internal standard. The quantity of epoxy groups contents (E, %) was determined by interaction with HCl in acetone and titration with 0.1 N NaOH [4].

3. Results and discussion The products of interaction of H2Sq with AlkGE or PhGE are maybe compounds including 1 mol H2Sq and 1 mol glycidyl ether or oligomers (in the case of catalytic reaction). Since the structures of its molecules are different from polystyrene standards, GPC was first carried out on glycidyl ethers and after that on the samples. In the chromatograms of the samples there are peaks for free glycidyl ethers and for two or three oligomers with degree of polymerization from 2 to 5 and no peak with bigger retention time than for the glycidyl ethers: all the H2Sq was reacted and there was no free acid. The degree of polymerization was calculated from the relations of molecular weight of olygomer/molecular weight of glycidyl ether. In the polymers containing C–O–C groups, the absorbance at 1250 cm⫺1 characterizes not only the quantity of this group, but also the structure of macromolecules and the crystallinity of the polymers [5,6]. It is evident from GPC that the products of the H2Sq and glycidil ethers are oligomers. According to [7] for quantitative IR analyses and for H-bond formation of copolymers of epychlorohydrin and PhGE or butylglycidyl ethers, absorbances are available for (C–O–C) at 1137 and 916 cm⫺1. For quantitative analyses of epoxy group content in bisphenol A based epoxy resin, the most suitable absorbance is at 916 cm⫺1 [8]. According to [9] the most available absorbances for quantitative IR analyses of copolymers of trioxane and butyl and phenyl glycidyl ethers are the ν (C–O–C) at 1100 cm⫺1 and internal standard at 1470 cm⫺1. In IR spectra of epoxy resin based on phenolphthalene there are absorption bands at 1288, 1255, 1086, 1035, 1015, 965, 940 and 925 cm⫺1 for (C–

O–C) groups. In the IR spectra of AlkGE and of the sample with H2Sq, water and ethanol there is no absorption band in the region 1130–1140 cm⫺1 because the peak for (CH2) in 1142 cm⫺1 is strong. In the spectra of samples with PhGE there is a small peak at 1128 cm⫺1, but we decided not to work with this absorbance. We investigated the absorption bands for n(C–O–C) at 1250, 1080, 1040 and 910 cm⫺1. The internal standards for samples with AlkGE No I, II, III and IV are the absorption bands for CH2 group Nos 1–5 and for samples with PhGE No V, VI, VII, and VIII are the absorption bands for benzene ring (Nos 6–9). The values A⬘=AC–O–C/Aint.st. (20 for samples with AlkGE and 20 for samples with PhGE) were calculated from the obtained IR spectra. From the values of epoxy group content, E% of samples No I, II, III, IV and A⬘ were calculated the equation: E⫽aA⬘⫹b, where a is the slop of the linear dependence and b is the intercept. The variation of experimental points were characterized by the coefficient of correlation k. The obtained results are in Table 1. The results for samples No V, VI, VII, VIII are in Table 2. It is evident from Table 1 that for quantitative IR analyses of oligomers obtained from AlkGE and H2Sq the most available absorbances are 1251 and 907 cm⫺1 for n(C–O–C) and internal standard at 1143 cm⫺1. For the oligomers from PhGE and H2Sq the most available absorbances are at 1250 and 1038 cm⫺1 and internal standard at 1606 cm⫺1 (Table 2), because the values of k are minimal. By comparison of the IR spectra of the mixtures and of glycidyl ethers the shift ⌬n of the absorption bands for n(C–O–C) was measured. Table 3 shows the values of ⌬n. It is evident that all values of n(C–O–C) in AlkGE are bigger than the n of absorption bands for PhGE because of H-bond formation. Only the absorption band at 905

Table 1 The values for samples with AlkGEa,b n(C–O–C) (cm⫺1) nint.st (cm⫺1)

a

b

k

1251 1251 1251 1251 993 907 907 907 907

0.0088 0.0156 0.0296 0.0041 0.0224 0.0116 0.0244 0.0472 0.0099

0.031 0.1762 0.3261 0.1707 0.0685 ⫺0.0601 ⫺0.0874 ⫺0.1866 0.0072

0.6400 0.0525 0.087 0.00494 0.027 0.0125 0.03173 0.0654 0.01025

a b

2980 1463 1385 1142 1385 2980 1463 1385 1143

k is a coefficient, characterizing the dispersion of the experimental results. The equations for another absorbances have the coefficient k bigger than k=0.64.

Z. Glavcheva et al. / Polymer Testing 20 (2001) 205–208

207

Table 2 The values for samples with PhGEa n(C–O–C) (cm⫺1) nint.st (cm⫺1)

a

b

k

1250 1250 1250 1038 1038 1038 912 912 912

0.3969 0.0657 0.0756 0.2574 0.0402 0.0546 0.2064 0.0334 0.0835

⫺4.2741 ⫺0.6005 2.6161 ⫺3.5802 ⫺0.4574 1.0232 ⫺4.7467 ⫺0.7427 ⫺1.5839

0.2262 0.0109 0.0900 0.1694 0.0145 0.0744 0.1110 0.0493 0.0514

a

2980 1606 1175 2980 1606 1175 2980 1606 1175

The equations for another absorbances have the coefficient k bigger than k=0.2262.

Table 3 The shift of absorption bands for n(C–O–C) Samples, no I

II

III

IV

V

VI

VII

VIII

n, cm⫺1

⌬n, cm⫺1

⌬n, cm⫺1

⌬n, cm⫺1

n, cm⫺1

⌬n, cm⫺1

⌬n, cm⫺1

⌬n, cm⫺1

1251 1083 1045 905

⫺1 1 3 5

⫺6 1 ⫺3 ⫺5

⫺4 7 5 4

1245 1073 1038 912

5 2 2 1

⫺5 4 ⫺1 1

1 5 2 1

Table 4 The values of ⌬h⬘1/2 for samples with AlkGEa

No

1251 cm⫺1 1 2 3

4

5

1063 cm⫺1 1 2 3

4

5

1045 cm⫺1 1 2 3

4

5

905 cm⫺1 1 2

3

4

5

I II III IV

1.15 1.15 1.08 1.15

1.6 1.56 1.48 1.66

2.33 2.36 2.43 2.44

0.3 – 0.51 0.44

0.42 – 0.7 0.64

0.61 – 1.14 0.94

0.16 – – 0.46

0.23 – – 0.66

0.33 – – 0.97

0.27 0.26 0.33 0.25

0.56 0.5 0.91 0.77

0.38 0.36 0.46 0.36

0.54 0.55 0.75 0.55

a

2.41 2.58 2.13 2.6

2.41 2.17 2.94 3.54

0.63 – 1.0 1.0

0.63 – 1.39 1.36

0.34 – – 1.03

0.34 – – 1.41

0.56 0.58 0.66 0.57

1—2980 cm⫺1; 2—1465 cm⫺1; 3—1385 cm⫺1; 4—1142 cm⫺1; 5—845 cm⫺1.

Table 5 The values of ⌬h⬘1/2 for samples with PhGEa

No

1245 cm⫺1 1 6 7

8

9

1033 cm⫺1 1 6 7

8

9

1038 cm⫺1 1 6 7

8

9

912 cm⫺1 1 6

7

8

9

V VI VII VIII

– – – –

3.91 4.09 3.5 3.64

2.26 2.37 2.21 2.22

⫺– – –

1.09 2.0 1.92 2.09

0.63 1.16 1.21 1.28

– – – –

1.46 2.09 1.92 2.01

0.84 1.21 1.21 1.28

– – – –

0.77 0.95 0.77 0.81

1.55 1.64 1.42 1.55

0.9 0.95 0.89 0.94

a

1.79 1.55 1.5 1.43

1.96 1.96 1.91 1.91

0.5 0.76 0.82 0.82

0.55 0.96 1.05 1.1

0.67 0.79 0.82 0.82

1—2980 cm⫺1; 6—1600 cm⫺1; 7—1500 cm⫺1; 8—1172 cm⫺1; 9—750 cm⫺1.

0.73 1.0 1.05 1.10

0.71 0.62 0.61 0.61

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cm⫺1 is batochromic and that fact is impossible to explain by H-bond formation. The most sensitive absorption band for H-bond formation in the spectra of the oligomers from PhGE and H2Sq is at 1073 cm⫺1 as well as at 1083 cm⫺1 for the oligomers from AlkGE and H2Sq. If the values of ⌬h⬘1/2 of the absorption bands of the samples with H2Sq (Nos II, III and IV) were compared with the same values for AlkGE (sample No I), it is evident that there is maximal increasing for the absorption band at 1045 cm⫺1 and for internal standard at 1385 cm⫺1 (Table 4). The absorption bands for the samples with PhGE (Table 5) with maximal increasing of ⌬h⬘ are at 1073 cm⫺1 for n(C–O–C) and at 1172 and 750 cm⫺1 for internal standards. This is the reason to work with these absorption bands to characterize H-bond formation in the compounds. From these results it is evident that the most sensitive absorption band for H-bond formation is different for each compound.

4. Conclusion Our experimental results show that the absorbances at 1251 and 907 cm⫺1 for n(C–O–C) and internal standard at 1143 cm⫺1 are available for quantitative IR analyses of oligomers from AlkGE and H2Sq. For oligomers from PhGE and H2Sq these absorbances are at 1250 and 1038 cm⫺1 and for internal standard at 1606 cm⫺1. The most sensitive absorption bands for H-bond for-

mation according to the increasing of n for (C–O–C) are at 1037 and 1083 cm⫺1. The most sensitive absorption bands for H-bond formation according to the value ⌬h⬘1/2 are 1045 cm⫺1 and internal standard at 1385 cm⫺1 for oligomers from AlkGE and H2Sq and 1073 cm⫺1 and 1172 or 750 cm⫺1 for oligomers from PhGE and H2Sq. Acknowledgements We thank The National Science Foundation (Bulgaria) for financial support of the project X-605 and the Chemische Werke Hu¨ls (Marl, Germany) for a generous gift of squaric acid. References [1] [2] [3] [4] [5] [6] [7] [8] [9]

US patent 5294582. S. Cohen, J.R. Pank, J. Am. Chem. Soc. 81 (1959) 3480. A.H. Schmidt, W. Ried, Synthesis 1978: 869. Bulgarian State Standard 13342-76. M. Mihailov, L. Terlemezjan, Comm. Dept. Chem. Bulg. Acad. Sci. 3 (1970) 267. L. Terlemezjan, M. Michailov, Makromol. Chem. 178 (1978) 2607. I. Glavchev, G. Sirachki, R. Mateva, Polym. Testing 19 (2000) 415–417. B. Danenberg, W.R. Harp, Anal. Chem. 29 (1956) 86. G. Sirashki, I. Glavchev, R. Mateva, Polym. Testing 16 (1997) 3.