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Boletín de la Sociedad Chilena de Química

versión impresa ISSN 0366-1644

Bol. Soc. Chil. Quím. v.47 n.2 Concepción jun. 2002

http://dx.doi.org/10.4067/S0366-16442002000200014 

Bol. Soc. Chil. Quím., 47, 169-173 (2002)

 

POLYMERIZATION BY PHASE TRANSFER CATALYSIS. 28.
CONDENSATION POLYMERS DERIVED FROM A DIIODINE
DIPHENOL-AMIDE

L.H. Tagle*, F.R. Diaz and A. Vivanco

Departamento de Química Orgánica, Facultad de Química, Pontificia Universidad Católica
de Chile, P.O. Box 306, Santiago, CHILE (e-mail: ltagle@puc.cl)
(Received: September 24, 2001 - Accepted: March 28, 2002)

RESUMEN

A partir del difenol N-(2,6-diyodo-4-nitrofenil)-3,3-bis(4-hidroxifenil)-butanamida se describe la síntesis del poli(carbonato) con fosgeno, del poli(tiocarbonato) con tiofosgeno y de los poli(ésteres) con los cloruros de los ácidos adípico, isoftálico y tereftálico, usando condiciones de transferencia de fase y varias sales de amonio cuaternario como catalizadores. El comportamiento de los catalizadores fue evaluado a través de los valores de rendimiento y viscosidad inherente, y fueron comparados con aquellos obtenidos en ausencia de los mismos. En general el proceso de transferencia fue efectivo observándose un incremento de ambos parámetros. Todos los polímeros fueron insolubles en el medio de reacción, lo cual limitó el crecimiento de la cadena polimérica.
PALABRAS CLAVES: difenol-amida, poli(carbonato), poli(tiocarbonato), poli(éster), catálisis por tranferencia de fase.

SUMMARY

From the diphenol N-(2,6-diiodo-4-nitrophenyl)-3,3-bis(4-hydroxyphenyl)-butanamide, the synthesis of the poly(carbonate) with phosgene, the poly(thiocarbonate) with thiophosgene and the poly(ester)s with adipoyl chloride, isophthaloyl chloride and terephthaloyl chloride are described under phase transfer conditions using several quaternary ammonium salts as catalysts. The bahaviour of the catalysts was evaluated by the yields and the inherent viscosity values, comparing them with those obtained without catalyst. In general the phase transfer process was effective in all cases observing an increase of both parameters. All the polymers were insoluble in the reaction media which limited the growth of the polymeric chains.
KEY WORDS: diphenol-amide, poly(carbonate), poly(thiocarbonate), poly(ester)s, phase transfer catalysis.

INTRODUCTION

In the last years we have focussed our attention in the synthesis of condensation polymers containing two functional groups in the repeating unit. In this sense we have described the synthesis of poly(carbonate)s, poly(thiocarbonate)s and poly(ester)s derived from diphenols containing an ester group [1] or an amide one in the side chain [2-4], and also we have changed the length of the carbon side chain, using three, four and five carbon atoms. Normally these polymers have been insoluble in common organic solvents and in the reaction media, which has limited other studies as a function of the nature of the groups bonded to the side chain, and the growing of the polymeric chain, having this factor a great influence in the molecular weight.

As a polymerization technique we have used the phase transfer catalysis, in which the dianion is transferred as a ion-pair with the catalyst from the aqueous phase to the organic one in which the reaction takes place. This technique has been widely used in the synthesis of several kinds of polymers because it offers important technical advantages compared to other synthetics methods, such as solution or interphase polymerization [5].

As a continuing our woks on the synthesis of condensation polymers with two functional groups under phase transfer conditions [6], in this paper we described the synthesis of the diphenol N-(2,6-diiodo-4-nitrophenyl)-3,3-bis(4-hydroxyphenyl)-butanamide and the respective poly(carbonate) with phosgene, the poly(thiocarbonate) with thiophosgene and poly(ester)s with adipoyl chloride, isophthaloyl chloride and terephthaloyl chloride, using several ammonium quaternary salts as phase transfer catalysts, and evaluating the results by the yields and inherent viscosity values of the obtained polymers, which were characterized by espectroscopy methods.

EXPERIMENTAL PART

Reagents and solvents (from Aldrich or Riedel de Haen) were used without purification. The following catalysts (from Fluka) were used: tetrabutylammonium bromide (TBAB), methyltrioctylammonium chloride (ALIQUAT 336), benzyltriethylammonium chloride (BTEAC), and hexadecyltrimethylammonium bromide (HDTMAB).

The IR spectra were recorded on a Perkin-Elmer 1310 spectrophotometer and the 1H and 13C NMR on a 200 MHz instrument (Bruker AC-200), using DMSO-d6 as solvent and TMS as internal standard. Viscosimetric measurements were made in a Desreux - Bischof [7] type dilution viscosimeter at 25°C.

The diphenol-acid 3,3-bis(4-hydroxyphenyl)-butanoic was synthetized according to a procedure described previously [1].

The diphenol-amide N-(2,6-diiodo-4-nitrophenyl)-3,3-bis(4-hydroxyphenyl)-butanamide was synthetized according to the following general procedure: 0.244 mol of the diphenol acid were mixed with 30 ml of SOCl2 and the mixture refluxed for two hours. After this time, 6 g (0.29 mol) of 2,2-diiodo-4-nitro-aniline were added to the homogeneous mixture, and the heating was continued for six hours. After this time, the SOCl2 was destilled, and to the brown oil, a saturated NaHCO3 solution was added. The solid was filtered and washed with NaHCO3 solution. Then, the solid was dissolved in a NaOH solution for removing the unreacted aniline, and then precipited by HCl addition. This procedure was repeated again, obtaining a light brown solid corresponding to the diphenol-amide. The diphenol-amide decomposed before melting.

N-(2,6-diiodo-4-nitrophenyl)-3,3-bis(hydroxyphenyl)-butanamide: IR (cm-1) (KBr): 3329 (OH); 3020 (H arom.); 2972 (CH2, CH3); 1673 (C=O); 1610, 1513 (C=C); 833 (arom. p-subst.). 1H NMR (d) (ppm) (DMSO-d6): 1.95 (s,3H,CH3); 3.19 (s,2H,CH2); 6.74 (d,4H,arom.); 7.11 (d,4H,arom.); 8.65 (s,2H,arom.); 10.1 (s,1H,NH). 13C NMR (d) (ppm) (DMSO-d6): 27.8 (CH3); 43.4 (C quat.); 47 (CH2); 99.7; 114.6; 127.7; 133.2; 139.7; 145.9; 148.5; 154.7 (arom.); 168.6 (C=O).

Polymer synthesis

The poly(amide-ester)s were synthesized according to the following general procedure: 1 g (1.55 mmol) of the diphenol-amide and the catalyst (5% mol) were dissolved in 20 mL of 0.25 M NaOH at 20°C. Then, 20 mL of CH2Cl2 with 1.55 mmol of adipoyl chloride (I-a) or isophthaloyl chloride (I-b) or terephthaloyl chloride (I-c) were added. The mixture was stirred for one hour at 20C and then poured into 500 mL of methanol. Polymers were filtered, washed with methanol, dried until constant weight, and characterized.

The poly(amide-carbonate) and the poly(amide-thiocarbonate) were synthesized according to the following general procedure: in a 250 ml flask 1 g (1.55 mmol) of the diphenol-amide and the catalyst (5% mol) were dissolved in 20 mL of 0.25 M NaOH at 20°C. Then, 20 mL of CH2Cl2 and 1.55 mmol of phosgene (II-d) or thiophosgene (II-e) were added, and the mixture stirred for one hour at 20C. After this time the mixture was poured into 500 ml of methanol. The polymer was filtered, washed with methanol, dried until constant weight, and characterized.

RESULTS AND DISCUSSION

Poly(amide-ester)s derived from the diphenol-amide N-(2,6-diiodo-4-nitrophenyl)-3,3-bis(hydroxyphenyl) -butanamide and adipolyl chloride (I-a), isophthaloyl chloride (I-b) and terephthaloyl chloride (I-c), with the following structure

and the poly(amide-carbonate) with phosgene (II-d) and the poly(amide-thiocarbonate) with thiophosgene (II-e) with the following structure:

were synthesized under phase transfer conditions in CH2Cl2 as solvent at 20C, and characterized by IR spectroscopy and elemental analysis.

The structures were in according with those proposed. In all polymers it was possible to see the disappearance of the OH band, showing a new band corresponding to the C=O group, at 1736 cm-1 for the ester group of the poly(ester)s and at 1768 cm-1 for the poly(amide-carbonate). For the poly(amide-thiocarbonate) there was an increase of the intensity of the band at 1272 cm-1 due to the C=S group. In all polymers it was possible to see the band corresponding to the C=O of the amide in the same position (1676 cm-1) and the band at 3447 cm-1 corresponding to the NH of the amide group. Due to the low solubility of the polymers in the deuterated solvents it was not possible to obtain the NMR spectra.

In this work only the nature of the phase transfer catalyst was studied by the yields and the inherent viscosity values (hinh). The reaction time, solvent, catalyst and base concentration, and temperature remained constant. The reaction time was one hour and was determined by evaluating the stability of the diphenol-amide monomer in the reaction media by dissolving it in 0.25 M NaOH mixed with CH2Cl2 and the catalyst. After this time the diphenol-amide monomer was recovered quantitatively.

Table I shows the yields and hinh values obtained for the three poly(amido-ester)s. Without catalyst the poly(amido-ester)s were obtained due to an interphasial polycondensation process between the diphenolate dissolved in the aqueous phase and the acid dichloride dissolved in the organic one. The principal limitation of the polymerization process was the insolubility of the poly(amido-ester)s in the reaction media, which limited the growth of the polymeric chain. This behaviour was observed in the synthesis of polymers with a similar structure [3-4]. When the catalysts were used there was a slow increase of both parameters, which nonetheless permits to show the effectivity of the transfer process of the dianion. On the other hand the low differences obtained in the hinh values does not permit obtain conclusions about their behaviour, but it is necessary to point out the effectivity of BTEAC, which has been described as hydrophilic [8] and suitable for transporting dianions of lypophilic character or with a high organic content such this. This behaviour was described in the synthesis of other analogous polymers. Also this catalyst has Cl- as counter ion, which is interchanged more easily than Br-.

Table II shows the yields and hinh values obtained for the poly(amido-carbonate) II-d and the poly(amido-thiocarbonate) II-e. Also without catalyst the polymers were obtained due to an interphasial polycondensation process between the diphenolate dissolved in the aqueous phase and the phosgene or thiophosgene in the organic one. When the catalysts were used there was an important increase of the yields for both polymers, but a moderate increase of the hinh values for the poly(amido-carbonate). For the poly(amido-thiocarbonate) there was an important increase of the hinh values. This behaviour shows the effectivity of the phase transfer process. Nevertheless this increase, the effect of the catalysts was very similar which can be due to the insolubility of the polymer in the reaction media, which limited the growth of the polymeric chain. However TBAB showed an important effectivity due probably to its symmetrical structure with C4 chain bonded to the N central atom, which confers a good separation between the cation and anion in the ion pair. An analogous behaviour was observed in the synthesis of other analogous polymers but with a longer side chain [2,4], and in other poly(carbonate)s [9-10].

In general, the yields obtained were not very high, which may be due to a hydrolytic process of both, the monomer or the polymeric chain. We can discard a hydrolysis of the monomer because after one hour in analogous conditions we recovered it quantitatively, but a hydrolytic process of the polymeric chain is possible and has been shown in the synthesis of other poly(carbonate)s and poly(thiocarbonate)s influenced by the nature of the catalyst [11-12].

In this type of phase transfer polycondensations process, the limiting step is the transfer of the dianion to the organic phase rather than the reaction in this phase because both, the acid chlorides and phosgene and thiophosgene are very reactive. The principal limitation of this process is the insolubility of the polymeric chains in the reaction media which limited their growth and giving consequently similar values of hinh independently of the catalyst nature. In spite of the observed limitations it is possible to conclude that the phase transfer process was effective in the synthesis of this kind of polymers being one of the advantages the mild conditions used.

ACKNOWLEDGEMENTS

The authors acknowledge the financial support of FONDECYT through grant 8970011.

REFERENCES

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