ELSEVIER P@,mer Vol. 37 No. 15, pp. 3427 3429, 1996 Copyright 1996 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0032-3861 96/$15.00 + 0.00 polymer communications X-ray crystallographic structure of cyclic tetramer ester based on bisphenoI-A and o-phthaloyldichloride Hongyan Jiang, Tianxi Liu, Hongfang Zhang, Tianlu Chen and Zhishen Mo* Changchun Institute of Applied Chemistry, Chinese Academy of Scmnces, Changchun 130022, People's Republic of China (Received 26 October 1995) The polycrystalline powder of the cyclic tetramer ester based on bisphenol-A and o-phthaloyldichloride has been prepared by recrystallization from nitrobenzene and its crystal structure determined by wide-angle X-ray diffraction. The unit cell is orthorhombic and has dimensions a = 0.967nm, b = 0.8699nm, c = 2.0859nm. With two tetramers per unit cell, the crystal density is 1.36gcm -3. Indices of crystal diffraction peaks are also detailed in the present work. Copyright 1996 Elsevier Science Ltd. (Keywords: cyclic tetramer ester; wide-angle X-ray diffraction; unit cell parameters) Introduction Polyarylates constitute an important class of engineer- ing polymers. They are tough materials having excellent mechanical and thermal properties. However, these poly- mers generally suffer the problem of very high melt viscosity, which limits their applications in some areas. Therefore the use of low-molecular-weight macrocyclic precursors to prepare these polymers via ring-opening polymerization during processing has received consider- able attention in recent years 14. Macrocyclic precursors have the advantage of a lower viscosity at processing temperature than the final polymer, and may find appli- cations in such areas as compositions for reaction injec- tion moulding 5. A research programme on the synthesis and ring- opening polymerization of cyclic ester oligomers was initiated in our laboratory several years ago, and an efficient way to prepare cyclic ester oligomers was found. The cyclic oligomers obtained by this method are a mix- ture of ring sizes, ranging from dimer to octomer, with the cyclic tetramer being the main product. Although the latter has been reported by Tyuzyo and Harada 6, its crystal structure has not been determined so far. The dimensions of the single-crystal sample prepared in our laboratory are not suitable for X-ray diffraction. The present communication reports the preparation, isola- tion and X-ray crystal structure of the polycrystalline powder of the cyclic tetramer prepared from bisphenol-A and o-phthaloyldichloride. Experimental The cyclic oligoesters were prepared as a mixture of different ring sizes in 70-80% yields via a PTC catalysed interfacial condensation of bisphenol-A and o-phthaloyldichloride using CHzCI 2 and NaOH under pseudo-high-dilution conditions v (see Scheme 1 ). On the basis of the solubility difference on the cyclics and high-molecular-weight linear polymer in CH2C12, a * To whom correspondence should be addressed mixture of cyclic tetramer and a small amount of cyclic dimer was obtained; the cyclic tetramer was then purified as an individual species by recrystallization as follows. The cyclic oligomer mixture (~0.20 g) was dissolved in hot nitrobenzene (analytical grade, 10ml). The solution was then brought to room temperature over a period of at least 2h, and the crystals of cyclic tetramer were obtained by gently tapping the outside of the flask. The colourless crystals of the tetramer were removed by filtration and washed with cold nitrobenzene (2 x 10 ml). The wide-angle X-ray diffraction (WAXD) pattern was taken on a Rigaku D/max-IIB diffractometer from 20 = 5 to 55 °. Cuk~l radiation was provided by a 2 kW Philips X-ray tube (40 kV, 20 mA). As monochromator and analyser we used curved graphite crystals. Results and discussion The cyclic tetramer (Scheme 2) is a crystalline solid that melts at 302.8-304.0°C, and has been characterized by gel permeation chromatography (g.p.c.), fast atom bombardment mass spectrometry (f.a.b.-m.s.), Fourier transform infra-red spectroscopy (FTi.r.) and elemental analysis. The g.p.c, trace shown in Figure 1 indicates that the cyclic tetramer is isolated, recrystallized as a pure compound. F.a.b.-m.s.: m/z 717 (M + molecular ion), 701 (M + - CH3 - H). FTi.r. absence of phenolic stretching and all other peaks are common to the corresponding polymer. Elemental analysis: calcd for the cyclic tetramer C, 77.16; H, 5.03. Found: C, 77.08; H, 5.06. The density of the cyclic tetramer was determined using the suspen- sion method as 1.26 g cm -3. Using a trial-and-error method, the orthorhombic unit cell was determined with cell dimensions a = 0.9676 nm, b = 0.8699 nm, c= 2.0859 nm. Comparing the observed d-spacing with the calculated ones, the results were quite satisfactory (Table 1). Figure 2 shows the WAXD pattern of the cyclic tetramer. The diffraction pattern with 30 diffraction peaks was indexed in terms of an orthorhom- bic unit cell. The Miller indices of all the reflections and relative intensities are also displayed in Table 1. Using POLYMER Volume 37 Number 15 1996 3427