PoZy ( 2-EthyZ-2- n -Bu tyZ Trimethylene Sulfone )

Polysulfones of several types have been of practical interest for some time as potential rigid plastics with high softening points: or gas-permeable biomedical material^.^ The dynamical behavior of poly(o1efin sulfones) in dilute solution is unusual in that dielectric relaxation appears to proceed essentially only by entire molecule tumbling: in contradistinction to the rather normal chain mobility revealed by l3C spin-lattice relaxation times."" In seeking a structural rationalization of this behavior, we were impelled to look for a soluble sulfone polymer with three backbone carbon atoms per repeat unit. None of the polymers that we could make had the requisite solubility in nonpolar media, but because one of them appears to be new it is briefly reported here.

Several sulfone polymers of the structure (CH2-CR1R2-CH2-S02),; R I = H, CH3; R2 = H, CH3, C2H5 have been ~ynthesized.~-~ All are characterized by high crystalline melting points and correspondingly low or negligible solubilities in solvents of low polarity suitable for dielectric work. It was supposed that separation between chains could be increased by substituting bulkier groups at the central carbon, reducing the strong dipole-dipole interactions, and thus increasing solubility. Preparation of the polymer with R1 = C2H5 and R2 = n-C4H9 was therefore carried out by oxidation of the corresponding polysulfide. The latter was prepared by a boron-trifluoride-etherate-initiated ring-opening polymerization of 3-ethyl-3-n-butyl thietane.12 The thietane was prepared from 2- ethyl-2-n -butyl-1-3 propanediol via the cyclic carbonate intermediate.'3J4

The polysulfone obtained was a powdery material with unobservably low solubility in benzene, toluene, dimethyl sulfoxide, dioxane, or chloroform. Limited solubility is found in n-cresol and trifluoracetic acid. Differential scanning calorimetry (Perkin-Elmer D.S.C.-lB) indicated an en- dothermic transition at 279OC with some darkening and decomposition. This is close to the melting temperatures for the dimethyl- (29OOC) or methyl-ethyl- (28OOC) substituting polymers reported earlier.4 Evidently no significant decrease in the intermolecular forces is produced by the larger butyl group substituent in the present polymer. An x-ray powder pattern gave detectable, though rather broad diffraction rings corresponding to crystalline repeat distances of about 5.2 and 4.4 8,. A faint ring corresponding to a 2.0 8, distance was also observed. The 5.2 8, distance is likely to be the sulfur-sulfur intrachain distance. I t corresponds to the distance calculated, if a trans configu- ration, tetrahedral bond angles, and standard bond lengths are assumed, and is also consistent with x-ray data reported2 on unsubstituted hexa- and pentamethylene sulfones when reduction for fewer backbone carbons is made. The 4.4 8, distance may be the sulfur-sulfur distance between chains, although it is slightly less than the 4.6 8, distance reported for the unsubstituted pentamethylene chain.

These observations are consistent with a sheet-like structure of parallel polymer chains in extended t ram configurations, with strong head-to-tail dipole interactions between SO2 groups on adjacent chains. The substituent ethyl and butyl groups could then be thrust out above and below the plane and would not significantly interfere with the planar regularity. The increase in the number of SO2 groups per unit length in the trimethylene sulfone chain compared with the pentamethylene chain may account for the decreased sulfur-sulfur interchain distance. The apparent lack of a third x-ray ring at interchain distances would also be consistent with well-defined crystalline sheets and poorly defined order between sheets.

EXPERIMENTAL

5-Ethyl-5-n-butyl-l,3-dioxan-2-one was prepared from 2-ethyl-2-n-butyl-l,3-propanediol (Al- drich) by ester interchange with ethyl carbonate as described in the literature.'3 The viscous liquid obtained, which is previously unreported, had a boiling point of 13SoC/0.5 mm and the nuclear magnetic resonance (NMR) in CDC13 showed 4-H at 4.1 p, 8-H centered at 1.3 p, and 6-H centered at 0.9 p.

3-Ethyl-3-n-butyl-thietane was prepared from the cyclic carbonate by reaction with potassium thiocyanate, as described in the 1iterat~re.l~ The liquid obtained, also previously unreported, had a boiling point of 8143°C at water aspirator pressures and the NMR in CDCl3 showed 4-H at 2.8 g and 14-H spread between 0.7 and 1.8 p. The peak at 2.8 p was resolved somewhat and the inner peaks of an A-B quartet could be seen, separated by about 3 Hz.

Journal of Polymer Science: 0 1978 John Wiley & Sons, Inc.

Polymer Chemistry Edition, Vol. 16,3001-3002 (1978) 0360-6376/7S/0016-301$01.00

3002 J. POLYM. SCI.: POLYM. CHEM. ED. VOL. 16 (1978)

Poly(2-ethyl-2-n-butyl trimethylene sulfide) was prepared from the cyclic sulfide by a boron- trifluoriae-etherate-induced, ring-opening polymerization in bulk, as described in the literature.** The procedure was modified by allowing the polymerization to proceed at 25OC for 48 hr. The re- sulting polymer, after being taken up in chloroform and twice reprecipitated in methanol, had an inherent viscosity of 0.23 d l g-' (0.41 g dl-' CHC13 at 25°C).

Poly(2-ethyl-2-n-butyl trimethylene sulfone) was prepared from the polysulfide by oxidation with HzOz at 25OC in a trifluoroacetic acid solvent in a manner similar to that described in the lit- e r a t ~ r e . ~ Some of the polysulfone precipitated as it formed; the rest was obtained by precipitation in water. An infrared (IR) spectrum of the polymer in a KBr pellet showed strong S=O stretching bands at 1275 and 1125 cm-' in agreement with the literature on other polysulfone~.~

I am grateful for the advice and helpful suggestions of Dr. Walter Stockmayer, Dr. Keizo Matsuo, and Dr. David Lemal and for the hospitality of Dartmouth College. In addition, the assistance of Dr. Allan Tice in obtaining and evaluating the differential thermogram and Dr. Roger Soderberg in obtaining and evaluating the x-ray data is acknowledged. This work was supported by the Na- tional Science Foundation and the Petroleum Research Fund.

References

1. H. D. Noether, U.S. Patent 2,534,366 (1950). 2. H. D. Noether, J. Polym. Sci., 25,217 (1957). 3. V. S. Foldi and W. Sweeny, Makromol. Chem., 72,298 (1964). 4. G. L. Brode, Polym. Prepr., 6,626 (1965). 5. J. K. Stille and J. A. Empen, J. Polym. Sci. Part A, 5,273 (1967). 6. W. A. Lee and R. A. Rutherford, in Polymer Handbook, J. Brandrup and E. H. Immergut,

7. J. E. Crawford and D. N. Gray, J. Appl. Polym. Sci., 15,1881 (1971). 8. T. W. Bates, K. J. Ivin, and G. Williams, Trans. Faraday SOC., 63,1964 (1967). 9. W. H. Stockmayer, A. A. Jones, and T. L. Treadwell, Macromolecules, 10,762 (1977).

Eds., Wiley-Interscience, New York, 1975,2nd ed., p. iii-166.

10. R. E. Cais and F. A. Bovey, Macromolecules, 10,757 (1977). 11. A. H. Fawcett, F. Heatley, K. 3. Ivin, C. D. Stewart, and P. Watt, Macromolecules, 10,765

12. J. A. Empen and J. K. Stille, Macromolecular Synthesis, Vol. 3, p. 53. 13. S. Searles, D. G. Hummel, S. Nukina, and P. C. Throckmorton, J. Am. Chem. SOC., 82,2928

14. S. Searles, H. R. Hays, and E. F. Lutz, J. Org. Chem., 27,'2828 (1962).

(1977).

(1960).

ROBERTCOOK

Department of Chemistry Lafayette College Easton, Pennsylvania 18042

Received August 24,1977 Revised September 26,1977