The Preparation of "Bouncing Putty": An Undergraduate Experiment in Sillcone Chemistry "Bouncing putty" has been sold as a novelty for children but adults, particularly scientists, find it much more entertaining. Perhaps one can rationalize this by assuming1 that only the mature intellect can appreciate the paradox of bauncing putty! Bouncing putty is one of the many products that can he isolated from dimethylsilicone oil. The silicones are organic derivatives of silicon of general formula RsSiO. While formally resembling ketones, they do not contain the Si-0 double bond and are polymeric. They are best prepared by hydrolyzing chlorosilanes, which may in turn be conveniently synthesized2 by heating a mixture of silicon and copper with alkyl chlorides a t 300°C. Silicones have uses in most branches of commerce and industry. Bouncing putty is a polymer with novel properties produced from dimethylsilicon dichloride. The followine describes the method used a t Queen Elizabeth Colleee .. to oreoare bouncine...outtv. , Commercial oroducti utmrnitl add~timnlfiller, tu give grearer mechamral rtrength, tOyCtrlQrw t h additives such ns lrrrie ox~de.3The rx. prriment attracted G p e a t deal of inrrreir amuny the undergraduates. In most cases they ohrainrd a produrr which had good bounce properties hut rather poor mechanical strength.
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Preparation The experiment should be carried out in a fume cupboard. Distil 20 ml. of dimethylsilicon dichloride (boiling point 69.7-C) using carefully dried apparatus fitted with a Silica Gel drying tube. Add to 40 ml. of diethylether and hydrolyze by adding 40 ml. of water dropwise (the reaction proceeds vigorously if the water is added too quickly). Separate the ether laver a t the comoletion of the hvdralvsis reaction and wash it with dilute bicarbonate solution until it is no longer acidic.~. , , nnd finally wirh Hntrr. Dry the rrhrr *olutwn w e r anhydrou; m a ~ e s i u msulfate. Decant rhe ether solution, filter off any nmgnaslum s ~ l f n r rand , distil off the ether using a watrr barh. Pump nlf the fmal traces of ether. Tote rhe yirld 61 the dimethylsilicone oil
Add about 5% boric oxide (by weight), stirring continuously during the addition and for a further few minutes. Heat the ail in a Pyrex boiling tube to about 200'C in a n oil bath, and leave a t this temperature for three hours. Allow to cool and remove the product from the bailing tuhe. The product will have putty-like properties, but will bounce when rolled into a ball and dropped. 'Eahom, C., "Organosilicon Compounds," Butterworths, 1960, p. 460. 2Rochaw, E. G., and Patnode, W. I., U S . Patent 2,380,996; CA, P48896, 39, (1945); Patnode, W. I., U.S. Patent 2,380,997: CA, P505U5, 39, (1945); Rochow, E. G., J.Aner. Chem. Soc., 963.67,(1945). 3McGregar, R. R., and Warrick, E. L., U.S. Patent 2,431,878; CA, P1761h. 42, (1948); Wright, J.G.E., U S . Patent 2,541,851; CA, P44851, 45, (1951). Queen Elizabeth College D. A. Armitage M. N. Hughes Campden Hill Road A. W. Sinden London W8 7AH, United Kingdom
434 /Journal o f Chemical Education
