Silicon Polymer (Bouncing Putty)

On Tuesday 9-20-11, we made a silicon polymer that looked like a clear gel and bounced like a bouncy ball. We started by combining diethyl ether and dimethyldichlorosilane in a round bottom flask. When we started adding some water dropwise into the mixture, the flask got very hot (even when we had it in an ice bath!) and emitted some fumes. The fumes were actually hydrogen chloride gas, which is given off in the reaction we were doing-- hydrolysis of dimethyldichlorosilane. The product of the hydrolyzation (a silanol) was what we needed to make our putty. Of course, now there were two layers in the flask so we had to hearken back to organic chemistry and grab a separatory funnel.

We wanted to keep the organic layer, so we separated, washed the aqueous layer with hexanes, separated again, and combined the two organic phases. We used sodium hydrogen carbonate to neutralize the HCl that was formed in the reaction.

We dried the product over magnesium sulfate and filtered it. Then, we got to use the rotary evaporator to evaporate off the ether and obtain our product. Here are a few pictures of the roto vap:

We put our sample in the roto vap, filled the condenser up with ice, and turned it on. It heated the sample and evaporated the ether from it. The ether then went over to the condenser, where it was turned from gas to liquid and was collected in the round flask at the side. This left just our product in the vial inside the roto vap.

After this, we took the IR of the oily product and massed it to find out how much boric acid to add to the liquid (we needed about 7% by mass). When we added the boric acid, it just sat on the bottom of the beaker and wouldn't dissolve into solution. When we heated it with continual stirring, it started to get thick and gummy after about 15 minutes.

Once it seemed like all the liquid had turned to putty, we scraped it out of the beaker, put it on a preweighed watchglass, and found the mass. If it was left to sit too long on the watchglass, it would "melt" into a liquidy puddle but then would form right back into a putty again if you rolled it in your hands. Here is our bouncing putty...which actually did bounce!!