Chapter 82: Synthesis experiment (medium)

　　 "Are the main valve and pressure reducing valve not open." Xu Qiu said.
　　 "It makes sense, maybe Duan Yun turned it off," Chen Wanqing said:
　　 "If the nitrogen cylinder is not used in the laboratory for a long time, you need to close the main valve, otherwise it may slowly leak."
　　 Chen Wanqing unscrewed the main valve and the pressure reducing valve, and opened the nitrogen valve again, but the balloon still showed no sign of getting bigger.
　　 "Why are you still out of breath?"
　　 Xu Qiu pointed to the pressure reducing valve barometer next to him and said:
　　 "The indication is 0, this cylinder should be empty."
　　 Then, he unscrewed the main valve of a cylinder next to him and saw that the pressure gauge of the pressure reducing valve had an indication, then opened the pressure reducing valve and said:
　　 "Senior sister, you can try this time."
　　 "I'm getting gas this time." Chen Wanqing slowly unscrewed the nitrogen valve, and the sound of airflow heard, and the balloon was slowly getting bigger.
　　The three-way valve connected to the balloon has three ports ABC and one valve. Rotating the valve can make the three-way valve in four states: AB connected, BC connected, AC connected or three blocked.
　　The A port corresponds to a balloon, the B port can be inserted into a 19-port glassware, and the C port can be connected to a rubber hose to connect to a nitrogen stream or a vacuum pump.
　　……
　　 When the balloon was inflated to the size of a fist, Chen Wanqing closed the nitrogen valve and turned the three-way valve to connect the balloon with the outside world. Then, the balloon was flattened and the residual gas inside was discharged.
　　Senior sister filled with nitrogen and exhausted again.
After 　　 lasted three times, she filled the balloon with a large amount of nitrogen to inflate it to the size of a human head, and then turned the three-way valve to a three-way state.
　　 Next, she took a nitrogen ball with a three-way valve and inserted it above the spherical condenser.
　　 Then, connect the vacuum pump to the C port of the three-way valve, and connect the vacuum pump to the distillation device.
　　 Start the vacuum pump to pump air until the toluene boils. At this time, the air in the distillation device is basically cleaned. Turn the three-way valve to connect AB and use a nitrogen ball to add nitrogen to the distillation device.
　　 Continuously pump and deflate, repeat three to five times to ensure that the atmosphere in the system is basically nitrogen.
　　 After completing this operation, Chen Wanqing sighed:
　　"In fact, our synthesis equipment is a beggar version. Like a research group that specializes in synthesis experiments, they will use double-row tubes to achieve nitrogen protection operation, which is not so troublesome.
　　 There is also a microwave reactor dedicated to polymerization, which can greatly save the time required for the reaction. "
　　 "It is estimated that the equipment is very expensive, Teacher Wei is reluctant to buy it." Xu Qiu guessed.
　　"Yes, it doesn't cost tens of thousands to hundreds of thousands to buy any instrument. After Mr. Wei returned to China, he had three million research start-up funds, which has now been spent more than half.
　　 However, he has also applied for the National Natural Science Foundation of China and other small funds, which add up to more than 1 million yuan, which is not short of money for the time being. "
　　 Chen Wanqing replied, turning on the condensate pipe, setting the temperature of the magnetic constant temperature heating stirrer to 130 degrees Celsius, and adjusting the speed to 400r.p.m.
　　 The temperature rises slowly.
　　 Soon after the temperature stabilized at 130 degrees Celsius, the toluene in the round bottom flask began to boil.
　　Toluene vapor passes through the solvent distillation head, reaches the spherical condenser, condenses into a liquid state, and flows back to the solvent distillation head again.
　　 There is also a three-way valve on the solvent distillation head to connect the round bottom flask at the bottom and the outside.
　　 Chen Wanqing adjusted the three-way valve to connect to the round bottom flask and said:
"In this way, the condensed toluene solvent can be refluxed into the round bottom flask again.
　　The solution is still white now. We have to wait for the indicator to turn blue before we can collect the distilled toluene.
　　Because it is a newly opened toluene reagent, it should turn blue quickly.
　　While waiting, we can do some preparatory work, such as cleaning and drying glassware.
　　Because this is a new glass instrument, you only need to rinse the inner wall of the glass instrument with absolute ethanol, and the stir bar can be rinsed in a disposable PE cup.
　　 After cleaning, pour ethanol into the waste liquid bucket, and then use an oven to dry the glass instrument, the oven temperature is set at 70 degrees Celsius.
　　 This time we each cast a reaction test water. Each person needs to prepare a 25ml two-necked flask, a 19-necked spherical condenser, a three-way valve, and a magnetic stirrer. "
　　 Xu Qiu followed the senior sister's instructions to clean the glass instruments and put them in the oven.
　　"Then calculate the feed ratio. The molar ratio of monomer with trimethyltin, monomer with bromine group and catalyst is generally 1:1:0.05.
　　 Before weighing, the relative molecular mass of each material should be calculated, and then converted to the corresponding mass.
　　Calculate the relative molecular mass You can use Chemdraw software to draw the molecular structure, and then use the software's own function to calculate the relative molecular mass.
　　 In our first experiment, we used less raw materials and kept the total mass of materials at about 200 mg.
　　You can fix the mass of one of the monomers to 100 milligrams, and then calculate the mass of the other monomer and catalyst, so that it is easier to weigh.
　　My calculations have already been calculated. Go to the office and use the computer to do the calculations, then write it on a sticky note and bring it over. "Chen Wanqing said.
　　 Xu Qiu nodded, took off his protective suit, and returned to the A501 office.
　　 As for the goal of the first experiment to test the water, he has already thought about it.
"A monomer is a T-BT-T unit with a bromine group, in which two T units also have 14 carbon alkyl side chains to ensure the solubility of the final polymer product.
　　 The other unit is a 2T unit with trimethyltin. He bought one gram of each of these two materials, so he is not afraid of waste.
　　The main chain of the expected polymer looks like this:
　　……BT-T-T-T-T-BT-T-T-T-T-BT-……
　　 Xu Qiu even thought of the name of the polymer~EbookFREE.me~ It is called PBT4T, where P stands for polymer, 4T stands for four continuous thiophenes, and BT stands for BT unit.
　　 This is a product of his own synthesis, which is naturally qualified to name it.
　　 Like some researchers or research groups, in order to save trouble, the naming will be simplified. For example, a researcher surnamed Xu can name a series of materials he synthesized as X1, X2, X3,....
　　 Of course, whether other researchers admit it is another matter, because everyone can give these structures a different name.
　　 But in order to facilitate communication, there is generally a set of general naming methods. For example, Xu Qiu uses a general method, starting with P and following the name of each monomer unit.
　　 Xu Qiu used Chemdraw software to draw the molecular structure, and after obtaining the relative molecular mass of each, he set the BT unit with bromine group to 100 mg.
　　 Then calculate the feed quality of another monomer and catalyst, and copy them on the label paper.
　　 He returned to the laboratory again and put on his protective suit again.
　　 "It's all right so soon?" Chen Wanqing said:
　　 "You didn't miss the branch when calculating the relative molecular mass, right?"
"No."
　　 "The trimethyltin and bromine groups are not missing."
"No."
　　 "That's good," Chen Wanqing said:
　　 "The first time I responded, Teacher Wei was staring at the side. I was too nervous and missed both.
　　 In the end, a pile of scum was formed and was scolded by Teacher Wei.
　　 The past is unbearable. "