I Have a Research Support System

The three of them first came to Room 530 of Xiancai Building.

Inside, the gel chromatograph has stopped functioning.

Chen Wanqing turned on the computer next to the instrument, found their test data, and started data processing.

There is a special software for data processing, you only need to import the results, and then apply the processing algorithm written in advance to automatically fit and calculate.

However, if the curve shape of the test result is abnormal, there may be a situation where automatic fitting cannot be performed. In this case, manual operation is required.

Fortunately, Xu Qiu and the others did not encounter such a situation, all the data were imported and the results were automatically obtained.

If every data has to be processed manually, it may take an entire morning to explain it here.

The results showed that the number-average molecular weights of the eight polymer materials were all between 20,000 and 50,000, and the polydispersity coefficients were between 1.6 and 1.9.

This is normal data in polymer donor materials in the field of organic photovoltaics.

If the molecular weight is too small, it indicates that the polymer main chain is too short, and the charge transport performance of the material will be deteriorated;

Molecular weight is too large, unless there are very long chain branches, or there will be solubility problems.

If the polydispersity coefficient is too large, such as exceeding 2.0, then the repeatability of the device performance data obtained by using this batch of materials to make batteries will be very poor.

Maybe the same batch of materials, the same conditions, some can achieve 8%, some only 7%, 6% or even lower.

As for the polydispersity coefficient less than 1.5, that is really good, and the repeatability of the experiment will be very good.

Xu Qiu also wanted to achieve such a result, but based on the current synthesis conditions, it was impossible.

After processing the data and copying it with a USB flash drive, the three of them disposed of the waste liquid and other experimental garbage, locked the door and left.

It only took about half an hour in total.

...

Next, come to room 528 next to it.

There are three instruments inside, including DSC and TGA to be used today, and a TMA thermomechanical analyzer.

TMA is a technique for measuring the functional relationship between the deformation of a substance and the temperature and time under a programmed temperature and a non-vibration load. It mainly measures parameters such as the expansion coefficient and phase transition temperature of the substance.

Generally, structural materials such as rubber and fibers are tested. The polymer materials used by Xu Qiu and others for organic photovoltaics are functional materials, and this characterization method is not used.

Xu Qiu didn't return all the experimental skills of DSC and TGA to the teacher, after all, they were experiments just learned last year.

He and his senior sister performed the experimental operation together, while the junior sister watched and studied by the side.

TGA is relatively simple in principle. It is to gradually heat the material in an atmosphere of nitrogen protection, increase its temperature, and detect the change of the weight of the material over time.

Because it is programmed temperature control, temperature and time are in one-to-one correspondence, so the curve of the weight of the material with temperature can be obtained.

When the material loses weight significantly, it may mean that the solvent in the material evaporates, loses crystal water, decomposes, and re-decomposes.

The corresponding temperature is the critical temperature at which the above reaction occurs.

The operation is also simple. You only need to put the weighed sample into the crucible, then hang it in the instrument, and set the heating program according to the requirements, and then execute it.

DSC also uses programmed temperature control, but it can achieve precise temperature control from minus 80 degrees Celsius to more than 1,000 degrees Celsius above zero.

Because it involves low-temperature experiments, low-temperature cooling devices are used, and pre-cooling needs to be turned on in advance.

The DSC in the material department is a power compensation type.

Internally heated, the holders for the sample and the reference are independent components, and there is a platinum thermal resistance for heating and a platinum sensor for temperature measurement at the bottom of the sample and reference.

In thermal testing, many components are made of the precious metal platinum.

It adopts the principle of dynamic zero balance, which requires the temperature of the sample and the reference to maintain a dynamic zero balance state no matter when the sample is endothermic or exothermic, that is, to keep the temperature difference between the sample and the reference tending to zero.

By measuring the energy difference required to maintain the sample and reference at the same temperature, the change in enthalpy of the sample can be reflected, and the glass transition temperature and crystallization temperature of the material can be obtained.

However, polymer materials generally used in organic photovoltaics are weakly crystalline, and most of the measured DSC images are flat, and the curve shape is similar to a parallelogram.

Such a graph has no distinction at all, and apart from proving its weak crystallinity, no other useful information can be obtained.

But after all, it is a routine characterization test, and the process that should be followed still needs to be followed.

Eight samples, starting from the senior sister's.

Weigh the sample, put it into a crucible, and place it on the platform of the DSC instrument.

Set the temperature control program, from normal temperature to high temperature slowly, such as 250 degrees Celsius, then return to minus 20 degrees Celsius, and then rise to high temperature, and cycle again.

Generally, the set temperature of high temperature is lower than the decomposition temperature of the material, that is, the temperature tested from TGA.

It is worth noting that if the material will release a large amount of gas or explode at high temperature, DSC and TGA cannot be tested.

Otherwise, halfway through the test, the material exploded inside the instrument.

Test failures are trivial and have the potential to damage the instrument.

The department may not directly trouble you, but it will definitely ask your supervisor for compensation, and then you are ready to face the angry supervisor.

When the temperature of the DSC cooling device reaches minus 80 degrees Celsius, start the test.

The test time is very long, and it usually takes about an hour for a sample. During the test, people can leave as long as the door is locked.

However, neither of these two instruments can change samples automatically, so changing samples still requires manual operation.

There is a key problem. The first floor of materials and the second floor of materials were built at the same time. The two buildings are next to each other. The advanced materials building was built later, which is far away from material one and material two.

Counting the time spent going up and down the stairs, it takes about fifteen minutes to walk from Caiyi to Xiancai, and it takes half an hour to go back and forth.

It is faster to ride a shared bicycle, but the shared bicycles on campus may be parked for ten minutes, and then come back to look for them, and the bike will be gone.

Xu Qiu thought for a while and said:

"I'll stay and watch later, you can go back, anyway, I want to write an article, and it's the same here.

It’s just that my computer is still on the first floor of the material…”

"Leave it to me. I'll send it to the senior brother later." Han Jiaying said.

"Okay then, you go back first."

This school girl is still on the road.

...

After saying goodbye to the two, Xu Qiu looked at the layout of the laboratory.

The area of ​​this laboratory is about the same as Caiyi 216, but there are only three equipments, so it looks relatively empty.

There is an air conditioner hanging on the wall, and there are several tables and round stools.

The air conditioner wasn't on, and he didn't intend to.

Just three days ago, Qiuhu came to the devil's capital.

It's not so hot during the day, and it's starting to get cold at night.

As if that day separated summer and autumn.

Half an hour later, the DSC curve of the first sample of the senior sister has run halfway, and its shape is indeed flat.

Xu Qiu shook his head, counting the time in his mind, the school girl should be here soon.