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Some Experiences on Improving the Classroom Teaching Effect of Polymer Physics
Paper Keywords Polymer Physics Teaching Effect
According to the characteristics of polymer physics course, this paper expounds how to improve the teaching effect of polymer physics course and cultivate students' professional learning interest and professional thinking ability from four aspects: historical background, basic concept formula, integrating theory with practice and typical cases, and making full use of multimedia.
Polymer physics is a subject that studies the structure, properties and relationship of polymers. It is closely related to the synthesis, processing and application of polymer materials, and is a very important professional basic course for polymer specialty. The study of this course has a far-reaching impact on students' in-depth mastery of professional basic knowledge and skills. However, polymer physics has many abstract concepts, complex structure and changeable performance, which is recognized as the most difficult professional course for polymer majors. Many students think that polymer physics is theoretical and there are many mathematical deductions, so they lack enough interest in learning in class. Some students report that they can understand the teacher's teaching content in class, but they feel that they don't know how to solve the specific problems of polymer physics in practice. In view of the above typical problems, polymer physics teachers have carried out reform research on the teaching of this course, and explored various teaching methods such as case teaching, heuristic teaching and interactive question-and-answer teaching. The author's school arranged this course in the first semester of the third year of college. At present, students' understanding of this major is still relatively limited. In order to improve the teaching effect and cultivate students' interest, enthusiasm and professional thinking ability, the author has adopted some methods and measures suitable for the characteristics of this major in the classroom teaching of polymer physics. In this process, the author has the following experiences and feelings.
1 Pay attention to the explanation of the history of polymer physics
Every concept and formula of polymer physics has its time and age, and it is put forward to solve some problems. Teaching the history of polymer physics properly will help students to understand polymer physics through the historical signals of polymer physics and polymer physics scientists, and help students to understand the development of this discipline and accumulate some perceptual knowledge. For example, when explaining the cross-linking of polymer chain structure, the invention history of rubber vulcanization is introduced: 2,500 years ago, Indians in the Amazon River Basin painted rubber tree juice on their feet and invented rubber boots, but after a day, the boots will gradually disintegrate. Until 1839, Goodyear added sulfur to rubber juice to crosslink rubber molecules to produce stable rubber, which opened the era of rubber industry. In addition, combined with the characteristics of coating specialty in our department, the frontier of coating development-self-repairing coating is introduced. The basic principle is that polymers are physically crosslinked by hydrogen bonds. Through the above explanation, students can realize the importance of crosslinking and its influence on the properties of materials, appreciate the charm of polymer physics, expand their knowledge and deepen their understanding of polymer physics.
2. Teach basic concepts and formulas in simple terms.
Most basic concepts are a prominent feature of polymer physics course, and some concepts are highly abstract and difficult to understand, which is quite difficult for students who are new to polymer physics. If students follow the book when explaining, they will not only be impressed, but also forget before learning, which will easily confuse concepts. So, how to achieve the learning effect of "more without confusion" and "more without forgetting"? Take the concept of "polymer chain random coil" as an example. The definition in the textbook is abstract and difficult to understand. Can be embodied in the lecture. Staudinger thought that polymer chains were hard rods, but they could not show the elastic characteristics of rubber. Kuhn suggested that polymer chains are as elastic and flexible as spaghetti. The vivid metaphor of polymer chains above deepens students' understanding of polymer chain conformation. Taking the concept of "glassy state and rubber state" as an example, the polymer segment is compared to a snake. Because the snake is a cold-blooded animal, its internal heat mainly comes from the surrounding environment, and it is frozen at low temperature to save energy. This state is somewhat similar to the glassy state of polymer, which can move when energy is obtained from the outside at high temperature, similar to the rubber state of polymer. The above metaphor makes it easy for students to understand the movement of glassy and rubbery polymers, which is impressive. Another example is the statistical mechanical stress-strain state equation of cross-linked rubber elasticity, which relates the microstructure of polymer with its macro-mechanical properties. The deduction in textbooks is complicated, with many steps and formulas, which are difficult to understand and easy to forget. In fact, as long as the contribution of internal energy to rubber elasticity is zero and the essence of rubber elasticity is direct elasticity, students can easily understand the physical meaning of each parameter in the formula according to the following ideas, which is clear and easy to understand.
3. Integrating theory with practice, typical case teaching.
Polymer physics has strong theory and application. Due to the limited space, the textbook of polymer physics mainly expounds the basic principles and theories, and is rarely used. When teaching these basic knowledge, teachers should not simply describe them in highly summarized language in textbooks, but should pay attention to integrating theory with practice and explain them with rich and constantly updated examples, so that students can better understand and master polymer physics. For example, in the section of liquid crystal state of polymers, the famous aramid fiber poly (p-phenylene terephthalamide) (DuPont's trade name is Kevlar) is rarely introduced in textbooks. In the explanation, the relationship between the structure and properties of this polymer can be analyzed in detail. It is composed of rigid long molecules, whose molecular chains are highly oriented along the length direction, and there are strong hydrogen bonds between the molecules, the strength of which is 5-6 times that of steel wire, so the fabric composed of this fiber can prevent bullets from passing through, so it can be used as a bulletproof vest. In addition, the melting point of liquid crystal polymer is above 500℃, so it is difficult to melt, and it is very crystalline and difficult to dissolve. Kwolek uses compound solvent N- methylpyrrolidone and a small amount of inorganic salt calcium chloride for dissolution. The main function of calcium chloride is to break the hydrogen bond between molecules, thus solving the dissolution problem. The above cases enable students to deeply understand the structure and properties of liquid crystal polymers, as well as their dissolution principles and processing methods. The author is mainly engaged in the research of organic and inorganic nanocomposites, and has accumulated some photos, data and samples about the structure and properties of nanocomposites. In the chapter "Glass Transition, Crystallization, Mechanical Behavior and Viscoelasticity of Polymers", a number of research achievements and experiences of our research group are listed, which not only deepen students' understanding of the structure and performance of multi-component systems, but also stimulate students' interest in scientific research, make students realize the importance of learning theories and improve their initiative in learning.
4 Make full use of multimedia teaching
Polymer physics involves many polymers and many abstract concepts, models, formulas and curves, which are difficult for students to imagine and understand out of thin air. Making full use of multimedia teaching can make abstract teaching content concrete and clear, at the same time, it can greatly increase the amount of classroom information and improve teaching efficiency. For example, because students in the first half of junior year are studying polymer chemistry and polymer physics at the same time, some students who participate in the explanation of high physics are not familiar with its structure. When making courseware, the author gives the molecular structural formula of polymer to help students understand the structural characteristics of polymer. For example, when explaining the configuration and conformation of polymers, the crystal structure of polymers such as single crystal, spherulite, tandem crystal and spherulite growth, the dissolution process of polymers, and the quaternary model of polymer viscoelasticity, pictures and FLASH animation can make students observe from multiple angles, intuitively, vividly and vividly, and visualize the contents that are difficult to understand, which is helpful for students to play their initiative in learning, think positively and participate in teaching activities with interest.
In a word, polymer physics is the most important basic course for polymer majors. Teachers should cultivate students' interest in learning polymer physics in the teaching process, stimulate students' enthusiasm for learning, make students want to learn, and enable students to have the ability of autonomous learning and professional thinking, so as to lay a good foundation for students to study subsequent professional courses or engage in polymer-related work in the future.
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Please ask questions about the destruction of hydrogen bonds and the improvement of hydrophilicity (reply ~)
Author: baitao8888
Please tell me the related methods of hydrogen bond breaking. I do polymer polymerization, but because the self-hydrogen bonding ability of this substance (2- vinyl-4,6-diaminotriazine) is too strong, it is easy to aggregate and precipitate in water, so it is difficult to apply (this substance is only soluble in DMSO). Please help me find ways to improve its hydrophilicity ~ it doesn't require clarity or specificity to a certain substance, just have a direction and an idea.
Finally, if you can, please recommend relevant literature and books. Thank you very much! !
Just now, the editor made a mistake ... I will send it myself ... two replies. ...
User comments
scuccc
Sofa, this question is a bit difficult.
However, in order to get a more professional answer, I suggest downloading the Woodworm APP. Don't be afraid of trouble. There are a lot of very professional materials in the APP, and many professionals answer all kinds of questions for free. Now you can install and download resources for free. Download the Woodworm APP and try it!
zph405
Generally speaking, polar solvents are added to break hydrogen bonds. I suggest dropping methanol into water to see if it can dissolve. By the way, is your product a polymer formed by hydrogen bonds? Like us, it is generally achieved by changing the side chain, that is, introducing a side chain with good hydrophilicity!
zph405
By the way, you can also mix methanol with some common organic solvents, or you can make your products dissolve in common solvents.
Zhiyuan Li
Can you reduce your polymerization degree? Low polymerization degree can be better dissolved.
Youhun
Lowering the temperature can reduce polymerization.
Youhun
Or reduce the concentration.
Jianwei _85
Can acidification be considered to destroy its hydrogen bond?
zph405
Originally published by baitao8888 on 2009-10-110: 40:
Please tell me how to break the hydrogen bond. I do polymer polymerization, but because the self-hydrogen bonding ability of this substance (2- vinyl-4,6-diaminotriazine) is too strong, it is easy to aggregate and precipitate in water, so it is difficult to apply (this substance is only soluble in DMSO). Please help me find a way to change it. ...
It is the best proof that this substance can be polymerized and dissolved in DMSO, because DMSO is a polar solvent. I wonder if the landlord has tried methanol or a mixture of methanol and other solvents? If the judgment is good, it can be accommodated in it!
zph405
Introduction: Hydrophilic (peg) block * * * polymers can't even contain dmso, but only have random free aggregation and capacity. I think this may be the destruction of self-hydrogen bonding. What do you think?
I don't understand. Can the landlord explain it more clearly?
Baitao 8888
Originally published by zph405 on 2009-10-1118: 45:
Introduction: Hydrophilic (peg) block * * * polymers can't even contain dmso, but only have random free aggregation and capacity. I think this may be the destruction of self-hydrogen bonding. What do you think?
I don't understand. Can the landlord explain it more clearly?
Well, well, I said that ethylene diaminotriazine has a hydrogen bond acceptor and a hydrogen bond donor, which is very hydrophobic. Only DMSO can dissolve its monomer, but it cannot be dissolved in any solvent after polymerization. We have used PEG for block polymerization with polytriazine, but it is still insoluble. Random polymers of PEG and triazine can be dissolved in DMSO (because randomness can make triazine relatively dispersed in size). Therefore, we consider that triazine is easy to gather together to form precipitation because of its strong hydrogen bonds, so I consider whether there is a way to reduce the interaction of hydrogen bonds to improve solubility. what do you think? Thank you very much !
Baitao 8888
Originally published by zph405 on 2009-10-1118: 45:
Introduction: Hydrophilic (peg) block * * * polymers can't even contain dmso, but only have random free aggregation and capacity. I think this may be the destruction of self-hydrogen bonding. What do you think?
I don't understand. Can the landlord explain it more clearly?
Well, well, I said that ethylene diaminotriazine has a hydrogen bond acceptor and a hydrogen bond donor, which is very hydrophobic. Only DMSO can dissolve its monomer, but it cannot be dissolved in any solvent after polymerization. We have used PEG for block polymerization with polytriazine, but it is still insoluble. Random polymers of PEG and triazine can be dissolved in DMSO (because randomness can make triazine relatively dispersed in size). Therefore, we consider that triazine is easy to gather together to form precipitation because of its strong hydrogen bonds, so I consider whether there is a way to reduce the interaction of hydrogen bonds to improve solubility. what do you think? Thank you very much !
zph405
Well, the current mechanism is not very clear. I also synthesized a compound recently. Because of the hydrogen bond, it forms a polymer, which is not allowed in ordinary nonpolar solvents. It will always be a suspension, so I added a few drops of methanol and shook it, and it became clear. I think yours and mine should be somewhat similar. Another method is heating. The polymer formed by hydrogen bonding is unstable, and heating can destroy its aggregation mode. The landlord can try.
Baitao 8888
See if there is any other way.
Baitao 8888
Originally published by zph405 in 2009-10-1120:17:
Well, the current mechanism is not very clear. I also synthesized a compound recently. Because of hydrogen bonding, it forms a polymer, which is not allowed in ordinary nonpolar solvents. It is always a suspension, so I added a few drops of methanol and shook it, and it became clear. I think yours and mine should be somewhat similar. ...
By the way, I just found out, does your methanol play a role in regulating the polarity of solvents?
After all, you are a nonpolar solvent. ...
Liyuan z
This is a bit like supramolecular polymers (the driving force of polymerization is hydrogen bonding, etc. ), because hydrogen bonds are far less effective than valence bonds, they are greatly influenced by temperature: high temperature naturally weakens hydrogen bonds, so the landlord may wish to think from this angle.
Bug is a rookie, and this opinion has both elegance and vulgarity.
Baitao 8888
Originally published by liyuanZ on 2009-10-1122: 06:
This is a bit like supramolecular polymers (the driving force of polymerization is hydrogen bonding, etc. ), because hydrogen bonds are far less effective than valence bonds, they are greatly influenced by temperature: high temperature naturally weakens hydrogen bonds, so the landlord may wish to think from this angle.
Bug is a rookie, and this opinion has both elegance and vulgarity.
It's okay to raise the temperature, I know that, but it will still precipitate when the temperature drops, so ...
Nanjing Zhang yanyang
Have you tried any other solvents?
Baitao 8888
Originally published by njzhangyanyang on 2009-10-1122: 36:
Have you tried any other solvents?
DMSO is dying. Is there anything better than him?
Katie Pan Xiao
Add polar solvent to observe.
David Shen
Try dropping methanol into water to see if it can dissolve.
the wise man has no perplexity
I really don't know. I will learn from the landlord. Isn't it unkind to accept gold coins like this?
the wise man has no perplexity
Look, the man in front said that polar solvents can be added to break hydrogen bonds. I wonder if the landlord can try adding acetic acid, which is much more polar than methanol. If you don't care about the cost, try trifluoroacetic acid.
Anxi blanket
Not very clear; )
huofj2008
You are too selfish. Need to add something else, can you? Such as tertiary amines.
Baitao 8888
Originally published by huofj2008 on 2009-10-1216: 56:
You are too selfish. Need to add something else, can you? Such as tertiary amines.
This thing has both hydrogen bond acceptor and hydrogen bond donor. I wonder if your method is effective. thank you
Riyan
I think it is possible to use dispersant (if allowed).
For good dispersibility, I have to add dispersant to my cooking.
hwbsbm
It will be fine after curing.
xjr840 107
Can an acidic environment work?
Baitao 8888
Published on 2009-10-1216: 39:
Look, the man in front said that polar solvents can be added to break hydrogen bonds. I wonder if the landlord can try adding acetic acid, which is much more polar than methanol. If you don't care about the cost, try trifluoroacetic acid.
You inspired me ~ ~! !
the wise man has no perplexity
Originally published by baitao8888 on 2009-10-12 at 22: 36:
You inspired me ~ ~! !
We encourage each other: D.
hhl7865
Can you reduce your polymerization degree?
gg 103 1986
What about the derivative?
Ceciro
Usually, the method to improve the hydrophilicity of drug molecules is to add hydrophilic groups such as amino groups, carboxyl groups and hydroxyl groups, and polymers can also be modified by adding hydrophilic side chains. As for intramolecular hydrogen bonds, many stable conformations of DNA protein are formed by intramolecular hydrogen bonds, which can be improved by heating or adding some salts.
kpyu 1226
The polarity of chemical bonds is not enough to form hydrogen bonds. Therefore, if the ability of hydrogen bonding is broken, it is necessary to add substances with strong polarity.
Fannitao
Add some acid to see.
Sifonne
I think we should use the mixed solvent mentioned above.
My idea is to provide energy to break the hydrogen bond, which is heating. This is the mechanism I think. Please give me more advice.
So smooth
Try adding polar solvent.