Ep22 Mechanical properties of polymers & viscoelastic models NANO 134 UCSD Darren Lipomi 

I wish my teacher explained as clearly. Good work man!

STUNNING! Thanks for the content; I am glad to see something real before the midterm exam

people like you makes students love science thanks sir

Awesome lecture… was struggling with leathery vs rubbery vs rubbery flow comparison. Those graphs on right side and explanations really demystified it. Thank you Liporni.

19:31 "So when you are talking to somebody who has faced a lot of adversity and overcome a lot of challenges, and someone calls them 'That's a stong person', you said 'No. That's a TOUGH person.'" Love it.

Hello Dr. Darren Lipomi. I really enjoy all of your videos. I was always interested in polymers and material science. Thank you for all the helpful videos! Regards Smita

Thank you, this lecture was so precise and clean.

thank you. This really helps me understand it much better.

one of the great lectures i have ever attended.....

Very clear! Thank you so much !

Superb explanation! :D

thank you prof. Lipomi

Thank you from the UK bruv

Great explanation. can't wait for your talk in emts2018 Hanoi.

Thank you sir ☺

Thank so much !! Now, I actually understand :)

Good day, Really comprehensive explanation. I would like to comment on the last model, as I agree with the student on the elastic deformation . It should be equal in amplitude with the deformation on the beginning of the load.

Thanks from Iran

at 7:20 what if we take polymer which has more ionic character than covalent character , will the graph be still same ? at 19:45 why the extra strong one is not tough one ?

I think your student was right. If the response of the top spring was instantaneous when you applied the force (leading to a vertical line on the graph) then you should have an instantaneous response when the force is removed. The length of the vertical line after the force is removed should be equal to the length of the first vertical line. There is also no reason why the final strain should be equal to the elastic strain (the strain at the top of the first vertical line). It could be higher or lower. Apart from this your explanations were remarkably clear, thanks!

Like a champ

Wow, very great lecture! I wonder for what happens microscopically at a semi-crystalline polymeric sample between the proportionality limit and the elastic limit. Why if the sample deformation is still reversible the stress in that region is not linearly proportional to strain?

Dr. Lipomi, Thankyou for the great lecture, but, at what regime does the complex model accomodate in the relaxation modulus graph.

Dear Prof I need what is the right method to find viscosity for high concentrated PEO Polymer solution, I used Plate and cone method but at high conc the viscoity is fluctuating at high shear rate but at low conc it is constant

Thank you so much for your superb explanation. I am wondering about the difference between Visco-Elasticity and Visco-Plasticity. It would be really kind if someone can please explain them to me.

Hi Darren, I have a question; 34:35 where you describe the behaviour of the polymers in the different regions, in the glassy region you described the behaviour as having "complete elastic recovery", wouldn't that only be the case in hypothetical purely crystalline polymers?, in reality wouldn't the amorphous regions of a given polymer still give some losses there? Many Thanks and I really enjoyed the video, Tom

Can this model be applied to EVA (Ethylene Vinyl Acetate) ?

Hello, thank you very much for the explanation!! I did nanoidentation on a same photoresist (CAR) with 3 different layer thicknesses (4.5um, 5.2um and 6.5um) with a penetration depth of 500nn. i'v come to the conclusion that when the thickness of the photo resist is bigger, then the foto resist is harder. Do you have an idea why?? Thank you very much!!!

Sir I need all lectures about polymer chemistry that u have done.

Hi Prof. Lipomi, I'm just wondering if you can provide a reference regarding breaking/rupture of covalent bonds at ultimate tensile stress, at your earliest convenience please . Thank you

"e-ta" not "a-da".