Depending on the polymer you are dealing with, side reactions are likely to cause such color change, oxidation, unsaturations formation are the usual reactions able to impart color.

the studied polymer is poly allyl diglycol carbonate (PADC) commonly known as CR-39. this polymer is irradiated by Argo ions and its color is transformed from high transpeent to yellow to brown with the irradaition dose.  I want to know how to investigate this color change?

Dear All,

the color change uppon irradiation is a witness that some alteration is taking place on the chemical (level) structure engendering hanse this physical changes (color, mechanical properties,...). The depth of these changes depends on the irradiation type, dose and duration, and the permitivity of the matrix, however the major changes are more abandent on the surface. So, any characterization technique used to study the state if the surface may be used (to quote: AFM, Raman Spectroscopy, and others). Regards

thanks, but how to measure color changes and tristimulus values.

Hi,

You most likely have degradation (oxidation) of your polymer. The ionic radiation that are using is probably penetrating through the material if you are working with polymer films or porous materials. By AFM you will be able to detect structural changes which won't give you  (if) much information. The most straight forward and easiest thing to do  would be an IR, before, after and maybe gradually (different time points). You could also redissolve your polymer and run a GPC to check if your polymer chains are now shorter, depending on how far does the degradation go.

Hope this helps.

Thanks Sandra,

your answer is good and matched with literature. thanks also for the suggested GPC measurement, I think it will help.

I found the following article from which one could learn how to calculate some color parameters such as color changes and tristimulus parameters.

Dear all;

I start with a small remark concerning the last answer of Dr. Sandra Camarero Espinosa. Instead of degradation (loss of molecular weight), sometimes irradiation provokes crosslinking, thus the molecular weight increases and may reaches even an unmeasured values (i.e., infinity).

If you need references on how to calculate the "tristimulus values", use it as a keyword in the following free website and you will find plenty of documents on how to do that: www.booksc.org. Regards

Thanks Dr. Abdelkader,

In my case the studied polymer suffers degradation as confirmed by UV-vis spectoscopy and XRD paterns. I think GPC will be helpfull, any way I'll try it.

Tristimulus values are exist as you mentioned in many articles but not in details. I am now on the way to know it from the collected papers. the above mentioned article is a good one and have some good details. the used software is not free and not available for me. I will try to find one.

Dear Ashraf;

please do a simple search in the website I have given, I am sure you will find better and precious answers. Regards

I do what you say Dr. Abdelkader, I found many article i will do it again.

I believe that sharing ideas and discussion with experts are shorter ways to reach the goals. So that I like research gate, it gives me the opportunity to know respectable personalities like you.

This is right. You may have cross-linking if you have a photoinitiator or you generate some radicals. I guess that to generate a radical you will need some initial degradation...

Anyway both, cross-linking and degradation will give you a different IR profile. If your polymer is now cross-linked you won't be able to redissolve it.

Thanks

This polymer is very stable, FTIR reveals that CO2 and H2O are produced. CO2 trapped inside the polymer and H2O released. Do you think CO2 may be responsible for color changes??!

also I made ESR study which shows an increase in the radicals density.

I made a study before on CR-39 irradiated by low energy electrons and shows degradation followed by crosslinking as revealed from the intrinsic viscosity study.

the same polymer irradiated by Ar ions in another study and shows only degradation.

degradation and crosslinking depends on the irradaition dose and species. but in all cases there are color change its density depends on the deposited local heat (energy).

as a result of degradation process there are bond cleavage which causes the migration of carbon atoms which for the so cold polymer blackening or cluster. the optical density of theses clusters causes the visual color change. the rate of change depends on the applied dose. the color difference (dE) doesn't always observed by the naked eye. when dE

That's a nice explanation. Good to share and learn with others.

Dear all,

usually when color goes to darkening upon degradation indictaes the formation of double bond conjugates (successive adjucent repetion of double bonds), and cyclization. Other groups such carbonyl and oxygenated groups are more likely to occur. Regards

yes thats right, double and triple bonds causes color darkening besides carbon clusters, these acts as a non-radiaative sites on the polymers surface . these kinds of structure changes is confirmed by PL in the decrease of the luminescence peaks intensity.The emission bands are associated with the less energetic π⁎–π and π⁎-n

electronic transitions. This type of emission occurs in the unsaturated

centers of the molecules, i.e. in compounds containing multiple bond or

aromatic species, which are responsible for PL intensity decrease.

Dear all;

these attached two books are important for a specialist background enrichment. Best Regards.

Generous gesture Dr. Abdelkader, Thanks.

No thanks, it is nothing against what we are having from this splendid area (RG) by exchanging ideas and opinions to learn and enrich more our background. Regards