Dear Dr. Ahmed Elbedwehy;

both polymers are semicrystalline, for the polyacrylamide it was found that the physical system for polymerizaztion (solution, precipitation, dispersion,....) has a strong influence on the degree and perfection of crystallinity.

For the second part of the question it is not clear enough and it should be said otherwise in a more comprehensible fashion. The hydrolysis of PAN is something very straight forward. Generally, it passes through the formation of the amide followed by the formation of the acid group. Regards

I agree with Dr. Abdelkader BOUAZIZ  that both polyacrylamide & PAN are semicrystalline. The method of polymerization also plays a role in determining the degree of crystallinity. If free radical polymerization is used, then atactic polyacrylamide is expected & atactic polymers have disorder which increases the amorphous regions within the matrix of the polymer but this does not necessarily mean total loss of the ordered "crystalline" domains since , at least, there are repeated head-to-tail configurations in the main chain "which means order". The product will be in between.

I agree with Dr. Matar, the polymerization process is very important with respect to the structure of the polymer. You need to check the stereoregularity of your polymers and determine the polymerization process that will promote regular structures (isotactic, syndiotactic) which encourage crystallization.

Thanks for all replying but @Dr.Abdelkader BOUAZIZI and @Dr. Nizar Matar

I agree with you that polyacrylamide not completely amorphous (give broad halo) but as you can see from attached data that the two polymers are completely difference in ordering , one is very order than another.

Also they are polymerized in the same conditions, same redox initiator concentration, same temperature, same solvent (water) and same non solvent extractor (methanol)

Crystallinity is the degree of structural order.

Acrylamide monomer by itself is crystalline; however, when it polymerizes to Polyacrylamide it turns to crystalline- amorphous. The reason for  crystallinity of acrylamide monomer is the strong hydrogen bonds between its O, N and H in its structure. These groups cannot move easily in Polyacrylamide structure as they are bounded to polymer backbone. This is the reason for crystalline- amorphous structure of polyacrylamide.

I think the reason for higher crystallinity of Polyacrylonitrile compared to Polyacrylamide is:

1- Polyacrylonitrile has only N and H in its structural unit that can form hydrogen bonds. However, Polyacrylamide has O N and H. This makes more regularity in the structure of Polyacrylonitrile as compared with Polyacrylamide

2- Polyacrylamide can give you higher molecular weight at the same experimental condition. This also brings irregularity in the structure of polyacrylamide.

This is my idea. Let me know if I am wrong on anything please.

Note: The peak you observed for Polyacrylamide may be correlated to the remaining acrylamide monomer. Did you washed your polymer several times in Methanol?