I Have a question in polymer.
solution 1:polyvinyl chloride soluble with THF a .Solution 2: 2.5 g of NAHS and dissolve it in DMF
after that I mixed solution 1 ,2 with distillation and reaction start under N2 - the atmosphere at 60 C. After 8 hours , the reaction was stopped by precipitating the mixture in water . Then I collect and I put it in an oven to make sure it is dry very well . the problem is why after the reaction the final product isn't dissolved with THF and other solvents cause I try using xylene -methanol-methylacetamide-cyclohexane ,but it isn't dissolved what I should do to dissolve cause I want to make a film .when I did characterization by using FTIR I find peak at 1654 cm-1 so that mean there is a double bond how is that come and why ? cause my objective is to eliminate chlorine and replace with thiol group to get sulfur .
Hi Mohammed,
what is "NAHS"?
Is it NaHS?
Cause it looks some precipitation from a reaction...
http://pubs.rsc.org/is/content/articlehtml/2016/ra/c6ra03143a
Please refer this link where pvdf has been thlated using thio glycolic acid by introducing C=C using alkaline treatment. You can proceed in similar fashion.
If you look at the chemical structure of PVC you can find H and Cl are present on adjacent carbon. In presence of alkali (I do not know NAHS) there occurs dehydrochlorination generating double bond. Try other methods.
In the first stage of dehydrochlorination, conjugated polyene sequences are created by a nonfree-radical route. They react with HCl to give cation monoradicals and/or excited cation diradicals. One or both of these species, or other radicals formed from them, can then abstract methylene hydrogen in order to produce new radicals that are also carbon-centered. Their attack on the polymer leads to formation of thermally labile structural defects, such as internal allylic chloride units, which initiate growth of new polyene sequences by a non-freeradical route. Consequently, autoacceleration of dehydrochlorination occurs. THF is a stronger base and popular solvent for PVC. I haven't heard of alkali to initiate dehydrochlorination but it can certainly inhibit further dehydrochlorination by scavenging HCl formed which is responsible for dehydrochlorination. Also boiling point of THF is 66 degree celsius which is close to your operating temperature. So I think thermal degradation can be the reason for dehydrochlorination. This link might prove useful.
http://pubs.acs.org/doi/abs/10.1021/ma0352835?journalCode=mamobx
Cross-linking can result in highly insoluble polymers. In reference to the replies above the conditions would be given. As far as I understood, you wanted to substitute Cl by SH in a nucleophile substitution but instead an elimination reaction occurred, resulting in C=C (and cross-linking). As a wild guess I would say your nucleophile is too weak and so in the presence of weak base you might not be lucky with this approach, especially with PVC where elimination reaction of adjacent units are obviously favored.
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