بررسي ريزساختار پلي وينيل كلريد به وسيله روش هاي رزونانس مغناطيسي هسته يك و دو بعدي

Microstructural Study on Polyvinyl Chloride by One and Two Dimensional Nuclear Magnetic Resonance Spectroscopy Methods

I n this research, the tacticity and microstructure of polyvinyl chloride (PVC) were studied through back bone methylene and methine carbons and protons splitting by carbon (13C NMR), proton (XH NMR) and two-dimensional (2D NMR) nulear magnetic resonance spectroscopy in deuterated tetrahydrofuran. Polyvinyl chloride was synthesized by emulsion polymerization of vinyl chloride (VCM) under pressure to about %90 conversion with %45 solid content at 60°C. The assignments of all stereosequences were done at tetrad and pentad levels of methyl¬ene and methine carbons of the polyvinyl chloride respectively, using by 13C liquid NMR. Bernoullian and first-order Markov statistics models were calculated and the results are compared with the experimental NMR results. It was shown that Bernoullian and first-order Markov statistics fit almost equal for the assigned meth¬ylene and methine carbons and that the probability of meso addition (Pm) value in polyvinyl chloride chains was calculated to be 0.447. NMR of PVC was assigned via heteronuclear multiple quantum coherence technique (HMQC) for methylene and methine groups at triad sequence levels. Finally, by increasing the NMR acquisition temperature from 20 to 50°C higher resolution in methylene and methine carbons were achieved. In this case, the atactic sequence peaks splitted more than isotactic and syndiotactic sequence peaks.