³⁵Cl Nuclear Quadrupole Resonance: A Cl-specific Probe of Local Structural Motifs in PVC

Area of Science:

• Materials Science
• Solid State Physics
• Polymer Chemistry

Background:

• Polyvinyl chloride (PVC) properties are influenced by its chlorine environments.
• Detecting structural defects in PVC is crucial for understanding its stability, degradation, and recycling.

Purpose of the Study:

• To characterize chlorine environments in PVC using 35Cl NQR and DFT.
• To identify and differentiate various chlorine sites and structural defects within PVC samples.

Main Methods:

• Combined experimental 35Cl nuclear quadrupole resonance (NQR) spectroscopy.
• Computational Density Functional Theory (DFT) calculations.
• Analysis of commercial high-molecular-weight (MW) and low-MW PVC samples.

Main Results:

• Classified two main chlorine signal groups: terminal and internal.
• Predicted distinct NQR signatures for chlorine vacancies and multi-chlorinated sites.
• Observed numerous Cl environments and defects in analyzed PVC samples.
• Determined that dechlorination primarily affects terminal chlorine positions.

Conclusions:

• 35Cl NQR combined with DFT is a sensitive method for distinguishing chlorine sites in PVC.
• This approach enables direct detection of defects impacting PVC stability, degradation, and recycling.
• The findings provide insights into PVC structure-property relationships and material processing.