Determination of polymer crystallinity by the multivariable curve resolution method in ¹³C solid NMR spectrum

Area of Science:

• Polymer Science
• Solid-State Nuclear Magnetic Resonance (NMR) Spectroscopy
• Materials Characterization

Background:

• Polymers consist of crystalline, amorphous, and interfacial regions with distinct properties.
• Overlapping peaks in solid NMR spectra hinder the accurate determination of polymer crystallinity.
• Existing methods struggle to resolve these overlapping signals effectively.

Purpose of the Study:

• To develop a novel method for resolving overlapping peaks in polymer solid NMR spectra.
• To accurately quantify the crystallinity of polymers, specifically polyethylene oxide (PEO).
• To leverage spin-lattice relaxation time (T1) information for improved spectral analysis.

Main Methods:

• Utilized the Torchia pulse sequence in conjunction with Multivariate Curve Resolution (MCR).
• Acquired two-dimensional (2D) cross-polarization magic-angle spinning (CP/MAS) NMR spectra.
• Applied reciprocity relation corrections to spectral data.

Main Results:

• Successfully resolved overlapped peaks in the solid NMR spectrum of polyethylene oxide (PEO).
• Quantified spectral components along with their spin-lattice relaxation times (T1).
• Determined polymer crystallinity based on component content ratios and their T1 values.

Conclusions:

• The combined Torchia pulse sequence and MCR method effectively resolves spectral overlaps in solid NMR.
• This approach enables natural observation and quantification of polymer crystallinity.
• The method provides a more accurate assessment of polymer structure by incorporating T1 information.