The integration discrepancy for polyvinyl alcohol (PVA) in DMSO-d₆ could stem from hydrogen bonding, relaxation differences, or polymer chain effects. DMSO-d₆ may form hydrogen bonds with the hydroxyl group on PVA, altering the chemical environment of the alpha proton (H-C(OH)), which could broaden or shift its peak, impacting integration. Relaxation issues are also likely, as high-field instruments like a 600 MHz NMR can cause protons near polar groups to relax more slowly. Macromolecular effects, including chain entanglements, may further influence the integration ratio. Adjusting relaxation delays might help address these variances.

Integration discrepancies in 1H NMR spectra for polyvinyl alcohol (PVA)'s α-proton (the methine proton, -CH(OH)-) primarily stem from three interrelated factors: polymer microstructure, experimental conditions, and data processing artifacts. The inherent structural complexity of PVA, particularly its tacticity distribution (isotactic, syndiotactic, atactic sequences), creates distinct chemical environments for the α-proton that result in varying chemical shifts and peak broadening, making accurate integration challenging. These effects are further compounded by strong hydrogen bonding interactions within the polymer matrix that promote rapid proton exchange and signal broadening, particularly for the α-proton which is directly involved in these interactions. From an experimental standpoint, inadequate relaxation delays (typically requiring >5 seconds for PVA) fail to account for the α-proton's relatively long T1 relaxation time due to restricted mobility in the polymer chain, while improper pulse calibration or poor shimming can disproportionately affect this signal's intensity. Sample preparation issues such as incomplete dissolution, residual solvents, or the presence of acetate groups from incomplete hydrolysis of the polyvinyl acetate precursor may introduce overlapping signals that interfere with integration of the α-proton resonance. For reliable integration, it is essential to optimize NMR parameters including sufficient relaxation delay (10-15 seconds), use elevated temperature (50-60°C) to reduce hydrogen bonding effects, employ appropriate solvent systems (DMSO-d6 for observing hydroxyl protons or D2O for simplified spectra), and carefully process the data with proper baseline correction and integration boundary selection to account for the broad, overlapping peaks characteristic of polymer NMR spectra. Validation through complementary techniques such as 13C NMR for tacticity assessment or end-group analysis can help confirm the accuracy of the 1H NMR integrations for this challenging proton environment.