A Multidimensional and Multinuclear Nuclear Magnetic Resonance Spectroscopy Strategy for Fine Structural Elucidation of Perhydropolysilazane

Perhydropolysilazane (PHPS) is a silicon-nitrogen backbone polymer widely utilized as a ceramic precursor; however, a deep under-standing of its molecular structure has been hindered by the complex and highly branched architecture. This work presents a systematic and quantitative investigation into the molecular structure of PHPS by integrating advanced characterization techniques, including multidimensional nuclear magnetic resonance spectroscopy ( 1 H-/ 29 Si-/ 15 N-NMR), gel permeation chromatography with multi-angle light scattering and differential viscometry (GPC-MALS-Vis), and molecular simulations. Through multidimensional NMR analysis, five fundamental structural units (−SiH, −SiH 2 , −SiH 3 , −NH, and −N) were identified, with no detectable −NH 2 groups. A dual-nucleus quantification strategy based on 1 H- and 29 Si-NMR enabled the precise determination of the molar ratios of these structural units. Building upon these results, two structural parameters—branching degree ( D b ) and number of cyclization ( N c )—were introduced to quantitatively characterize the network topology of PH-PS. Subsequently, three-dimensional molecular models were constructed via density functional theory (DFT) simulations to reveal the micro-conformations of the polymer. This study establishes a robust characterization framework that reveals the fine structure and network topology of PH-PS, thereby providing a significant theoretical foundation and technical support for structural tailoring and performance optimization to meet the demanding requirements of integrated circuits, functional coatings, and advanced functional materials.