Xu Chen, Changzhu Lv, Yahui Li, Zishuo Wu, Renkuan Cao, Weihang Fei, Jin Lv and Wei Chen*. Precise Characterization of the Sequence Distribution of Poly(vinyl butyral) (PVB) by 2D-NMR and Isotope Enrichment. Macromolecules, 2023, XX, XXXXX. DOI: 10.1