The thermal properties and hydrogen bonding behavior of B-a type polybenzoxazine (PBZZ)/PVP blends were investigated by DSC and FIFIR. The DSC result shows a single T-g over the entire compositions and a large positive deviation based on Kwei equation was observed in the T-g versus composition diagram, implying that strong hydrogen bonding interaction exists between PBZZ and PVP segments. The strength of hydrogen bonding interaction is in the order of inter-association between the hydroxyl group of PBZZ and the carbonyl group of PVP (K-A = 594 L mol(-1)) > self-association between the hydroxyl group of pure PBZZ (K-B = 72.6 L mol(-1)) > inter-association between the hydroxyl and the Mannich-based bridge of pure PBZZ (K-C < 10 L mol(-1)). Good correlation between DSC and FIFIR analysis were observed. (C) 2003 Elsevier Science Ltd. All rights reserved.