This paper reports a FTIR study of blends of poly(mono n-alkyl itaconates) with poly(N,N-dimethylacrylamide) (PDMA) and poly(ethyloxazoline) (PEOX). Strong hydrogen bonding has been found, and both polybases have shown similar acceptor strengths. The extent of the interassociation has been estimated by spectral curve fitting of the polybase carbonyl band. The solvent medium employed to cast the sample has been shown to have a negligible influence on the interassociation degree attained in the blend, whenever casting did not lead to phase-separated blends due to the Delta(chi) effect. Results show that the interaction degree in blends with PEOX does not depend on the length of the poly(monoalkyl itaconate) side group, while an interassociating ability loss is observed in blends with PDMA as the side group size of the polyacid increases. This different behavior is attributed to the greater interspacing between vicinal carbonyl groups in PEOX. In any case, this band shows conformational sensitivity and reflects the conformational changes that the polymer is forced to adopt as the steric hindrances present in the medium (due to the bulky side groups of the polyacids) increase.