The interaction of poly(N,N-dimethylacryl-amide)-b-poly(N,N-diethylacrylamide) (PDMA(207)-b-PDEA(177)), (DHBC), with 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), 1,2-dipalmitoyl-sn-glycero-3-phospho(1'-rac-glycerol) (sodium salt) (DPPG) and stearic acid (SA), was investigated at the air-water interface. The pi - A isotherms of DHBC/DPPC and DHBC/DPPG binary mixtures are nearly the sum of the contribution of components weighted by the molar composition, - the additive rule. The pi - A curves of the mixtures show a plateau at similar to 7 mN m(-1), owing to the immersion of the hydrophilic block PDMA, and other at similar to 27 mN m(-1) attributed to the immersion of the less hydrophilic PDEA block. Differently, the binary mixtures of DHBC/SA and PDEA homopolymer/SA do not follow the additive rule of the components showing an expanding effect at low surface pressures. Brewster angle microscopy images show that both DHBC and PDEA polymers interact with lipid monolayers, strongly disturbing their morphology. (C) 2013 Elsevier B.V. All rights reserved.