Adhesion promotion between a homopolymer probe and a glass substrate coated with a block copolymer monolayer

The adhesion between a homopolymer matrix and a diblock copolymer is shown to depend on the length of the non-adsorbing block that penetrates the matrix chains. The tack or short-time adhesion was measured using a probe-tack set-up consisting of a thick (similar to 100 mum) polystyrene, PS, adhesive layer with degree of polymerization (DP), 1923, brought into contact with a monolayer of poly(deuterated styrene-block-methyl methacrylate), dPS-b-PMMA, deposited on a glass substrate. Experiments performed at 130degreesC, above the glass transition temperatures, show that the maximum debonding stress increases from 1.4 MPa for the glass to 2.3 MPa for the copolymer. Also, the adhesion energy increases dramatically as the non-adsorbing block length, N-dPS, increases from below to above the entanglement DP of PS. These observations suggest a difference in the debonding mechanism between the nude glass, which undergoes fragile rupture, and the glass covered by dPS-b-PMMA, which exhibits increasing cavity formation with increasing N-dPS. After normalizing by the chain areal density, the adhesion dissipation is observed to increase by a factor of 4 as N-dPS increases from 100 to ca. 1000. These results suggest that entanglements between matrix chains and the non-adsorbing block impart good stress transfer and interfacial strength across the interface. (C) 2004 Elsevier Ltd. All rights reserved.