화학공학소재연구정보센터
Macromolecules, Vol.37, No.9, 3431-3437, 2004
Surface-induced selective delamination of amphiphilic ABA block copolymer thin films
We demonstrate the unforeseen property of selective adhesion/delamination of amphiphilic block copolymer films in coating hydrophobic and hydrophilic substrates. When spin-coated from THF solutions onto hydrophilic substrates (e.g., glass and O-3-treated silicon wafer), amphiphilic poly(oligoethylene glycol methyl ether methacrylate) (POEGMA)-based ABA block copolymers 1 and 2 formed thin films with hydrophobic surfaces. Upon exposure to water, these films undergo a fast rearrangement to a hydrophilic surface before they delaminate from the substrate. In contrast, when deposited on a hydrophobic substrate (e.g., Au, Si, Ag), the same copolymer films do not undergo any surface rearrangement and remain as coherent thin films on the substrate. From contact angle measurements it becomes clear that the delamination is accompanied by a rapid surface rearrangement from a hydrophobic to hydrophilic nature. This rearrangement is not observed for the copolymer over hydrophobic surfaces despite the identical constitutions of the copolymers and identical microphase-separated surface morphologies. It is shown that within the range of polymers investigated this behavior was only observed for POEGMA-containing triblock copolymers. Moreover, it is also shown that in order to show this delamination behavior the polar A-block must be large compared to the apolar B-block. On the basis of XPS and AFM data, we propose that this selective adhesion/delamination is a direct consequence of the self-organization of the block copolymers in the polymer thin films.