Figure 2

Chemical structures of the initiator and monomers (a) and the construction of the three-layered system (b).

(a) Chemical structure of the dithioacetal compound (Compound 1, the W-shaped initiator) and two monomers: OEGMA₄₇₅ and OEGMA₅₂₆. (b) SAM of 1 acted as the initiator for the SIP. The polymer brushes with –OCH₃ or –OH side chains were prepared via SIP. When the pH shifted from 5.0 to 1.0, proton penetration was largely blocked by the OH-rich poly(OEGMA₅₂₆) layer, leaving a local pH value of at least 5.0 and resulting in no significant loss of surface mass. The acid-sensitive and -insensitive types of 1 were represented in red and black. Note that a non-existent magnifying glass was drawn to highlight the –OCH₃ and –OH side chain ends.