Figure 3AFM topography (a) and phase image (c) of droplet inside the movie of first thickness of 43.9nm (b) could be the corresponding cross-section line profiles in (a).Figure 4PLM picture of spherulite free overnight delivery from the droplet in the film of preliminary thickness of 43.9nm.So as to recognize the surface composition reference 2 during the as-prepared films and annealed films, water speak to angle measurement was carried out. Figure five mapped a plot on the shifting contact angle value before and soon after annealing in a variety of thickness movies. The water make contact with angle on the silicon substrate having a native SiOx surface layer, the spin-coated homopolymer films of PS, and PEO are measured to become 21.6��, 95.8��, and 21.0��, respectively. For that PEO-b-PS film with different thickness just before annealing, the typical make contact with angle value is about Ca.
34��. This worth is close to that of homopolymer PEO film, exhibiting the surface of as-prepared film is hydrophilic and it is wealthy with PEO block. Right after it had been annealed at 393K for 8h, the get hold of angle worth improved to ~94��, that is close to that of homopolymer PS movie, indicating that the surface altered to hydrophobic along with the surface is rich with PS block.Figure 5The make contact with angles of PEO-b-PS films with distinct original thickness (a) ahead of and (b) soon after annealing at 393K for 8h.4. DiscussionThe nature and power with the interfacial interactions at the asymmetric interfaces (block/solid and block/air interface) drastically influence the block copolymer thin film morphology, phase separation, and orientation of microstructures.
If one block in the symmetric diblock copolymers is preferred for just about any with the interfaces (substrate or free interface), a lamellae orientation parallel to the substrate may be observed . For your films of original thickness of 2.three and 5.8nm right after annealing, the film surface was kept smooth and no droplets have been viewed through the AFM measurement. This observation suggests that dewetting is prohibited and also a copolymer layer is adsorbed over the surface of oxidized silicon.Due to the fact PEO is adsorbed about the hydroxyl groups about the surface from the silicon oxide substrate, the PEO blocks have preferential wettability and stronger affinity for the Si wafer. Plus the surface vitality of PSRaltitrexed block (��PS = forty.7mN/m) is reduced than that of PEO block (��PEO = 42.9mN/m).
This helps the PS element using the lower surface vitality to aggregate on the free air/film surface.
The general effects are that these asymmetric boundary conditions trigger the PEO block to preferentially segregate on the substrate though the PS block on the air interface. The copolymer chains oriented along the typical of your film/substrate interface, forming a copolymer brush using a lamellar construction parallel to your interface.Even so, the droplets formed during the movie of first thickness higher than ten.7nm.