Environmental Engineering Reference
In-Depth Information
Strategies adopted for
design of new
anti-fouling surfaces
Homogeneous
surface
Heterogeneous
surface
3D surface
Micrro-
topograhic
patterned
surface
Hydrophilic
surface
Hydrophobic
surface
Amphiphilic
surface
Mixed
surface
Patterned
surface
Figure 2.19 Various strategies adopted for designing anti-fouling polymer surfaces
Krishnan and co-workers [83] demonstrated that a non-polar hydrophobic surface
can be created by self-assembly of block copolymers with liquid crystalline semi-
fluorinated alkyl side chains ( Figure 2.20 ). These block copolymers have the
advantages of both the hydrocarbon and the luorocarbon polymers. The amorphous
nature of the former imparts solubility and the latter imparts surface stability.
The copolymer coatings prepared from blends of luorinated polymer and a tri-block
hydrocarbon polymer display a tremendous release of the green marine alga, Ulva [49].
These copolymers with semi-luorinated alkyl side chains show lower settlement than
the commercially available Silastic T-2 ® PDMS coatings. However, the hydrophobic
luorinated surfaces show poor release of the 'glassy' Navicula diatoms because they
allow protein adsorption. The low surface energy of the perluoromethyl head groups
causes these luorinated blocks, with mesogenic semi-luorinated alkyl side chains, to
segregate at the air-polymer interface [10].
Krishnan and co-workers [49] observed that PS block copolymers with methoxy
terminated PEG side chains caused signiicantly weaker adhesion of Navicula
diatoms when compared to PDMS. The surface active PEGylated block copolymer
is synthesised with PS- block -polyisoprene (PI) precursors. Because the PS surface
has a lower surface energy compared to PEG, the PS preferentially segregates at the
surface when it comes into contact with air. This tendency is reversed when immersed
in water. Although Navicula showed a weak attachment on the PEGylated surface,
Ulva sporelings attached to the surface strongly. The larger area of contact of the
adhesive pads secreted by Ulva and the lower contact angle of the adhesive matrix
with the surface are the reasons for their stronger attachment on hydrophilic surfaces.
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