Marine Biofouling of Polymers - Polymers in a Marine Environment - page 63

an important role in the biocidal activity and the mechanical properties of the coating.
It was found that with 4 wt% of QAS moieties, 50% reduction in a Cellulophaga
lytica bioilm was caused without any leachate toxicity. A further increase in the levels
of QAS resulted in the delamination or fracture of the coating from the substrate.
A moisture curable coating that allows higher crosslink densities to be achieved reduced
the C. lytica bioilm by more than 80% and also inhibited the growth of Navicula
incerta . These coatings also had enhanced stability after immersion in seawater.
A moisture-curable polysiloxane coating containing tethered QAS signiicantly
inluences the anti-fouling and foul release behaviours of marine microorganisms.
Utilisation of the ethoxysilane-functional QAS provides enhanced anti-fouling
characteristics when compared to coatings based on methoxysilane-functional
analogues because of the enhanced surface segregation of QAS groups at the coating-
air interface [99].
Polymers integrated with zwitterionic molecules are shown to be anti-fouling polymers
[10]. Kitano and co-workers [100] synthesised polymerised methacrylate monomers
with different zwitterionic groups using disulide carrying N , N -diethyldithiocarbamoyl
derivatives as the chain transfer agents. The oligomers formed self-assembled
monolayers and brushes on gold surfaces which inhibited the adsorption of proteins.
Li and co-workers [101] developed biomimetic polymers with a zwitterionic moiety
for ultra-low fouling and a catechol end group for surface anchoring.
2.5.3.3.3 Three-dimensional Surfaces
The third approach researched to prevent biofouling of surfaces is to design polymers
with 3D surfaces, which would modify the surface topography that would inluence
the marine organisms to stick to the coating surface [10].
PDMS elastomers have been used to fabricate microtopographic patterned surfaces
using non-network forming PDMS-based oils with photolithographic techniques
[29, 102, 103]. The topography contained 5 µm wide pillars separated by 5, 10 or
20 µm wide channels with depths of 5 or 1.5 µm [102]. The results showed that
the Enteromorpha zoospores adhered in channels and against pillars of 5, 10 and
20 µm dimensions. Similarly, with the surface topography containing 5 µm wide pillars,
spores adhered to the walls of the pillars. Therefore, narrower channels and pillar
spacing (2−3 µm) may be more eficient in decreasing settlement of organisms [102].
A biomimetic surface topography inspired by shark skin (Sharklet AF ™ ) containing
2 µm wide rectangular rib like periodic features (4, 8, 12, and 16 µm in length) spaced
at 2 µm intervals was studied by Carman and co-workers [104]. They observed that