Environmental Engineering Reference
In-Depth Information
at preventing the settlement and release of fouling when compared to the other
xerogels. The more hydrophobic C8-TEOS − TMOS xerogel ilms had the lowest γ
c
and exhibited the greatest release of eight day old
Ulva
sporelings and the barnacle,
B. amphitrite
.
McMaster and co-workers [91] demonstrated that active hybrid halide-permeable
xerogel ilms prepared from sols containing 50 mol% of APTES and 50 mol% of TEOS
or 10 mol% of APTES and 90 mol% of TEOS and 0.015 M selenoxide or telluride
catalyst in the sol reduced the adhesion of
B. amphitrite
larvae and the tubeworm
H. elegans
larvae in the presence of artiicial seawater (ASW) and H
2
O
2
(5−100 µM).
They also observed that 50 mol% of APTES and 50 mol% of TEOS xerogels with
a telluride catalyst reduced the settlement of
Ulva
zoospores in the presence of
100 µM of H
2
O
2
in ASW when compared with the coating with no added H
2
O
2
.
Finlay and co-workers [42] found that barnacle settlement was considerably lower on
a xerogel prepared from aminopropylsilyl-, luorocarbonsilyl-, and hydrocarbonsilyl-
containing precursors, when compared to settling on a PDMS elastomer. The strength
of adhesion on the xerogels was the highest on surfaces with the highest and the lowest
γ
c
. Although the initial attachment of larvae of
B. amphitrite
was similar on all the
xerogel surfaces, the percentage removal of attached cells increased with increased
surface tension and wettability. Xerogels synthesised by Gunari and co-workers with
varying ratios of C8-TMOS (C
18
, 1−5 mole%), and
n
-C8-TEOS showed signiicantly
lower settlement of barnacle larvae when compared to glass and PS [92].
A non-hazardous, less adhesive and mechanically stable FRC was designed and
synthesised with a series of crosslinkable perluoropolyether graft terpolymers
containing various alkyl MMA monomers with glycidal methacrylate (GMA) as the
cure-site monomer [93] (
Figure 2.24
). Curing of the GMA moieties was carried out
to avoid the restructuring of the polymer surface in water, and retain its non-polar
character. The contact angle hysteresis could be signiicantly reduced (by as much
as 50°) by changes in the bulk polymer composition, the chemical nature of the
monomers, crosslink density, modulus, and environmental conditions during curing.
The MMA-GMA based polymers showed a 10 and 25% lower settlement density
and higher percent removal of
Ulva
zoospores than glass and the DMS elastomer,
respectively. But when the spores were allowed to germinate into sporelings, their
release was lower. This could be attributed to the possible increase in polar groups
on the coating-water interface [93].
The development of amphiphilic polymeric coatings with incorporation of different
ratios of PEG and semi-luorinated side chains with two PS-
block
-poly(ethylene-
ran
-
butylene)-
block
-PI, ABC triblock copolymer precursors have been reported [94].
This difference in ratio provides hydrophobic and hydrophilic groups to the isoprene
fragment. The attachment of
Ulva
zoospores was higher on surfaces, which had a large
