The results observed (Table 1) are quite complicated compared
to the theoretical expectation that a surfactant with a higher number
of oxyethylene units such as n = 6 should form the biggest
micelles. Consequently, the pore size should decrease from n = 6
to n = 4 under similar synthesis conditions, as mentioned in the
previous paragraph. The general observed trend was that, under
the same conditions of surfactant/PFE ratio molar composition, the
synthesised carbon foams with ethoxylated nonylphenol n = 6 gave the highest pore diameter compared to those with ethoxylated
nonylphenol n = 4, which showed the smallest pore aperture. The
pore diameter of the materials obtained for a surfactant/PFE ratio
molar composition varied with the number of oxyethylene units
and was in accordance with the theoretical expectation. Different
factors should be taken into account to explain this observation. The
first is the possible swelling effect of PFE for a surfactant/PFE ratio at
the molar ratios used in this research. However, we also have to look
at the cloud point, which arises from a balance of intermolecular
van der Waals attractions and hydration repulsion. The cloud point
values are not available in the literature for C15(EtO)n but are available
for C15(EtO)3, so we can assume that the surfactants C15(EtO)4
and C15(EtO)6 have a similar cloud point as C15(EtO3), being 48 ◦C
and 77 ◦C, respectively for C15(EtO)n (n = 4, 6) surfactants. As for
longer ethoxy groups, the hydration repulsion is increased, and a
higher temperature is required before attraction and repulsion are
balanced, so C15(EtO)6 should have the highest cloud point, i.e. a
cloud point that is greater than 77 ◦C. Second, it is possible that it is
more likely that a longer ethylene oxide chain penetrated deeper
into the PFE resin hydrophilic phase, can be produced pores after
the surfactant is burnt out.