Lignin: Functional Biomaterial with Potential in Surface Chemistry and Nanoscience - The Nanoscience and Technology of Renewable Biomaterials - page 197

Lignosulfonate has also been used successfully as an acid template in synthesis of
inherently conducting polymers (ICPs) through polymerisation of aniline or pyrrole
(Berry and Viswanathan 2002, Roy et al . 2002). One benefit from using lignosulfonates
is the increased dispersibility in a range of solvent including water. The final product
has been proven to possess corrosion protective ability when coated on metals, and is
also evaluated for use where electrostatic dissipative (ESD) materials are needed; e.g. in
sensitive electronic equipment, explosive materials, and when static electricity is gener-
ated in dangerous amounts. Ferromagnetic nanocomposites based on the lignosulfonic
acid-doped polyanilin have also been prepared recently.
In 1998, Westvaco marketed a variety of specialty lignin chemicals derived from
kraft black liquor, finding uses as dyes and pigment chemicals, in mineral technology,
asphalt, agricultural, lead storage batteries and phenolic resins (McCarthy and Islam
2000). The chemical heterogeneity however limits the potential for use in phenolic
resins to an additive level of about 5-10% with a consequential increase in molecu-
lar weight of the resins (Turunen et al . 2003). Another area where there has been
strong interest is utilising lignin in epoxy resins. Simionescu et al . (1993) showed
that high lignin loads could be sustained without a significant drop in the important
mechanical properties of the epoxy resin. Lignin has also been incorporated into the
production of polyolefins such as polyethylene and polypropylene with mixed success
with results indicating a reduction in strength and poor adhesion between lignin and
the polyolefin (Gosselink et al . 2004a, 2004b, Cazacu et al . 2004). This was perhaps
due to once again the heterogeneity of the lignin samples used. However, the increased
biodegradability due to the incorporation of lignin into the matrix material presents
an interesting method for improving the environmental compatibility of this common
polymer.
A critical factor that will enhance the potential of using polymeric lignin in nanotech-
nological applications will be the ability to produce a well-defined raw material with
reproducible properties. This may be achieved through biosynthetic control (Boudet
et al . 2003), the extended use of synthetic lignins through the polymerisation of mono-
lignols components or through the better processing of technical lignins isolated from
pulping liquors (Chakar and Ragauskas 2004). Already, there are numerous reports
detailing the use of lignin in applications as diverse as the production of carbon fibre
(Kadla et al . 2002, Kubo and Kadler 2005) and activated carbon materials (Suhas et al .
2007). The advantage in these two applications in particular is that the use of highly het-
erogeneous technical lignins is possible without the need for molecular reproducibility.
Activated carbons prepared from kraft lignin have also been used to study the adsorption
of phenol (Fierro et al . 2008) and benzene vapour (Blanco et al . 2008) in sensor type
applications.
However, still today the available technical lignins are always by-products and the
properties of the lignins produced are thus substantially dependent on the core process
that is mainly dedicated to pulp and paper production. A change is foreseen in the future
due to emerging environmental demands in substituting oil-based sources for production
of fuels and chemicals. The huge economical efforts attributed in the ongoing worldwide
development of different biorefinery concepts, utilizing parts of the wood and other
plants for the main purpose of making other things than fibre products will possibly