Environmental Engineering Reference
In-Depth Information
As detailed elsewhere, furan-based monomers can be used to produce even
more types of polymers [68]. Two types of particular interest in electronic
applications are poly-Schiff bases and polyhydrazides [73]. The poly-Schiff
bases produced by furanic chemistry are typically oligomers, with degrees of
polymerization reaching only approximately 10 [116]. Despite the low degree
of polymerization, poly-Schiff bases between furanic dialdehyde and aromatic
diamine have sufficient conjugations to achieve a conductivity of 10
-8
S cm
-1
for
undoped materials and 10
-4
S cm
-1
for iodine-doped materials [116]. In addition,
polyhydrazides with their highly polar macromolecules are potentially useful for
electronic and optical applications [73].
5.3.8
Furan Conclusion
This introduction to furan-based chemistry illustrates the vast opportunities
afforded by this special class of chemicals. It is possible to consider furan chemistry
as an entirely new realm of polymer chemistry, capable of producing macromo-
lecular materials comparable to or surpassing those derived from fossil fuel
sources [67]. Both FA from furfural and 2,5-FDCA from 5-HMF have already
secured a spot on the commodities market. As other furan chemistries are optimized,
the market applications for furan-based polymers will grow to include the
applications currently serviced by fossil-based polymers.
5.4 Terpenes
Terpenes are volatile organics, produced mainly by plants as secondary metabo-
lites. The basic structure of terpenes is based on 5C isoprene with a hydrocarbon
chain containing one or more carbon-carbon double bonds. Typically, monoterpe-
nes have a general formula of C
10
H
16
with a large range of available structures as
illustrated in Figure 5.3. Two important features of monoterpenes are the vast
number of stereoisomers available to a given structure accessible via facile
isomerization and the wide variety of oxygenated derivatives that can be produced
from the basic structures [117].
This section will briefly touch on the industrial production of turpentine, a mix-
ture of monoterpenes, cationic polymerization of α-pinene and β-pinene, both
homopolymerization and copolymerization, the polymerization of non-pinene
terpenes, and conclude with a mention of terpenoids. Outside the scope of this
discussion, terpenes find wide use in the production of fragrances and flavors
[120]. In addition, terpenes hold promise as environmentally friendly solvents;
camphene, which has been shown to be harmless, has been tested as a solvent for
polypropylene [121]. Also not covered is isoprene, a hemiterpene. One of the
most-studied monomers, isoprene has traditionally been produced as a by-product
of the ethylene industry but recent advances in fermentation techniques have
allowed for a renewable pathway to the production of isoprene [122].
