Advances in Materials Physics and Chemistry, 2012, 2, 221-225
doi:10.4236/ampc.2012.24B056 Published Online December 2012 (http://www.SciRP.org/journal/ampc)
Sustainable Polymers Derived From Naturally Occurring
Materials
Bimlesh Lochab, I. K. Varma, J. Bijwe
1Department of Chemistry, Shiv Nadar University, Greater Noida, India
2CPSE; ITMMEC, IIT, Delhi, New Delhi, India
Received 2012
ABSTRACT
Nearly 95% of monomers or chemical intermediates used today are based on fossilized carbon such as coal and petroleum. This has
resulted in a high rate of depletion of fossilized reserves, continuous escalation in petroleum prices, environmental impact with the
increase in emission of greenhouse gases, and accumulation of non-biodegradable waste on earth. Current global main challenges are
moving towards green sources - need for vast new and sustainable material resources; supplement, reuse and replace petroleum based
polymeric materials; biodegradability of materials to prevent build up of waste; toxicity associated with the preparation, usage and
environmental safety. Recent investigations are therefore, focused on procuring materials from the plant resources, agricultural waste
and their utility in synthesis of polymeric materials. Amongst the polymers derived from natural resources poly(lactic acid) is a lead-
ing candidate. Commercial quantities of natural oil-based polyols such as castor, soya bean oil have been available over the past sev-
eral years and currently used for synthesis of polyesters, polyurethanes etc, but today many other natural materials are also being
investigated. It should be possible to produce sustainable polymers commercially and economically.
Keywords: Natural Phenols; Cardanol; Lignophenol; Sustainable Polymers; Phenolic Resin; Benzoxazine
1. Introduction
Next decade challenges and opportunities are vast and alarming
with the current use of non-renewable based chemical sources
for synthesis of polymers and other architectures. There is a
need to explore agricultural waste materials for synthesis of
polymers such as phenolic resins, polyesters, polyurethanes, etc.
Phenolic sources are vast and widely distributed in wood, seeds,
shell, cashew nut shell liquid (CNSL), lignin, palm oil and
other plant-based resources which are usually thrown as agri-
cultural and agro-based industrial waste, while lactic acid and
long chain alcohols are derived from corn starch, soya bean and
castor oil respectively. The extraction and utilization of renew-
able monomers for a variety of bio-based polymers have been
investigated in the past.
However, there are several problems associated with naturally
occurring renewable resources. These are (1) limited knowl-
edge about the organic contents in the natural source, (2) vary-
ing percentage of chemical content and composition with spe-
cies, geographical area, and climatic conditions (3) usually, a
complex Department of Science & Technology, Delhi, India
chemical composition of the extracted material comprising of
several compounds such as phenols, carboxylic acids, alde-
hydes, esters etc. needs higher costs of desired chemical recov-
ery, (4) low percentage of the desired chemical species requires
further processing and adds to additional costs.
The shifting of the resource base for organic chemicals from
fossil fuels to renewable resources creates a unique opportunity
for shifting plastics from their current unsustainable course to a
more sustainable life cycle. The research in this area is still at a
nascent stage and scientists have to unfold the chemistry in this
upcoming area.
2. Sources of Renewable Materials
2.1. Naturally Occuring Phenolic Compounds
Currently the agricultural wastes such as empty fruit bunches
[1], seed [2-3], fibre, shell [4], wood, bagasse [5] are being
investigated as a potential source of phenolic derivatives. Their
main utilization at the moment is to generate energy to run the
mill by incinerating the waste for power and fertilizer purposes.
However, these wastes are rich in potential chemicals and py-
rolysis is considered to be an emerging and potential technol-
ogy to produce value added products, fuel, oil and chemicals
from such waste. Moreover, an appropriate separation and ex-
traction method is required to maximize the desired chemical
from the agricultural waste. Some of these materials contain a
very high concentration of phenol and its derivatives, viz., cre-
sol, catechol, guaiacols, syringol, eugenol etc. These products
are very high-value chemicals from the point of view of price,
lower toxicity and environmental impact as compared to petro-
leum based products. Such waste could be utilized as an alter-
native source of phenols and its derivatives for the variety of
applications ranging from the production of polymers and res-
ins. The main naturally occurring phenolic sources that will be
considered are cashewnut shell liquid (CNSL, Figure 1), lign-
ins (Figure 2), palm oil and coconut shell tar.
2.2. Naturally Occuring Acids
Lactic acid is major by product of carbohydrate hydrolysis. It is
one of the most studied renewable monomer. The monomer

B. LOCHAB ET AL.
222
OH
COOH
R
OH
R
OH
RHO
OH
RHO
H
3
C
R=
(a) (b)
(c)
(d)
Figure 1. Components in CNSL: (a) anacardic acid, (b) cardanol, (c) cardol, (d) 2-methylcardol [4].
L-lactide (LLA) can be prepared with relatively high enantio-
purity from corn starch fermentation.
2.3. Naturally Occuring Alcohols
1) Vegetable oils
Vegetable oils are triglycerides of long chain fatty acid moie-
ties (Figure 3), with unsaturated bonds and free hydroxyl
groups. The ester moieties are hydrolyzed to give carboxylic
acid functionality (Figure 4).
HO OCH
3
HO
O
HO
H
3
CO
O
OCH
3
OH
Figure 2. Representative structure of (a) Lignin [6].
Figure 3. Triglycerides R1=R2=R3 (aliphatic unsaturated or satu-
rated).
Figure 4. Modifications and occurrence of fatty acid in oils: source
for monomers and polymers from renewable resources [7].
Soyabean oil triglycerides are a-linolenic acid (18C, 3 double
bonds, 7-10%); linoleic acid (18C, 2 double bonds, 51%);
and oleic acid (18C, 1double bond, 23%). Mustard oil contains
erucic acid (22C, 1double bond, 42%), linolenic and linoleic
acid (21%), oleic acid (12%). Castor oil consists of ricinoleic
acid (85-95%) which is monounsaturated, 18-carbon fatty acid,
is unusual in that it has a hydroxyl functional group on the 12th
carbon.
2) Glycerol
Glycerol (propan-1,2,3-triol) is a byproduct of soap industry
as result of transesterification reaction of fat in alkaline medium
to form soap (Figure 5).
Products such as glycerol carbonate and esters are good in-
termediates for several polymers (Figure 6) [8].
Mono-di-or tri ester could be produced by esterification with
carboxylic acid or transesterification with carboxylic acid me-
thylesters (Figure 7) [9].
3. Polymers
Incorporation of monomers obtained from green sources pro-
vides new significant synthetic aspects and helps to produce
partly green goods with a finite content of renewable or recy-
clable material extracted without odor problems and less use of
fossil fuel reserves.
Figure 5. Transesterification of fatty acid.
Figure 6. Utilization of greener sources namely glycerol and carbon
dioxide to prepare carbonate.
Figure7. Monoesters of diglycerol.

B. LOCHAB ET AL. 223
3.1. Polymers Obatined from Phenolic Materials
The presence of phenolic –OH group, aromatic ring and side
chains such as long alkylene chain in cardanol, could be
utilized for various chemical transformations. Lignins have
phenolic hydroxyl groups and aliphatic groups at C-a and C-g
positions on the side chain. The presence of such groups has
enabled its utilization as a partial substitute for phenol in the
synthesis with a lot of applications. The reactivity of lignin is
determined both by its particular structure with specific
functional groups and its structural modifications induced by
separation methods derived from different raw materials.
1) Reactions due to –OH group
A variety of functional groups can be attached to the reactive
free hydroxyl group for derivatization. The reactions may be
divided into two categories a) nucleophilic aromatic/aliphatic
substitution (b) condensation reaction. A generalized scheme
for the possible modifications of –OH groups in naturally
occurring phenolic compounds (Figure 8). Benzoxazines (Bzs)
monomers are bicyclic heterocycles generated by the Mannich-
like condensation of a phenol, formaldehyde and an amine [10]
(Figure 9). Our group reported replacement of petro-based
phenolic compounds with agro-waste cardanol to synthesize
mono- and bis-oxazine derivatives using solventless method
and studied its ring-opening polymerization (ROP) to poly-
benzoxazine [11-13].
Figure 8. Modification of cardanol.
N
R'
OHHO
OH
R
O
NR'
R
2CH
2O+R'NH 2
Figure 9. Synthesis of 3,4-dihydro-2H-1,3-benzoxazines.

B. LOCHAB ET AL.
224
2) Reactions due to aryl group
Aryl group present in lignophenol, cardanol, palm oil and
CST undergoes electrophilic aromatic substitution reactions. A
generalized reaction pathways possible for such structural
modifications shown in Figure 10.
3) Reaction due to side chain
Depending on the source of phenolic compound (i.e. carda-
nol, palm oil, lignophenols) the side group may be alkylene
chain, methyl or methoxy group etc. The modification of side
chain allows further possibilities to tailor the structure. The
polymers obtained from the phenolic monomers can be either
used as such crude or modified.
Naturally occurring phenolic compounds could act as a
source for synthesis of several polyme r s (Figure 11).
3.2. Polymers from Lactic Acid
High molecular mass poly(lactic acid) (PLA, Figure 12) is
obtained either by the polycondensation of lactic acid or ROP
of the cyclic dimer 2,6-dimethyl-1,4-dioxane-2,5-dione com-
monly referred as dilactide or lactide. PLLA is a versatile,
semi-crystalline, degradable polymer having excellent me-
chanical properties, good biocompatibility and low toxicity. It
has been used in a variety of applications in the pharmaceutical
and biomedical fields, as well as used as a degradable plastic
for disposable consumer products. In tissue engineering, PLLA
has been used as biodegradable scaffold where the transplanted
cells can remold their intrinsic tissue super-structural organiza-
tion and thereby lead to the desirable 3-dimensional structure
and physiological functionality of a regenerated organ. The
properties of PLLA can be tailor made by copolymerization
(random, block, and graft), change in molecular architecture
(hyperbranched polymers, star shaped, or dendrimers), func-
tionalization (end group functionalization or pendant groups
such as carboxyl, amino, or thiol), or blending with other
polymers [14].
3.3. Polymers from Alcohol
Aliphatic fatty acids saturated and or unsaturated acids are pre-
sent in vegetable oils. They contain hydroxyl, carboxylic func-
tionality and double bonds which are available for further func-
tionalization to transform them to respective monomers [7] e.g.
linseed oil, soyabean oil, sunflower oil, rape seed oil, castor oil,
mustard oil, palm and coconut oil etc. These oils can be used in
OH
N
N
OH
OH
N
2+
Cl
-
HO
Diazotised derivative
HOH
2
CO
OH
CH
2
OH
OH
CH
2
OH
OH
R
Base, CH
2
O
Methylol derivative
CH
2
O
Novolac resin
A
A
A
A
A
A = side chain
Figure 10. Modifications of aromatic ring
synthesis of polyurethane, polyester, polyamide, polyacrylate,
nylon and epoxy resin. For example, ozonolysis of oleic acid
yields polyamide 6.9; ricinoleic acid which may be used to give
polyamide 10.10 and 6.10; 11-undecanoic acid obtained from
castor oil has been used for the production of nylon-11, poly-
amide 6.10 and polyols from sources such as castor oil are un-
dertaken by several industries such as Emery Oleochemicals,
Evonik, Arkema, BASF [15]. The industry needs to become
more competitive and this includes breeding strains of plant
with higher levels of useful fatty acids, like high oleic acid
containing sunflower oil.
Glycerol dimethacrylate diester monomer can be used for the
synthesis of copolymers [16], glycerol carbonate for synthesis
of hyperbranched polymers [17].
3.4. Utility of Carbon Dioxide
Carbon dioxide is green, environmentally benign, solvent and
reactant that is cheap, non-toxic, non-flammable and naturally
abundant. It can be fixed and inserted in various compounds
(Figure 13) to from cyclic carbonates, caboxylates, carbamates,
urea, salicylates etc.
The cyclic carbonates prepared by insertion of carbon diox-
ide into an oxirane ring of ethylene/propylene oxide to form
5/6-membered cyclic carbonates which then undergo ring-
opening polymerization to form polycarbonates (Figure 14).
PF resins
Polybenzoxazine
PU/ Polyester
resins
Methylol resins
Benzoxazine
Acrylate or
metha cr yla te
oxirane
derivative
polyols
Epoxyresin
Poly(meth)acrylates
Novolac
Phenolic
Derivatives
Figure 11. Scheme depicting polymers obtained from naturally
occurring phenolic monomers.
Figure 12. Poly(lactic acid).
Figure 13. Carbon dioxide as the reactant for various monomer
synthesis.

B. LOCHAB ET AL. 225
Figure 14. Ring-opening polymerization of cyclic carbonates.
Unlike aromatic polycarbonates which either use toxic phos-
gene or diphenyl carbonate which accounts for high toxicity,
these showed good bio-compatibility, biodegradability, low
toxicity, and find applications in biomedical fields [18].
3.5. Conclusio n
The surge in living standards resulted in more dependence on
polymers articles for our daily needs. The usage of non-re-
newable based materials affects our environment tremendously
and measures are required to deal with it both scientifically and
globally. Polymers derived from renewable starting materials
are attractive because of safety and ecology issues over petro-
based materials such as (a) environmental and economic con-
cerns associated with waste disposal and (b) rising cost of pe-
troleum production resulting from the depletion of the most
easily accessible reserves. These are the guiding principles for
the next generation polymers which have zero or less ecology
impact, sustainability, eco-efficiency and green chemistry. Bio-
polymers based on renewable resources include cellulosic-
plastics, polylactides (PLA), starch-plastics, soy-plastics, phe-
nol plastics.
The challenge for development of biodegradable polymers
lies in the fact that such polymers should be able to be proc-
essed on the existing equipments, stable during storage and
usage, and degrade when disposed off after their intended life-
time [19]. There is a need for a research to develop new tech-
niques for utilization of renewable resources to synthesize new
intermediates/monomers for polymers for greener sustainable
future.
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