Renewable resource-based polymeric microencapsulation of natural pesticide and its release study: An alternative green approach

Article abstract of DOI:10.1039/c4ra01558d

Recently, the use of renewable sources in synthesizing polymers has been remarkably increased due to numerous reasons, such as finite as well as unreliable petroleum sources and increasing environmental awareness. Considering the need of the day, we are reporting the preparation of polymeric microcapsules based on cardanol as a renewable source by an in situ polymerization technique to encapsulate the biobased core. Comparative study for successful encapsulation of karanja oil by cardanol formaldehyde and conventional phenol formaldehyde-based microcapsules is made. The success of polymerization is characterized by structure and thermal analysis using FTIR and TGA, respectively. Distinctive surface morphologies of the prepared microcapsules are examined by SEM, which confirmed formation of wrinkle-free and globular-shaped microcapsules. The size of prepared microcapsules is determined by a particle-size analyzer. The amount of encapsulated core material released is estimated quantitatively by solvent extraction, and gravimetric and UV spectrophotometric methods. Thus, the current research is oriented towards the exploration of biobased, renewable shell material for the microencapsulation of biobased cores for the structural design of a new generation of pesticide formulations. Therefore, the most recent advancements include an interdisciplinary combination of biobased polymers and agrochemicals, which is a significant requirement for attaining a cleaner global environment.

Full text of DOI:10.1039/c4ra01558d

RSC Advances
View Article Online
View Journal | View Issue
PAPER
Renewable resource-based polymeric
microencapsulation of natural pesticide and its
Cite this: RSC Adv., 2014, 4, 18637
release study: an alternative green approach†
*
Rahul Kishore Hedaoo and Vikas Vitthal Gite
Recently, the use of renewable sources in synthesizing polymers has been remarkably increased due to
numerous reasons, such as finite as well as unreliable petroleum sources and increasing environmental
awareness. Considering the need of the day, we are reporting the preparation of polymeric
microcapsules based on cardanol as a renewable source by an in situ polymerization technique to
encapsulate the biobased core. Comparative study for successful encapsulation of karanja oil by
cardanol formaldehyde and conventional phenol formaldehyde-based microcapsules is made. The
success of polymerization is characterized by structure and thermal analysis using FTIR and TGA,
respectively. Distinctive surface morphologies of the prepared microcapsules are examined by SEM,
which confirmed formation of wrinkle-free and globular-shaped microcapsules. The size of prepared
microcapsules is determined by a particle-size analyzer. The amount of encapsulated core material
released is estimated quantitatively by solvent extraction, and gravimetric and UV spectrophotometric
methods. Thus, the current research is oriented towards the exploration of biobased, renewable shell
material for the microencapsulation of biobased cores for the structural design of a new generation of
pesticide formulations. Therefore, the most recent advancements include an interdisciplinary
combination of biobased polymers and agrochemicals, which is a significant requirement for attaining a
cleaner global environment.
Received 22nd February 2014
Accepted 25th March 2014
DOI: 10.1039/c4ra01558d
www.rsc.org/advances
regarding biopolymers based on CNSL provided an interesting
platform to substitute conventional raw materials of phenol
formaldehyde (PF) by using biobased feedstock.6 Although bio-
Introduction
In this scenario, the synthesis of polymers from renewable
resources has attracted the attention of researchers throughout
the globe because of the escalating cost of petrochemicals,
increasing demand and concern regarding depletion of the
mineral oil sources along with political and environmental
concerns.1–5 Although there is a signicant response in the
development of biopolymers, limitations exist such as the
higher cost of renewable polymers and their poor performance,
compared with petroleum-based polymers.6 A limited number
of successful examples of polymers based on renewable sources
include polyurethanes derived from alditols and other polyols
such as polyamides, polyesters, polyanhydrides, poly-
phosphazenes, polysaccharides, benzoxazines, epoxy resins and
phenolic resins.7
resources have proven their role in the preparation of such
polymers as polyesters, polyurethanes, PF and phenolics, their
applications as a shell for microencapsulated cores is limited to
water-soluble renewable sources only. Research on the prepa-
ration of renewable sources based on polymeric shells by using
in situ polymerization is not available. Hence, the use of
appropriate renewable sources as sustainable feedstocks for
thermosetting materials can be considered a novel path for the
eld of encapsulation.
Encapsulation can be described as enclosing some internal
medium with a semi-permeable membrane that controls the
exchange between the environment and such internal contents
as fragrance oils, cosmetics, self-healing agents, immobilized
extraction reagents, and pesticides.9–12 The most recent
advancements in the core of biopolymers is focused on appli-
cations, which are well established on the basis of petroleum
feedstocks and their applications include composites, foams,
drug delivery, coatings, etc. Comparatively, encapsulation is
among the more recent applications of polymers for protecting,
delivering with persistent rate of release, masking of undesired
odours, converting liquid components to free-owing powders
and improving the physical or chemical stability of the core.
With consideration for renewable resources, non-toxic and
non-volatile cashew nut shell liquid (CNSL) contains a phenolic
moiety with a side chain of 15-carbons, and it has been explored
considerably more for polymer preparation.8 Attempts
Department of Polymer Chemistry, School of Chemical Sciences, North Maharashtra
University, Jalgaon-425 001, India. E-mail: vikasgite123@gmail.com
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c4ra01558d
This journal is © The Royal Society of Chemistry 2014
RSC Adv., 2014, 4, 18637–18644 | 18637

View Article Online
RSC Advances
Paper
Several reports are available for the encapsulation of cores by sodium lauryl sulfate (Loba Chemicals, Mumbai, India), car-
different shells; in fact, most of them have covered such routine danol (Sigma Aldrich, Mumbai, India) and xylene and resor-
shells as PF, urea formaldehyde (UF), melamine formaldehyde cinol (S d Fine Chemicals Ltd., Mumbai, India). Karanja oil
(MF), polyurea, polyurethane. Due to the requirement in selected as both a core and model bio-pesticide for encapsula-
different elds and tailored properties for shells, the search for tion was supplied by Vishal Chem., Mumbai, India. All of the
the development of new shells is a recent topic.13–15
chemicals used were of synthetic grade and used as such in the
Currently, all polymeric shell materials used for encapsula- experiment. Other chemicals such as NH4Cl and HCl used in
tion by in situ polymerization are based on petroleum feed experiments were of analytical grade.
stock. However, there are reports regarding renewable sources
based on cores, including neem and karanja oils. This is the
rst report regarding efficient encapsulation of a biobased core
(karanja oil) by biobased shell-wall material (cardanol based)
via in situ polymerization. In addition, our investigation has
focused on designing shell components and the release of core
substances, wherein both are based on renewable sources.
The continuous application of synthetic organic pesticides in
the agricultural eld for controlling pests affects bio-diversity,
leading to environmental damage affecting living organisms and
human health.16,17 Hence as a alternative green approach, agri-
culturists are now interested in the application of formulated
bio-pesticides, which have attracted the attention and interest of
those concerned with integrated crop management (ICM) as an
efficient method of pest management by developing formula-
tions that are safer and environmentally friendly.18
On parallel ground, neem and karanja oils have proven them-
selves as effective biobased insect growth-inhibiting pesticides,
active materials against insects and repellent materials to
insects.19,20 Due to the presence of such sensitive moieties as
epoxide rings, carbonyl esters and ‘p’ electrons, the compound
may have a short shelf life in an exposed environment, which can
be overcome by microencapsulation.21 Because it protects the
contents against adverse environmental conditions within inert
coating or wall material and prevents the loss of volatile ingredi-
ents with the added advantage of controlled release.22–25 The
literature reported encapsulation of bio-pesticides, i.e. neem seed
and karanja oils by biobased barrier of shell walls, including Ca-
alginate,19 starch21,23 and guar gum matrices.26,27 However, the
beauty of the current research is the exploration of biobased,
cardanol formaldehyde polymeric shell walls as a new shell
material by an in situ polymerization technique for the efficient
microencapsulation of karanja oil and in the future for other cores.
In cardanol, i.e. two ortho and one para positions would have
the same degree of activation as those in phenol. These three
possible reactive sites permit the eventual formation of a cross-
link network to PF during polymerization as in the case of
phenol.6 The potential objective of the current investigation was
to develop biobased shells from cardanol for biobased pesticides.
As an exciting achievement, this work demonstrated a
framework for an eco-design of biobased polymeric microcap-
sules based on renewable resources that can be further
extended for drugs, self-healing agents, catalysts, among others.
Preparation of renewable sources based on microcapsules
Reaction schemes for the preparation renewable sources based
on (cardanol) novel microcapsules are depicted in Fig. 1. Car-
danol-based microcapsules were prepared by adapting an in situ
polymerization technique at the interface of the organic and
aqueous phases. Typically, 50 mL aqueous solution of PVA
(2.5 wt%) was mixed in 50 mL of deionized water in a three-
necked round-bottomed ask, which was suspended in an oil
bath maintained at ambient temperature. The solution was
homogenized by agitation with the help of a mechanical stirrer;
0.45 g (0.0014 mol) of cardanol was added into the solution.
0.16 g (0.0021 mol) of butanol and 0.01 g of sodium lauryl sulfate
were then gradually added to the solution under continuous
stirring. The solution was adjusted to a pH value of 7.5 by taking
appropriate amount of NH4Cl (approx. 0.5 g). Aer attaining a
slight alkaline pH, the reaction mixture was stirred for 5 min to
which karanja oil as a bio-pesticide (10 mL) was added slowly to
form an emulsion and allowed to stabilize for 30 min under
constant agitation. Aer stabilization of the emulsion, 2.07 g
(0.0689 mol) of 37 wt% aqueous solution of formaldehyde was
added to it. To initiate a reaction, the emulsion was slowly
heated up to 65 ꢀC under stirring at 300 rpm for 2 h. Aerwards,
several drops of 5 wt% of HCl were added to it to adjust the pH to
around 4. Subsequently, 0.14 g (0.0012 mol) of resorcinol was
added to it, and the reaction was continued at the same
temperature for about 3 h. The reaction mixture was monitored
for the formation of microcapsules under an optical microscope;
upon conrmation, the reaction mixture was cooled to room
temperature. The prepared polymeric microcapsules from the
suspension were recovered by ltration under vacuum, rinsed
with water and then dried under vacuum.
Synthesis of non-biobased microcapsules
The probable reaction scheme for the preparation of non-bio-
based phenol formaldehyde (PF) microcapsules is given in
Fig. S1.† These microcapsules were also fabricated by the same
Experimental
Materials
The materials used in experiments consist of phenol, formalin
Fig. 1 Reaction scheme for renewable sources based on cardanol
(37 wt% formaldehyde), poly(vinyl alcohol) (PVA), butanol and formaldehyde (CF) novel microcapsules.
18638 | RSC Adv., 2014, 4, 18637–18644
This journal is © The Royal Society of Chemistry 2014

View Article Online
Paper
RSC Advances
procedure that was adapted for the cardanol based microcapsules drying method and, subsequently, on a UV spectrophotometer
i.e. in situ polymerization of phenol, formaldehyde and resorcinol (mini UV, Shimadzu and UV-3600 Spectrophotometer, North
by using an oil-in-water interface emulsion technique. At room America). The vacuum-dried samples of the microcapsule in
temperature, typically 50 mL aqueous solution of PVA (2.5 wt%) triplicate were weighed accurately for each analysis. To extract
was added to 50 mL of deionized water, which was previously the encapsulated core by xylene (10 mL) at regular time inter-
placed in a three-necked, round-bottomed ask and suspended in vals, cross-linked microcapsules were subjected to mechanical
an oil bath. Under constant agitation, 0.94 g (0.0099 mol) of jerks by swirling for 5 min and ltered with a Gooch crucible.
phenol was gradually added to the PVA solution and the pH Quantitatively, the ltrate collected from each interval was
adjustment to a value of 7–8 by having an appropriate amount of diluted to 100 mL in a volumetric ask by using xylene as a
NH4Cl (approx. 0.75 g; 0.0140 mol). To form an emulsion, karanja solvent. The UV plot of absorbance for the samples extracted at
oil (10 mL) was added slowly to the previous solution and allowed various time intervals and standards were measured in a 1 cm
to stabilize for next 30 min under constant stirring at 300 rpm.
quartz cell by using the mode of spectral measurement in
Aer taking 1.61 g (0.0536 mol) of formalin (37 wt% aqueous combination with a reference cell containing a xylene. The
solution of formaldehyde), the stabilized emulsion was initiated absorbance of known concentrations of a core was measured in
and slowly heated to 65 ꢀC and continued for the next 2 h. The a xed wavelength measurement mode of UV equipment.
emulsion was then acidied (pH ¼ 4) by adding 2–3 drops of Similarly, the absorbance of the extracted core was also deter-
5 wt% of HCl. Aer acidication, 0.12 g (0.0010 mol) of resor- mined and quantied accordingly. The UV absorbance of kar-
cinol was added to the emulsion, and the reaction was allowed anja oil (standard and extracted cores) was measured at 230–
to continue for next 3 h under the same conditions. Further, the 275, 300–320 and 335–400 nm. As the selected core is soluble in
reaction mixture was cooled to room temperature, and micro- xylene, it was selected as a solvent to investigate and predict the
capsules were separated by ltration under vacuum. The general trend of the release prole. Different solvents, which
prepared microcapsules were washed with water followed by can easily soluble core, might be used to analyze the release
xylene (to remove suspended oil) and then dried under vacuum. pattern and for forecasting in practical agricultural elds.
Analyses of microcapsules
Results and discussion
The FTIR spectra of the core and shells were considered to
The preparation of novel biobased microcapsules from carda-
nol and non-biobased microcapsules from simple phenol were
completed in our research laboratory. The results obtained for
the formation of shells, morphology, particle size and thermal
behavior of microcapsules, and the controlled release of the
core are subsequently discussed.
detect chemical changes that took place during microencap-
sulation of monomers. The FTIR spectra of the isolated core and
microcapsules were recorded on a Fourier transform infrared
spectrophotometer (FTIR Shimadzu 8400, Japan) by using KBr
pellets. Preliminary observations and physical appearance of
cardanol- and phenol-based microcapsules were completed on
an optical microscope (Labomed Sigma, 2124001, Texas) from
40–100ꢁ resolution. The prepared microcapsules were analyzed
for their morphological study under a scanning electron
microscope (JEOL JSM 6360 and JEOL JSM 5400, Japan). The
mean sizes and size distributions of the synthesized micro-
capsules were determined by suspending microcapsules in
distilled water by a laser particle-size analyzer (Mastersizer
2000, M41100167, Malvern, UK) at 25 ꢀC. The thermal behavior
of the microcapsules and bio-pesticides was evaluated with a
thermo gravimetric analyzer (TGA-50, Shimadzu) in which the
FT-IR analysis of microcapsules
The FTIR spectra of core material, i.e. karanja oil as a bio-pesti-
cide, biobased and conventional PF microcapsules loaded with
bio-pesticides are shown in Fig. S2.† The characteristic sharp
band that appeared at 1743 cmꢂ1 was due to the presence of a
carbonyl group of ester in an oil.28 The bands at 1610 and 1513
cmꢂ1 represented the characteristics of the C–C–O asymmetric
stretching and C–C stretching of aromatic rings, respectively.29
Broad bands observed in the range of 3000–3150 cmꢂ1 may be
due to –OH groups present in polymeric shells.30 The presence of
–C–H stretching of the methylene group was conrmed by the
ꢀ
samples were heated from room temperature to 600 C at the
ꢂ1
ꢀ
heating rate of 10 C min in an inert nitrogen environment.
appearance of two bands at 2926 and 2852 cmꢂ1 31 The previously
.
Encapsulation yield and loading
mentioned similar bands appeared in the biobased novel, as well
as non-biobased PF microcapsules. Further, evidence for the
presence of the –OH group of cardanol and phenol with form-
aldehyde in microcapsule shells came from the appearance of
The amount of bio-pesticide entrapped in the fabricated
microcapsules (novel biobased and non-biobased shells) was
determined by xylene extraction of the core material by using a
Soxhlet apparatus. The total quantity of core content entrapped
by shell materials was determined.28
broad bands in the range of 3000–3450 cmꢂ1
.
Additionally, the band with increased intensity at 723 cmꢂ1
indicated the frequency of 2,4,6-trisubstituted phenol and
substituted cardanol in the prepared microcapsules. The pres-
ence of such bands in the case of biobased and non-biobased PF
Controlled release of core (bio-pesticide) through polymeric
shells
The controlled release rate of a bio-pesticide encapsulated in shells conrmed the polymerization of cardanol and phenol.
microcapsules was quantitatively analyzed by a weight-loss The band at 1348 cmꢂ1 was observed for the phenol –OH in
This journal is © The Royal Society of Chemistry 2014
RSC Adv., 2014, 4, 18637–18644 | 18639

View Article Online
RSC Advances
Paper
plane bending was also detected for phenol formaldehyde
The development of rough structures (Fig. S3†) on the
resin.32 The characteristic sharp peak that appeared at surfaces of microcapsules might have acted as a better barrier
1743 cmꢂ1 did not alter even aer the formation of microcap- for the core to be released as compared with smooth and so
sules, thereby indicating the absence of chemical interactions surfaces as seen in Fig. S4.†,33
between a core and a shell.
SEM images (Fig. 3) of non-biobased PF microcapsules
Thus, the core molecule retained all its functional groups containing bio-pesticides are given for examining surface
during the processing of novel biobased and non-biobased morphology. SEM analysis revealed that conventional PF
microcapsules. The same frequencies for functional groups microcapsules were found to be smooth and so, compared
present in FTIR of core and microcapsules demonstrated that with that of cardanol-based. Phenol-based microcapsules might
core remained inactive for any chemical interaction during enable the presence of a sustained releasable membrane.29,30
polymerization and additionally conrmed the formation of the The smooth surface morphology of the microcapsules could be
polymeric barrier, i.e. novel biobased and non-biobased PF as useful with regard to the protection and sustained release of the
shell materials for the encapsulation of a bio-pesticide.
interior for the core.29 Additionally, when microcapsules were
exposed for longer periods of time, the shrinkages resulted to
greater support of the fact of higher release rates of bio-pesti-
cides as a core material, rather than the microcapsules prepared
by using cardanol (Fig. S4†).
Surface morphology of microcapsules
Scanning electron microscopy (SEM). SEM images of the new
biobased microcapsules are visualized in Fig. 2 by using 10 kV of
energy source from a bundle of electron clouds and a magni-
cation of 1–2 times. Biobased microcapsules were seen as an
individual sphere with the least aggregations that conrmed the
formation of biobased polymeric microcapsules. The surfaces of
biobased microcapsules seen in SEM were rough with single,
hard sheet-like structures as seen in Fig. 2g–h.
Particle-size analysis
The particle-size distribution of the prepared biobased novel
and conventional PF microcapsules containing bio-pesticides
as a core was evaluated by a particle-size analyzer, and
Fig. 3 SEM micrographs of non-biobased PF microcapsules exposed
Fig. 2 SEM micrographs of biobased microcapsules exposed to 50 ꢀC to 50 ꢀC for (a and b) 00 h, (c and d) 48 h, (e and f) 96 h and (g and h)
(a and b) 00 h, (c and d) 48 h, (e and f) 96 h and (g and h) 144 h.
144 h.
18640 | RSC Adv., 2014, 4, 18637–18644
This journal is © The Royal Society of Chemistry 2014

View Article Online
Paper
RSC Advances
histograms are displayed in Fig. 4. The graphical distribution of
For a pure-core moiety, the initial stage weight loss of about
ꢀ
the mean diameters for different microcapsules is indicated in 28% was observed at 103 C, which might be due to traces of
Fig. S5.† From the particle-size histogram, it was determined moisture present in a core (karanja oil). About 24% of second-
that the biobased microcapsules have broad particle-size stage weight loss was attributed to the degradation of karanja
distribution in the range of 30–600 mm and mean diameter of oil at 260 ꢀC. With weight loss of approximately 48%, signicant
about 125 mm. The microcapsules prepared from non-biobased changes may occur at the molecular level around 403 ꢀC, which
PF had narrow distribution of particle size, i.e. in the range of 5– was third-stage degradation. Thermal degradation of the bio-
180 mm with mean diameter of about 30 mm. When we based microcapsules was observed in two steps, and the rst
compared mean particle sizes and the distributions of bio- and step started at about 264 ꢀC with approximate weight loss of
non-biobased microcapsules, we determined that both values about 31% due to the presence of active-core karanja oil. The
were larger in the case of biobased microcapsules than in that of second step of weight loss of around 68% was observed aer
the non-biobased.
The probable reason may be the various size ingredients bonds of the main polymeric chain may be broken.11
involved in the reaction systems. As the procedure and all Further, conventional phenol–formaldehyde microcapsules
420 ꢀC temperature onwards during which the C–C and C–O
parameters involved remained same for the fabrication of both experienced three stages of weight loss. The initial stage weight
polymeric microcapsules, we concluded that it would be the loss around 25% was seen at 225 ꢀC (from 125–270 ꢀC),
only reason for having microcapsules with various particle sizes presumably due to the elimination of formaldehyde and the
and distributions in the cases of bio- and conventionally based decomposition of small molecular minor fractions.35 In the case
phenol–formaldehyde microcapsules. It is generally observed of the second step, decomposition occurred at 350 ꢀC with
that many microcapsules are also being formed on account of approximate weight loss of 28% attributed to the degradation of
the turbulence in uid ow around the propeller blades.29 On karanja oil, coupled with depolycondensation reaction. The
the other hand, conventional phenols are engaged, due to good third stage, i.e. a residual weight loss of about 47%, was clearly
ꢀ
miscibility and homogenous reaction mass, comparatively than observed above 415 C that may be associated to the cracking
cardanol and resulted in ner microcapsule formation. Particle and degradation of shell-wall material. Not surprising, the
sizes and shapes are believed to affect release rates,34 smaller- thermal stability of the core is evidently enhanced by the
sized microcapsules have higher surface area, thereby releasing shielding effect due to the presence of a polymeric shell because
the core to a higher extent and that larger size and distribution it has already been proven that the capsule shell wall (novel and
might result in the delayed release of a bio-pesticide.
conventional) provides additional thermal stability to the core.36
Encapsulation yield and oil loading capacity
Thermogravimetric analysis
From the Soxhlet extraction, it was determined that the carda-
nol-based novel microcapsules had 28% encapsulated yield of
core and that of routine PF microcapsules possessed 31% yield,
whereas the remaining material had a residual mass contrib-
uted by the shell-wall materials of synthesized microcapsules.
Thus, the Soxhlet extraction study of encapsulated cores in both
types of microcapsules conrmed the presence of the core and
also provided information of the encapsulated yields of both
In this study, TGA investigation was carried out for a pure core,
novel and conventional microcapsules from ambient to 700 C
ꢀ
temperature. Fig. 5 shows a TGA diagram of the novel micro-
capsules, conventional microcapsules and pure-core material.
Both, i.e. pure core (karanja oil) and conventional, microcap-
sules showed highly similar weight losses with three stages of
degradation. Conversely, the novel microcapsules showed only
two steps of degradation with progress in temperature.
Fig.
5 TGA curves (a) cardanol-based novel microcapsules; (b)
Fig. 4 Particle-size histograms: (a) biobased; (b) non-biobased PF phenol–formaldehyde conventional microcapsules; and (c) core bio-
microcapsules.
pesticides.
This journal is © The Royal Society of Chemistry 2014
RSC Adv., 2014, 4, 18637–18644 | 18641

View Article Online
RSC Advances
Paper
microcapsules, which was in agreement with the yield obtained shells with cracks; shells become saturated with the core or by
by thermal analysis.
the presence of a very high-loading of the core.37 In our case, it
was evident that controlled-release formulations prepared on
the basis of microcapsule suspension irrespective of shell
materials; the release rate was of the rst order, indicating that
shells were without cracks and had no saturated core
environment.
Release experiments
The release rate of encapsulated karanja oil from both types of
microcapsules in xylene as a solvent was determined by two
different techniques viz. loss on drying and UV spectroscopic
methods; results of both are subsequently compared to check
any discrepancy.
Release based on UV spectroscopic method
UV plots for the extracted core material in a solvent xylene are
depicted in Fig. 7. The absorbance data for standard solutions
and extracted cores at different intervals are indicated in Tables
SII and SIII,† respectively.
A bio-pesticide, i.e. karanja oil, possessing different types of
unsaturations that showed absorbance lmax at 230–275, 300–
320 and 335–400 nm, which is in good agreement with the
previous reports.38,39 In both types of microcapsules, with
successive increases in the time interval, the absorbance (in
terms of release) appeared to be linear. In comparison, PF
showed a release-rate prole higher than the cardanol-based
system, irrespective of the time interval.
From the UV, it can be further inferred that the extracted
core at different intervals conrmed the presence of oil, i.e.
bio-pesticides present in different concentrations. In addition
to this, the extracted core can be quantied by interpolating
with standard absorbance on the UV spectrophotometry
curve.
The presence of the same core absorbance lmax as such and
core-extracted for the UV method veried the conclusion made
during the discussion of FTIR; i.e. the core remained inactive
during the polymerization reactions of shells. The conrmation
regarding the presence of bio-pesticides obtained by a UV
method was in agreement with an outcome derived from a loss-
on-drying method. This also helped to validate the loss-on-
drying method used to determine the release rate of karanja oil
as a core.
Release based on loss on drying method
The release rate (%) of bio-pesticide as a core material was
calculated by the loss on drying method,30 the results of which
are summarized in the Table SI† and represented in Fig. 6. It
was evidently observed that the biobased microcapsules showed
a delayed release of the core in comparison to routine micro-
capsules. Moreover, in the case of cardanol based system, the
percentage release rate was also slow within dened time
interval. Even though the cardanol–formaldehyde resins
exhibited a lower content of oil, i.e., oil-holding capacity than
that of phenol–formaldehyde resins, slower release may be due
to steric hindrance imparted by the presence of a bulky C15 side
chain of cardanol.6 Conversely, the absence of any disturbance
at the molecular level for routine PF would have triggered the
release during a given time period. During the morphological
study (SEM), observations made regarding the hard structure of
a shell for biobased microcapsules is in full accord with the
release rate studied by a loss-on-drying method. Additionally,
the lower mean diameter size with narrow particle-size distri-
bution of non-biobased systems may have higher surface areas
than that of biobased with broad, particle-sized distribution
and comparatively bigger mean diameter size. This may be
considered a signicant contributing factor for providing large
surface areas, which might be responsible for higher shoots of
release from non-biobased polymeric shells than biobased
polymeric shells. It is critical to design microcapsules to have
desirable release proles. As per the literature, zero and rst-
order kinetics are achieved for the release of the core from
microcapsules. Zero-order release kinetics are attributed to
Fig.
6 Release rate from (a) biobased and (b) non-biobased Fig. 7 UV plots for extracted core material: (a) biobased microcap-
microcapsules.
sules; (b) conventional non-biobased microcapsules.
18642 | RSC Adv., 2014, 4, 18637–18644
This journal is © The Royal Society of Chemistry 2014

View Article Online
Paper
In addition to this, a higher percentage of crystallinity
(Fig. S6†) with ordered structures of biobased novel shells
(89.40%, compared with 57.20%) than non-biobased shells
creates a straight forward hindrance for the slower release of a
biobased core. This is likely attributed to the removal of
amorphous components allowing for better alignment of
RSC Advances
7 C. F. Wang, J. Q. Sun, X. D. Liu, A. Sudo and T. Endo, Green
Chem., 2012, 14, 2799.
8 S. I. Kattimuttathu and K. S. Vadi, Ind. Eng. Chem. Res., 2005,
44, 4504.
9 B. Pena, C. Panisello, G. Areste, R. G. Valls and T. Gumi,
Chem. Eng. J., 2012, 179, 394.
polymeric chains as evident from optical and SEM 10 D. B. Biesel, Curr. Opin. Colloid Interface Sci., 2011, 16, 3.
micrographs.
11 K. Zhao, Y. Hu, W. Xu, L. Song, B. Wang and H. Feng, Polym.
Adv. Technol., 2012, 23(5), 894.
CNSL holds considerable promise as an excellent biobased
monomer for the preparation of microcapsules. The synthe- 12 Y. K. Song and C. M. Chung, Polym. Chem., 2013, 4, 4940.
sized biobased novel and non-biobased microcapsules were 13 R. K. Hedaoo, P. P. Mahulikar, A. B. Chaudhari, S. D. Rajput
analyzed by FTIR spectroscopy for determining structural
changes. The SEM study demonstrated regular spherical shape
and V. V. Gite, Int. J. Polym. Mater. Polym. Biomater., 2013,
63, 1.
along with hard lm-like structures for the biobased and 14 R. K. Hedaoo, P. D. Tatiya, P. P. Mahulikar and V. V. Gite,
smooth morphology of non-biobased microcapsules without Des. Monomers Polym., 2014, 17(2), 111.
any agglomeration in both cases. The synthesized microcap- 15 X. Huangab and B. Voit, Polym. Chem., 2013, 4, 435–443.
sules found good thermal stability, which is necessary for the 16 M. D. Lopez, A. Maudhuit, M. J. Villalobos and D. Ponceleta,
long-term preservation of the core. A process for the micro-
encapsulation of karanja oil as a bio-pesticide by using in situ 17 H. M. Nguyen, H. J. Park, I. C. Hwang and J. W. Park, Pest
polymerization of renewable sources based on cardanol Manage. Sci., 2012, 68, 1062.
formaldehyde and non-biobased phenol–formaldehyde (PF) in 18 L. G. Copping and J. J. Menn, Review biopesticides, a review of
J. Agric. Food Chem., 2012, 60, 1187–1192.
an oil-in-water emulsion has been successfully developed
independently in the present investigation to fulll the
their action, applications and efficacy, An introduction, in the
encyclopedia of agrochemicals, Wiley, New York, 1999.
requirements for controlled-release applications. The release 19 M. Pant, S. Dubey, S. K. Raza and P. K. Patanjali, J. Sci. Ind.
behavior of bio-pesticides is based on loss on drying and, Res., 2012, 71, 348.
subsequently, by UV-conrmed faster release of cores from 20 E. S. Chan, Carbohydr. Polym., 2011, 84, 1267.
non-biobased and the slower release from biobased 21 S. A. Riyajan and J. T. Sakdapipanich, Polym. Bull., 2009, 63,
microcapsules.
Therefore, the current state of the art technology with an 22 T. Szaboa, L. M. Nagyb, J. Bognarb, L. Nyikosa and
interdisciplinary combination of renewable sources based on J. Telegdia, Prog. Org. Coat., 2011, 72, 52.
polymers and agrochemicals, emphasized by the encapsulation 23 A. R. Kulkarni, K. S. Soppimath, T. M. Aminabhavi,
609.
of bio-pesticides like karanja oil for better preservation and an
efficiently controlled release application, has been proven as a
signicant requirement of a cleaner global environment.
A. M. Dave and M. H. Mehta, J. Controlled Release, 2000,
63, 97.
24 Z. Zhu and R. Zhuo, Eur. Polym. J., 2001, 37, 1913.
25 G. Ruan, S. S. Feng and Q. T. Li, J. Controlled Release, 2002,
84, 151.
Acknowledgements
26 A. Knowles, Microencapsulation (CS). New Developments in
Crop Protection Product Formulation, Taylor and Francis
Informa UK, Ltd., New York, 2005, pp. 89–114.
27 A. R. Kulkarni, K. S. Soppimath, T. M. Aminabhavi,
A. M. Dave and M. H. Mehta, J. Appl. Polym. Sci., 1999, 73,
2437.
Authors are thankful to Department of Science and Technology,
Government of India, New Delhi for the sanction of INSPIRE
Research Fellowship.
28 P. D. Taitya, R. K. Hedaoo, P. P. Mahulikar and V. V. Gite,
Ind. Eng. Chem. Res., 2013, 52, 1562.
Notes and references
1 H. P. Bhunia, R. N. Jana, A. Basak, S. Lenka and G. B. Nando, 29 A. V. Bagle, R. S. Jadhav, V. V. Gite, D. G. Hundiwale and
J. Polym. Sci., Part A: Polym. Chem., 1998, 36, 391.
2 S. Cheng, I. Dcruz, Z. Yuan, M. Wang, M. Anderson,
P. P. Mahulikar, Int. J. Polym. Mater. Polym. Biomater.,
2013, 62(8), 421.
M. Leitch and C. Xu, J. Appl. Polym. Sci., 2011, 121, 30 R. K. Hedaoo, P. P. Mahulikar and V. V. Gite, Polym.-Plast.
2743. Technol. Eng., 2013, 52, 243.
3 D. R. Lu, C. M. Xiao and S. J. Xu, eXPRESS Polym. Lett., 2009, 31 S. Ozcan, A. Tor, M. E. Aydin, F. Beduk and I. Akin, React.
3(6), 366.
Funct. Polym., 2012, 72, 451.
4 V. V. Goud, N. C. Pradhan and A. V. Patwardhan, J. Am. Oil 32 I. Poljansek and M. Krajnc, Acta Chim. Slov., 2005, 52, 238.
Chem. Soc., 2006, 83(7), 635.
5 S. Maiti, D. Ray and D. Mitra, J. Polym. Environ., 2012, 20,
33 A. A. Pawar, D. R. Chen and C. Venkataraman, Int. J. Pharm.,
2012, 430, 228.
749.
34 J. M. Park and S. J. Park, Macromol. Res., 2010, 18(12), 1191.
6 J. M. Raquez, M. Deleglise, M. F. Lacrampe and P. Krawczak, 35 R. Wang, H. Li, H. Hu, X. He and W. Liu, J. Appl. Polym. Sci.,
Prog. Polym. Sci., 2010, 35, 487.
2009, 113, 1501.
This journal is © The Royal Society of Chemistry 2014
RSC Adv., 2014, 4, 18637–18644 | 18643

View Article Online
RSC Advances
Paper
36 H. Jin, C. L. Mangun, D. S. Stradley, J. S. Moore, N. R. Sottos 38 P. A. Shenoy, S. S. Khot, M. C. Chavan, J. V. Takawale and
and S. R. White, Polymer, 2012, 53, 581. S. Singh, Int. J. Green Pharm., 2010, 4(4), 270.
37 J. M. Lakkis, Encapsulation and Controlled Release 39 V. K. Gore and P. Satyamoorthy, Anal. Lett., 2000, 33(2),
Technologies in Food Systems, Blackwell Publishing Ltd.,
UK, 2007, pp. 1–11.
337.
18644 | RSC Adv., 2014, 4, 18637–18644
This journal is © The Royal Society of Chemistry 2014