Antibacterial and antioxidant bio-based networks derived from eugenol using photo-activated thiol-ene reaction

Article abstract of DOI:10.1016/j.reactfunctpolym.2016.02.002

Bio-based networks derived from eugenol and linalool were prepared with an eco-friendly process by photoactivated thiol-ene reactions. Allyl derivative Eugenol, AE, prepared by a nucleophilic substitution was combined with linalool, L, a monoterpene prese

Full text of DOI:10.1016/j.reactfunctpolym.2016.02.002

Antibacterial and antioxidant bio-based networks derived from eugenol using
photo-activated thiol-ene reaction
Tina Modjinou, Davy-Louis Versace, Samir Abbad-Andallousi, Noured-
dine Bousserrhine, Pierre Dubot, Vale´rie Langlois, Estelle Renard
PII:
S1381-5148(16)30021-9
DOI:
Reference:
doi: 10.1016/j.reactfunctpolym.2016.02.002
REACT 3630
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Revised date:
Accepted date:
15 July 2015
2 February 2016
2 February 2016
Please cite this article as: Tina Modjinou, Davy-Louis Versace, Samir Abbad-Andallousi,
Noureddine Bousserrhine, Pierre Dubot, Val´erie Langlois, Estelle Renard, Antibacterial
and antioxidant bio-based networks derived from eugenol using photo-activated thiol-ene
reaction, (2016), doi: 10.1016/j.reactfunctpolym.2016.02.002
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ACCEPTED MANUSCRIPT
Antibacterial and Antioxidant bio-based Networks derived from Eugenol
using photo-activated thiol-ene reaction
Tina Modjinou a, Davy-Louis Versace a, Samir Abbad-Andallousi b, Noureddine
Bousserrhineb, Pierre Dubot a, Valérie Langlois a, Estelle Renard a*
a Université Paris Est, ICMPE (UMR7182), CNRS, UPEC, F-94320 Thiais, France
b Université Paris-Est, Institut d’écologie et des sciences de l’environnement de Paris,
Département SoléO, 61 avenue du Général de Gaulle, 94010 Créteil cedex, France
Keywords : eugenol, linalool, thiol-ene, antibacterial network, antioxidant properties
Abstract
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Bio-based networks derived from eugenol and linalool were prepared with an eco-friendly
process by photoactivated thiol-ene reactions. Allyl derivative Eugenol, AE, prepared by a
nucleophilic substitution was combined with linalool, L, a monoterpene presents in the
lavender essential oil, well known to its antibacterial activity or with Eugenol, E, a sustainable
antioxidant molecule major component of the essential oil of clove. The photoactivated thiol-
ene reaction is a quick room temperature straightforward way to obtain renewable crosslinked
networks. Two bacteria strains were used in vitro to evaluate the resistance to bacterial
adhesion and the DPPH method was used to determine the antioxidant properties of the
networks. As expected, the results showed a promising anti-adhesion activity against S.
aureus and E. coli due to the presence of eugenol moieties. Moreover, the phenol groups of
eugenol provide an antioxidant activity characterized by a radical scavenging activity of 90%.
Introduction
Nowadays, industrial chemicals and materials are mainly derived from fossil resources that
are both less available and a a major source of greenhouse gas emissions. The challenges of
reducing the emissions of CO2, and more generally, the impacts on the environment, weigh
more and more in balance of the governments, industries and consumers. The share of
renewable carbon in the products of the chemical industry should raise 15% in 2017 against
7% today [1]. In the same way, American studies estimate that 90% of organic chemical
products will be based on renewable resources by 2090 [2]. Therefore, it is crucial to
propose new renewable resources as an alternative of petrochemical products especially for
the polymer industry. Various monomers derived from bio-sourced materials (starch,
cellulose, vegetal oils…) are already used for the production of polymers [3] but the
monomers obtained by bio-refinery process are only aliphatic or cycloaliphatic componds.
The bio-based aromatic compounds can be extracted from the lignin or tannins but their
industrial valorisation is limited by their structural complexity. Currently, only vanillin is
industrially extracted from the lignin and consequently a variety of high performance resins
[4, 5] and polymers [6, 7] have been recently developed with the derivatives of vanillin. The
essential oils constitute another source of free mono-aromatic compounds having a large
spectrum of chemical structures. Among them, Eugenol extracted from the clove oil is a very
interesting phenolic compound, readily available which can be considered as an inexpensive
functional monomer. The presence of two functional groups, a vinyl and a phenol group,
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allowed the preparation of polyacetylenes [8, 9], aromatic copolyesters [10] and multiblock
copolymers [11]. A variety of eugenol derivatives including the bisphenol [12], bisepoxy [13],
allyl-etherified eugenol [14, 15] or methacrylic derivatives have also been used to prepare
renewable resins [16]. The biological properties of eugenol are used for a long time in
dentistry [17-20] to prepare dental resins. The terpenes are also abundant and inexpensive bio-
based molecules. Several recent publications report the incorporation of essential oils as
additives to prepare active packaging [21-24]. Linalool, L, is an oxygenated terpenoid, that
has very attractive antibacterial properties [25-29].
In this context, we prepared UV-cured networks by using thiol-ene formulation with allyl
eugenol, (AE), Eugenol (E) or Linalool (L) as shown in Scheme 1. To overcome the problem
of the diffusion of antibacterial molecules over time, it is worth considering to covalently link
these molecules to ensure a more sustainable antimicrobial property. The main challenge of
our study is, on the one hand, assuming the preservation of the antibacterial property of the
cross-linked eugenol and, on the other hand, to enhance the activity by using eugenol (E) and
linalool (L). The covalent insertion of eugenol in the network should enhance the antibacterial
and antioxidant properties thanks to the presence of phenol groups. Moreover, the
introduction of an anti-bacterial acyclic monoterpene, linalool, should modulate the
mechanical properties of the material. The thermomechanical properties of these materials
were investigated and the effects of the composition are discussed. Their antioxidant activity
and their action against bacterial adhesion are tested by using against the both pathogenic
mono-species, Staphylococcus aureus and Escherichia coli.
Experimental
Materials
Trimethylolpropane tris(3-mercaptopropionate) ≥ 95% (Trithiol), linalool (L) 97% and
potassium carbonate (K2CO3) 99% were purchased from Aldrich. Eugenol (E) 99% and allyl
bromide 99% stab. with 300-1000 ppm propylene oxide were obtained from Alfa Aesar. 2,2-
dimethoxy-1,2-diphenylethan-1-one (DMPA) was provided by BASF company. N,N-
dimethylformamide anhydrous, methanol and ethyl acetate were purchased from Carlo Erba
Reagents. 2,2-diphenyl-1-picrylhydrazyl (DPPH) and Lysogeny Broth, Miller (LB medium)
were purchased from Aldrich. Other chemicals for this study were analytic reagents obtained
from Aldrich and used without purification.
Instrumentation
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1H NMR (400 MHz) spectra were recorded on a Brucker AV 400M in CDCl3 at 25°C. FT-IR
spectra were recorded on a Brucker Tensor 27 spectrometer with 32 scans equipped with an
ATR apparatus. Measurements were performed on a Horiba Xplora confocal Raman
microscope (Horiba Jobin Yvon) equipped with an external excitation source (638 nm He-Ne
laser). The objective lenses used in the study were 50x long-working distance (Long Working
Distance M Plan Semi-Apochromat, LMPLFL50x, Olympus) and 10x (M Plan Achromat,
MPLN10x, Olympus), operating in air. Spectral acquisition was obtained using LabSpec
software (Horiba Scientific, Edison, New Jersey). Raman spectra were recorded at a
resolution of 1 cm-1 in the range between 4000 and 200 cm-1. Repeated acquisitions using the
highest magnification were accumulated to improve the signal-to-noise ratio. Spectra were
calibrated using the 520.5 cm-1 line of a silicon wafer. Spectral details were as following;
objective: × 50, filter: 100 %, exposition: 10, slit: 50, hole: 500. Spectra were averaged from
two to five accumulations, each with an acquisition time ranging from 15 s to 5 min. The
conditions of measurement were adjusted depending on the type of the matrices to obtain a
good signal-to-noise ratio.
X-ray photoelectron (XPS) measurements were made with a Thermo Scientific K-Alpha
apparatus. Survey scans were done using a monochromatic Mg Kα X-ray source (12 KeV, 2
mA) with a spot diameter of 25 mm2 operated in a low power mode (24 W). A pass energy of
10 eV was used for the detailed XPS scans. XPS spectra were obtained with an energy step of
0.05 eV with a dwell time of 200 ms. Data acquisitions have mainly been focused on the C1s,
O1s core level lines. The spectra obtained were treated by means of the “Avantage” software
provided by ThermoFisher. The C1s and O1s envelopes were analyzed and peak-fitted using
Gaussian line shapes. The binding energy scale was fixed by assigning a binding energy of
284.8 eV to the−CH− carbon (1s) peak.
Water contact measurements were performed with the Drop Shape Analysis system Krûss
Easy DROP Contact Angle measuring system apparatus controlled by the DSA software.
The thermal properties of the networks were measured by Differential Scanning Calorimetry
(DSC). The measurements were conducted on Perkin Elmer Diamond DSC apparatus
according to the following heating programs: heating from −60 to 170°C at 20°C.min-1,
cooling to −60°C at 200°C.min-1 holding at 60°C for 5 min and heating to 170°C at
20°C.min-1 to determine the glass transition temperatures. Thermogravimetric analyses (TGA)
were performed on a Setaram Setsys Evolution 16 apparatus by heating from 20°C to 800°C
at 10°C.min-1 under argon atmosphere. Mechanical properties were conducted at room
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temperature on an Instron 5965 apparatus equipped with a 20mN sensor at a crosshead
displacement rate of 1mm.min-1.
Preparation and characterization of the samples
Synthesis of allyl-eugenol (AE)
Allyl-eugenol was synthesized by the Williamson reaction. Eugenol (2 g, 1.2.10-2 mol) was
dissolved in 20 mL of N,N-dimethylformamide and 2eq of K2CO3 were added. The mixture
was cooled in an ice bath. The solution became yellow and turned green. Allylbromide (2 eq)
were added dropwise by a funnel and the solution was stirred for 72h. Then, a large volume of
water was added and the solution was stirred 30min. Finally, the solution was several
extracted with ethyl acetate and the organic layer was washed with water, then dried under
MgSO4 and concentrated to give the final yellow liquid product with a yield of 90%. The 1H
NMR spectrum (Fig. 1) shows the appearance of new signals at 5.96, 5.39 and 5.26 ppm
characteristic of unsaturated allyl groups derived from etherification reaction of eugenol
which confirms the success of the reaction. The etherification reaction was quantitative as
indicated by the ratios of both alkene groups.
Allyl-eugenol/eugenol networks preparation, AE/E networks
As an example, the synthesis of 70-30 (w/w%) AE/E network (1eq SH/C=C) is described
here. E (84µL, 90 mg, 4.4.10-4 mol) and DMPA (3% w/w) were dissolved in AE (210 mg,
1.3.10-3 mol). Trithiol (429 mg, 1.1.10-3 mol, 1eq. SH/C=C) were added to the solution. The
formulation was poured into a silicone mould (1.8 x 4 cm) and heated at 60°C during at least
1h then irradiated 5 min at room temperature by Lightning LC8 (L8251) from Hamamatsu
equipped with a mercury-xenon lamp (200W) coupled with a flexible light guide. The end of
the guide was placed at 11cm of the sample to give the transparent and flexible resulted
material. The maximum UV light intensity at the sample position was measured by
radiometry (International Light Technologies ILT 393) to be 180 mW.cm-2 in the 250-450
nm. The extent of conversion was measured via FT-Raman spectroscopy from the band 2600
cm-1 corresponding to the SH bonds after the normalization of the spectrum to the ester
carbonyl peak at 1735 cm-1. The relative conversion
was calculated according to the
following equation:
(eq. 1)
= ʠꢀ ͯꢀ ʡ × 100
ꢀ
t
t
ħ
ꢁ
ꢁ
Čā
Čā
With ͌ =
ͤ
, before irradiation and ͌ =
/
, after irradiation
ꢁ
ꢁ
ü€Ĉ
ü€Ĉ
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Water uptake determination
Prior to the water uptake measurements, the samples were dried under vacuum. They were
placed in a conditioning closed chamber over a saturated solution of NaCl to obtain a water
saturated atmosphere of 75% at room temperature. The percentage uptake of moisture into the
material was measured by a coulometric method at t = 0 s and after 18 h. The 831 K F
Coulometer Metrohm was equipped with a 728 Stirrer and an 860 KF Thermoprep Metrohom.
Soluble extract determination
The samples were treated with 10 mL of diethyl ether stirred in a flask during 3h at room
temperature. The remaining residue and the film were weighted after the solvent evaporation
under vacuum.
Real Time Fourier Spectroscopy kinetics of allyl eugenol AE conversion in network
formed by photochemistry
Kinetics of the photo-addition reactions were followed by Real-Time Fourier Transform Infra
Red Spectroscopy (RT-FTIR) using a Thermo-Nicolet 6700 instrument and a 80µL of a liquid
mixture composed of AE, L or E and trithiol. The photoinitiator (DMPA) was dissolved to a
3% w/w dilution. This sample was applied to a BaF2 chip by a calibrated wire-wound
applicator. The thickness of the UV curable film was evaluated at 4 µm. The RT-FTIR
analyses were carried out under laminated conditions: a polypropylene film was deposed on
the top of the photosensitive layer to prevent oxygen diffusion. Samples were simultaneously
exposed for a few seconds to both the UV beam, which starts the photoreaction, and the IR
beam which analyzes the extent of the photoreaction in situ. The mixture was irradiated at
room temperature with the Hamamatsu lightening cure LC8 (L8251), equipped with a
Mercury-Xenon lamp (200 W) coupled with a flexible light guide. The end of the guide was
placed at a distance of 11 cm of the sample’s surface. The light intensity on the surface of the
sample was about 180 mW. cm-². The thiol-ene photo-addition was monitored by the
disappearance of the C=C bonds of (AE) at 1647 cm-1 and of the SH bonds of the trithiol at
2560 cm-1.
Bacterial adhesion
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The anti-adherence activity of the networks was evaluated using two pathogenic bacterial
strains: Staphylococcus aureus ATCC6538 (Gram- positive) and Escherichia coli
ATCC25922 (Gram- negative) which were grown aerobically at 37°C overnight on LB
medium before the bacterial adhesion tests. The samples of AE-based networks were
immersed 1h at 37°C and stirred in the bacterial suspension of the two different strains
(OD600nm = 0.05). The non-adherent bacteria were then removed from the network surface by
several washes with a physiological saline buffer. The networks were then submitted to vortex
and ultrasounds in a minimum volume of saline buffer to unhook fasten bacteria. Finally, 100
µL of this resulting viable bacteria suspension were inoculated onto the surface of a PCA agar
(Plate Count Agar) Petri dish. After 24h of incubation at 37°C in aerobic conditions, the
antibacterial activity was measured by counting the overall number of bacteria (CFU-Colony
Forming Units) for the different strains. Each experiment was performed in six replicates.
The software R was used to analyse the data. At least, six replicates of the experiments were
conducted in order to allow a significant statistical analysis. The ANalysis Of the VAriance
(ANOVA) statistical test was used and significant differences (p <0.05) among antibacterial
properties of the networks were detected thanks to the multiple range test of Duncan.
Antioxidant Activity
The antioxidant activity of the networks was determined according to the DPPH (2,2-
diphenyl-1-picrylhydrazyl) method [22, 30-32]. About 100mg of the network were immersed
in 4mL of 0.1mM DPPH solution (in methanol). This solution was then left in the dark for
60min at room temperature. The radical scavenging activity was measured by using a Varian
Cary 50 Bio UV-Visible spectrophotometer controlled by the CaryWinUV software. The
DPPH solution is well known to have a maximum of absorption at 517nm. The antioxidant
activity was therefore determined by monitoring the decrease of the absorbance at this
wavelength. The radical scavenging activity was calculated according to the following
equation:
Aref-As
ʚ ʛ
͕͕͌͗͘͝͠ ͕͙ͧ͗ͪ͛͛͢͢͝ ͕͗ͨͪͨͭ͝͝ % = ʠ
(eq. 2)
ʡ × 100
Aref
where Aref corresponds to the absorbance of the 0.1mM DPPH solution without network and
As corresponds to the absorbance of the 0.1mM solution of DPPH with the network at 517nm.
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Results and discussion
Preparation of networks
This study entails the design of photoinduced thiol-ene networks based on allyl-eugenol (AE),
eugenol (E) or linalool (L) in presence of DMPA (Scheme 1). The first step consisted in the
synthesis of allyl eugenol (AE) by reaction of eugenol with allyl bromide. The eugenol
networks were prepared by thiol-ene reaction of unsaturated AE with the trithiol in presence
of DMPA as photoinitiator under UV irradiation. This procedure is an easy synthetic
methodology for the preparation of networks with variable properties as it was previously
described [33]. For this study, materials containing different percentage of AE, from 50 to
100%, were prepared. For all compositions studied, the initial stoichiometry C=C/SH was
maintained to 1/1. Figure 2 shows the FT-IR spectra of the mixture E, AE and AE/E (70/30)
before irradiation. The stretching band of C=C groups for both AE and E appears at 1647 cm-
1 and the absorption of the SH groups is identified at 2560 cm-1. The success of the reaction
was confirmed by the decrease of the SH bond after irradiation. The kinetics profiles of the
disappearance of the SH functions was determined (Fig. 3). After 50s of irradiation, high
conversion(80-85%) of SH were obtained, confirming the efficacy and the high speed of the
reaction. Raman spectroscopy has been also used to follow the cross-linking process of the
different compositions. Figure 4 shows a characteristic peak at 1700 cm-1 for the carbonyl
group and a strong characteristic peak at 2570 cm-1 . The conversion is determined by
comparison of the intensities of these bonds. Different samples were prepared by varying the
percentage of linalool from 0 to 100%.
In the case of the monofunctional eugenol, only 30% can be added since higher amounts led
to a insufficient crosslinking . Nevertheless, the content of linalool can reach 50% thanks to
the presence of the two double bonds able to react by thiol-ene reaction. As reported in Table
1, the conversion of SH group, determined by Raman spectroscopy was higher than 90 % in
comparison with the one measured in laminated conditions by FTIR (80-85%). This
difference can be explained by the difficulty to monitoring the SH band by Real-Time FTIR
due to the weakness of the SH band. However, despite the stoichiometry, a total conversion
was not achieved. By contrast, the study of the soluble extract (< 5%) highlighted a high
cross-linking density. The non-quantitative conversion may due to the decrease of the
molecules mobility at high conversion that diminishes the access to reactive groups.
Characterization of the networks
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As expected, the water contact angle diminishes from 73° to 62° with the decrease of the
aromatic moieties amount from 100% to 50% (Table 2). To investigate the presence of
functional groups to the surface of the networks, XPS analyses were performed. The
deconvolution of the C1s band (Fig.5) reveals that AE/L (70/30 and 50/50) and AE/E (70/30)
are composed of five peaks. Table 3 presents the values of binding energy and the relevant
content of the functional groups. Based on the value of binding energy, the peaks at 284.3,
284.8, 285.7, 286.4 and 289.2 eV are attributed to C-C aromatic (A), C-C/C-H aliphatic (B),
C-OH phenolic and aromatic ether (C), C-OH and aliphatic ether (D), and C=O (E)
respectively. The assignments are in agreement with the literature [34-37] and the C-S peak
cannot be distinct in the spectra due to the overlap by the C-C peak [38]. For 100% AE, an
additional peak appears corresponding to the π-π* transitions of the aromatic carbon at 289.5
eV (F). As reported in the Table 3, the intensities of the peaks C and D corresponding to both
C-O (aromatic and aliphatic) are higher for AE network than those obtained in the case of the
AE/E (70/30) network. This is in line with the chemical structure of AE that contains two
types of Caromatic-O-Caliphatic bonds. The C1s peaks of AE/L are quite similar to those of the
AE/E, but the ratio D/C in AE/L networks is higher than those obtained in the AE/E material.
This ratio increases slightly with the linalool content suggesting that the hydroxyl groups from
linalool are located at the surface. In the same way, for an equal proportion of eugenol
(Fig.5b-5c) the peak C is higher for the AE/E network in comparison with the AE/L meaning
that phenol groups are present at the surface. They should play a valuable role in the
biological properties.
Furthermore, the water sensitivity of the networks was investigated by measuring the amount
of water taken up by conventional Karl Fisher titration. The water uptakes remained lower
than 5% after 18h of exposition to an atmosphere containing 75% of relative humidity
indicating that the samples were not sensitive to water. These results can be explained by the
presence of aromatic moieties coming from the eugenol. Thus, the mechanical integrity will
be preserved after being exposed to an aqueous medium and no degradation reactions will be
occurred.
Mechanical and thermal properties were investigated and reported in Table 2. The formation
of flexible thioether linkages induces low glass transition temperatures (< 0°C) as reported
previously [39-41]. The Tg values do not vary significantly with the composition of the
networks suggesting that the cross-linking density is similar. Thermal degradation was
determined by TGA by considering the temperature corresponding to 5% of mass loss. The
thermal degradation temperatures of AE/L and AE/E networks were between those of linalool
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and AE networks. The presence of AE aromatic units increases the thermal stability. The
determination of the Young’s modulus (E), the strain (ε) and the tensile stress (σ ) were
r
performed. The mechanical results obtained from stress-strain curves are listed in Table 2 and
presented in Figure 6. Similar trends were observed in the strain and the tensile stress values
of the materials, reflecting the relation between the presence of the linear soft linalool units
and the crosslink density. The introduction of the monofunctional eugenol in the formulation
leads to a reduction in the mechanical properties due to a decrease of crosslinking density.
Anti-adhesion activity
The anti-adhesion properties of the networks were studied with the two strains of bacteria
after 1h of incubation in the bacterial suspension. Figure 7 shows the number of adhered
bacteria (CFU/cm2) calculated by the ANOVA and StatAdvisor post-tests. The bacterial
adhesion depends on the strains of the bacteria. The CFU/cm2 values of S. aureus were
systematically lower than those obtained with E.coli. These results indicate that the systems
based on AE alone or associated with eugenol or linalool present intrinsic antibacterial
properties. Indeed, the adhesion is lower in presence of eugenol derivatives, indicating that
the presence of the aromatic moieties induces an increase of the antibacterial efficiency. It
can be assumed that the decreasing of the bacterial adhesion can be related to the higher
hydrophobicity of the AE networks. The presence of linalool led to a lower efficiency towards
the bacteria adherence. Presumably, these results are partly linked to the presence of the
aromatic derivatives and are independent of the hydroxyl amounts. S. aureus exhibits a
preference for the attachment on hydrophobic surfaces [42, 43] and, the anti-adherence
activity showed here can be explained by the presence of the aromatic moieties of the
eugenol. Furthermore, the phenol group in the AE/E 70/30 networks showed an improved
anti-adhesive property as it was reported in the case of free eugenol [44, 45]. The presence of
30 wt % of eugenol in the AE networks decreased the CFU cm-2 values of 57% for S. aureus
strains. There was no statistically significant difference for E.coli according to the ANOVA
statistical test. The AE networks exhibit a promising anti-adhesive property which was not
significantly improved by introducing 30 wt % of eugenol (Fig.7).
Antioxidant activity
DPPH is a free radical widely used to determine the antioxidant activity of molecules [22, 30,
31, 46, 47]. Indeed, when this radical having a maximum of absorption at 517 nm, reacts with
an hydrogen donor such as antioxidant, the absorbance decreases [48] and consequently there
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is a discoloration of the solution from purple to pale yellow. The results of the antioxidant
activity of the networks are shown in Figure 8. An increase in the presence of phenol groups
in the networks led to an increase of the activity from 23% to 90% for the AE and AE/E
(70/30) networks respectively. These results confirmed by the discoloration of the DPPH
solution show the importance of the presence of phenol group for keeping an antioxidant
activity.
Conclusions
The powerful and green process of thiol-ene addition was used to design solvent-free bio-
based networks from eugenol and linalool. The transparent networks from sustainable
compounds were successfully synthesized. The photoinitiated thiol-ene addition of allyl-
eugenol AE and linalool L or eugenol E is a straightforward and efficient route to design
renewable networks with a high crosslinking density. Moreover, the anti-bacterial properties
against S.aureus and E. coli were particularly significant for the AE/E (70/30) network. The
presence of 30 % of native eugenol with free phenol moieties promotes the anti-adhesion
activity and leads to anti-oxidant properties. Finally, the new bio-based materials are not
affected by water penetration under high moisture conditions. Eugenol represents a very
promising compound for the elaboration of new bio-based networks. The intrinsic
antibacterial and antioxidant properties of this compound could be very interesting in many
fields such as food packaging.
AUTHOR INFORMATION
Corresponding Author
* Phone: 33 (0)1 49 78 12 17. E-mail: renard@icmpe.cnrs.fr.
Acknowledgment
We would like to thanks CNRS and UPEC for financial support. The authors thank the French
Ministry of Research for providing Tina Modjinou with a grant.
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Scheme 1. Synthesis of the allyl-eugenol AE and the formation of the allyl-
eugenol /eugenol AE/E or allyl-eugenol /linalool AE/L networks by thiol-ene
reaction.
O
HO
(E)
Eugenol
DMF anhydrous
K2CO3
Br
O
O
Allyl-eugenol (AE)
O
O
O
HS
HS
O
O
O
SH
OH
CH3
or
O
OH
Eugenol
Trimethylolpropane tris(3-mercaptopropionate)
Linalool
Trithiol
L
E
DMPA,
ν
h
S
S
S
E or L
S
R
S
R
AE
S
AE
R
S
S
S
R
S
S
S
S
S
S
AE
R
S
R
S
S
S
E or L
E or L
S
S
R
AE
S
R
S
S
S
S
AE
S
R
AE
E or L
AE/E or AE/L networks
14

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Figure 1. 1H NMR spectrum of allyl-eugenol AE in CDCl3.
d
Ha2
Ha1
H5
H6Hb
Hb'
O
c
c'
H2
O
Ha'2
CH
Ha'1
2, 5,6
d 3
c
a1, a2
a’1, a’2
c’
b’
Chemicalshift (ppm)
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Figure 2. FTIR spectra of allyl-eugenol AE, linalool L and allyl-
eugenol/linalool AE/L (70/30) in presence of trithiol before irradiation.
C=C
AE
E
-
S-H
AE/E with trithiol
0
500 1000 1500 2000 2500 3000 3500 4000 4500
Wavenumber (cm-1)
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Figure 3. Real -time FTIR kinetic profiles of the formation of allyl-eugenol AE
networks with trithiol in presence of DMPA in laminated conditions Xe-Hg
lamp.
100
80
60
40
20
0
C=C
SH
C=C
SH
0
50
100
150
200
250
300
Irradiation time (s)
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Figure 4. RAMAN spectra of AE/L (70/30) (a) before and (b) after 300s of
irradiation.
14000
12000
10000
(a)
8000
-SH
(b)
6000
4000
2000
0
C=C
C=O
-2000
0
500 1000 1500 2000 2500 3000 3500 4000
Raman shifts (cm-1)
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Figure 5. XPS spectra of (a) allyl-eugenol AE (100%), (b) allyl-
eugenol/eugenol AE/E (70/30), (c) allyl-eugenol/linalool AE /L (70/30) and (d)
allyl-eugenol/linalool AE /L (50/50) networks.
30000
a
30000
25000
20000
15000
10000
5000
0
c
25000
20000
15000
10000
5000
0
B
D
C
B
F
D
E
A
E
C
A
292 290 288 286 284 282 280
290
285
Binding Energy (eV)
Binding Energy (eV)
30000
25000
20000
15000
10000
5000
0
d
b
40000
30000
20000
10000
0
B
B
C
A
D
E
D
E
C
A
292
290
288
286
284
282
292
290
288
286
284
282
Binding Energy (eV)
Binding Energy (eV)
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Figure 6. Tensile tests of (a) allyl-eugenol AE (100%) (b) allyl-eugenol/linalool
AE/L (70/30) (c) allyl-eugenol/linalool AE/L (50/50) and (d) allyl-
eugenol/eugenol AE/E (70/30) networks.
(a)
2,0
1,5
(b)
(c)
1,0
(d)
0,5
0,0
0
50
100
150
ε
(%)
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Figure 7. Antibacterial tests of allyl-eugenol/eugenol AE/E and allyl-
eugenol/linalool AE/L networks.
* * *
* *
16000
* * *
14000
* * *
4000
12000
3500
* *
10000
3000
* *
2500
2000
1500
1000
500
8000
6000
4000
2000
0
* *
*
0
AE (100%)
AE/E (70/30)
AE/L (70/30)
AE/L (50/50)
AE (100%)
AE/E (70/30)
AE/L (70/30)
AE/L (50/50)
S.aureus
E.coli
* Are statistically different with p < 0.05
* * Are statistically different with p < 0.01
* * * Are statistically different with p < 0.001
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Figure 8. Antioxidant activity of the networks.
100
90
80
70
60
50
40
30
20
10
0
(a) (b) (c) (d)
AE (100%)
AE/L (70/30)
AE/L (50/50)
AE/E (70/30)
(a)
(b)
(c)
(d)
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Table 1. Characteristics of allyl-eugenol/eugenol AE/E or allyl-eugenol/linalool
AE/L networks .
Composition
AE/L (100/0)
AE/L (70/30)
AE/E (70/30)
AE/L (50/50)
(w/w%)
Thickness
(mm)
0.25 ± 0.01
0.43 ± 0.01
0.24 ± 0.03
0.34 ± 0.03
SH Conversiona)
95
92
1
93
3
92
3
(%)
Soluble extractb)
3
(%)
a)
Determined by Raman
b)
Determined by gravimetric analysis
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Table 2.Characterization of AE-E or AE-L networks .
Water up
takee)
(%)
b)
d)
d)
γc)
σR
εR
Composition
(w/w%)
Tga)
(°C)
T5%
Ed)
(°C)
323
301
271
305
(MPa)°
(°)
(MPa)
(%)
AE/E
(100/0)
AE/L
-1
-5
73
70
62
83
5.1 ± 0.4
3.7 ±0.3
3.1 ± 0.2
2.1 ± 0.1
48 ± 4
0.2
0.4
0.5
0.3
2.7 ± 0.3
2.3 ±0.1
50 ± 6
50 ± 3
(70/30)
AE/L
-5
-4
(50/50)
AE/E
1.1 ± 0.1 0.7 ± 0.02 92 ± 10
(70/30)
a)
Determined by DSC
b)
c)
T5% : temperature of 5% weight loss of the networks determined by TGA
Determined by water contact measurements
d)
e)
Determined by tensile measurements
Determined by coulometry after 18h of exposure to water saturated air
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Table 3. C1s peaks assignments and surface concentration of C1s peaks fitting
(at. %)
Peak
A
B
C
D
E
F
C-O/C-OH C-O/C-OH
C=C
C-C/C-H
C=O
π-π*
Composition
aromatic
285.7 eV
23.1
aliphatic
286.4 eV
29.1
284.2 eV 284.8 eV
288.5 eV
289.3 eV
AE/E (100/0)
AE/E (70/30)
AE/L (70/30)
AE/L (50/50)
8.6
17.1
5.4
24.7
46.5
60.7
58.5
5.8
7.6
9.4
9.4
8.6
16.2
12.6
9.9
14.5
6.2
9.6
16.2
25