Sustainable bisphenols from renewable softwood lignin feedstock for polycarbonates and cyanate ester resins

Article abstract of DOI:10.1039/c7gc00776k

The selective reductive catalytic depolymerisation of softwood lignin (e.g. pine, spruce) yields predominantly 4-n-propylguaiacol (4PG; 15-20 wt% on lignin basis), an interesting platform chemical for bio-based chemistry. This contribution specifically shows promising technical, sustainable and environmental advantages of such a bio-phenol for various polymer applications. The bisphenolic polymer precursor, 5,5′-methylenebis(4-n-propylguaiacol) (m,m′-BGF-4P), was therefore first synthesized by acid-catalysed condensation, and its synthesis and isolation are compared with shorter chain analogs, viz. 4-methyl- and 4-ethylguaiacol. A thorough GC-GPC/SEC analysis of the crude condensation mixture was developed to assess the purity of the isolated dimers. Isolation is done by a single-step crystallization, yielding 57 wt% of m,m′-BGF-4P in >99% purity. This pure m,m′-BGF-4P bisphenol displays a notably reduced potency to activate human estrogen receptor alpha (hERα; EC₅₀ at 10^-5 M) in comparison with commercial bisphenols, and is therefore useful for future polymer applications. As a proof of concept, polycarbonates and cyanate ester resins were prepared from m,m′-BGF-4P and compared to other bisphenols. The polycarbonate had M_n = 5182 g mol^-1, T_g = 99 °C, T_m = 213 °C, T_d,5% = 360 °C, and displayed improved processability in common solvents, as opposed to the methylated and ethylated bisguaiacols. A fully cured resin disk exhibited a T_g = 193 °C, T_d,5% = 389 °C and a water uptake of only 1.18% after being immersed in 85 °C water for four days. These results underscore the potential of the intrinsic functionality of lignin-derived building blocks to transcend the scope of renewability.

Full text of DOI:10.1039/c7gc00776k

View Article Online
View Journal
Green
Chemistry
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: S. Koelewijn, S.
Van den Bosch, T. Renders, W. Schutyser, B. Lagrain, M. Smet, J. Thomas, W. Dehaen, P. Van Puyvelde, H.
Witters and B. F. Sels, Green Chem., 2017, DOI: 10.1039/C7GC00776K.
This is an Accepted Manuscript, which has been through the
Volume 18 Number
7 7 April 2016 Pages 1821–2242
Royal Society of Chemistry peer review process and has been
accepted for publication.
Green
Chemistry
Accepted Manuscripts are published online shortly after
Cutting-edge research for a greener sustainable future
www.rsc.org/greenchem
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1463-9262
CRITICAL REVIEW
G. Chatel et al.
Heterogeneous catalytic oxidation for lignin valorization into valuable
chemicals: what results? What limitations? What trends?
rsc.li/green-chem

Please do not adjust margins
Green Chemistry
Page 1 of 11
View Article Online
DOI: 10.1039/C7GC00776K
Green Chemistry
Full Paper
Sustainable bisphenols from renewable softwood lignin feedstock
for polycarbonates and cyanate ester resins
S.-F. Koelewijn,a S. Van den Bosch,a T. Renders,a W. Schutyser,a B. Lagrain,a M. Smet,b J. Thomas,c
W. Dehaen,c P. Van Puyvelde,d H. Witterse and B.F. Selsa*
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
Selective reductive catalytic depolymerisation of softwood lignin (e.g. pine, spruce) yields predominantly 4-n-
propylguaiacol (4PG; 15-20 wt% on lignin basis), an interesting platform chemical for bio-based chemistry. This
contribution specifically shows promising technical, sustainable and environmental advantages of such bio-phenol for
various polymer applications. The bisphenolic polymer precursor, 5,5’-methylenebis(4-n-propylguaiacol) (m,m’-BGF-4P),
was therefore first synthesized by acid-catalysed condensation, and its synthesis and isolation are compared with shorter
chain analogs, viz. 4-methyl- and 4-ethylguaiacol. A thorough GC-GPC/SEC analysis of the crude condensation mixture was
developed to assess the purity of the isolated dimers. Isolation is done by a single-step crystallization, yielding 57 wt% of
m,m’-BGF-4P in >99% purity. This pure m,m’-BGF-4P bisphenol displays a notably reduced potency to activate human
estrogen receptor alpha (hERα; EC50 at 10-5 M) in comparison to commercial bisphenols, and is therefore useful for future
polymer applications. As proof of concept, polycarbonates and cyanate ester resins were prepared from m,m’-BGF-4P and
www.rsc.org/
o
o
o
compared to other bisphenols. The polycarbonate had Mn = 5 182 g.mol-1, Tg = 99 C, Tm = 213 C, Td,5% = 360 C, and
displayed improved processability in common solvents, as opposed to the methylated and ethylated bisguaiacols. A fully
o
o
o
cured resin disk exhibited a Tg = 193 C, Td,5% = 389 C and a water uptake of only 1.18% after being immersed in 85 C
water for four days. These results underscore the potential of the intrinsic functionality of lignin-derived building blocks to
transcend
the
scope
of
renewability.
with carbonate salts12) to close the loop towards the original
monomeric constituents,13 ideally, without considerable losses
of carbon. Thermoset recyclability proves to be more
challenging, but promising strategies (e.g. acid/base-digestion
or pyrolytic recycling) are being established.14-17
Introduction
The transition from a linear to a circular (bio)economy will
reduce demands on finite raw materials and input of
lignocellulosic feedstock in future bio-refineries, by minimizing
waste and closing loops in industrial ecosystems.1,2 As a
consequence, future thermoplastic polymers and thermosets
are preferably bio-renewable and recyclable.3,4 This implies a
pivotal role for poly(ester)s and poly(carbonate)s, such as
Some industrially relevant and chemically recyclable polymers,
such as bisphenol A (BPA)-based polycarbonates and epoxy
resins, currently lack the perspective of bio-renewability.
Poly(BPA carbonate), together with the market for phenolic
resins, currently accounts for >77% of the global phenol
demand,18 and is still dependent on traditional cumene-based
technology, which relies on volatile benzene markets. Hence,
literature has proposed several approaches for benzene-free
synthesis of bio-phenol from renewable resources, like
glucose,19 shikimic acid20 and in particular lignin.21-23
poly(butylene
succinate),4
poly(hydroxyalkanoates),4
furanoate),7
poly(lactic
acid),5,6
poly(ethylene
poly(dihydroferulic acid)8 and poly(limonene carbonate).9 Ester
and carbonate linkages are prone to undergo controlled
depolymerization (e.g. via solvolysis10,11 or by decarboxylation
Bio-phenol synthesis from lignin, the world’s largest source of
renewable phenolics (ca. 40 wt% benzene units),24 remains a
foremost challenge. Several pathways to depolymerise lignin
streams have been reported.25-30 A very appealing lignin-first
biorefinery concept, simultaneously extracts and disassembles
the protolignin from the lignocellulosic matrix, followed by
oxidative,31-33 redox-neutral34,35 or reductive36-50 stabilization.
While many state-of-the-art depolymerization strategies
produce a wide variety of products, with a phenol yield limited
to ca. 5%, the lignin-first process converts respectively about
20% and 50% of the softwood and hardwood protolignin -
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 2 of 11
View Article Online
DOI: 10.1039/C7GC00776K
ARTICLE
Journal Name
values close to the theoretical maximum - into a handful of and 4-methylguaiacol were tested in parallel to provide
methoxylated alkylphenols. This allows substantial higher valuable structure-property relationships (Scheme 1).
yields of bio-phenol upon catalytic demethoxylation and
dealkylation compared to the state-of-the-art single-step
processes.51
Results and discussion
Alternatively, the direct use of these methoxylated
alkylphenols to design novel BPA monomers could not only
lead to bio-renewable and recyclable polymers, but perhaps
also to environmentally safer bisphenols.52-57 BPA, one of the
highest-volume chemicals produced worldwide, with an
annual production of 5.4 Mt in 2015 and a forecast to reach
7.3 Mt by 2020, has come under close scrutiny when evidence
for environmental leaching was found in 1993.58,59 BPA
leaching, together with its (long-known) ability to replace
natural estrogen, potentially links BPA to health issues upon
exposure during critical developmental phases (e.g. puberty,
pregnancy). Public awareness, and the negative connotation
associated with BPA, now demands a shift towards safer
alternatives. Surprisingly, the presence of methoxy
functionalities in ortho position relative to the phenolic OH-
group in BPA strongly abates or even abolishes the ability to
bind and/or activate estrogen receptors in both
alkylphenols,60-62 bisphenols63-65 and estradiols.66 Interestingly,
the lignin-first-derived methoxylated alkylphenols naturally
possess such a favourable design.
Bisphenol synthesis and in-depth product analysis
To synthesize the bisphenol, 4PG and formaldehyde (i.e. 37
wt% solution in water) were stoichiometrically reacted in a
biphasic system in the presence of aqueous hydrochloric acid.
Our group very recently demonstrated that also
heterogeneous Brønsted acidic zeolites are able to selectively
catalyze this reaction.70 An in-depth product analysis was
performed on the crude condensation mixture after
decantation of the aqueous phase. A thorough analysis of this
organic phase was acquired by GC and complemented by
GPC/SEC analysis (see Experimental). Higher condensation
products (such as trimers and tetramers) are further denoted
as oligomers, and their yield is calculated from the mass
balance (Table 1). Six hours of reaction yields 81 and 13 wt% of
total di- and oligomers respectively, at 94% conversion.
Besides m,m’-methylenebis(4-n-propylguaiacol) (m,m’-BGF-4P;
69 wt%), the dimer fraction also comprises o,m’- (12 wt%) and
o,o’-isomers (<1 wt%) as confirmed by GC-MS analysis (Fig. S3,
see ESI†). The selectivity towards the desired m,m’-isomer,
expressed as the ratio of m,m’-isomers to the total dimers,
equals 85% for 4PG.
Furthermore, polymer chemistry typically requires highly pure
monomers with the degree of purity depending on the type of
polymer. For example, the synthesis of thermoplastic poly(BPA
carbonate) necessitates a purity of >99% (for the p,p’-isomer),
To evaluate the steric (and electronic) effect of the alkyl chain
length, 4-ethyl- (4EG) and 4-methylguaiacol (4MG) were
reacted under similar conditions. On the one hand, shorter 4-
alkyl chains result in less ortho-coupled dimers (i.e. o,m’- and
o,o’-isomers; 6-10 wt%) and therefore a somewhat higher
m,m’-selectivity (88-93%). On the other hand, shorter alkyl
chains limit the total dimer yield (to ca. 81-83%) due to a
higher tendency to form oligomers. Overall, even though the
propyl chain displays higher steric hindrance, high m,m’-yields
(69-75%) are obtained in all cases. As a measure of process
efficiency, the total organic phase recovery is also reported in
Table 1. This recovery is excellent (≥98%) thanks to a high
hydrophobicity in both substrate and product.71
while for BPA-based epoxy resins
a purity of >95% is
sufficient.67,68 As polycarbonate and epoxy resins production
accounts for nearly 95% of the global BPA usages, the
synthesis and high-purity isolation of bio-renewable and
environmental benign bisphenols, which remain functional,69 is
imperative.
Herein, we disclose a bio-derived bisphenol with substantially
(ca. 10-100 times) lower estrogenic potency, that is
synthesized from 4-n-propylguaiacol (4PG), a methoxylated
alkylphenol resulting from the lignin-first process (in about 15-
20 wt% yield based on total lignin, see Table S1 in ESI†), and
can be isolated in polymer-grade purity (>99%). Finally, the
synthesis and characterization of both thermoplastic
polycarbonates and cyanate ester thermosets are performed.
In all aspects, 4-ethyl-
Both chemo- and regioselectivity are directed by the (o-
methoxy) substitution in the substrate, as illustrated by
comparison of GC and GPC/SEC data for 4-n-propylphenol
(4PP)
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 3 of 11
View Article Online
DOI: 10.1039/C7GC00776K
Green Chemistry
Full Paper
Scheme 1. Synthesis, purification and estrogenic activity testing of m,m’-bis(4-n-propylguaiacol) and its potential as precursor to thermoplastic polycarbonates and
cyanate
esters
thermosetting
resins.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 4 of 11
View Article Online
DOI: 10.1039/C7GC00776K
ARTICLE
Journal Name
Table 1. Composition of the organic product phase after biphasic reaction in aqueous acidic medium as quantified by GC-FID.a
t
[h]
6
Recoveryb
[wt%]
>99
Conversionc
Yield dimersd [wt%]
o,m’-isomer m,m'-isomer
Yield oligomerse
Selectivityf
Monomeric
Substrate
[%]
94
o,o'-isomer
total
81
[wt%]
13
m,m’ [%]
4-n-propylguaiacol
4-ethylguaiacol
4-methylguaiacol
<1
-
12
10
6
69 (57)
73 (69)
75 (72)
85
88
93
6
99
97
83
14
4
98
>99
-
81
19
a reaction conditions: 18 mmol formaldehyde (37 wt% in H2O), 36 mmol 4-alkylphenol, 50 mL 2.5 M HClaq, 100oC, 1000 rpm. All experiments were performed in duplicate and average values are
b
shown. For photographs of the general lab-scale set-up (Fig. S1) and the reacꢀon mixture before and aꢁer reacꢀon (Fig. S2) see ESI†. calculated as wt% of theoretical organic phase at full
dimer yield. c assuming complete insolubility of monomeric substrate in aqueous phase. d definition of x,x’-coupling as illustrated in Fig. 1C; values in parentheses are isolated yields. e calculated
from closing the mass balances, qualitative confirmation by GPC/SEC. f defined as percentage m,m’-isomer in total dimer fraction.
hydroxy group) in acidic medium (C). For abbreviaꢀons and condiꢀons: see ESI†.
Standards (P, G and BPF) are not present in GPC/SEC trace.
and 4PG (Fig. 1). Unsubstituted alkylphenols, such as p-cresol,
are typically used to produce novolac-type resins consisting of
m,m’-dimer in very high purity (>99%). A facile one-step
oligomeric species (up to 10-20 phenolic units). This
crystallization is achieved by solubilisation of the raw (mono-,
chemoselectivity also applies to 4PP (tested as reference);
di- and oligomer-containing) organic phase in either acetone-
under stoichiometric conditions formation of oligomeric
heptane or diethyl ether-heptane, followed by gradual
species is still substantial (up to 6-7 phenolic units; Fig. 1A and
evaporation, without prior fractionation by extraction or
1B red). However, for guaiacyl analogs, dimer formation clearly
column chromatography (see ESI†). In contrast, classic
predominates and oligomer formation is limited (up to 4
precipitation yields no crystals (in the case of propyl chains) or
phenolic units; Fig. 1A and 1B blue). The shift in regioselectivity
impure microcrystals.55 These contain residual isomeric and
(from ortho to meta coupling) is clarified in Fig. 1A and 1C. For
oligomeric impurities, which are poorly detected by NMR due
4PP, the electrons donated by the hydroxy group only direct
to structural similarity, but are clearly detectable by GPC/SEC,
coupling in ortho position, resulting in undesirable o,o’-
TGA and melting point determination by DSC (Fig. S4, ESI†).
bisphenols. Unlike para-alkylated phenols, the donating effect
Selective one-step crystallization of m,m’-bisguaiacols yields
of the o-methoxy group in 4-alkylguaiacols strongly reduces
large faceted crystals (Fig. 2) in 57-72 wt% (values in
the ortho-directing effect of the hydroxyl functionality,
parenthesis, Table 1). The larger discrepancy between GC and
preferably steering towards coupling at the meta position. The
isolated yield for the propyl derivatives results from their
presence of minor quantities of o,m’-isomers is presumably
higher solubility in the crystallization medium. The molecular
governed by the bulkiness of the 4-alkyl chain. In conclusion,
structure of these m,m’-bisguaiacols was unambiguously
the intrinsic lignin-functionalities selectively steer towards (i)
1
1
confirmed by MS, FT-IR and liquid-state H, 13C and 2D H-13C
HMBC NMR spectroscopy (Fig. S3, S5-8, ESI†). 1H and 13C NMR
data of the asymmetric o,m’-isomers is provided as well (Fig.
S9-S11, ESI†).
m,m’-coupling and (ii) dimer formation, hence, m,m’-bis(4-
alkylguaiacol)s are the main product.
Purification via one-step crystallization
Assessment of the melting temperature reveals a marked
influence of chain elongation. m,m’-BGF-4P melts at 78oC,
which is about 50-60oC lower than that of the corresponding
ethyl (129oC) and methyl (138oC) bisguaiacols and at least 80oC
lower than that of conventional BPA (158-159 oC) and
Considering the purity criteria for synthesis of high-molecular
weight thermoplastics via polycondensation,67,68 the presence
of o,m’-dimers and oligomers (which could act for instance as
chain-terminators, colouring agents and cross-linkers) is highly
unfavorable. Surprisingly, multigram-scale crystallization of the
bisguaiacols proves to be simple and enables the isolation of
the
o
bisphenol F (BPF; 163 C). Thermal degradation, as measured
by TGA, takes place at similar (Td,max ≥244 oC; methyl) or higher
temperatures (ethyl and propyl) in comparison with standard
BPA and BPF. All thermal characteristics are summarized in
Table S2, ESI†. Advantageous from an industrial point of view,
lower melting temperatures combined with similar or higher
thermal stabilities provide a broader liquid state processing
window, that is especially notable for 4PG-derived
bisguaiacols.
Figure 1. Development of substrate-directed selective dimerization from 4-n-
propylphenol (4PP; top) to 4-n-propylguaiacol (4PG; blue) as detected by GC-FID
(A) and GPC/SEC (B) with indication of preferred coupling positions (relative to
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 5 of 11
View Article Online
DOI: 10.1039/C7GC00776K
Journal Name
ARTICLE
Figure 2. High-purity (>99%) faceted crystals obtained by a facile one-step
crystallization of the crude condensation mixture. Left to right: m,m’-
methylenebis(4-ethylguaiacol) and m,m’-methylenebis(4-n-propylguaiacol).
Figure 3. In vitro screening of the estrogenic potency of bis(4-alkylguaiacol)s via
an estrogen-responsive reporter assay in human MCF-7 cells (MELN-assay).
Three zones of sigmoidal responsiveness are indicated for reference estrogen
(blue), commercial bisphenols (magenta) and bisguaiacols (green). The individual
Human estrogen receptor α (hERα) activity
Before evaluating the potential polymeric properties, novel
bisphenol monomers should undergo preliminary toxicity
tests, as to obey the concept of ‘safety by design’.72,73 Suitable
monomers are expected to exhibit less or no estrogen
receptor (binding) activity. Thereto, purified bisguaiacols were
assessed in an estrogen-responsive reporter assay in a human
MCF-7 breast cancer cell line stably transfected with the
estrogen responsive gene ERE-βGlob-Luc-SVNeo (MELN
assay),74,75 benchmarked against 17β-estradiol and commercial
bisphenols (i.e. BPF, BPE and BPA) (Fig. 3). In general, 4-
test compounds: E2 (blue, ●), BPF (dark mag.,
(mag., ), 4-methyl- (light green, ), 4-ethyl- (dark green,
brown, □) and 5-methyl- (dark brown, ) bisguaiacols.
⟐
), BPA (light mag.,
∎), BPE
), 4-n-propyl- (light
▲
∇
◓
▲
Synthesis of thermoplastic polycarbonates
Encouraged by the low estrogen activity of m,m’-BGF-4P, a
first exploratory synthesis of the corresponding aromatic
poly(carbonate)s and aromatic cyanate ester resins was
pursued to demonstrate its potential in material applications.
First, the corresponding poly(carbonate)s were evaluated and
synthesized by reacting the m,m’-bis(4-alkylguaiacol)s with
triphosgene (i.e. a solid phosgene substitute) via a standard
lab scale procedure (Scheme 1; see details in ESI†). Three
quasi-white powders were obtained in >60 wt% yield under
non-optimized conditions (Fig. S14, ESI†). Phosgene and
derivatives (i.e. di- and triphosgene)77,78 were selected here, as
they remain to play a pivotal role in industrial polycarbonate
synthesis (i.e. 80-90% of total PC synthesis in 2007).79
Nevertheless, more sustainable CO2-based non-phosgene
procedures (e.g. Asahi-Kasei process) exist on an industrial
scale as well.80
alkylated m,m’-bisguaiacols display
a significantly lower
relative estrogenic induction (% vs. vehicle control) at higher
concentration (log10 M), which makes them less potent for
binding to the estrogen receptor. Whereas the sigmoidal
response of m,m’-bis(4-methylguaiacol) still closely resembles
the response for bisphenols, the relative induction for ethyl
and propyl derivatives substantially decreased, up to a factor
two. Meanwhile, potencies (expressed as EC50 values) shift to
ca. 10-100 times lower values (see also ESI†, Table S3). To
illustrate the strong influence of the substitution type and
pattern, as
a
proof-of-concept, 4,4’-methylenebis(5-
The molecular structures of these poly[methylene bis(4-
1
methylguaiacol) (p,p’-BGF-5M) was synthesized in an
analogous manner (Fig. S12-13, ESI†) and an even lower
potency was achieved (Fig. 3 dark brown). This together with
the fact that bisguaiacols typically display a lower solubility
(~10-4 M; in water with 0.1 vol% DMSO at 25 oC) than
alkylguaiacol) carbonate]s were confirmed by H and 13C NMR
in deuterated trifluoroacetic acid (TFAA-d) (Fig. S15-16, ESI†)
and FT-IR spectroscopy (Fig. S17, ESI†) and are shown in Figure
4A. The molecular weight (distribution) for these novel types
of polycarbonate was evaluated by both 1H NMR end-group
analysis (see details in ESI†) and GPC/SEC analysis (Fig. 4B).
End-
o
conventional bisphenols (~10-3 M in water at 25 C) will likely
reduce the environmental impact for lignin-derivable
bisphenols, regarding their endocrine disrupting potential.
Future research should however also evaluate possible
agonistic and antagonistic interactions with other members of
the human nuclear receptor family, such as the androgen and
thyroid hormone receptor. Furthermore, besides in vitro whole
cell activity assays, progression towards whole animal
assessment (e.g. fish, amphibian and mammalian) is
indispensable and necessary to consider all of the possible
sites of action and mechanisms of endocrine disruption.72,76
group analyses provide number-average molecular weights
(Mn) of 2503, 4783 and 5182 g.mol-1 for methyl-, ethyl- and
propyl-substituted polycarbonates respectively. GPC/SEC
analyses in hexafluoroisopropanol (HFIP) against a commercial
poly(BPA carbonate) (PC-BPA, Mw = 64,000 g.mol-1) standard,
reveal broad bimodal mass distributions (9.0 – 13.0 min).
Similar bimodal distributions were found in a previous study
on the interfacial polycondensation of BPA with triphosgene
catalyzed by triethylamine, yielding mixtures of cyclic and OH-
terminated polycarbonates.81,82 Furthermore, these bimodal
distributions partially overlap the standard (9.6 – 11.8 min),
indicating that favorable molecular weights are attainable, in
particular for propyl-chained polycarbonates. These results
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 6 of 11
View Article Online
DOI: 10.1039/C7GC00776K
ARTICLE
Journal Name
motivate a follow-up study to attain higher molecular weight nitrogen). Though no clear trend was observable, both ethyl
poly[methylene bis(4-alkylguaiacol) carbonate]s.
and propyl substituents seem to result in slightly higher
thermal stabilities compared to methyl groups. In theory,
proper end-capping of free reactive phenolic groups could
result in even higher thermal stabilities.84 In general, it must be
taken into account that aforementioned properties correlate
with the molecular weight of the polycarbonates.85 For
example, a PC-BPA with a similar Mn as the novel propyl-
substituted polycarbonate (~5000 g.mol-1) would display a Tg
of 125 oC, about 20-25 oC lower than high molecular weight
PC-BPA (145-150 oC).
Table 2. PXRD and DSC data of poly[methylene bis(4-alkylguaiacol) carbonate]s.
Type of
Initial
crystallinity b
high
Tendency to
crystallize c
fast (hot/cold)
slow (cold)
slow
Tg, hot
(DSC) d
125
Tm
polycarbonate a
PC1 (4-methyl)e
PC2 (4-ethyl)
PC3 (4-n-propyl)
(DSC)
292-305
236-273
205-220
medium
low
116
99
Figure 4. Molecular structure of poly[methylene bis(4-alkylguaiacol) carbonate]s
as confirmed by FT-IR and NMR in TFAA-d (A), and analysis of their molecular
weight (distribution) by GPC/SEC in HFIP against a known standard (B).
a
b
literature values reported for PC-BPA are Tg = 145-150 and Tm = 225oC. estimated
c
from PXRD and DSC. based on the presence of a crystallization exotherm in DSC, see
Fig. S19. d measured upon heating/cooling at 20 oC.min-1
Chen et al.56 are Tg = 122 and Tm = 314 oC.
.
e literature values reported by
Commercial PC-BPA are typically amorphous and well known
for their optical transparency. In the solid state their molecular
structure is random and disordered, the long chain molecules
all being entangled.83 Suitable replacements therefore ideally
share this amorphous nature with poly(BPA carbonate). Yet, a
recent study showed that polycarbonate made from m,m’-
bis(4-methylguaiacol) was highly crystalline and quasi-
insoluble, despite the favorable thermal properties (Tg = 122
and Tm = 314oC).56 To combat this tendency for crystallization,
we envisioned that especially the longer 4-propyl chain could
be used as a bio-inherent tool to inhibit alignment and
promote the required disorder and entanglement. Hence, the
initial crystallinity of the precipitated polycarbonates was
inspected by powder X-ray diffraction (PXRD; Table 2 and Fig.
S18 in ESI†). Remarkably, upon 4-alkyl chain elongation, the
highly crystalline nature fades out and a more amorphous
character appears. This trend is confirmed by DSC data, which
shows the loss of both hot and cold crystallization exotherms
for propyl-substituted polycarbonate (Table 2 and Fig. S19,
ESI†).
Table 3. TGA data of poly[methylene bis(4-alkylguaiacol) carbonate]s.
Type of
Td,5% in N2 (air)
oC
Td,10% in N2 (air)
oC
Td,max in N2 (air)
oC
polycarbonatea
PC1 (4-methyl)b
PC2 (4-ethyl)
PC3 (4-n-propyl)
346 (311)
376 (329)
360 (341)
373 (345)
392 (352)
376 (359)
422 (411)
429 (398)
424 (414)
a literature values reported by Dong et al.86 for PC-BPA in N2 (air) are Td,5% = 445
(436) and Td,max = 504 (505) oC. b literature values reported by Chen et al.56 are Td,5%
= 382, Td,10% = 392 and Td,max = 420 oC.
Extension of the 4-alkyl chain affects not only (i) the
crystallinity, but also (ii) the glass transition temperature (Tg),
(iii) the melt temperature (Tm) and (iv) the solubility. The
propyl-substitution displays a Tg of 99 oC, which is 17 and 26 oC
lower than the ethyl (116 oC) and methyl analog (125 oC),
respectively. A similar trend is observed for the Tm, which
drops from about 299 to 213 oC. A concise overview is given in
Table 2. Next, chain elongation proves to be beneficial for the
solubility of the polycarbonates. Especially the propyl-
substitution displays improved solubility in CHCl3, DCM and
THF, which may be beneficial for interfacial polymerization
strategies. Finally, the thermal stability of the polycarbonates
was determined by thermogravimetrical analysis (TGA; Table 3
and Fig. 5). Single-stage degradation was observed for all
samples with an onset of degradation (Td,5%) between 345-375
Figure 5. Weight loss profile of poly[methylene bis(4-alkylguaiacol) carbonate]s
upon heating (at 10 oC.min-1) under nitrogen atmosphere as measured by TGA.
Synthesis of cyanate ester thermosets
Cyanate ester resins are a relatively new class of high-
performance thermosets that have been studied extensively
over the last decades.87,88 The combination of low water
uptake, high Tg’s , excellent electrical properties, reduced fire-
smoke-toxicity (FST) and outstanding mechanical properties
makes them attractive alternatives to standard BPA-based
epoxy resins. Recently, several novel aromatic cyanate esters
were constructed from renewable bio-phenols, such as
anethole,89,90 resveratrol,91,92 creosol (i.e. 4MG),16 eugenol,93,94
vanillin95 and carvacrol.96 Both the properties of the cyanate
o
oC and a maximum weight loss (Td,max) around 425 C (under
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 7 of 11
View Article Online
DOI: 10.1039/C7GC00776K
Journal Name
ARTICLE
ester monomer (e.g. Tm, cure exotherm, processing window) results in a slower curing. This is indicated by the cure enthalpy
as well as the polymer network (e.g. Tg, water uptake) can be values, which typically lie at about 100 kJ.(mol OCN)-1,16 and is
fine-tuned by the choice of substituents on the bisphenolic confirmed by the weight loss profile of uncured bis(cyanate
precursor.97
ester)s during TGA (Fig. S24, ESI†).
To evaluate the influence of the propyl chain, the To determine the glass transition (Tg) of the thermoset
corresponding bis(cyanate ester)s were first synthesized by network, oscillatory thermomechanical analyses (TMA) were
reaction of the m,m’-bis(4-alkylguaiacols) with cyanogen performed, which involves measuring flexing of a polymer
bromide (CNBr) (Scheme 1; see procedure in ESI†). The specimen upon exposure to heat.92 Bulk samples were cured in
cyanate esters were obtained in excellent yield (≥97%) and a silicone mold by heating under ‘standard cure’ conditions (1
their molecular structure was confirmed by 1H and 13C NMR h at 150 oC followed by 210 oC for 24 h). Previous reports
and FT-IR spectroscopy (Fig. S20-23, ESI†).
showed that this standard curing schedule was not sufficient
Subsequently, these cyanate ester monomers were used to to completely polymerize the monomers.91,92 To obtain
study the effect of the propyl chain on (i) the cure chemistry, complete cure, samples were ‘post-cured’ at 280 oC for 4 h.
(ii) the thermal properties (Tg, Td and char yield) and (iii) the The preparation of homogeneous, void-free thermoset discs
water uptake. Insight into the cure chemistry of the resins was was achieved in all cases (Fig. S25, see method in ESI†). The
probed by DSC (Fig. 6 and Table 4). The propyl- and ethyl- propyl chain proves to have a clear effect on the Tg. Whereas
substituted monomers melted cleanly at about 108-109oC and methyl and ethyl substitutions show similar Tg values (~231
both display a cure exotherm maximum at 309oC with a cure oC), the TMA thermogram of a fully cured propyl substituted
enthalpy of about 130-121 kJ.mol-1 or 65-61 kJ.(mol OCN)-1. sample shows a Tg of about 193 oC in the storage modulus
o
This presence of a broad processing window, i.e. the difference curve, which is about 35-40 C lower (Fig. S23, ESI†). Although
between Tm and onset of cure (ca. 110-115 oC), for the molten this Tg value is lower than a typical BPE and BPA-derived
resins renders them highly suitable for the fabrication of cyanate ester (post-cure Tg of 289-305 oC),89 the value is
composites. The melting temperature of the bis(cyanate ester) comparable to high performing epoxy resins (Tg of 150-200 oC).
with 4-methyl chains lies 15-17 oC higher (at 125 oC) and has a The thermal stability and char yield of the polycyanurates after
peak cure
post-curing was studied by TGA (Table 5 and Fig. 7). No
Table 5. TGA data of post-cured cyanate ester thermosets.
Type of
Td,5% in N2 (air)
oC
Td,10% in N2 (air)
oC
Td,max in N2 (air)
oC
Char yield
a
%
alkyl chain
4-methylb
4-ethyl
375 (380)
389 (387)
383 (389)
392 (391)
393 (394)
396 (400)
401 (401)
411 (411)
30 (28)
26 (28)
22 (22)
4-n-propyl
389 (389)
a
b
at 850 oC in N2 (air), literature values reported by Meylemans et al.16 for Td,5%
Td,10% and char yield are 360 (357), 366 (362) oC and 35% respectively
,
Figure 6. DSC traces of (a) 4-methyl-, (b) 4-ethyl- and (c) 4-n-propyl-substituted
bis(cyanate ester)s from first (solid) and second (dashed) heating cycle at 10oC.min-1
Values for (a) and (b) are offset with 6 and 3 W.g-1 respectively.
.
Table 4. DSC data of uncured and cured bis(cyanate ester)s.
Type of alkyl chain
Tm (standard)a oC
Tm (DSC) / o
parent Tm
Cure exotherm / max. o
Processing window / o
4-n-propyl
108-110
109.4
78-79
309
4-ethyl
107-108
107.7
128-129
309
4-methyl
123-126
124.7b
138-139
272
/
Figure 7. Weight loss profile of post-cured cyanate ester resins upon heating (at
10 oC.min-1) under nitrogen atmosphere as measured by TGA.
C
oC
/
C
significant differences could be observed for heating in
nitrogen versus air. Chain elongation results in slightly higher
thermal stabilities with maximum values attained for propyl-
substituted resins. Here, the degradation starts at 389 oC
C
~110
~115
~75
Cure enthalpy / kJ.(mol OCN)-1
65
61
88
Degree of cure / %
<70
<65
<90
o
a
b
as determined with sealed capillaries in melting point apparatus. literature
(Td,5%) and reaches a maximum loss at 411 C (Td,max), which is
value reported by Meylemans et al.16 is 125.4 o
C
about 10-15 oC higher
than methyl-substituted resins. Unlike earlier reports,16 the
char yield (measured at 850 oC) was quasi similar under
nitrogen and air. The char yield ranged from 22-30% with the
lowest value obtained for propyl chains, which might be
exotherm at 272 oC, reducing its stable molten temperature
range to ca. 75 oC. Here, the enthalpy change for the cure was
88 kJ.(mol OCN)-1. Overall, chain elongation (from methyl to
propyl) brings about a wider stable processing window, but
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 8 of 11
View Article Online
DOI: 10.1039/C7GC00776K
ARTICLE
Journal Name
explained by the lower aromatic/aliphatic carbon ratio and the For a complete list of all used chemicals and materials as well
fact that aliphatic groups are more prone to oxidative as a more detailed description of all experimental methods
degradation.96
and procedures, the reader is kindly referred to the ESI†.
Finally, the fully cured resin discs were exposed to hot water
(85oC) for four days to determine their water uptake. It was Reaction procedure
hypothesized that the hydrophobic character of the propyl
Reactions were conducted as previously described with minor
modifications.55 In a typical reaction, to alkylphenol or -
guaiacol (36 mmol) in a 100 mL Duran® laboratory bottle with
screw cap, 37 wt% formaldehyde (18 mmol) and concentrated
HCl (50 mL, 2.5 M in Milli-Q H2O) were added, as well as a
magnetic stirring bar (45 mm). At the start of the reaction, the
bottle is partially (2/3) submerged in a pre-heated stirred
temperature-controlled oil bath. The bath is held at 100 oC
under continuous stirring (1000 rpm) for the indicated time.
Once at room temperature, the aqueous acidic phase was
decanted and the resulting ‘organic phase’ analysed.
chains could significantly reduce moisture uptake. Indeed, a
propyl substituted resin displays an uptake of only 1.18%, in
comparison with respectively 1.36 and 1.75% for ethyl and
methyl groups. This value is lower than for BPE and BPA-based
based resins (respectively 1.75 and 1.34%).89 Hence, the
presence of propyl chains has a favourable impact on the
hydrophobicity of the thermosetting material, broadening its
applicability to humid conditions.
Conclusions
We demonstrate the production of bio-renewable m,m’-
bisguaiacols from methyl-, ethyl- and propylguaiacols, the
latter being abundantly available in the reductive catalytic bio-
refinery (in 15-20 wt% on lignin basis from softwood). The
effect of the propyl (vs. ethyl and methyl) chain was
systematically examined for (i) the acid-catalysed synthesis of
the m,m’-bisphenols, (ii) the purification via crystallization, (iii)
the estrogenic potency, as well as for (iv) the final properties
of aromatic polymers.
Reaction product analysis
The ‘organic phase’ contains dimers, oligomers, unreacted
monomers and trace amounts of the aqueous acidic phase (<3
wt%). To avoid overestimation of ‘total organic phase
recovery’, underestimation of product yields or damaging the
column, this ‘organic phase’ was dissolved in acetone or
diethyl ether and dried with MgSO4. After filtration, the
solvent was removed by rotary evaporation (150 mbar at 80 oC
for 1 h) yielding a semi-solid or viscous oil. This ‘dried organic
phase’ was analysed by both GC and GPC/SEC (see ESI†) for
determining product yields and monomer conversion. Due to
the high chemical similarity between reagent and products,
the dimer yield and monomer conversion can only be
measured accurately by GC. Due to the limited volatility of
(derivatized) higher oligomers, the use of GC is excluded for
their quantification. To confirm their presence, GPC/SEC
measurements were performed. The ‘total organic phase
recovery’ is calculated from the ratio of the weight of the
‘dried organic phase’ and the weight of the ‘theoretical organic
phase at full dimer yield’ (cf. n mol dimer, resulting from the
ideal stoichiometrical reaction between the initial n mol
formaldehyde and 2n mol methoxylated phenols without
oligomer formation).
The original substitution pattern of the guaiacols directs the
selectivity to primarily m,m’-coupled bisguaiacols, while
undesired oligomer formation is restricted for steric reasons,
being most pronounced for the propyl-substituted guaiacols.
Despite the unusual m,m’-regioselectivity, highly pure crystals
(devoid of o,m’-isomers and oligomers) are easily formed upon
controlled crystallization in all cases. From the m,m’-isomers,
especially the propyl-substituted bisguaiacol (m,m’-BGF-4P)
displays strongly reduced in vitro estrogenic receptor (binding)
activity and are therefore the most sustainable bisphenol
alternatives for the synthesis of novel aromatic polymers, like
polycarbonates and cyanate ester resins. In thermoplastic
polycarbonates, the propyl chain (i) lowers the tendency to
crystallize, and (ii) improves its solubility in common solvents,
which facilitates downstream processing. Propyl-substituted
cyanate ester thermosetting resins on the other hand benefit
from (i) a broad processing window (ca. 110 oC) during resin
synthesis, and (ii) reduced water uptake (1.18%). Both type of
polymers exhibited a high thermal stability (>360 oC) that is
not compromised by the presence of the aliphatic propyl
chain. From a more conceptual point-of-view, this work
highlights the benefits gained from deliberately exploiting
nature’s intrinsic functional groups, present for instance in
lignin.
Acknowledgements
This work was performed in the framework of an IAP-PAI net-
work from BELSPO (Federal Agency) and was supported by the
IWT-SBO project ARBOREF (S.-F.K.). W.S., S.V.d.B and T.R.
acknowledge doctoral and postdoctoral fellowships from the
Research Foundation – Flanders (FWO). B.L. acknowledges the
Industrial Research Fund of KU Leuven. The authors kindly
thank Karel Duerinckx for the NMR measurements, Leander
Verbelen and Nico Coenen for the DSC measurements, An
Jacobs for MELN testing, Lien Telen for her assistance with
GPC/SEC in HFIP and Danny Winant and prof. Jan Van
Humbeeck for their technical and scientific guidance in the
TMA experiments. The authors acknowledge dr. Patrick
Balaguer (INSERM) who kindly provided the MELN cells.
Experimental
Chemicals, materials and methods
8 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 9 of 11
View Article Online
DOI: 10.1039/C7GC00776K
Journal Name
ARTICLE
25 J. Zakzeski, P. C. Bruijnincx, A. L. Jongerius and B. M.
Weckhuysen, Chem. Rev., 2010, 110, 3552-3599.
26 C. Xu, R. A. D. Arancon, J. Labidi and R. Luque, Chem. Soc.
Rev., 2014, 43, 7485-7500.
Notes and references
1
2
W. R. Stahel, Nature, 2016, 531, 435.
W. R. Stahel, in The circular economy - a wealth of flows, ed.
K. Webster, Ellen MacArthur Foundation, 2015, pp. 86-103.
Ellen MacArthur Foundation, World Economic Forum and
27 J. Bozell, Selective Catalysis for Renewable Feedstocks and
Chemicals, Springer International Publishing, Switserland,
2014.
3
McKinsey
& Company, The New Plastics Economy:
Rethinking the Future of Plastics, Ellen MacArthur
28 A. Rahimi, A. Ulbrich, J. J. Coon and S. S. Stahl, Nature, 2014,
515, 249-252.
Foundation, 2016.
4
5
6
7
Y. Zhu, C. Romain and C. K. Williams, Nature, 2016, 540,
29 R. Rinaldi, R. Jastrzebski, M. T. Clough, J. Ralph, M.
Kennema, P. C. A. Bruijnincx and B. M. Weckhuysen, Angew.
Chem. Int. Ed., 2016, 55, 8164-8215.
354-362.
M. Dusselier, P. Van Wouwe, A. Dewaele, E. Makshina and
B. F. Sels, Energy Environ. Sci., 2013, , 1415-1442.
6
30 A. J. Ragauskas, G. T. Beckham, M. J. Biddy, R. Chandra, F.
Chen, M. F. Davis, B. H. Davison, R. A. Dixon, P. Gilna and M.
Keller, Science, 2014, 344, 1246843.
M. Dusselier, P. Van Wouwe, A. Dewaele, P. A. Jacobs and
B. F. Sels, Science, 2015, 349, 78-80.
A. Gandini, A. J. D. Silvestre, C. P. Neto, A. F. Sousa and M.
Gomes, J. Polym. Sci., Part A: Polym. Chem., 2009, 47, 295-
298.
31 V. E. Tarabanko, N. V. Koropatchinskaya, A. V. Kudryashev
and B. N. Kuznetsov, Russ. Chem. Bull., 1995, 44, 375-379.
32 V. E. Tarabanko and N. V. Koropatchinskaya, Chem. of Plant
8
9
L. Mialon, A. G. Pemba and S. A. Miller, Green Chem., 2010,
12, 1704-1706.
Raw Mat. (Russia), 2003,
33 N. V. Koropatchinskaya, V. Е. Tarabanko and M. J. Chernyak,
Chem. of Plant Raw Mat. (Russia), 2003, , 405-418.
1, 5-25.
O. Hauenstein, S. Agarwal and A. Greiner, Nat. Commun.,
4
2016, 7.
34 M. V. Galkin and J. S. Samec, ChemSusChem, 2014, 7, 2154-
10 D. E. Nikles and M. S. Farahat, Macromol. Mater. Eng.,
2005, 290, 13-30.
2158.
35 M. V. Galkin, A. T. Smit, E. Subbotina, K. A. Artemenko, J.
Bergquist, W. J. Huijgen and J. S. Samec, ChemSusChem,
2016.
11 V. Sinha, M. R. Patel and J. V. Patel, J. Polym. Environ., 2010,
18, 8-25.
12 G. O. Jones, A. Yuen, R. J. Wojtecki, J. L. Hedrick and J. M.
36 J. R. Bower Jr, L. M. Cooke and H. Hibbert, J. Am. Chem.
Soc., 1943, 65, 1192-1195.
García, Proc. Natl. Acad. Sci. U. S. A., Early Ed., 2016, 113
,
7722-7726.
37 J. Pepper, C. Brounstein and D. Shearer, J. Am. Chem. Soc.,
1951, 73, 3316-3319.
13 S. L. Kristufek, K. T. Wacker, Y.-Y. T. Tsao, L. Su and K. L.
Wooley, Natural Product Reports, 2017.
38 J. Pepper and Y. Lee, Can. J. Chem., 1969, 47, 723-727.
39 K. Sudo, D. J. Mullord and J. M. Pepper, Can. J. Chem., 1981,
59, 1028-1031.
14 J. M. García, G. O. Jones, K. Virwani, B. D. McCloskey, D. J.
Boday, G. M. ter Huurne, H. W. Horn, D. J. Coady, A. M.
Bintaleb and A. M. Alabdulrahman, Science, 2014, 344, 732-
735.
40 N. Yan, C. Zhao, P. J. Dyson, C. Wang, L.-T. Liu and Y. Kou,
ChemSusChem, 2008,
41 Q. Song, F. Wang, J. Cai, Y. Wang, J. Zhang, W. Yu and J. Xu,
Energy Environ. Sci., 2013, , 994-1007.
42 C. Li, M. Zheng, A. Wang and T. Zhang, Energy Environ. Sci.,
2012, , 6383-6390.
1, 626-629.
15 T. E. Long, Science, 2014, 344, 706-707.
16 H. A. Meylemans, B. G. Harvey, J. T. Reams, A. J. Guenthner,
L. R. Cambrea, T. J. Groshens, L. C. Baldwin, M. D. Garrison
and J. M. Mabry, Biomacromolecules, 2013, 14, 771-780.
17 A. Maiorana, A. F. Reano, R. Centore, M. Grimaldi, P.
6
5
43 P. Ferrini and R. Rinaldi, Angew. Chem. Int. Ed., 2014, 53
,
Balaguer, F. Allais and R. A. Gross, Green Chem., 2016, 18
,
8634-8639.
4961-4973.
44 T. Parsell, S. Yohe, J. Degenstein, T. Jarrell, I. Klein, E.
Gencer, B. Hewetson, M. Hurt, J. I. Kim, H. Choudhari, B.
Saha, R. Meilan, N. Mosier, F. Ribeiro, W. N. Delgass, C.
Chapple, H. I. Kenttämaa, R. Agrawal and M. M. Abu-Omar,
Green Chem., 2015, 17, 1492-1499.
18 R. Peacock, Market Outlook: Phenol/acetone markets are
under pressure, ICIS Chemical Business, 2016
19 N. J. P. Wierckx, H. Ballerstedt, J. A. M. de Bont and J. Wery,
Appl. Environ. Microbiol., 2005, 71, 8221-8227.
20 J. M. Gibson, P. S. Thomas, J. D. Thomas, J. L. Barker, S. S.
Chandran, M. K. Harrup, K. M. Draths and J. W. Frost,
Angew. Chem. Int. Ed., 2001, 40, 1945-1948.
45 S. Van den Bosch, W. Schutyser, R. Vanholme, T. Driessen, S.
F. Koelewijn, T. Renders, B. De Meester, W. J. J. Huijgen, W.
Dehaen, C. M. Courtin, B. Lagrain, W. Boerjan and B. F. Sels,
21 D. T. A. Huibers and H. J. Parkhurst, US Pat., 4 420 644,
1983.
Energy Environ. Sci., 2015,
46 J. Chen, F. Lu, X. Si, X. Nie, J. Chen, R. Lu and J. Xu,
ChemSusChem, 2016, , 3353-3360.
47 S. Van den Bosch, W. Schutyser, S.-F. Koelewijn, T. Renders,
8, 1748-1763.
22 D. J. Engel and K. Z. Steigleder, US Pat., 4 647 704 A, 1987.
23 G. Kakemoto, H. Sagara, N. Suzuki and S. Kachi, US Pat., 4
900 873 A, 1990.
9
C. M. Courtin and B. F. Sels, Chem. Commun., 2015, 51
,
24 M. N. Belgacem and A. Gandini, Monomers, polymers and
composites from renewable resources, Elsevier, Amsterdam,
2011.
13158-13161.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 9
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 10 of 11
View Article Online
DOI: 10.1039/C7GC00776K
ARTICLE
Journal Name
48 W. Schutyser, S. Van den Bosch, T. Renders, T. De Boe, S.-F. 71 P. Azadi, R. Carrasquillo-Flores, Y. J. Pagán-Torres, E. I.
Koelewijn, A. Dewaele, T. Ennaert, O. Verkinderen, B.
Gürbüz, R. Farnood and J. A. Dumesic, Green Chem., 2012,
14, 1573-1576.
Goderis and C. Courtin, Green Chem., 2015, 17, 5035-5045.
49 T. Renders, W. Schutyser, S. Van den Bosch, S.-F. Koelewijn, 72 T. Schug, R. Abagyan, B. Blumberg, T. Collins, D. Crews, P.
T. Vangeel, C. M. Courtin and B. F. Sels, ACS Catalysis, 2016,
, 2055-2066.
DeFur, S. Dickerson, T. Edwards, A. Gore and L. Guillette,
6
Green Chem., 2013, 15, 181-198.
50 T. Renders, S. Van den Bosch, T. Vangeel, T. Ennaert, S.-F. 73 N. D. Anastas, Green Chem., 2016, 18, 4325-4331.
Koelewijn, G. Van den Bossche, C. M. Courtin, W. Schutyser 74 P. Berckmans, H. Leppens, C. Vangenechten and H. Witters,
and B. F. Sels, ACS Sustainable Chem. Eng., 2016,
4
, 6894-
Toxicol. In Vitro, 2007, 21, 1262-1267.
6904.
75 H. Witters, A. Freyberger, K. Smits, C. Vangenechten, W.
Lofink, M. Weimer, S. Bremer, P. H. J. Ahr and P. Berckmans,
Reprod. Toxicol., 2010, 30, 60-72.
51 D. Verboekend, Y. Liao, W. Schutyser and B. F. Sels, Green
Chem., 2016, 18, 297-306.
52 A. Arcoleo and T. Garofano, Anal. Chim., 1957, 47, 1142- 76 D. Li, Q. Chen, J. Cao, H. Chen, L. Li, N. Cedergreen, H. Xie
1162. and L. Xie, Aquat. Toxicol., 2016, 170, 199-207.
53 V. Halaška, E. Leukaničová, J. Kahovec and J. Pospíšil, Chem. 77 H. Eckert and B. Forster, Angew. Chem. Int. Ed., 1987, 26
Prum., 1971, 21/46, 277-279. 894-895.
54 K. Kratzl and I. Wagner, Holzforsch. Holzverw., 1972, 24, 56- 78 L. Cotarca and H. Eckert, Phosgenations: a handbook, John
61. Wiley & Sons, Hoboken, 2006.
55 H. A. Meylemans, T. J. Groshens and B. G. Harvey, 79 T. Sakakura, J.-C. Choi and H. Yasuda, Chem. Rev., 2007,
ChemSusChem, 2012, , 206-210. 107, 2365-2387.
56 Q. Chen, W. Huang, P. Chen, C. Peng, H. Xie, Z. K. Zhao, M. 80 S. Fukuoka, M. Kawamura, K. Komiya, M. Tojo, H. Hachiya,
Sohail and M. Bao, ChemCatChem, 2015, , 1083-1089. K. Hasegawa, M. Aminaka, H. Okamoto, I. Fukawa and S.
Konno, Green Chem., 2003, , 497-507.
,
5
7
57 Q. Chen, K. Gao, C. Peng, H. Xie, Z. K. Zhao and M. Bao,
Green Chem., 2015, 17, 4546-4551.
5
81 H. R. Kricheldorf and G. Schwarz, Macromol. Rapid
Commun., 2003, 24, 359-381.
58 A. V. Krishnan, P. Stathis, S. F. Permuth, L. Tokes and D.
Feldman, Endocrinology, 1993, 132, 2279-2286.
82 H. R. Kricheldorf, S. Böhme, G. Schwarz and C.-L. Schultz,
Macromolecules, 2004, 37, 1742-1748.
59 J. A. Brotons, M. F. Olea-Serrano, M. Villalobos, V. Pedraza
and N. Olea, Environ. Health Perspect., 1995, 103, 608.
60 R. M. Blair, H. Fang, W. S. Branham, B. S. Hass, S. L. Dial, C.
L. Moland, W. Tong, L. Shi, R. Perkins and D. M. Sheehan,
Toxicol. Sci., 2000, 54, 138-153.
83 V. Goodship, in Practical Guide to Injection Moulding, ed. V.
Goodship, Ismithers Rapra Publishing, 2004, ch. 6, pp. 81-
82.
84 O. Phillips, J. M. Schwartz and P. A. Kohl, Polym.
Degradation Stab., 2016, 125, 129-139.
61 H. Fang, W. Tong, L. M. Shi, R. Blair, R. Perkins, W. Branham,
B. S. Hass, Q. Xie, S. L. Dial and C. L. Moland, Chem. Res. 85 G. A. Adam, J. N. Hay, I. W. Parsons and R. N. Haward,
Toxicol., 2001, 14, 280-294. Polymer, 1976, 17, 51-57.
62 D. Miller, B. B. Wheals, N. Beresford and J. P. Sumpter, 86 Q. Dong, C. Gao, Y. Ding, F. Wang, B. Wen, S. Zhang, T.
Environ. Health Perspect., 2001, 109, 133.
Wang and M. Yang, J. Appl. Polym. Sci., 2012, 123, 1085-
63 S. G. Shetty, J. H. Kamps, G. Chandra, A. Tanwar, R. R.
1093.
Gallucci, V. R. G. Bhotla, E. J. Nesakumar and M. S. Kumar, 87 I. Hamerton and J. N. Hay, Polym. Int., 1998, 47, 465-473.
US Pat., 0 338 423 A1, 2015.
88 I. Hamerton and J. N. Hay, High Perform. Polym., 1998, 10,
64 G. Chandra, E. J. Nesakumar, V. R. G. Bhotla, S. G. Shetty, J.
163-174.
Mahood, R. R. Gallucci, J. H. Kamps and M. S. Kumar, US 89 M. C. Davis, A. J. Guenthner, T. J. Groshens, J. T. Reams and
Pat., 9 120 893 B1, 2015.
J. M. Mabry, J. Polym. Sci., Part A: Polym. Chem., 2012, 50,
65 K. H. Reno, J. F. Stanzione III, R. P. Wool, J. M. Sadler, J. J.
4127-4136.
Lascala and E. D. Hernandez, WO Pat., 2015 183 892 A1, 90 M. C. Davis, A. J. Guenthner, C. M. Sahagun, K. R. Lamison, J.
2015.
T. Reams and J. M. Mabry, Polymer, 2013, 54, 6902-6909.
91 J. J. Cash, M. C. Davis, M. D. Ford, T. J. Groshens, A. J.
Guenthner, B. G. Harvey, K. R. Lamison, J. M. Mabry, H. A.
66 P. Wang, C. McInnes and B. T. Zhu, PloS One, 2013,
8,
e74615.
67 G. Yadav and N. Kirthivasan, Appl. Catal., A, 1997, 154, 29-
Meylemans and J. T. Reams, Polym. Chem., 2013, 4, 3859-
53.
3865.
68 R. Kumar, G. R. Ravi, H. M. Bastian, G. Sathyanarayana, S. J. 92 L. R. Cambrea, M. C. Davis, M. D. Garrison, T. J. Groshens, R.
Shafer, K. K. Ramamurthy, D. M. Murukutla and V. R. N. G.
E. Lyon and N. Safronava, J. Polym. Sci., Part A: Polym.
Chem., 2017, 55, 971-980.
Bhotla, US Pat., 7 371 902 B2, 2008.
69 H. Hong, B. G. Harvey, G. R. Palmese, J. F. Stanzione, H. W. 93 B. G. Harvey, C. M. Sahagun, A. J. Guenthner, T. J. Groshens,
Ng, S. Sakkiah, W. Tong and J. M. Sadler, Int. J. Env. Res.
Public Health, 2016, 13, 705.
L. R. Cambrea, J. T. Reams and J. M. Mabry, ChemSusChem,
2014, , 1964-1969.
7
70 P. Ferrini, S.-F. Koelewijn, J. Van Aelst, N. Nuttens and B. F.
Sels, ChemSusChem, 2017, DOI: 10.1002/cssc.201700338.
10 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 11 of 11
View Article Online
DOI: 10.1039/C7GC00776K
Journal Name
ARTICLE
94 B. G. Harvey, A. J. Guenthner, G. R. Yandek, L. R. Cambrea,
H. A. Meylemans, L. C. Baldwin and J. T. Reams, Polymer,
2014, 55, 5073-5079.
95 B. G. Harvey, A. J. Guenthner, H. A. Meylemans, S. R.
Haines, K. R. Lamison, T. J. Groshens, L. R. Cambrea, M. C.
Davis and W. W. Lai, Green Chem., 2015, 17, 1249-1258.
96 B. G. Harvey, A. J. Guenthner, T. A. Koontz, P. J. Storch, J. T.
Reams and T. J. Groshens, Green Chem., 2016, 18, 2416-
2423.
97 A. J. Guenthner, B. G. Harvey, M. C. Davis, M. D. Ford, H. A.
Meylemans, M. E. Wright, A. P. Chafin and J. M. Mabry, in
Green Polymer Chemistry: Biobased Materials and
Biocatalysis, eds. H. N. Cheng, R. A. Gross and P. B. Smith,
ACS Publications, 2015, vol. 1192, ch. 26, pp. 431-452.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 11
Please do not adjust margins