Ring-opening polymerization of lactones using binaphthyl-diyl hydrogen phosphate as organocatalyst and resulting monosaccharide functionalization of polylactones

Article abstract of DOI:10.1002/pola.26612

Binaphthyl-diyl hydrogen phosphate has been assessed for the first time as a catalyst for the ring-opening polymerization of ε-caprolactone (CL) and δ-valerolactone (VL). In the presence of benzyl alcohol as coinitiator at 40-60 °C, the polymerization is

Full text of DOI:10.1002/pola.26612

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Ring-Opening Polymerization of Lactones using Binaphthyl-diyl Hydrogen
Phosphate as Organocatalyst and Resulting Monosaccharide
Functionalization of Polylactones
Yong Miao,1,2,3,4 Yupin Phuphuak,5,6 Cyril Rousseau,1,7 Till Bousquet,1,2,3,4
1,2,3,4
Suwabun Chirachanchai,5,6 Philippe Zinck1,2,3,4
ꢀ
Andre Mortreux,
1
ꢀ
Universite Lille Nord de France, F-59000 Lille, France
2
ꢀ
ꢀ
Ecole Nationale Superieure de Chimie de Lille, Unite de Catalyse et Chimie du Solide, CCM, F-59652 Villeneuve d’Ascq, France
3
ꢀ
ꢀ
Universite de Lille 1, Science et Technologie, Unite de Catalyse et Chimie du Solide, CCM, F-59655 Villeneuve d’Ascq, France
4Centre National de la Recherche Scientifique, UMR 8181, F-59652 Villeneuve d’Ascq, France
5The Petroleum and Petrochemical College, Chulalongkorn University, Bangkok, Thailand
6Center for Petroleum, Petrochemical, and Advanced Materials, Chulalongkorn University, Bangkok, Thailand
7
ꢀ
ꢀ
Centre National de la Recherche Scientifique, UMR 8181, Universite d’Artois, Faculte des Sciences Jean Perrin, rue Jean
Souvraz, SP18, 62307 Lens Cedex, France
Correspondence to: P. Zinck (E-mail: philippe.zinck@ensc-lille.fr)
Received 29 November 2012; accepted 29 January 2013; published online 22 February 2013
DOI: 10.1002/pola.26612
ABSTRACT: Binaphthyl-diyl hydrogen phosphate has been assessed
for the first time as a catalyst for the ring-opening polymerization
of e-caprolactone (CL) and d-valerolactone (VL). In the presence of
benzyl alcohol as coinitiator at 40–60 ꢀC, the polymerization is
quantitative and controlled both in terms of dispersity and of num-
ber-average molecular weight corresponding to the monomer/ini-
tiator ratio. The use of a selectively protected D-glucose derivative
bearing the primary C6 hydroxyl group as initiator leads to the
quantitative end-functionalization of the polyesters in rather short
reaction times (ca. 10 min at 60 ꢀC for d-VL) with dispersities
around 1.08–1.10. Methyl-a-D-glucopyranoside has been used as a
carbohydrate polyol initiator in bulk. The initiation efficiency is par-
tial, leading to hydrophilic carbohydrates functionalized polylac-
C
V
tones in a one-step procedure.
2013 Wiley Periodicals, Inc.
J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2279–2287
KEYWORDS: biopolymers; catalysis; cationic polymerization;
ring-opening polymerization; polyesters
INTRODUCTION Organocatalyzed ring-opening polymeriza-
tion of cyclic esters has gained much interest these last
years.1 Numerous catalysts such as organic acids,2–14 nitro-
gen bases,15–17 phosphines,18 and carbenes19 among others
have been assessed. The polymerization of lactones can be
catalyzed by a variety of organic acids, including carboxylic
acids,4,5 naturally occurring acids5,6 such as citric, lactic, tar-
taric, and amino acids.5 High catalyst loadings and high tem-
peratures are required in these latter cases, and hydroxy
acids do furthermore initiate the polymerization via the
hydroxyl group in addition to their catalytic activities. This
leads to poor functionalization efficiencies in the presence of
a protic coinitiator. The H2O/HCl/Et2O and the n-BuOH/HCl/
Et2O systems afford the controlled and living cationic ring-
opening polymerizations of e-caprolactone (CL) and d-valero-
lactone (VL) in dichloromethane in mild conditions, with
substantial catalyst loadings, however.2,3 Sulfonic acids
including trifluoromethane sulfonic acid present also good
potentialities for the controlled cationic ring-opening poly-
merization of lactones and lactides in combination with
protic coinitiators.7–14 The controlled polymerization of lac-
tones was also reported using a phosphoric acid, diphenyl-
phosphate, in combination with an alcohol in mild conditions
in toluene.20–22
Biodegradable aliphatic polyesters are widely used in the field
of packaging and for biomedical applications. The functionali-
zation of these polymers with carbohydrates derivatives6,23–39
enables to tailor properties related to biodegradability and
drug delivery such as hydrophilicity, crystallinity, and the pos-
sibility of form inclusion complexes among other. Monosaccha-
ride end-capped polylactides have been reported as good can-
didates for excipients in oral sustained release tablets for
example.34 The use of organocatalysts for the carbohydrate
functionalization of aliphatic polyesters is of particular inter-
est, as it will lead to polymers that do not contain any residual
metal contaminant that can hamper their use for specific
applications. Hydroxyl bearing carbohydrate end-capped ali-
phatic polyesters are are interesting materials in this frame, as
Additional Supporting Information may be found in the online version of this article.
C
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hydrophilic monosaccharide functionalized polyesters via
organocatalysis in a one-step procedure.
EXPERIMENTAL
Materials
Rac-, (R)-, and (S)-1,10-BNPH were synthesized from corre-
sponding binols and POCl3 according to a literature proce-
dure.40 e-CL and d-VL were dried over calcium hydride and
distilled under reduced pressure before use. Benzyl alcohol
(BnOH) was dried with sodium metal for 48 h at room tem-
perature, refluxed over magnesium, and distilled prior to
use. Methyl 2,3,4 tri-O-benzyl-a-D-glucopyranoside (Glc-1r,
represented Scheme 4, synthesis described hereafter) and
methyl-a-D-glucopyranoside (Glc-Me, represented Scheme 4,
Aldrich) were purified by 3 distillations over toluene before
their use as polymerization initiator.
SCHEME 1 Phosphoric acid used as catalyst (BNPH).
the hydrophilic character plays an important role for the solu-
bility and the biodegradation of the resulting polymer. Three-
step strategies involving protection/deprotection chemistries
are usually used to obtain such hydrophilic carbohydrates
functionalized polyesters.26–33,36 The development of one-step
procedures for this purpose is thus of particular interest.35,37
We envisioned in this frame the use of a bulky and potentially
chiral organocatalyst for the ring-opening polymerization of
lactones. The bulkiness may indeed hinder sterically the initia-
tion using a carbohydrate polyol. Additionally, carbohydrates
such as methyl-a-D-glucopyranoside show stereocenters of
well-defined configurations. Using one of the catalyst enan-
tiomers versus the other may afford a certain control over the
regioselectivity of the initiation step that may lead to favor or
disfavor the initiation of the polymerization by certain
hydroxyl groups.
Carbohydrate Synthesis
Methyl-2,3,4-tri-O-benzyl-a-D-glucopyranoside (referred to as
Glc-1r hereafter) is easily obtained in three steps from the
methyl-a-D-glucopyranoside (referred to as Glc-Me hereafter)
after selective tritylation of the O-6 position and benzylation of
the position O-2, O-3, and O-4 in well established conditions in
a 66 and 78% yield, respectively (Scheme 2). The trityl group is
selectively removed by refluxing in a mixture of acetic acid and
water to give Glc-1r (Compound 3) in a 60% yield with the O-6
position differentiated ready to be tested as initiator.
Methyl-6-O-trityl-a-D-glucopyranoside-(1)
A solution of methyl-a-D-glucopyranoside (6.0 g, 0.03 mol),
trityl chloride (11 g, 1.2 eq), triethylamine (8 mL), and
DMAP (290 mg, 0.5 eq) in DMF (50 mL) was stirred over-
night at room temperature under nitrogen. After 12 h stir-
ring, the reaction mixture was poured into ice-water and
extracted with dichloromethane. The organic extracts were
washed with water, and dried with magnesium sulfate. After
removal of the solvents, the solid was recrystallized from
ethanol to yield compound 1 (8.9 g, 66%) as a white solid.
We present in this frame the unprecedented use of a bulky,
sterically hindered, and potentially chiral phosphoric acid,
1,10-binaphthyl-2,20-diyl hydrogen phosphate (BNPH–Scheme
1) as a catalyst for the ring-opening polymerization of e-CL
and d-VL. The polymerization in the presence of benzyl alco-
hol as coinitiator is controlled in mild conditions in bulk,
affording a solvent-free well-controlled polymerization. The
use of a selectively protected D-glucose derivative as initiator
leads to the straightforward end-functionalization of the
polyester. The polymerization in bulk enables to use com-
mercial carbohydrate polyols as coinitiators, leading to
Methyl-2,3,4-tri-O-benzyl-6-O-trityl-a-D-glucopyranoside (2)
A solution of 1 (8.9 g, 0.03 mol) in DMF was added at 0 ꢀC
NaH (60% in mineral oil, 3.6 g, 4.5 eq). After 30 min BnBr
SCHEME 2 Synthesis of Glc-1r.
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TABLE 1 Polymerization of Lactones in Bulk at 608C using 1 mol % rac-BNPH in Combination with Benzylic Alcohol (BnOH)
Ma
M/BNPH/BnOH
Time (h)
Yield (%)
Mn Calc.
Mn NMR
Mn SEC
DM
BnO/CH2OHe
b
c
d
d
Entry
1
2
3
4
5
6f
7
8
a
VL
VL
CL
CL
CL
CL
CL
CL
50/0.5/1
50/0.5/1
50/0.5/1
100/1/1
100/1/1
100/1/1
100/1/0
100/0/1
10 min
85
96
99
80
99
100
–
4400
4900
5700
9200
11,400
11,500
–
4400
5300
5600
n.d
n.d
n.d
–
4500
4600
6100
10,300
12,600
12,200
–
1.08
1.17
1.11
1.13
1.15
1.14
–
1.01
1.01
0.99
n.d
n.d
n.d
–
1
1
1
4
7
4
4
–
–
–
–
–
–
Monomer. CL ¼ e-caprolactone and VL ¼ d-valerolactone.
dispersity. Correction factors are applied because the calibration is
done using polystyrene standards, see Experimental part.
b
Number-average molecular weight calculated considering the growth
of one macromolecular chain per OH group and the yield: Mn ¼ M/BnO-
e
Ratio between the signals of ArACH2OA polymer (5.1 ppm) and poly-
H*yield%*Mmonomer þ Minitiator
.
mer-CH2OH (3.6 ppm) end-groups.
c
f
Number-average molecular weight determined by 1H NMR (see experi-
Reaction conducted at 40 ꢀC.
mental part).
d
Number-average molecular weight measured by SEC and corrected
by a factor 0.56 and 0.57 for poly(e-CL) and poly(d-VL), respectively, and
(10.5 mL, 4.5 eq) was added and the reaction mixture was
stirred overnight at room temperature. The reaction was
then quenched with water (40 mL) and the aqueous layer
was washed with ethyl acetate (4 ꢁ 50 mL). The organic
extracts were dried with magnesium sulfate. After removal
of the solvents, the residue was purified by chromatography
(eluent gradient, EtOAc/petroleum ether 1/5 to 1/3), to
afford the Compound 2 as a white solid (11 g, 78%).
from the ratio of the signal of the ACH2OH end groups (3.64
ppm in CDCl3) versus the ACH2OA groups in the polymer
(4.06–4.07 ppm in CDCl3).
MALDI-TOF-MS was performed on a Ultraflex II spectrometer
(Bruker). The instrument was operated in either the reflec-
tor or linear mode. The spectra were recorded in the posi-
tive-ion mode. The samples were prepared by taking 2 lL of
a THF solution of the polymer (10 mg/mL) and adding this
to 16 lL of 1,8-dihydroxy-9(10H)-anthracenone (dithranol,
10 mg/mL in THF) to which 2 lL of CF3SO3Ag (2 mg/mL in
THF) had been added. A 1 lL portion of this mixture was
applied to the target and 50–100 single shot spectra were
accumulated. The given masses represent the average masses
of the Agþ adducts. The spectrometer was calibrated with an
external mixture of angiotensin I, ACTH 18–39, and bovine
insulin or PEG 1500.
Methyl-2,3,4-tri-O-benzyl-a-D-glucopyranoside
(3 or Glc-1r)
A solution of 2 (11 g, 0.015 mol), in a mixture of acetic
acid/water (9/1) was stirred at reflux during 5 h. The sol-
vent was coevaporated with toluene and the residue was
purified by chromatography (eluent gradient, EtOAc/ petro-
leum ether 1/3 to 1/1), to afford the Compound 3 as a white
solid (4.2 g, 60%).
Polymerization
RESULTS AND DISCUSSION
In a typical polymerization procedure (Entries 4–6), the
protic coinitiator (0.09 mmol), BNPH (0.09 mmol), and the
lactone (9 mmol) were added in a flask in a glove-box. The
mixture was allowed to react at a given temperature for a
given time. The viscous reaction product was dissolved in a
small amount of dichloromethane and precipitated into
methanol. The resulting polyester was filtered and put under
vacuum at room temperature until constant weight.
Polymerization of e-CL and d-VL using rac-BNPH and
Benzyl Alcohol as Coinitiator
Representative entries of the polymerization of e-CL and d-
VL using rac-BNPH in combination with benzyl alcohol are
given in Table 1. The reaction is quantitative in one to sev-
eral hours using 1 mol % catalyst and 1–2 mol % initiator at
40 and 60 ꢀC (Entries 1–6), with a yield of 85% after 10
min using d-VL and 2% initiator. The polymerization activity
is higher using d-VL, as reported in the literature for cationic
polymerizations.42 The number-average molecular weight
corresponds well with the calculated one considering the
growth of 1 macromolecular chain per initiator, and the dis-
tribution is narrow (DM: 1.08–1.17). MALDI-ToF analyses
(see Fig. 1 for a representative example) reveal that all poly-
mer chains formed are end-capped with the benzyl alcohol.
This is confirmed by NMR analysis (Fig. 2). The ratio
between the signal of the ArACH2OApolymer signal around
5.1 ppm and the polymerACH2AOH end group at 3.64 ppm
is close to 1 (Table 1). It is noteworthy that using rac-BNPH
Analytics
Size exclusion chromatography (SEC) was performed in THF
ꢀ
as eluent at 40 C using a Waters SIS HPLC-pump, a Waters
410 refractometer and Waters Styragel columns (HR2, HR3,
HR4, and HR5E). The calibration was done using polystyrene
standards. Correction factors of 0.56 and 0.57 were applied
for the determination of the true number-average molecular
weight of poly(e-CL) and poly(d-VL), respectively.41 NMR
spectra were recorded on a Bruker Avance 300 spectrometer
at room temperature in CDCl3 or DMSO-d6. The number-av-
erage molecular weight of the polylactones was determined
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FIGURE 1 MALDI-ToF analysis of Entry 3.
in bulk affords a controlled polymerization with 1 mol %
catalyst load, while 2–2.5 mol % are required using diphe-
nylphosphate in toluene.21,22 Blank reactions conducted in
the presence of the catalyst or the initiator alone did not
lead to a precipitate under similar experimental conditions
(Entries 7–8). Previous studies of the literature on the poly-
merization of lactones using diphenylphosphate/alcohol com-
binations21,22 proposed an activated monomer mechanism.43
Computational studies suggest a bifunctional mechanism
with participation of both the acidic proton and the basic
P¼¼O moiety, analogous to that observed for sulfonic acids.22
A similar mechanism can be proposed for BNPH, as repre-
sented in Scheme 3.
Polymerization of e-CL and d-VL using BNPH and
Monosaccharides as Coinitiators
The selectively protected D-glucose derivative Glc-1r bearing
a primary hydroxyl group (Scheme 4) was assessed as ring-
opening polymerization initiator using rac-BNPH as catalyst.
The reaction is almost quantitative at 60 ꢀC in 10 and 60
min for d-VL and e-CL, respectively (Entries 9 and 10 in Ta-
ble 2). The reaction is well controlled, with dispersities
around 1.08–1.10. The Mn calculated considering the growth
of one macromolecular chain per hydroxyl group corre-
sponds well to the Mn measured by NMR or GPC, highlight-
ing quantitative functionalization efficiency.
The 1H NMR spectra of the Glc-1r initiator and the corre-
sponding functionalized polylactone (Fig. 3) show the shift of
the resonance peaks after the polymerization. The initiator
FIGURE 2 1H NMR analysis of Entry 3 in CDCl3.
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SCHEME 3 Activated monomer mechanism for the cationic polymerization of e-CL using 1,10-binaphthyl-2,20-diyl hydrogen phos-
phate and benzyl alcohol.
Glc-1r bears one free OH group, which is able to initiate the
polymerization. This free OH group has two neighboring pro-
tons, H6. The chemical shift value of protons 6 can be used as
indicator, to know whether the polymerization is initiated by
the OH group of the monosaccharide, due to the change of the
chemical environment of protons 6 after the polymerization. In
particular, we found that the resonance peaks at 3.62 ppm,
which are assigned to the protons 6 of the methylene group of
Glc-1r disappeared and new resonance peaks around 4.25
ppm were assigned to the protons 6 of the Glc-1r end-capped
polyester. Unambiguous assignments of the signals, were done
polymerization using either metal based catalysts25–29,32,33
or enzymes.23–25 Lactic acid was reported as an organocata-
lyst for this purpose, but the functionalization was reported
to be only partial due to a side initiation via the hydroxyl
group of the hydroxyacid catalyst.6 It is noteworthy that this
drawback is overcome using BNPH as organocatalyst.
The polymerization in bulk enables furthermore to use car-
bohydrates polyols as initiators as these compounds are not
soluble in most organic solvents. Representative examples of
the polymerization of d-VL and e-CL using rac-BNPH com-
bined to methyl a-D-glucopyranoside (Glc-Me in Scheme 4)
is reported in Table 2, Entries 11–15. For a monomer/OH ra-
tio of 50, the polymerization is quantitative after about 1
and 2.5 h for d-VL and e-CL, respectively. It can also be seen
from the value of the number-average molecular weight that
the initiation efficiency is partial, and increases along the po-
lymerization to reach a maximum of about 55%. The initia-
tion is thus not instantaneous or fast versus the propagation,
in contrast to that observed in the presence of benzyl alco-
hol or Glc-1r as initiator. The hydroxyl groups of the mono-
saccharide polyol present thus a different reactivity for the
initiation step. In cationic ring-opening polymerizations, sec-
ondary alcohols are usually less reactive than primary
1
by H-1H correlations (COSY) analysis presented in Figure 4.
The signal of proton H1 can be easily found, due to its special
chemical environment. Two oxygen atoms around makes pro-
ton H1 the most unshielded (chemical shift d ¼ 4.58 ppm)
among all the other protons of the monosaccharide. H1 has
one neighbor proton H2, so it should have coupling with H2.
With the help of COSY spectrum, the coupling between H1 and
H2 (H1AH2) can be clearly observed in Figure 4. Similarly, the
other protons of the monosaccharide were assigned in this
way, with peaks of protons H6 at 4.25 ppm.
Previous studies of the literature reported the monosaccha-
ride functionalization of aliphatic polyesters by ring-opening
TABLE 2 Polymerization of Lactones in Bulk at 60 8C using 1 mol % BNPH in Combination with 0.5% Carbohydrate Coinitiator
(Monomer/OH 5 50)
c
d
Time
(min)
Yield
(%)
Mn per
Mn per
Initiation
Ma
Ib
OH Calc.
OH NMR
efficiency (%)
Mn SEC
DM
e
e
Entry
Cata.
9
rac-BNPH
rac-BNPH
rac-BNPH
rac-BNPH
rac-BNPH
rac-BNPH
rac-BNPH
(R)-BNPH
(S)-BNPH
VL
CL
VL
VL
CL
CL
CL
VL
VL
Glc-1r
10
60
5
92
94
27
86
84
33
93
85
76
4600
5400
1400
4300
500
4600
5600
3500
8100
3000
6800
9400
8800
7200
100
96
40
53
16
31
56
49
53
4500
6200
1.08
1.10
1.13
1.18
1.19
1.14
1.18
1.19
1.17
10
11
12
13g
14
15
16
17
a
Glc-1r
Glc-Me
Glc-Me
Glc-Me
Glc-Me
Glc-Me
Glc-Me
Glc-Me
4300
13,400f
20
10
60
150
20
20
5300
2100
5300
4300
3800
e
8100
21,100f
11,900f
10,800f
Monomer. CL ¼ e-caprolactone and VL ¼ d-valerolactone.
Number-average molecular weight measured by SEC and corrected by
a factor 0.56 and 0.57 for poly(e-CL) and poly(d-VL), respectively, and
dispersity. Correction factors are applied because the calibration is
done using polystyrene standards, see Experimental part.
b
c
Initiator.
Number-average molecular weight per OH group calculated consider-
ing the growth of one macromolecular chain per OH group and the
yield: Mn ¼ M/OH*yield%*Mmonomer (the molecular weight of the carbo-
hydrate initiator is not considered).
f
Distributions showing a slight shoulder.
g
CL/OH ¼ 5.
d
Number-average molecular weight per OH group determined by 1H
NMR (see Experimental section–the molecular weight of the carbohy-
drate initiator is not considered).
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FIGURE 3 1H NMR spectra of Entry 9 (top) and of the Glc-1r initiator (bottom) in CDCl3. Bn ¼ benzyl.
FIGURE 4 COSY analysis of Entry 9 in CDCl3.
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lymerization (Entries 11 and 14), and for low monomer/OH
ratio (Entry 13). The molecular weight distributions show a
slight shoulder at higher conversions for high monomer/OH
ratio. This may be attributed to the difference of reactivity of
the hydroxyl groups toward the initiation step.
The partial initiation efficiency observed using Glc-Me as ini-
tiator leads interestingly to hydrophilic monosaccharide
functionalized poly(d-VL) and poly(e-CL) via organocatalysis
in a one-step procedure, as around one half of the hydroxyl
functions of the sugar do not initiate the polymerization for
a monomer/OH ratio of 50. Experiments with a lower mono-
mer/OH ratio were conducted for NMR analysis of the
resulting polymer. A typical example (Entry 14) leads to an
initiation efficiency of 16%. The spectrum in the zone 4.4–
5.4 ppm recorded in DMSO-D6 is presented in Figure 6.
Numerous signals can be seen, mainly doublets. OH protons
on carbohydrates can lead to doublets when analyzed by 1H
NMR in DMSO-d6, depending on the number of neighboring
protons. This can for example be seen on the 1H NMR
analysis of methyl-a-D-glucopyranoside. See the spectrum
and explanations in the SI. The addition of D2O was
SCHEME 4 Carbohydrates used as polymerization initiators
(Bn ¼ benzyl).
alcohols.42 1H NMR analysis of Entry 12 is presented in Fig-
ure 5. The signal of the methyl group of the carbohydrate
[Fig. 5(e)] is split into several peaks, showing that the initia-
tion step is not regioselective. Reactions conducted with the
chiral (R)-BNPH and (S)-BNPH catalysts did not induce a sig-
nificant effect on the polymerization features (Entries 16–17
vs. 12, and similar signals of the methyl group e on the 1H
NMR spectra) highlighting an initiation influenced by steric
rather than chiral factors. Unimodal and narrow molecular
weight distributions are obtained in the first steps of the po-
FIGURE 5 NMR spectra of Entry 12 in CDCl3. * traces of monomer.
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FIGURE 6 1H NMR spectra of Entry 14 recorded in DMSO-d6 in the zone 4.4–5.4 ppm before (bottom) and after (top) addition of
D2O.
REFERENCES AND NOTES
performed to confirm the presence of OH groups. Proton
deuterium exchanges efficiently occurred as shown by the
disappearance of several doublets. This confirms the pres-
ence of unreacted hydroxyl groups on the carbohydrate core
of the polymer. Such functionalized polyesters are notably
used as precursors for the synthesis of miktoarm polymers25
or biodegradable gels.32 Protection/deprotection chemistries
are usually used to obtain hydrophilic carbohydrates func-
tionalized polyesters,26–33,36 one-step procedures being less
observed.35,37 Alkyl glucopyranoside initiated enzymes23,24
and lactic acid6 catalyzed ring-opening polymerization of e-
CL were reported for the one-step synthesis of hydroxylated
monosaccharide functionalized poly(e-CL). This work extends
the catalytic systems reported for this purpose to the BNPH
phosphoric acid.
1 M. K. Kiesewetter, E. I. Shin, J. L. Hedrick, R. M. Waymouth,
Macromolecules 2010, 43, 2093–2107.
2 Y. Shibasaki, H. Sanada, M. Yokoi, F. Sanda, T. Endo, Macro-
molecules 2000, 33, 4316–4320.
ꢀ
3 X. Lou, C. Detrembleur, R. Jeroˆ me, Macromolecules 2002, 35,
1190–1195.
4 F. Sanda, H. Sanada, Y. Shibasaki, T. Endo, Macromolecules
2002, 35, 680–683.
ꢀ
5 J. Casas, P. V. Persson, T. Iversen, A. Cordova, Adv. Synth.
Catal. 2004, 346, 1087–1089.
6 P. V. Persson, J. Schroder, K. Wickholm, E. Hendenstrom, T.
Iversen, Macromolecules 2004, 37, 5889–5893.
7 D. Bourissou, B. Martin-Vaca, A. Dumitrescu, M. Graullier, F.
Lacombe, Macromolecules 2005, 38, 9993–9998.
8 S. Gazeau-Bureau, D. Delcroix, B. Martin-Vaca, D. Bourissou,
C. Navarro, S. Magnet, Macromolecules 2008, 41, 3782–3784.
9 M. Basko, P. Kubisa, J. Polym. Sci. Part A: Polym. Chem.
2006, 44, 7071–7081.
CONCLUSIONS
The BNPH phosphoric acid is an efficient catalyst for the
ring-opening polymerization of lactones in bulk. In combina-
tion with benzyl alcohol, the polymerization is quantitative
and controlled in mild conditions, with dispersities around
1.08–1.17. Monosaccharides mono- and poly-ols can be used
as initiators, affording the organocatalyzed synthesis of car-
bohydrate-functionalized polyesters. Partial initiation effi-
ciency could be reached using the bulky BNPH, leading to
the one-step synthesis of hydrophilic monosaccharide end-
capped polyesters. The chirality of the catalyst did in turn
not allow to induce a controlled selectivity of the initiation
step. The results reported in this work extend the range of
applications of phosphoric acids as catalysts for the ring-
opening polymerization of lactones to the functionalization
of polylactones by monosaccharide derivatives.
10 M. Basko, P. Kubisa, J. Polym. Sci. Part A: Polym. Chem.
2007, 45, 3090–3097.
11 M. Basko, P. Kubisa, J. Polym. Sci. Part A: Polym. Chem.
2008, 46, 7919–7923.
12 M. Basko, P. Kubisa, J. Polym. Sci. Part A: Polym. Chem.
2010, 48, 2650–2658.
13 F. A. Jaipuri, B. D. Bower, N. L. Pohl, Tetrahedron: Asymme-
try 2003, 14, 3249–3252.
14 N. Susperregui, D. Delcroix, B. Martin-Vaca, D. Bourissou, L.
Maron, J. Org. Chem. 2010, 75, 6581–6587.
€
15 F. Nederberg, E. F. Connor, M. Moller, T. Glauser, J. L.
Hedrick, Angew. Chem. 2001, 40, 2712–2715.
16 B. G. G. Lohmeijer, R. C. Pratt, F. Leibfarth, J. W. Logan, D.
A. Long, P. A. Dove, F. Nederberg, J. Choi, C. Wade, R. M.
Waymouth, J. L. Hedrick, Macromolecules 2006, 39,
8574–8583.
17 C. Thomas, F. Peruch, A. Deffieux, A. Milet, J. P. Desvergne,
B. Bibal, Adv. Synth. Catal. 2011, 353, 1049–1054.
ACKNOWLEDGMENTS
€
18 M. Myers, E. F. Connor, T. Glauser, A. Mock, G. Nyce, J. L.
Hedrick, J. Polym. Sci. Part A: Polym. Chem. 2002, 40, 844–851.
ꢀ
The authors want to acknowledge Sebastien Georges for NMR
ꢀ
analyses, Aurelie Malfait for SEC analyses, and Johan Hachani
€
19 E. F. Connor, G. Nyce, M. Myers, A. Mock, J. L. Hedrick, J.
for MALDI-ToF analyses. The French embassy in Bangkok and
the French ministry of foreign affairs are gratefully acknowl-
edged for funding via the PHC Siam Franco-Thaı¨ project.
Am. Chem. Soc. 2002, 124, 914–915.
20 C. Navarro, D. Bourissou, B. Martin-Vaca, D. Delcroix. Fr.
Patent PCT/0958742, 12, 2009.
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JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
21 K. Makiguchi, T. Satoh, T. Kakuchi, Macromolecules 2011,
44, 1999–2005.
32 Y. Morikawa, H. Kinoshita, M. Asahi, A. Takasu, T. Hirabaya-
shi, Polym. J. 2008, 40, 217–222.
22 D. Delcroix, A. Couffin, N. Susperregui, C. Navarro, L.
Maron, B. Martin-Vaca, D. Bourissou, Polym. Chem. 2011, 2,
2249–2256.
33 M. Tang, F. A. Haider, C. Minelli, M. M. Stevens, C. K. Wil-
liams, J. Polym. Sci. A 2008, 46, 4352–4362.
€
€
34 S. Vuorinen, J. Heinamaki, O. Antikainen, M. Lahcini, T.
ꢀ
23 A. Cordova, T. Iversen, K. Hult, Macromolecules 1998, 31,
Repo, J. Yliruusi, AAPS Pharm. Sci. Tech. 2009, 10, 566–573.
1040–1045.
35 P. Zinck, Rev. Environ. Sci. Biotech. 2009, 8, 231–234.
24 K. S. Bisht, F. Deng, R. A. Gross, D. L. Kaplan, G. Swift, J.
Am. Chem. Soc. 1998, 120, 1363–1367.
36 Y. Miao, C. Rousseau, A. Mortreux, P. Martin, P. Zinck, Poly-
mer 2011, 52, 5018–5026.
25 F. Deng, K. S. Bisht, A. R. Gross, D. L. Kaplan, Macromole-
cules 1999, 12, 5159–5161.
37 P. Zinck, In Biomedical Engineering, Trends in Materials Science;
A. N. Laskovski, Ed.; Intech: Vienna, 2011; pp. 489–512 (http://
www.intechopen.com/articles/show/title/synthetic-strategies-
for-biomedical-polyesters-specialties).
26 K. Yasugi, T. Nakamura, Y. Nagasaki, M. Kato, K. Kataoka,
Macromolecules 1999, 32, 8024–8032.
27 T. Ouchi, T. Uchida, Y. Ohya, Macromol. Biosci 2001, 1,
371–375.
38 Q. Hao, F. Li, Q. Li, Y. Li, L. Jia, J. Yang, Q. Fang, A. Cao,
Biomacromolecules 2005, 6, 2236–2247.
28 T. Hamaide, M. Pantiru, H. Fessi, P. Boullanger, Macromol.
Rapid Commun. 2001, 22, 659–663.
39 Y. Miao, P. Zinck, Polym. Chem. 2012, 3, 1119–1122.
40 J. Jacques, C. Fouquey, Org. Synth. 1993, 8, 50.
ꢀ
29 K. Bernard, P. Degee, P. Dubois, Polym. Int. 2003, 52,
406–411.
41 M. Save, M. Schappacher, A. Soum, Macromol. Chem. Phys.
2002, 203, 889–899.
30 M. Pantiru, C. Iojoiu, T. Hamaide, F. Delolme, Polym. Int.
2004, 53, 506–514.
42 Y. Okamoto, Makromol. Chem. Makromol. Symp. 1991,
42–43, 117–133.
31 C. K. Williams, Chem. Soc. Rev. 2007, 36, 1573–1580.
43 P. Kubisa, S. Penczek, Prog. Polym. Sci. 1999, 24, 1409–1437.
WWW.MATERIALSVIEWS.COM
JOURNAL OF POLYMER SCIENCE, PART A: POLYMER CHEMISTRY 2013, 51, 2279–2287
2287