Polyethylenes bearing a terminal porphyrin group

Article abstract of DOI:10.1039/c1cc12620b

An α-[Cu(ii)-porphyrin]-polyethylene was synthesized for the first time using copper catalyzed 1,3-dipolar azide-alkyne Huisgen cycloaddition yielding highly colored moiety-substituted polyethylene.

Full text of DOI:10.1039/c1cc12620b

View Article Online / Journal Homepage / Table of Contents for this issue
Dynamic Article Links
ChemComm
Cite this: Chem. Commun., 2011, 47, 7057–7059
www.rsc.org/chemcomm
COMMUNICATION
Polyethylenes bearing a terminal porphyrin groupw
Miriam M. Unterlass,a Edgar Espinosa,a Fernande Boisson,b Franck D’Agosto,*a
Christophe Boisson,*a Katsuhiko Ariga,cd Ivan Khalakhan,ce Richard Charvetc and
Jonathan P. Hill*cd
Received 4th May 2011, Accepted 16th May 2011
DOI: 10.1039/c1cc12620b
An a-[Cu(II)-porphyrin]-polyethylene was synthesized for the first
time using copper catalyzed 1,3-dipolar azide–alkyne Huisgen cyclo-
addition yielding highly colored moiety-substituted polyethylene.
Polyolefins, including polyethylene (PE) and isotactic poly-
propylene (iPP), are commercially the most important family of
polymers with annual production exceeding 100 Mt.1 Polyolefins
have reached wide application, since they combine excellent
mechanical, physical and chemical properties. However, their
use in certain applications is limited by their low polarity, leading
to a lack of adhesion, dyeability, paintability, and compatibility
with other polymers.2 Also, their chemical inertness precludes post-
synthesis functionalisation with colorants or other useful moieties.
We have recently shown3 that PE chains of controlled length,
obtained by using the catalytic system (C5Me5)2NdCl2Li(OEt2)2/
Scheme 1 Chemical structures of azido polyethylene 1 (n = 69),
alkyne-substituted porphyrin 2 and the target polyethylene PE–Por.
MgR2, could be highly functionalized with a variety of reactive
groups including azide end groups3c (PE–N3, 1 in Scheme 1). As
a result, azide–alkyne 1,3-dipolar Huisgen cycloaddition4
could be performed permitting conversion of these PE building
blocks into macromonomers using acrylate and methacrylate
propargyls.3c The high efficiency of these PE-end group function-
alizations led us to further investigate the synthesis of PE chains
by the same 1,3-dipolar Huisgen cycloaddition of azido PE with
various alkyne containing reagents. Here we report for the first
time the end-functionalization of PE with organic chromophores
of the porphyrin type.
Porphyrin 2 (Scheme 1) was first reacted with 1 (2010 g molÀ1
PDI = 1.2, functionality of 90%) using CuBr as a copper(I)
source and PMDETA as a ligand. Since copper cations are easily
complexed by 2, a large excess of CuBr was used (molar ratios
1:2: CuBr : PMDETA of 1 : 2 : 20 : 20) in order to catalyze the
cycloaddition reaction (see ESIw for synthesis details). Copper
cations are simultaneously incorporated by chelation of the 2
moieties with adventitious oxidation of Cu(I) to Cu(II) promoted
by the porphyrin ligand. Completion of the cycloaddition reaction
was signified by disappearance of the azido band from the infrared
spectrum of the product. Also, bands due to C–H stretching
vibrations of methylene at around 2900 cmÀ1 corresponding to
the polyethylene chain appear (see ESIw). The product (PE–Por)
was further characterized using UV-NIR spectroscopy (in
reflectance mode) on samples in the solid state (see Fig. 1). The
spectrum of PE–Por contains bands due to methylene (a, b and c
in Fig. 1) in the NIR range, where a and b are first overtones of
the C–H stretch mode at 1764 nm and 1732 nm, respectively.
Band c is the corresponding second overtone (1216 nm). In the
UV-vis range, below 600 nm, PE–Por showed broad absorption
bands corresponding to the porphyrin moiety (whole spectrum in
ESIw). Thus, the PE–Por spectrum represents the addition of the
two starting material spectra except that peaks d and e corres-
ponding to the first and second N–H stretching mode overtones
(1540 and 1142 nm, respectively) of the free base are not present.
,
a Universite´ de Lyon, Univ. Lyon 1, CPE Lyon,
CNRS UMR 5265 Laboratoire de Chimie Catalyse Polymeres et
`
´
´
Procedes (C2P2), LCPP team, Bat 308F, 43 Bd du 11 novembre
1918, F-69616 Villeurbanne, France. E-mail: dagosto@lcpp.cpe.fr,
boisson@lcpp.cpe.fr; Fax: +33 4 72 43 17 68;
Tel: +33 4 72 43 17 70
b
´
´
Service commun de RMN du Reseau des Polymeristes Lyonnais,
CNRS/UMR5223, INSA de Lyon, IMP, 20 avenue Albert Einstein,
69621 Villeurbanne Cedex, France
c Center for Materials Nanoarchitectonics, National Institute of
Materials Science (NIMS), Namiki 1-1, Tsukuba, Ibaraki,
305-0044, Japan. E-mail: jonathan.hill@nims.go.jp
d JST-CREST, Namiki 1-1, Tsukuba, Japan
e Department of Surface and Plasma Science, Faculty of Mathematics
and Physics, Charles University, V Holesovickach 2, 180 00 Praha 8,
Czech Republic
w Electronic supplementary information (ESI) available: Materials,
analytical techniques, syntheses of polyethylene, 1, 2 and PE–Por,
1H NMR, 1H COSY, 13C NMR, MALDI-ToF mass spectrometry
analyses and X-ray diffraction. See DOI: 10.1039/c1cc12620b
c
This journal is The Royal Society of Chemistry 2011
Chem. Commun., 2011, 47, 7057–7059 7057

View Article Online
Fig. 3 MALDI ToF mass spectrometry chromatogram of PE–Por.
Enlargement between 1800 amu to 1830 amu and corresponding
simulated distribution using Isopro 3.0 Software for PE–Por
(H(C2H4)n–C46H28N7Cu), n = 38.
Fig. 1 Solid state UV-NIR spectroscopy of PE–Por, 2 and 1.
This is consistent with metallation of the porphyrin to its corres-
ponding Cu(II) complex.
In order to confirm the formation of the triazole linkage
between the PE chain and the porphyrin moiety, NMR analyses
the distance between two isotopic distributions matched the molar
mass of one ethylene repetitive unit (28.0 amu). Molar masses and
isotopic distributions agreed exactly with the expected structure
including one copper atom per molecule. All these character-
izations confirmed that azide–alkyne 1,3-dipolar Huisgen cyclo-
addition using PE–N3 and an alkyne containing porphyrin leads
to the formation of the triazole ring and additional complexation
of copper into porphyrin. The desired compound PE–Por has
thus been successfully synthesized. DSC measurements showed
that the crystallinity decreased from 92% for a non-functional
PE to 63% for PE–Por. Optical micrographs of PE–Por and non-
functionalized PE (PE, Mn = 1670 g molÀ1, PDI = 1.1) were
obtained at room temperature from samples after cooling a
toluene solution of this compound from 90 1C (Fig. 4). Fibrous
aggregates apparent by macroscopic observation appear to be
composed of regular crystal-like formations, which are interleaved
leading to the fibre-like morphology. It is important to note the
pink coloration of the PE, as well as its crystallinity so that the
PE–Por material effectively combines the salient properties of
each of its components, i.e. the porphyrin chromophore and
crystallizable polyethylene.
1
of PE–Por were performed. Fig. 2 shows H NMR spectra of
PE–Por and the starting material, PE–N3 (1). The spectrum of
PE–Por is poorly resolved due to the presence of paramagnetic
Cu(II).5 However, it is apparent that no starting material remains
since the corresponding methylene protons adjacent to the azide
end group are absent from the PE–Por spectrum (this is consistent
with FTIR analyses). Aromatic protons of the porphyrin phenyl
groups can be clearly seen between 6 and 9 ppm in this spectrum.
The broad peak at 3.9 ppm most likely corresponds to the
methylene group at the a position to the triazole formed during
1
the cycloaddition. In fact, the H COSY spectrum of PE–Por
confirms the correlation between the methylene groups in a
and b positions (see Fig. 2 for a and b chemical shifts and
1
ESIw for H COSY spectrum). In addition, two resonances at
5.2 and 5.5 ppm may correspond6 to the formation of an enyne
compound between
2 and the very small fraction of
unavoidable3c–e vinyl chain ended PE (4.5% in 1, see ESIw).7
13C NMR analyses were also performed (see ESIw) and showed,
in addition to the expected multiplicity of carbons for PE, the
attachment of the porphyrin moiety through a triazole ring.
MALDI-ToF mass spectrometric analysis was undertaken
(Fig. 3). A very clean spectrum was obtained although PE being
apolar is usually not analyzable by this technique. As expected,
In order to characterize further the morphology of aggregates
of PE and PE–Por, obtained by their precipitations from cooling
Fig. 4 Optical microscopy of (a) PE–Por following its precipitation
by slow cooling to room temperature of a hot (90 1C) toluene solution
(c = 1 mg mLÀ1); (b) PE treated in a similar manner (c = 1 mg mLÀ1).
In (a) and (b), (i) and (ii) are Â50 and Â100 magnifications, respectively.
Note the red colour of the material in (a) due to the presence of the
porphyrin group.
Fig. 2 Comparison of 1H NMR spectra (250 MHz, C6D6/TCE:
1/2 v/v, 3072 scans) of PE–Por and 1. *: solvent impurities.
c
7058 Chem. Commun., 2011, 47, 7057–7059
This journal is The Royal Society of Chemistry 2011

View Article Online
indicating that crystallization may involve folding-in-half of
the molecules.8
Finally, we note that the spiral growth motif (Fig. 5(a)ii),
originating from a crystallisation screw dislocation,9 and the
preferential thickening at the edge of single crystals (Fig. 5(c)i)
are typical features of PE crystallisation.
In summary, we have prepared and analysed the first
examples of chromophore-labelled polyethylenes of highly
monodisperse molecular weight by using the azide–alkyne
1,3-dipolar Huisgen cycloaddition. The most notable feature
of these new materials is their incorporation of a functional
chromophoric organic moiety into PE without strongly
influencing its properties of crystallisability. This is important
since our method allows us to introduce a complex group but
maintain the desirable properties of PE. The main difference
with a mixture of polyethylene with a dye is that in the present
case the dye is chemically linked with the polyethylene.
Regarding simple mixing of dyes with polyethylene,10 the
chemical functionalisation of polyethylene may lead to better
colour-fastness and may improve the stability of the dyes. The
terminal functionalisation that we describe here opens the
way for development of novel applications of PE and also
introduces possibilities for discovery of new properties based
on self-organisation of the end-group augmented PE’s. We will
report on these properties in due course.
E. Espinosa acknowledges financial support from
CONACYT programs. The authors are grateful to F. Delolme
(IBCP, CNRS UMR 5086 Lyon, France) for MALDI-ToF
MS analyses. This work was also supported financially by the
World Premier International Research Center Initiative from
MEXT, Japan and the Core Research for Evolutional Science
and Technology (CREST) program of Japan Science and
Technology Agency (JST), Japan.
Notes and references
Fig.
5
(a) SEM images of PE–Por. (b) SEM images of PE:
(i) nanofibrous morphology; (ii) rhombic crystalline morphology
similar to PE–Por. (c) AFM imaging of PE–Por: (i) rhombic sheet;
(ii) polycrystalline growth; (iii) partial topographic image of growth
shown in (ii) showing a stepped structure; (iv) height profile across the
white line shown in (c(ii)). Individual step height = B10 nm. Samples
prepared by depositing suspensions of PE or PE–Por obtained by
cooling hot toluene solutions (c = 1 mg mLÀ1; substrate for SEM and
AFM: passivated silicon).
1 R. Muhlhaupt, Macromol. Chem. Phys., 2003, 204, 289.
¨
2 (a) T. C. Chung, Prog. Polym. Sci., 2002, 27, 39; (b) M. J. Yanjarappa
and S. Sivaram, Prog. Polym. Sci., 2002, 27, 1347; (c) R. Godoy,
F. D’Agosto and C. Boisson, Prog. Polym. Sci., 2007, 32, 419.
3 (a) R. Godoy Lopez, C. Boisson, F. D’Agosto, R. Spitz, F. Boisson,
D. Bertin and P. Tordo, Macromolecules, 2004, 37, 3540; (b) R. Godoy-
Lopez, C. Boisson, F. D’Agosto, R. Spitz, F. Boisson, D. Gigmes and
D. Bertin, J. Polym. Sci., Part A: Polym. Chem., 2007, 45, 2705;
(c) R. Briquel, J. Mazzolini, T. Le Bris, O. Boyron, F. Boisson,
F. Delolme, F. D’Agosto, C. Boisson and R. Spitz, Angew. Chem.,
Int. Ed., 2008, 47, 9311; (d) F. D’Agosto and C. Boisson, Aust. J. Chem.,
2010, 63, 1155; (e) E. Espinosa, J. Mazzolini, F. D’Agosto and
C. Boisson, Polym. Chem., 2010, 1, 793; (f) J. Mazzolini, R. Briquel,
I. Mokthari, V. Monteil, F. Delolme, O. Boyron, D. Gigimes, D. Bertin,
F. D’Agosto and C. Boisson, Macromolecules, 2010, 43, 7495.
4 (a) H. C. Kolb, M. G. Finn and K. B. Sharpless, Angew. Chem., Int. Ed.,
2001, 40, 2004; (b) C. W. Tornoe, C. Christensen and M. Meldal, J. Org.
Chem., 2002, 67, 3057; (c) H. C. Kolb and K. B. Sharpless, Drug
Discovery Today, 2003, 8, 1128; (d) C. Barner-Kowollik, F. E. Du Prez,
P. Espeel, C. J. Hawker, T. Junkers, H. Schlaad and W. Van Camp,
Angew. Chem., Int. Ed., 2011, 50, 60.
5 G. M. Godziela and H. M. Goff, J. Am. Chem. Soc., 1986, 108, 2237.
6 W. Weng, C. Guo, R. Celenligil-Cetin, B. M. Foxman and
O. V. Ozerov, Chem. Commun., 2006, 197.
7 T. Nishimura, H. Araki, Y. Maeda and S. Uemura, Org. Lett.,
2003, 5, 2997.
8 A. K. Winkel, J. K. Hobbs and M. J. Miles, Polymer, 2000, 41, 8791.
9 J. K. Hobbs, M. J. Hill and P. J. Barham, Polymer, 2001, 42, 2167.
10 A. Pucci, C. Cappelli, S. Bronco and G. Ruggeri, J. Phys. Chem. B,
2006, 110, 3127.
hot toluene solutions, microscopic analyses were undertaken,
including scanning electron microscopy (SEM) and atomic
force microscopy (AFM) (Fig. 5). SEM images (Fig. 5a and b)
indicate the crystalline nature of the insoluble material. The
rhombic formation is typical of other long chain alkane
materials of good molecular weight monodispersity.8 In this
case, however, it is noteworthy that PE itself exhibits an
additional nanofibrous morphology, which was not detected
for the porphyrin-appended derivative. AFM imaging of the
PE and PE–Por (Fig. 5c) deposited from hot toluene onto
passivated silicon substrates confirms the rhombic morphology
but gives additional information regarding the bulk structure.
That is, PE–Por (and PE) appears to form rhombic sheets.
Also, these sheets tend to form stacked structures with a
regularly stepped morphology and a step height around 10 nm,
which corresponds to half the molecular length (n = 70)
c
This journal is The Royal Society of Chemistry 2011
Chem. Commun., 2011, 47, 7057–7059 7059