Well-defined diblock copolymers possessing fluorescent and metal chelating functionalities as novel macromolecular sensors for amines and metal ions

Article abstract of DOI:10.1002/pola.24977

The amino- and metal-ion sensing capability of a novel type of well-defined block copolymers based on 9-anthrylmethyl methacrylate (AnMMA; hydrophobic, fluorescent) and 2-(acetoacetoxy)ethyl methacrylate (AEMA; hydrophobic, metal chelating) has been investigated in organic media. AEMA_x-b-AnMMA _y diblock copolymers were prepared for the first time using reversible addition-fragmentation chain transfer (RAFT) polymerization. All polymers were characterized in terms of molecular weights, polydispersity indices and compositions by size exclusion chromatography and ¹H NMR spectroscopy, respectively. The glass transition (T_g) temperatures of the AEMA_x and AnMMA_x homopolymers and the AEMA _x-b-AnMMA_y diblock copolymers were determined using differential scanning calorimetry. These systems were evaluated toward their ability to act as effective dual chemosensors (i.e., amino- and metal-ion sensors) in an organic solvent (chloroform). More precisely, the fluorescence intensity of both the AnMMA_x homopolymers and the AnMMA _x-b-AEMA_y diblock copolymers in solution exhibited a significant decrease in the presence of triethylamine. Moreover, the presence of iron (III) cations were also found to significantly affect the fluorescence signal of the anthracene moieties when those were combined in a block copolymer structure with the AEMA units, due to complex formation occurring between the β-ketoester groups of the AEMA_x segment and the cations.

Full text of DOI:10.1002/pola.24977

ARTICLE
WWW.POLYMERCHEMISTRY.ORG
Well-Defined Diblock Copolymers Possessing Fluorescent and Metal
Chelating Functionalities as Novel Macromolecular Sensors for Amines
and Metal Ions
Maria Demetriou, Theodora Krasia-Christoforou
Department of Mechanical and Manufacturing Engineering, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus
Correspondence to: T. Krasia-Christoforou (E-mail: krasia@ucy.ac.cy)
Received 6 May 2011; accepted 25 August 2011; published online 15 September 2011
DOI: 10.1002/pola.24977
ABSTRACT: The amino- and metal-ion sensing capability of a
novel type of well-defined block copolymers based on 9-
anthrylmethyl methacrylate (AnMMA; hydrophobic, fluores-
cent) and 2-(acetoacetoxy)ethyl methacrylate (AEMA; hydro-
phobic, metal chelating) has been investigated in organic
(i.e., amino- and metal-ion sensors) in an organic solvent (chlo-
roform). More precisely, the fluorescence intensity of both the
x x y
AnMMA homopolymers and the AnMMA -b-AEMA diblock
copolymers in solution exhibited a significant decrease in the
presence of triethylamine. Moreover, the presence of iron (III)
cations were also found to significantly affect the fluorescence
signal of the anthracene moieties when those were combined
in a block copolymer structure with the AEMA units, due to
complex formation occurring between the b-ketoester groups
x y
media. AEMA -b-AnMMA diblock copolymers were prepared
for the first time using reversible addition-fragmentation chain
transfer (RAFT) polymerization. All polymers were character-
ized in terms of molecular weights, polydispersity indices and
1
compositions by size exclusion chromatography and H NMR
of the AEMA
x
segment and the cations. VC 2011 Wiley Periodi-
spectroscopy, respectively. The glass transition (T
tures of the AEMA and AnMMA homopolymers and the
AEMA -b-AnMMA diblock copolymers were determined using
g
) tempera-
cals, Inc. J Polym Sci Part A: Polym Chem 50: 52–60, 2012
x
x
x
y
KEYWORDS: block copolymers; fluorescence; reversible addi-
differential scanning calorimetry. These systems were eval-
uated toward their ability to act as effective dual chemosensors
tion-fragmentation chain transfer (RAFT)
INTRODUCTION Polymeric materials possessing fluorescent
atom transfer radical polymerization, although successfully
moieties have attracted significant attention because of their
used in the preparation of well-defined polymers based on
1
,2
22,23
potential applications such as fluorescent chemosensors
anthracene,
fails in preparing well-defined polymers
3
4,5
and biosensors, fluorescent imaging agents, optical mate-
based on 2-(acetoacetoxy)ethyl methacrylate (AEMA), the
6
24
rials for organic light emitting devices, and metal-ion sen-
sors, to mention only a few.
second monomer used in this study.
7
Fluorescence quenching is an effective mechanism that can
be used for the identification of ions (both cations and
A widely used fluorescent molecule known for its interesting
photophysical properties is anthracene, a polycyclic aromatic
2
5,26
anions) in solution.
A structural requirement of a fluo-
8
–10
hydrocarbon.
Because of the lack of interaction with
rescent metal-ion sensor is the coexistence of a light-emitting
and a metal receptor group linked together via covalent
bonding. For high sensor efficiency, the ion–receptor interac-
tion must be able to modify the fluorescence properties of
polymeric materials, the anthracene group has been selected
1
1
by various research teams to be introduced into polymers.
Anthracene-containing polymers have been used in the
1
2–14
2
7,28
fabrication of optoelectronic devices,
photoluminescent
the light-emitting group.
Numerous examples appear in
15,16
17,18
19–21
films,
photoresists,
chemiluminescent fluorophores,
the literature describing the chemosensing ability of small
molecules combining a fluorescent group with a metal bind-
and so forth.
2
9–31
ing moiety.
Currently, the design and synthesis of poly-
To date, a limited number of reports appear in the literature,
dealing with the preparation of well-defined polymers based
on 9-anthrylmethyl methacrylate (AnMMA). Instead, most
reports refer to the noncontrollable conventional free radical
mer-based metal ion sensors combining fluorescent
and metal-chelating groups presents high interest. Polymer-
based metal-ion sensors have been reported by various
1
7,18
32–35
polymerization of anthracene-containing monomers.
An
groups.
However, most of the developed systems are
established controlled radical polymerization process namely
homopolymers characterized by a structural complexity and
V
C
2011 Wiley Periodicals, Inc.
52
JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 52–60

WWW.POLYMERCHEMISTRY.ORG
ARTICLE
FIGURE 1 Chemical structures of the two monomers and the CTAs used in this study.
demanding synthetic methodologies toward their prepara-
tion. In this work, a simple and cost-effective synthetic
approach involving a controlled radical polymerization pro-
cess was used toward this purpose.
This is the first demonstration of the capability of well-
defined block copolymer systems possessing specific func-
tionalities within the two block segments (i.e., fluorescent
and metal binding) to act as effective dual-chemosensors for
(
(
i) compounds with lone electron pairs such as amines and
ii) transition metal ions. The latter, that is, the effectiveness
We have chosen to combine AnMMA with AEMA, a monomer
possessing bidentate b-dicarbonyl moieties in a diblock co-
polymer architecture. The well-known strong affinity of the
of the AEMA -b-AnMMA diblock copolymers toward metal-
ion sensing is demonstrated by the strong fluorescence
quenching observed on complexation of the ions with the
x
y
3
6
latter to multivalent cations prompted some groups to syn-
thesize polymers with b-dicarbonyl or b-ketoester repeating
strong bidentate b-ketoester groups present on the AEMAx
3
7–41
units.
We first used two different routes for the prepara-
chelating block segment.
tion of well-defined coordinating block copolymers bearing
b-ketoester functionalities involving group transfer poly-
RESULTS AND DISCUSSION
4
2
merization
transfer (RAFT) polymerization.
versatile polymerization technique that allows for the prepa-
and reversible addition-fragmentation chain
2
4
Figure 1 illustrates the chemical structures and names of
monomers, initiator and the chain transfer agents (CTA)
used for polymer synthesis.
RAFT represents
a
4
3
ration of well-defined polymers of various architectures,
4
4–48
49–51
such as block copolymers,
star polymers,
graft poly-
and polymer (co)net-
The process shows many of the characteristics of
5
2
53–56
Molecular Weights and Composition of the AEMA
AnMMA Homopolymers and the AEMA -b-AnMMA
Diblock Copolymers
Well-defined AEMA
AEMA -b-AnMMA diblock copolymers were successfully syn-
x
and
mers, hyperbranched polymers,
5
7–59
x
x
y
works.
‘‘living’’ polymerizations, that is, control over the molecular
x
and AnMMA
x
homopolymers and
weight (MW), narrow MW distributions (MWDs) and linear
6
0
x
y
MW-conversion profiles. Furthermore, RAFT is compatible
6
1
thesized following typical RAFT methodologies described in
Experimental section. The RAFT polymerization of the AEMA
with a wide range of monomers
tions.
and reaction condi-
6
2,63
For the first time, AEMA is combined with AnMMA
2
4
monomer first described by Krasia et al. proceeds in a
well-controlled manner resulting in polymers characterized
by monomodal and narrow MWDs. To the best of our knowl-
edge for the first time in this study, well-defined AnMMAx
homopolymers and AEMA -b-AnMMA diblock copolymers
to yield well-defined functional diblock copolymers present-
ing fluorescent and metal chelating properties. Hence, this
work describes the unique combination of a rare example of
a ligating monomer polymerized by RAFT, with a fluorescent
polymethacrylate, the controlled polymerization of which has
been rarely reported. The RAFT process was readily used to
prepare well-defined AnMMAx homopolymers as well as
diblock copolymers based on AnMMA and AEMA. The molec-
ular and compositional characteristics of the resulting homo-
polymers and copolymers were determined by size exclusion
x
y
are prepared by RAFT. The molecular characterization of
these materials was carried out by means of SEC and
NMR. Table 1 summarizes the chemical structures of all
homopolymers and diblock copolymers prepared in this
study along with their MW and composition characteristics.
1
H
1
chromatography (SEC) and H NMR spectroscopy, respec-
Low to moderate polydispersity indices (PDIs) were
observed for the homopolymers and diblock copolymers,
varying between 1.23 and 1.43. However, as seen in the table
low polymerization yields were obtained in the cases of the
tively. Furthermore, differential scanning calorimetry (DSC)
was used for determining the glass tranasition tempera-
ture(s) of the polymers.
WWW.MATERIALSVIEWS.COM
JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 52–60
53

ARTICLE
WWW.POLYMERCHEMISTRY.ORG
TABLE 1 Characteristics of the Homopolymers and Block Copolymers Based on AEMA and
AnMMA Obtained by RAFT (Polymerization Yields, Molecular Weights, and Polydispersity
Indices)
c
SEC Results
b
Yield
(%)
Theor. MW
a
ꢀ1
Experimental Structure
(g mol
)
M
n
PDI
AnMMA36 (CDTB)
AnMMA47 (CPBD)
AEMA42 (CDTB)
37.5
90
18,381
25,062
5,694
16,177
13,228
9,235
1.31
1.27
1.23
1.33
1.43
1.26
1.34
85
AEMA42-b-AnMMA83 (CDTB)
AEMA42-b-AnMMA113 (CDTB)
AEMA21 (CDTB)
17
17,688
25,810
2,414
18,802
38,870
4,749
20
90
AEMA21-b-AnMMA43 (CDTB)
25
14,279
15,822
a
1
Determined by SEC and H NMR.
b
[
(g monomer)/(mol RAFT agent)] ꢁ (polymerization yield) þ MW of CTA (for homopolymers) and [(g
of macro-CTA (for diblock copolymers).
: number average molecular weight; PDI: polydispersity index; CDTB: cumyl dithiobenzoate; CPBD: 2-
cyano-2-propylbenzodithioate.
monomer)/(mol CTA agent)] ꢁ (polymerization yield) þ M
n
c
M
n
AnMMAx homopolymer and the AEMA -b-AnMMAy diblock
MWs compared to that of the homopolymer, demonstrating
the block efficiency from homopolymer to block copolymer.
x
copolymers when cumyl dithiobenzoate (CDTB) was used as
the CTA. A significant increase in the polymerization yield was
observed when 2-cyano-2-propylbenzodithioate (CPBD) was
used instead as the CTA for the preparation of the AnMMAx
homopolymer by following exactly the same experimental con-
The expected chemical structure of the polymers was con-
1
1
firmed by H NMR spectroscopy. Figure 3 shows the
H
NMR spectra of the AEMA21 homopolymer and the AEMA21
-
b-AnMMA43 diblock copolymer.
6
1
ditions. As reported by Moad et al., at certain RAFT agent
concentrations, retardation—that is partially manifested by an
inhibition period corresponding to the required time to con-
vert the RAFT agent into a polymeric RAFT agent—occurs in a
much less extent in the case of CPBD compared to CDTB.
The peak assignments are shown in the spectra. The AEMA
comonomer compositions were determined from the ratio of
the areas under the characteristic signals of the AEMA and
AnMMA, appearing at 3.6 and 5.6 ppm, respectively.
Figure 2 displays the SEC traces of the AEMA21 homopoly-
Thermal Properties
mer and the corresponding AEMA -b-AnMMA diblock co-
2
1
43
DSC measurements provided the glass transition (T ) tem-
peratures of the AEMA and AnMMA homopolymers and the
x x
polymer. The MWD of the latter is shifted toward higher
g
1
FIGURE 2 SEC eluograms of the AEMA21 (black) and the
AEMA21-b-AnMMA43 (gray).
FIGURE 3 H NMR spectra of the AEMA21 homopolymer and
the AEMA21-b-AnMMA43 diblock copolymer.
54
JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 52–60

WWW.POLYMERCHEMISTRY.ORG
ARTICLE
for amines in organic solvents. To demonstrate the effective-
ness of these new polymers toward amine sensing, triethyl-
amine was chosen as an example. For this purpose, the
fluorescence intensity of a polymer solution was monitored
in the presence of various concentrations of triethylamine
(
ranging from 3.6 mM to 1 M). As seen in Figure 5, an
increase in the amount of the amine present in solution
causes a decrease in the fluorescence intensity. As previously
stated, the fluorescence quenching through electron transfer
6
6
requires that the amine is adjacent to the anthryl groups.
The presence of triethylamine at a much higher concentra-
tion (varying between 3.6 mM and 1 M) compared to the
concentration of the anthracene moieties within the copoly-
ꢀ
4
mer (1 ꢁ 10
M) renders the electron transfer process
possible.
It should be noted at this point that the possibility of elec-
tron transfer from the anthracene groups to chloroform mol-
1
1
ecules is not possible; hence, the fluorescence quenching is
sorely attributed to the electron transfer of the electron lone
pair of triethylamine to the anthracene moieties as illus-
trated in Figure 5.
FIGURE 4 DSC thermograms of the AEMA42 homopolymer, the
AnMMA36 homopolymer, and the AEMA42-b-AnMMA83 diblock
copolymer.
AEMA -b-AnMMA diblock copolymers. The T of the AEMA
x
x
y
g
ꢂ
homopolymer was determined to be ꢀ3 C, which is close to
2
4
Fluorescence Sensing Toward Metal Ions
our previous findings
whereas the T
g
of the AnMMA
x
ꢂ
The AEMA -b-AnMMA block copolymers are expected to
homopolymer was found to be around 125 C. Block copoly-
x
y
ꢂ
complex and solubilize different metal-ion salts in organic
media due to the presence of the strong bidentate b-
ketoester groups within their structure. The latter are known
to act as effective stabilizers for various metal ions of differ-
mers exhibited two T s (ꢃ10 C for the AEMA block and
g
x
ꢂ
ꢃ144 C for the AnMMA block), suggesting that microphase
y
separation may exist in the bulk. In general, the T s in block
g
copolymers can be influenced by the sizes of the phases gen-
erated and the compatibility of the different components
3
6
ent geometries and oxidation states.
6
4
(
blocks). According to Buzin et al. in the case where the
The b-ketoester moiety exists in two tautomeric forms (the
two blocks in a diblock copolymer are incompatible, the
lengths of the two segments are the determining factor for
the sizes of the phases generated due to microphase separa-
tion; the morphology of the latter will depend on their ratio.
keto and the enol) which are in equilibrium. Both tautomers
are capable of complexing transition metal ions. For the sys-
1
tems investigated in this study (AEMA -b-AnMMA ), the
H
x
y
NMR spectra recorded in CDCl (an example is presented in
3
The T s of both components are affected by the continuing
g
Fig. 3) show that the keto tautomer is the dominant one.
molecules that cross the interface. Depending on the phase
The ability of the AEMA -b-AnMMA diblock copolymers to-
mobility, variation in the T s of the different block segments
x
y
g
ward metal-ion sensing (Fe(III)) has been investigated in
chloroform. Chloroform is a common solvent for both blocks
in these copolymer systems; hence, the polymer exists only
as unimers in solution. On FeCl ꢄH O addition in the solution,
can be observed compared to the Tg values of the corre-
sponding homopolymers. Moreover, in the case of the
AnMMA segment, the observed differences in the glass tran-
sition of the AnMMA36 homopolymer and the AnMMA83
3
2
a color change was observed within a few seconds from light
yellow to deep wine red, attributed to the complex formation
between the Fe(III) ion and the b-ketoester groups. Presum-
ably, as shown in Figure 6, the octahedral structure of the
ferric salt is preserved and only the four water molecules
adjacent to the iron atoms are replaced by two keto tauto-
meric b-ketoester ligands. Figure 7 presents the ultra-violet/
visible (UV–Vis) spectrum of the AEMA -b-AnMMA /
block segment incorporated within the diblock copolymer
ꢂ
(
appearing at 125 and 144 C, respectively) may be rein-
forced by the increased MW and the more pronounced p–p
interactions occurring between the AnMMA aromatic side
chains of the AnMMA83 segment present in the diblock,
6
5
which promotes chain immobility.
Fluorescence Sensing Toward Amines
4
2
83
Electron donating groups located in the proximity of anthra-
cene moieties result in a drastic decrease in the fluorescence
intensity of anthracene due to electron transfer phenomena
occurring between the lone electron pair of the amines and
FeCl ꢄ6H O complex in chloroform. In the spectrum, the sig-
3
2
67
nal appearing at 550 nm confirms the complex formation.
As chloroform is a good solvent for the FeCl ꢄ6H O salt, it
3
2
should be mentioned that an excess of chloroform favors
decomplexation. This is indicated by a color change of the
solution on dilution, from wine red to yellow/orange (color
of FeCl ꢄ6H O in CHCl ).
6
6
the photoexcited anthracene units.
The AnMMA36 and AEMA -b-AnMMA systems were exam-
42
83
ined toward their ability to act as macromolecular sensors
3
2
3
WWW.MATERIALSVIEWS.COM
JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 52–60
55

ARTICLE
WWW.POLYMERCHEMISTRY.ORG
ꢀ
4
FIGURE 5 AnMMA36 and AEMA42-b-AnMMA83 fluorescence spectra (polymer concentration ¼ 10 M based on anthracene groups)
recorded in chloroform in the presence of different quencher (Et
3
N) concentrations, ranging from 3.6 mM to 1 M.
It is noteworthy to emphasize at this point the importance
of the use of a block copolymer structure toward Fe(III)
sensing in this particular solvent, since, as previously dem-
resulted in the formation of aggregates consisting of a poly
(AEMA)-metal ion core and a poly(BuMA) corona. Therefore,
it is expected that in the case of a random copolymer con-
sisting of AnMMA and AEMA units, the complexation of
Fe(III) ions with the latter will cause the destabilization of
the random copolymer chains in solution due to the fact that
these are not capable of self-organizing into soluble core-
shell micellar nanostructures.
6
7
onstrated, complexation of FeCl ꢄ6H O performed in chlo-
3
2
roform using poly(butyl methacrylate)-block-poly((2-acetoa-
cetoxy)ethyl methacrylate) (BuMA -b-AEMA ) revealed that
x
y
the coordination of the Fe(III) onto the AEMAy segment
reduced its solubility in that particular solvent. The latter
FIGURE 6 Substitution of ‘‘L’’ type of ligand molecules (H
2
O) in FeCl
3
2
ꢄ6H O by the ‘‘keto’’ form of the b-ketoester group.
56
JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 52–60

WWW.POLYMERCHEMISTRY.ORG
ARTICLE
EXPERIMENTAL
Materials and Methods
Benzene (Fluka, ꢅ 99.5%), ethyl acetate (Scharlau, 99%), tet-
rahydrofuran (Scharlau, 99.9%) were stored over CaH
Merck, 99.9%) and distilled under reduced pressure imme-
diately prior to the polymerization reactions. Chloroform
Scharlau, 99.9%) was dried over anhydrous MgSO . Metha-
2
(
(
4
nol (LabScan, 99.9%), n-hexane (LabScan, 99%), toluene
(
(
Sigma-Aldrich), HCl (Merck, 37% solution), diethyl ether
LabScan, 99.5%), benzoic acid (Merck, 99%), aqueous solu-
tion of tetrabutylammonium hydroxide (Sigma-Aldrich, 40%
wt), triethylamine (Merck, ꢅ99%), pyridine (Sigma-Aldrich,
ꢅ99.9% [HPLC]), benzyl chloride (Sigma-Aldrich, 99%), car-
bon tetrachloride (Riedel de Ha e¨ n, ꢅ99.8%), a-methylstyrene
(
Sigma-Aldrich, 99%), sodium methoxide (Aldrich, 30% solu-
tion in methanol), methacryloyl chloride (Sigma-Aldrich), 9-
anthracenemethanol (Aldrich, 97%), 2-cyano-2-propyl benzo-
dithioate (Sigma-Aldrich, >97% [HPLC]) and deuterated
chloroform (Merck) were used as received by the manufac-
turer. The following inorganic compounds were used without
further purification: Sulfur (Aldrich, powder ꢃ100 mesh),
silica gel (Aldrich, 60 Å, 70–230 mesh), NaOH pellets (Schar-
lau), NaHCO3 (Sigma-Aldrich, 99.5%), NaCl (HiMedia), and
FIGURE 7 UV–Vis spectrum of AEMA42-b-AnMMA83/FeCl
3
ꢄ6H
2
O
complex formed by the keto form of the b-ketoester ligands in
chloroform.
Based on the above, it is expected that in the case of the
AEMA -b-AnMMA /Fe(III) systems, micellar nanostructures
x
y
4
anhydrous MgSO (Scharlau). 2-Acetoacetoxy ethyl methacry-
are generated in solution, consisting of a poly(AEMA)-Fe(III)
core. It is assumed that this self-organized micellar nanoen-
vironment leads to the confinement of the complexed transi-
tion metal ion and of the fluorescent moieties within nano-
sized domains, reinforcing the interaction between the two,
thus promoting chelation-enhanced fluorescence quenching.
late (Aldrich, 95%) was passed through a basic alumina col-
umn prior to the polymerizations and used without further
purification. 2,2-Azobis(isobutylnitrile) (AIBN, Sigma-Aldrich,
95%) was recrystallized twice from ethanol and dried
in vacuo at room temperature for 3 days.
Figure
recorded in chloroform at 368 nm excitation wavelength
kexc) as a function of the concentration of the Fe(III) salt. As
8 presents the fluorescence quenching curves
Synthesis of Cumyl Dithiobenzoate (chain transfer agent)
CDTB was synthesized in two steps, following a procedure
(
70
reported by Rizzardo and coworkers. Briefly, the first step
seen in the graphs, a drastic decrease in the fluorescence in-
tensity is observed on complexation. As expected, the
quenching effect on the anthracene chromophore is further
enhanced on increasing the salt concentration in the system.
These results are in agreement with similar observations
involved the preparation of dithiobenzoic acid via the reac-
tion of sulfur, sodium methoxide, and benzyl chloride in
7
reported by other groups and have been attributed to the
presence of unpaired d electrons in transition metal ions
that can effectively quench the anthryl chromophore. Accord-
1
1
ing to Buruiana et al., the quenching processes that can
take place in anthracene-containing systems may involve dif-
ferent quenching mechanisms namely excimer or exciplex
formation, metal–p complex, electron transfer and energy
5
transfer. Paramagnetic metal ions such as Fe(III) (d ) pos-
sessing unpaired d electrons, when present at high concen-
trations lead to an effective quenching of the anthracene flu-
orescence. The possible quenching mechanism in the AEMAx-
b-AnMMA /Fe(III) systems may involve the energy transfer
y
from the singlet excited-state anthracene chromophores to
the low-lying half-filled 3d orbitals of the Fe(III) paramag-
6
8
netic cation. Moreover, the decrease in the fluorescence in-
tensity is accompanied by a blue shifting in the spectrum.
Blue shifts in the fluorescence spectra were previously
ꢀ
4
FIGURE 8 AEMA42-b-AnMMA83 (polymer concentration ¼ 10
3
þ
observed on complexation of Fe
as well as other metal
M based on anthracene groups) fluorescence spectra recorded
in chloroform in the presence of different quencher
2þ
2þ
þ
3þ
ions including Pb , Fe , Cu , Sb and lanthanides with
2
8,69
polymers.
(FeCl
3
2
ꢄ6H O) concentrations (12.3 and 18.5 mM).
WWW.MATERIALSVIEWS.COM
JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 52–60
57

ARTICLE
WWW.POLYMERCHEMISTRY.ORG
methanol at room temperature for 18 h. Subsequently,
temperature. The produced AEMA (2.48 g, 85% polymeriza-
x
dithiobenzoic acid was left to react with a-methylstyrene in
carbon tetrachloride at 70 C for 18 h to obtain CDTB in
tion yield) was retrieved by precipitation in methanol and
was left to dry in vacuo at room temperature for 24 h.
ꢂ
1
9.3% yield after purification by column chromatography
1
H NMR (300 MHz, CDCl
.10 (br, s, ¼¼ CH (enol)), 4.2 (s, ACH ), 4.08 (s, ACH ), 3.6
3
) d (ppm): 11.90 (s, AOH (enol)),
(
silica gel), using n-hexane as a solvent.
5
2
2
1
H NMR (300 MHz, CDCl ) d (ppm): 7.87 (d, 2H), 7.58–7.22
(s, ACH ), 1.8 (s, ACOCH ), 1.74–0.76 (ACH , ACH ).
2 3 2 3
3
(
m, 8H), 2.01 (s, ACH3).
Synthesis of 9-Anthrylmethyl Methacrylate, AnMMA
For the synthesis of the AnMMA, anthracenemethanol (3 g,
Synthesis of AEMA -b-AnMMA Diblock copolymers
x
y
SEC
To a round-bottom flask, the macro-CTA, AEMA (Mn
¼
4
2
0
.014 mol) was dissolved in tetrahydrofuran (12 mL). Subse-
quently, triethylamine (3 mL, 0.016 mol), pyridine (2 mL,
.016 mol), and methacryloyl chloride (2.1 mL, 0.016 mol)
ꢀ
1
9
,235 g mol , 200 mg, 0.022 mmol) was placed and kept
under a dry nitrogen atmosphere. AIBN (1.6 mg, 0.0096
mmol) and AnMMA (1.08 g, 3.909 mmol) dissolved in tetra-
hydrofuran (1.3 mL) were then transferred into the flask via
a syringe. The reaction mixture was degassed by three
freeze–evacuate–thaw cycles and placed under a dry nitro-
0
were added with a 20% excess, in the reaction flask. The
methacryloyl chloride was added dropwise during stirring at
ꢂ
0
C. After addition, the mixture was allowed to reach room
temperature and was then left to stir for 1 h. Continuously,
water (10 mL) was added and the mixture was extracted
with diethyl ether followed by the extraction of the organic
ꢂ
gen atmosphere at 62 C for 20 h. The polymerization was
terminated by cooling the reaction down to room tempera-
ture. The produced diblock copolymer was retrieved by mul-
tiple precipitations in methanol and was left to dry in vacuo
at room temperature for 24 h.
phase with HCl (1 M, 3ꢁ 5 mL), then with NaHCO solution
3
(
(
5% in water 3ꢁ 5 mL) and with a saturated NaCl solution
3ꢁ 5 mL). Afterward, the solvent was removed under
1
reduced pressure and the product was recrystallized from
H NMR (300 MHz, CDCl
3
) d (ppm): 11.90 (s, AOH (enol)),
), 4.35 (s, ACH ), 4.16
s, ACH ), 3.56 (s, ACH ), 2.35 (s, ACOCH ), 0.85–1.74 (br,
methanol (42% yield).
7.16–8.03 (br, APh), 5.6 (br, ANCH
(
2
2
1
2
2
3
H NMR (300 MHz, CDCl ) d (ppm): 7.2–8.5 (m, APh), 6.2 (s,
3
ACH , ACH ).
2
3
ACH Ph), 6.05 (s, APh), 5.50 (s, APh), 5.30 (s, ¼¼ CH ), 3.49
2
2
(
s, ¼¼ CH ), 2.17 (s, ACH ), 1.9 (ACH ).
2
2
3
Synthesis of AnMMA Homopolymers
Characterization
AnMMA (800 mg, 2.87 mmol) was placed in a round-bottom
flask and dissolved in freshly distilled benzene (1.2 mL)
under a dry nitrogen atmosphere. CDTB (7.89 mg, 0.029
mmol) and AIBN (2.61 mg, 0.016 mmol) were dissolved in
benzene and then were transferred into the flask via a sy-
ringe. The reaction mixture was degassed by three freeze–
evacuate–thaw cycles, and placed under a dry nitrogen
NMR spectra were recorded in CDCl with tetramethylsilane
3
used as an internal standard using an Avance Brucker 300
MHz spectrometer equipped with an Ultrashield magnet. The
MWs and PDIs of the polymers were determined by SEC
using equipment supplied by Polymer Standards Service
(PSS). All measurements were carried out at room tempera-
ture using Styragel HR 3 and Styragel HR 4 columns. The
mobile phase was THF, delivered at a flow rate of 1 mL
ꢂ
atmosphere at 65 C for 20 h. The polymerization was termi-
ꢀ
1
nated by cooling the reaction down to room temperature.
The produced homopolymer (300 mg, 37.5% polymerization
yield) was retrieved by multiple precipitations in methanol
and was left to dry in vacuo at room temperature for 24 h.
The synthesis of AnMMA was also carried out using the
x
commercially available CPBD (6.4 mg, 0.029 mmol) as the
CTA following the same experimental conditions (718.7 mg,
min
using a Waters 515 isocratic pump. The refractive
index was measured with a Waters 2414 refractive index de-
tector supplied by PSS. The instrumentation was calibrated
using poly(methyl methacrylate) standards with low PDI
(MWs of 7,39,000, 4,46,000, 2,70,000, 1,26,000, 65,000,
31,000, 1,44,00, 4,200, 1,580, 670, 450, and 102 (methyl
ꢀ
1
isobutyrate) g mol ) supplied by PSS. DSC was used to
8
9.8% polymerization yield).
measure the T s of the homopolymers, and block copolymers
g
ꢂ
1
using a Q100 TA Instrument with a heating rate of 10
C
H NMR (300 MHz, CDCl ) d (ppm): 7.2–8.5 (m, br, Ph), 6.2
3
ꢀ1
min . Each sample was scanned twice between ꢀ100 and
(
br, ACH Ph), 1.99–0.7 (ACH , ACH ).
2
2
3
ꢂ
þ150 C. The second run (heat) was used for data analysis.
Synthesis of AEMA Homopolymers
UV–Vis spectra were recorded at room temperature using
dual-beam grating spectrophotometer (Jasco V-630). Meas-
urements were carried out in chloroform by placing the solu-
tions in a 1 cm quartz cells. Fluorescence emission spectra
were recorded in chloroform by using a Jasco 6300 spectro-
fluorimeter. The excitation wavelength was set at 368 nm.
To a round-bottom flask (25 mL) maintained under a dry
nitrogen atmosphere, AEMA (2.7 mL, 14.0 mmol) was added.
CDTB (127 mg, 0.47 mmol) and AIBN (14.0 mg, 0.09 mmol)
were dissolved in freshly distilled ethyl acetate (3.0 mL) and
were transferred into the flask with the aid of a syringe. Sub-
sequently, the resulting solution was degassed by three
freeze–evacuate–thaw cycles, placed under a dry nitrogen
ꢀ
4
The polymer concentration in solution was 1 ꢁ 10
M
(polymer concentration based on anthracene groups)
whereas the concentration of the triethylamine varied from
3.6 mM to 1 M and of the FeCl ꢄ6H O 12.3 and 18.5 mM.
ꢂ
atmosphere and heated at 65 C for 20 h. The polymeriza-
tion was terminated by cooling the reaction down to room
3
2
58
JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 52–60

WWW.POLYMERCHEMISTRY.ORG
ARTICLE
CONCLUSIONS
18 Chae, K. H.; Kim, Y. W.; Kim, T. H. Bull Korean Chem Soc
2
002, 23, 1351–1354.
In summary, we have presented for the first time the effec-
1
9 Xiaoping, Z.; Shuna, S.; Deqing, Z.; Huimin, M.; Daoben, Z.
tiveness of well-defined methacrylate-based AEMA -b-AnM-
x
Anal Chim Acta 2006, 575, 62–67.
y
MA diblock copolymers possessing b-ketoester metal chelat-
2
0 Vinyard, J. D.; Su, S.; Richter, M. M. J Phys Chem A 2008,
ing and anthryl fluorescent side-chain functionalities to act
as dual-chemosensors for amines and transition metal ions
in organic solvents. The preparation of these systems
involved an easy, cost-effective, and versatile controlled radi-
cal polymerization technique that enabled the synthesis of
polymeric materials characterized by predetermined MWs
and low MWD. The aforementioned block copolymer chemo-
sensors and the simple strategy followed for their synthesis
may be useful in the design and development of new and ef-
ficient chemosensors in the future.
1
12, 8529–8533.
2
1 Baumes, M. J.; Gassensmith, J. J.; Giblin, J.; Lee, J.-J.;
White, G. A.; Culligan, J. W.; Leevy, W. M.; Kuno, M.; Smith, D.
B. Nat Chem 2010, 2, 1025–1030.
22 Tong, J.-D.; Zhou, C.; Ni, S.; Winnik, M. A. Macromolecules
2001, 34, 696–705.
23 Lu, J.-M.; Xu, Q.-F.; Yuan, X.; Xia, X.-W.; Wang, L.-H.
J Polym Sci Part A: Polym Chem 2007, 45, 3894–3901.
24 Krasia, T.; Soula, R.; B o¨ rner, H.; Schlaad, H. Chem Commun
2
003, 4, 538–539.
2
5 De Silva, A. P.; Gunaratne, H. Q. N.; Gunnlaugsson, T.
This work was financially supported by the Cyprus Research
Chem Rev 1997, 97, 1515–1566.
Promotion Foundation (Program TEXNOKOCIA/HPIR/
2
6 Czarnik, A. W. In Topics in Fluorescence Spectroscopy:
0308(BE)/06). The authors are grateful to M. Zamfir for useful
Probe Design and Chemical Sensing; Lakowicz, J. R., Ed.; Ple-
num Press: New York, 1994; Vol. 4.
discussions, C. S. Patrickios and E. Leontidis for providing access
to the DSC apparatus and the fluorescence spectrophotometer
respectively. Finally, the authors thank the A. G. Leventis Founda-
tion for a generous donation that enabled the purchase of the
NMR spectrometer from the University of Cyprus.
2
7 Fabbrizzi, L.; Licchelli, M.; Pallavicini, P.; Perotti, A.; Sacchi,
D. Angew Chem Int Ed 1994, 33, 1975–1977.
28 Prodi, L.; Bolletta, F.; Montalti, M.; Zaccheroni, N. Coord
Chem Rev 2000, 205, 59–83.
2
9 Corradini, R.; Paganuzzi, C.; Marchelli, R.; Pagliari, S.; Dos-
sena, A.; Duchateau, A. J. Incl Phenom Macrocycl Chem 2007,
5
7, 625–630.
REFERENCES AND NOTES
3
0 Chang, J. H.; Jeong, Y.; Shin, Y.-K. Bull Korean Chem Soc
1
Kim, H. N.; Guo, Z.; Zhu, H.; Juyoung, Y.; He, T. Chem Soc
Rev 2011, 40, 79–93.
Basabe-Desmonts, L.; Reinhoudt, D. N.; Crego-Calama, M.
Chem Soc Rev 2007, 36, 993–1017.
Ambade, A. V.; Sandanaraj, B. S.; Klaikherd, A.; Thayumana-
van, S. Polym Int 2007, 56, 474–481.
2003, 24, 119–122.
1 Clark, M. A.; Duffy, K.; Tibrewala, J.; Lippard, S. J. Org Lett
2003, 5, 2051–2054.
3
2
3
3
2 Yanga, C.; Lee, T. S. Mol Cryst Liq Cryst 2000, 349, 283–286.
3 Chen, Z.; Xue, C.; Shi, W.; Luo, F.-T.; Green, S.; Chen, J.;
3
Liu, H. Anal Chem 2004, 76, 6513–6518.
4
Feng, X.; Liu, L.; Wang, S.; Zhu, D. Chem Soc Rev 2010, 39,
3
4 Wang, H.-W.; Cheng, Y.-J.; Chen, C.-H.; Lim, T.-S.; Fann, W.;
2
411–2419.
Lin, C.-L.; Chang, Y.-P; Lin, K.-C.; Luh, T.-Y. Macromolecules
2007, 40, 2666–2671.
5
Ghoroghchian, P. P.; Therien, M. J.; Hammer, D. A. Wiley
Interdiscip Rev Nanomed Nanobiotechnol 2009, 1, 156–167.
3
5 Thomas, S. W.; IIIJoly, G. D.; Swager, T. M. Chem Rev 2007,
6
Kalinowski, J. Opt Mater 2008, 30, 792–799.
107, 1339–1386.
7
Miao, L.; Liu, X.; Fan, Q.; Huang, W. Prog Chem 2010, 22,
36 Mehrotra, R. C.; Bohra, B.; Gaur, D. P. Metal b-Diketonates
2338–2352.
and Allied Derivatives; Academic Press:New York, 1978.
8
Hargreaves, J. S.; Webber, S. E. Macromolecules 1984, 17,
37 Teyssi e´ , P.; Smets, G. Makromol Chem 1958, 26, 245–
235–240.
251.
9
Gonzalez, C.; Lim, E. C. Chem Phys Lett 2000, 322, 382–388.
38 Masuda, S.; Sertova, N.; Petkov, I. J Polym Sci Part A:
Polym Chem 1997, 35, 3683–3688.
10 Mart ´ı nez-M a´ nˇ ez, R.; Sancen o´ n, F. Chem Rev 2003, 103,
4419–4476.
39 Inn, M.; G e´ rardin, C.; Lambard, J.; Sanchez, C. J. Sol-Gel Sci
Technol 1995, 5, 101–114.
11 Buruiana, E. C.; Olaru, M.; Simionescu, B. C. Eur Polym J
2007, 43, 1359–1371.
40 Masuda, S.; Minagawa, K. Prog Polym Sci 1996, 21,
5
57–591.
12 Hideharu, M.; Izumi, T.; Hiromi, T. Macromolecules 2010,
43, 7011–7020.
41 Agarwal, R.; Bell, J. S. Polym Eng Sci 1998, 38, 299–310.
13 Shuqiang, Y.; Lei X. Hongbo, W.; Ping L. Tetrahedron 2007,
42 Schlaad, H.; Krasia, T.; Patrickios, C. S. Macromolecules 2002,
63, 7809–7815.
34, 7585–7588.
14 Jong-Hwa, P.; Dae, S. C.; Dong Hoon, L.; Hoyoul, K.; In
43 Boyer, C.; Stenzel, M. H.; Davis, T. P. J Polym Sci Part A:
Hwan, J.; Moo-Jin, P.; Nam Sung, C.; Chan Eon, P.; Hong-Ku,
S. Chem Commun 2010, 46, 1863–1865.
Polym Chem 2011, 49, 551–595.
4
4 Pascual, S.; Blin, T.; Saikia, P. J.; Thomas, M.; Gosselin, P.;
1
5 Roberts, G. G.; McGinnity, M.; Barlow, W. A.; Vincett, P. S.
Solid State Commun 1979, 32, 683–686.
6 Hriz, K.; Jaballah, N.; Chemli, M.; Fave, J. L.; Majdoub, M.
J Appl Polym Sci 2010, 119, 1443–1449.
Fontaine, L.
5053–5062.
J Polym Sci Part A: Polym Chem 2010, 48,
1
45 McCormick, C. L.; Lowe, A. B. Acc Chem Res 2004, 37,
312–325.
17 Li, T.; Chen, J.; Mitsuishi, M.; Tokuji, M. J Mater Chem
46 Venkataraman, S.; Wooley, K. L. J Polym Sci Part A: Polym
2003, 13, 1565–1569.
Chem 2007, 45, 5420–5430.
WWW.MATERIALSVIEWS.COM
JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 52–60
59

ARTICLE
WWW.POLYMERCHEMISTRY.ORG
4
7 Gemici, H.; Legge T. M.; Whittaker, M.; Monteiro, M. J.; Per-
rier, S. J Polym Sci Part A: Polym Chem 2007, 45, 2334–2340.
8 Liu, L.; Zhang, J.; Lv, W.; Luo Y.; Wang, X. J Polym Sci Part
A: Polym Chem 2010, 48, 3350–3361.
59 Goh, Y. K.; Whittaker, A. K.; Monteiro, M. J. J Polym Sci
Part A: Polym Chem 2007, 45, 4150–4153.
4
60 Matyjaszewski, K. Curr Opin Solid State Mater Sci 1996, 1,
769–776.
49 Barner-Kowollik, C.; Davis, T. P.; Stenzel, M. H. Aust J Chem
61 Moad, G.; Rizzardo, E.; Thang, S. H. Aust J Chem 2005, 58,
2006, 59, 719–727.
379–410.
50 Audouin, F.; Knoop, R. J. I.; Huang, J.; Heise, A. J Polym Sci
62 Convertine, A. J.; Lokitz, B. S.; Lowe, A. B.; Scales, C. W.;
Part A: Polym Chem 2010, 48, 4602–4610.
Myrick, L. J.; McCormick, C. L. Macromol Rapid Commun 2005,
2
6, 791–795.
51 Kakwere, H.; Perrier, S. J Polym Sci Part A: Polym Chem
2009, 47, 6396–6408.
63 Moad, G.; Mayadunne, R. T. A.; Rizzardo, E. Macromol
Symp 2003, 192, 1–12.
52 Zhu, J.-L.; Zhang, X.-Z.; Cheng, H.; Li, Y.-Y.; Cheng, S.-X.;
Zhuo, R.-X.
J
Polym Sci Part A: Polym Chem 2007, 45,
64 Buzin, A. I.; Pyda, M.; Costanzo, P.; Matyjaszewski, K.; Wun-
5354–5364.
derlich, B. Polymer 2002, 43, 5563–5569.
53 Luzon, M.; Boyer, C.; Peinado, C.; Corrales, T.; Whittaker,
65 Allcock, H. R.; Lampe, F. W.; Mark, J. E. Contemporary Polymer
M.; Tao, L.; Davis, T. P. J Polym Sci Part A: Polym Chem 2010,
Chemistry, 3rd ed.; Pearson Education, Inc.: New Jersey, 2003.
4
8, 2783–2792.
6
6 Kim, J.-M.; Chang, T.-E.; Han, D. K.; Ahn, K.-D. J Photo-
polym. Sci. Technol 2000, 13, 273–276.
7 Krasia, T.; Schlaad, H. ACS Symp Ser 2006, 928, 157–
167.
54 Liu, B. L.; Kazlauciunas, A.; Guthrie, J. T.; Perrier, S. Poly-
mer 2005, 46, 6293–6299.
6
55 Carter, S.; Hunt, B.; Rimmer, S. Macromolecules 2005, 38,
4595–4603.
6
8 Weizman, H.; Ardon, O.; Mester, B.; Libman, J.; Oren Dwir,
5
6 Carter, S.; Rimmer, S.; Sturdy, A.; Webb, M. Macromol Bio-
O.; Hadar, Y.; Chen, Y.; Shanzer, A. J Am Chem Soc 1996, 118,
12368–12375.
sci 2005, 5, 373–378.
57 Krasia, T. C.; Patrickios, C. S. Macromolecules 2006, 39,
69 Wang, B.; Wasielewski, M. R. J Am Chem Soc 1997, 119,
2467–2473.
12–21.
58 Achilleos, M.; Krasia-Christoforou, T.; Patrickios, C. S.
70 Le, T. P. T.; Moad, G.; Rizzardo, E.; Thang, S. H. PCT Int.
Macromolecules 2007, 40, 5575–5581.
Appl. WO 9801478 A1 980115, 1998.
60
JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 52–60