JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
initiator. Pertinent data about its characteristics are reported
in Table 1.
refractometer (DR, Polymer Laboratories), connected in par-
allel, were used as detectors. The instrument was calibrated
with a mixture of five PMMA standards using PL-Caliber gel
permeation chromatography (GPC) software for the determi-
nation of average molecular masses of samples.
Synthesis of Copolymethyl Methacrylates
Containing Different Amounts of H2-P(TEG-ME)3Acr
Random copolymers have been synthesized by radical poly-
merization starting from mixtures of MMA and H2-P(TEG-
ME)3Acr.
1H and 13C NMR Spectroscopy
1H and 13C NMR spectra of the synthesized monomers and
copolymers were recorded on an AC 200 MHz Bruker spec-
trometer interfaced with an Aspect 3000 computer, using the
Bruker DISR 90 acquisition software. Spectra were recorded
in CD2Cl2 or CDCl3 at 25 ꢁC. 1H and 13C NMR data are
reported in parts per million (ppm) as chemical shift relative
to tetramethylsilane (in the case of CDCl3) or to residual
CH2Cl2 (in the case of CD2Cl2) as the internal standard. The
DEPT-135 13C NMR spectra were acquired using the Bruker
microprogram DEPT.AU.
Typically, to prepare a copolymer with a nominal H2-P(TEG-
ME)3Acr content of 10% (mol/mol), indicated in the follow-
ing as COP I, 50 mg of H2-P(TEG-ME)3Acr (0.045 mmol) and
40.3 mg of MMA (0.403 mmol) are solubilized in 10 mL of
toluene and heated at 80 ꢁC. Then, 2.2 mg of AIBN (0.013
mmol, 3% of the total molar monomer amount) is added,
and the solution is stirred at the same temperature for 1 h.
After cooling, the solution is poured in 50 mL of ethyl ether;
unreacted monomers and low-molecular-weights oligomers
remain in solution, whereas copolymer precipitates. The resi-
due is solubilized in 10 mL of toluene and precipitated in 50
mL of ethyl ether other three times to purify the copolymer.
MALDI-TOF Mass Spectrometric Analysis
MALDI-TOF mass spectra were acquired by a 4800 Proteo-
mics analyzer MALDI TOF/TOF mass spectrometer (Applied
Biosystems, Framingham, MA) in both linear and reflectron
mode and in positive polarity. The samples were prepared
by mixing about 0.1 mmol of monomer or polymer and
40 mmol of trans-3-indoleacrylic acid (used as a matrix) on
the sampler target, using THF as a solvent. The m/z values
reported in the spectra and in the text are referred to molec-
ular ions constituted by the most abundant isotopes of each
element present in the molecule.
Differently from some porphyrin homopolymers,8 in which
the proximity among dye units can cause some electronic
interactions leading, as an example, to the decrease of the
molar absorption coefficient of Soret band with respect to
that of starting monomers, the low porphyrin concentration
in our copolymers (lower than 19%, see Table 1) assures an
analogous behavior of both free and bound porphyrin mono-
mers. As a consequence, the actual porphyrin content in
copolymers can be valued by UV–vis spectroscopy using the
molar absorbance coefficient of 5.3 ꢂ 105 L molꢀ1 cmꢀ1 (in
THF) determined for H2-P(TEG-ME)3Acr.
UV–Visible Spectrophotometric Analysis
UV–visible spectra were recorded on a Perkin-Elmer Model
330 spectrophotometer at room temperature, using THF as a
solvent and 0.1-cm quartz cuvettes. The porphyrin content
in each copolymer sample was evaluated by considering the
absorption value at 424 nm (maximum absorption wave-
length for porphyrin groups in THF) using Beer’s law and a
molar absorption of 5.3 ꢂ 105 L molꢀ1 cmꢀ1, determined for
H2-P(TEG-ME)3Acr in THF.
Pertinent data about composition, yield, and molecular mass
of copolymers are reported in Table 1.
Sensor Device Assembly
To obtain a very thin layer of porphyrin copolymer stratified
on a transparent PMMA substrate, commercial PMMA plates
(1 cm ꢂ 5 cm ꢂ 0.1 cm) have been immersed in a very
diluted solution of copolyporphyrin acrylate [2 ꢂ 10ꢀ2 g Lꢀ1
in THF/ETOH (1/1.75, v/v)] for 1 s, extracted, and then
dried by air flow. Under these conditions, PMMA plates cov-
ered, on both sides, by a substantially homogeneous very
thin coating of porphyrin copolymer were obtained, in which
porphyrin units were all placed on the surface (or very near
to it) and therefore able to quickly interact with gaseous
analyte molecules (see Results and Discussion); besides, the
right choice of the solvent avoided any eventual alteration of
the substrate surface. In the following, these coated plates
will be indicated as ‘‘sensors.’’
Characterization
Gel Permeation Chromatography
A PL-GPC 110 (Polymer Laboratories) thermostated system,
equipped with two Mixed-D and one Mixed-E PL-gel 5 lm
columns joined in series, was used. The analyses were per-
formed at 35.0 6 0.1 ꢁC using THF as an eluent at a flow
rate of 1 mL minꢀ1. A UV–vis spectrophotometer (Hewlett
Packard series 1050, fixed at 424 nm) and a differential
UV–vis spectra of sensors have shown a Soret band intensity
comparable with that of a 5 ꢂ 10ꢀ7 M H2-P(TEG-ME)3Acr/
THF solution.
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