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Table 1 Fluorescence quenching response (%) at a given time for various similar conjugated polymers is feasible and applicable for directly
a
isocyanates using polymer P1
monitoring the isocyanate chemicals at a workplace.
This work was supported by the Natural Science and Engineer-
Time (s)
10
20
30
40
50
60
120
180
240
ing Research Council of Canada and National Natural Science
Foundation of China (21134005, 21074132, 20920102032 and
20834001).
PPDI
MDI
TDI
PI
NO PI
2
MeOPI
HDI
23
41
22
21
14
22
24
19
31
49
30
30
18
31
26
21
48
56
42
41
32
41
40
28
54
62
52
52
40
45
45
38
63
69
60
60
49
54
53
50
71
74
63
66
61
59
62
52
75
76
67
70
66
61
67
54
78
81
70
73
69
65
71
58
81
82
75
77
72
66
73
63
Notes and references
1
2
J. H. Saunders and R. J. Slocombe, Chem. Rev., 1948, 43, 203.
R. G. Arnold, J. A. Nelson and J. J. Verbanc, J. Chem. Educ., 1957, 34, 158.
IPDI
a
The film thickness is in a range of 4–7 nm for all measurements.
3 M. Sato, J. Am. Chem. Soc., 1960, 82, 3893.
4
5
6
M. Kaplan, J. Chem. Eng., 1961, 6, 272.
R. B. Seymour and G. B. Kauffman, J. Chem. Educ., 1992, 69, 909.
Flexible polyurethane foams. Technical bulletin 2008, Doc. No. AX-239.
At 60 s of exposure, the order of the FQR is MDI > PPDI > PI >
TDI > HDI > NO
2
PI > MeOPI > IPDI. The experimental results
7 R. P. Streicher, C. M. Reh, R. Key-Schwartz, P. C. Schlecht and M. E.
Cassinelli, NOISH Manual of Analytical Methods, 2004, 116.
A Summary of Health Hazard Evaluations: Issues Related to Occupa-
tional Exposure to Isocyanates, 1989 to 2002, 2004, 116.
indicate that polymer P1 can maintain a high sensitivity towards
aliphatic and aromatic isocyanates. The detection sensitivity or
FQR relates to the vapor pressure of the isocyanate. For aromatic
mono-isocyanates, polymer P1 shows a higher sensitivity towards
phenyl isocyanate, due to the higher vapor pressure of PI
8
9 L. H. Kormos, R. L. Sandridge and J. Keller, Anal. Chem., 1981, 53, 1122.
0 L. T. Budnik, D. Nowak, R. Merget, C. Lemiere and X. Baur, J. Occup.
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1 M. M. Methner, C. Achutan and A. Adebayo, Health Hazard Evalua-
tion Report, 2004-0349-2970 and the references there in.
1
1
(1.4 mmHg, Table S1, ESI†) than that of MeOPI (0.107 mmHg)
À3
12 See ref. 2 in ESI†.
or NO
2
PI (6.84 Â 10 mmHg). The detection sensitivity is also
1
3 (a) C. J. Purnell and R. F. Walker, Analyst, 1985, 110, 893; (b) R. J.
Rando and Y. Y. Hammad, Am. Ind. Hyg. Assoc. J., 1985, 46, 206.
related to the nature or reduction potential of isocyanates. Polymer
P1 shows a higher sensitivity towards aromatic diisocyanates than 14 (a) K. Marcali, Anal. Chem., 1957, 29, 552; (b) K. E. Grim and A. L.
Linch, Am. Ind. Hyg. Assoc. J., 1964, 25, 285.
5 J. Keller, K. L Dunlap and R. L. Sandridge, Anal. Chem., 1974, 46, 1845.
6 J. Keller and R. L. Sandridge, Anal. Chem., 1979, 51, 1868.
aliphatic diisocyanates, because the former is more electron
1
1
deficient than the latter, even though MDI has a much lower
À6
À3
vapor pressure (4.5 Â 10 mmHg) than HDI (5.26 Â 10 mmHg) 17 R. F. Walker and M. A. Pinches, Analyst, 1979, 104, 928.
À4
18 L. H. Kormos, R. L. Sandridge and J. Keller, Anal. Chem., 1981, 53, 1122.
or IPDI (3.0 Â 10 mmHg). For the same reason, PPDI has a vapor
1
9 W. E. Rudzinski, L. Pin, R. Sutcliffe, A. Richardson and T. Thomas,
Anal. Chem., 1994, 66, 1664.
À3
pressure less than 6.0 Â 10 mmHg but due to its highly electron-
deficient nature causes the highest FQR for polymer P1. Since MDI 20 (a) S. Gagn ´e , J. Lesage, C. Ostiguy, Y. Cloutier and H. V. Tra, J. Environ.
Monit., 2005, 7, 145; (b) D. Karlsson, M. Spanne, M. Dalene and
has the lowest vapor pressure or vapor concentration of 0.062 ng
G. Skarping, Analyst, 1998, 123, 117.
À1
mL among all the eight isocyanates tested, the detection limit of
2
1 B. Agarwal, S. J u¨ rschik, P. Sulzer, F. Petersson, S. Jaksch, A. Jordan
and T. D. M ¨a rk, Rapid Commun. Mass Spectrom., 2012, 26, 983.
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polymer P1 should be at the ppt level (i.e., 0.06 ppt) and is much
lower than the permissible exposure limit (PEL) of 5 ppb.
2
2
2
2
The FQR value is higher for MeOPI than NO PI during the
initial 60 s exposure but is lower for MeOPI than NO PI after 25 W. Theilacker, U. Berger-Brose and K.-H. Beyer, Chem. Ber., 1960, 93, 1658.
2
2
2
2
6 J.-S. Yang and T. M. Swager, J. Am. Chem. Soc., 1998, 120, 11864.
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6
0 s. This time-dependent FQR is likely due to the different
permeability of these two isocyanates in the polymer film. Since
the gas permeation involves adsorption of the permeating
species onto the polymer, diffusion through the polymer and
desorption of the permeating species from the polymer surface
and removal, the permeability can be affected by solubility and
diffusivity of isocyanate molecules in the polymer film. At the
beginning, the FQR is mainly controlled by the diffusion rate,
which is governed by the vapor pressure. Therefore, MeOPI with
a higher vapor pressure (0.107 mmHg) gives a higher FQR than
NO
desorption of isocyanate molecules in a polymer reach an
equilibrium and the FQR should now be governed by the
isocyanate solubility in the polymer. Thus, NO
affinity gives a larger FQR than MeOPI.
2
001, 1740; (b) B. Z. Tang, X. Zhan, G. Yu, P. P. S. Lee, Y. Liu and
D. Zhu, J. Mater. Chem., 2001, 11, 2974.
2
3
3
3
3
3
3
3
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À3
2
PI (6.84 Â 10 mmHg). At a later stage, the adsorption and
2
PI with a higher
In summary, a conjugated fluorescent polymer has been success-
fully synthesized and used for direct detection of various isocyanates
in air. Polymer P1 is highly sensitive to aromatic and aliphatic 37 Y. Liu, C. Deng, L. Tang, A. Qin, R. Hu, J. Z. Sun and B. Z. Tang,
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isocyanates with a detection limit at the ppt level. The isocyanate
sensing under ambient conditions is fast, typically within a period
3
3
of 10–60 s. A highly sensitive optical sensor based on P1 or other 40 Z. Zhu and T. M. Swager, Org. Lett., 2001, 3, 3471.
718 | Chem. Commun., 2014, 50, 716--718
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