Macromolecules, Vol. 37, No. 8, 2004
Communications to the Editor 2681
Ta ble 1. Su m m a r y of Activa tion Ra te Con sta n ts in CH3CN for Va r iou s Cop p er (I) Com p lexes a n d In itia tor s Used in th e
ATRP As Deter m in ed Usin g th e Stop p ed -F low Tech n iqu e
kact/M- s-1
1
∆H /kJ mol
‡
-1 a
∆S /J K mol-1 a
‡
-1
complex
initiator
EBriB
reaction order
pseudo first
T/°C
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Cu Br/2dNbpy
15
0.49 ( 0.01
33.5 ( 1.7
38.9 ( 3.6
20.3 ( 1.2
-134 ( 6
2
3
5
5
0.78 ( 0.02
1.3 ( 0.05
I
Cu Br/PMDETA
EBriB
PEBr
pseudo first
pseudo first
15
1.4 ( 0.03
-107 ( 12
-120 ( 4
2
3
5
5
5
5
5
5
2.3 ( 0.06
4.3 ( 0.07
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2
2
2
3
3
3
3
3
Cu Br/Me6TREN
(4.5 ( 0.2) × 10
(6.7 ( 0.2) × 10
(8.6 ( 0.3) × 10
(1.2 ( 0.3) × 10
(5.7 ( 0.3) × 10
(6.9 ( 0.1) × 10
(7.7 ( 0.2) × 10
(1.1 ( 0.3) × 10
1
2
3
EBriB
MBP
second
15
19.3 ( 3.1
-106 ( 11
2
2
0
5
pseudo first
25
a
2
For fit index (R ) see Figure 2 and Supporting Information.
I
same experimental conditions. The activation rate
, Cu Br/Me6TREN. The rate constants of activation
q
q
2
-1 -1
3
-1
constants and parameters (∆H and ∆S ), determined
for the copper(I) complexes and alkyl halides in CH3-
CN, are summarized in Table 1.
(kact) for PEBr (8.6 × 10 M
s
), MBP (1.1 × 10 M
-
1
3
-1 -1
s
), and EBriB (7.7 × 10 M
s ) at 25 °C for the
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Cu Br/Me6TREN complex were found to be orders of
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The activation rate constants for Cu Br/2dNbpy and
magnitude higher than the corresponding Cu Br/2dN-
bpy and Cu Br/PMDETA complexes. The demonstrated
effectiveness of the stopped-flow technique to measure
fast reaction rates opens a new way to systematically
determine activation rate constants and activation
parameters for other highly active ATRP complexes.
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Cu Br/PMDETA systems are in good agreement with
1
8,26,27,30
previously reported values using GC techniques.
Furthermore, the activation parameters for PEBr and
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I
EBriB using Cu Br/2dNBpy, Cu Br/PMDETA, and Cu -
Br/Me6TREN complexes can now be used to calculate
the corresponding activation rate constants at polym-
erization temperatures (T ) 60-110 °C). While it has
been shown that PEBr is a good model compound for a
polystyrene chain end,20 the same might not hold for
EBriB and methyl methacrylate, due to the recently
Ack n ow led gm en t. The financial support from the
CMU CRP Consortium and the NSF grant (CHE-
0096601) is greatly appreciated. R.P. and E.C. thank
the Conseil R e´ gional de Bourgogne for funds that
allowed the purchase of the stopped-flow apparatus.
3
0
demonstrated penultimate effect. These activation
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parameters for Cu Br/Me6TREN that were previously
unavailable, and the activation data for other highly
reactive systems yet to be measured will be critical when
Su p p or tin g In for m a tion Ava ila ble: Detailed experi-
mental procedures, Arrhenius plots for the determination of
∆H and ∆S , and time-dependent absorption spectra for alkyl
halides and copper(I) complexes used in the study (PDF). This
material is available free of charge via the Internet at
q
q
4
3
modeling the kinetics of such polymerization systems.
As indicated in Table 1, the activation rate constants
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for Cu Br/Me6TREN are much higher than for Cu Br/
2
I
dNbpy and Cu Br/PMDETA complexes. This is re-
flected in their redox potentials, and our previous
Refer en ces a n d Notes
I
investigation of these systems indicated that Cu Br/Me6-
TREN is a much more reducing catalyst.44 We are also
attempting to correlate the activation rate constant and
the catalyst structure as well as exploring the determi-
nation of the deactivation rate constants via measure-
ments of the overall equilibrium constant for ATRP
(1) Matyjaszewski, K.; Davis, T. P. Handbook of Radical
Polymerization; J ohn Wiley & Sons: Hoboken, 2002.
(
2) Matyjaszewski, K.; Xia, J . Chem. Rev. 2001, 101, 2921-
2
990.
(
3) Kamigaito, M.; Ando, T.; Sawamoto, M. Chem. Rev. 2001,
101, 3689-3745.
(
KATRP ) kact/kdeact) using the persistent radical effect.
(4) Wang, J .-S.; Matyjaszewski, K. J . Am. Chem. Soc. 1995, 117,
5
614-5615.
When the stopped-flow apparatus is set up on the
(
5) Patten, T. E.; Xia, J .; Abernathy, T.; Matyjaszewski, K.
benchtop, there is the potential for slow diffusion of
oxygen through the apparatus to the sample. Monitoring
Science 1996, 272, 866-868.
(
6) Matyjaszewski, K.; Patten, T. E.; Xia, J . J . Am. Chem. Soc.
1997, 119, 674-680.
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the absorbance spectra of Cu Br/2dNbpy in the ap-
paratus for 1000 s in the absence of alkyl halide revealed
the complex was slowly oxidized (<10%). This oxidation
was not significant enough to affect the measurement
(7) Xia, J .; Matyjaszewski, K. Macromolecules 1997, 30, 7697-
7
700.
8) Xia, J .; Gaynor, S. G.; Matyjaszewski, K. Macromolecules
998, 31, 5958-5959.
(
(
1
I
of activation rate constants for Cu Br/2dNbpy and
9) Xia, J .; Zhang, X.; Matyjaszewski, K. In Transition Metal
Catalysis in Macromolecular Design; Boffa, L. S., Novak,
B. M., Eds.; American Chemical Society: Washington, DC,
EBriB because the reaction was complete long before
significant diffusion of oxygen through the system could
occur.
2
000; Vol. 760, pp 207-223.
(
(
10) Fischer, H. Chem. Rev. 2001, 101, 3581-3610.
11) Coessens, V.; Pintauer, T.; Matyjaszewski, K. Prog. Polym.
Sci. 2001, 26, 337-377.
In conclusion, the stopped-flow technique was used
to determine the activation rate constants in CH3CN
at variable temperatures for alkyl halides and very
(12) Patten, T. E.; Matyjaszewski, K. Acc. Chem. Res. 1999, 32,
895-903.
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active Cu X/Ln complexes, which were previously not
(
(
13) Matyjaszewski, K. Chem.sEur. J . 1999, 5, 3095-3102.
14) Patten, T. E.; Matyjaszewski, K. Adv. Mater. 1998, 10, 901-
accessible due to the limitations in measuring fast
reaction rates with current GC and NMR techniques.
The activation rate constants for EBriB were found to
9
15.
(
15) Davis, K. A.; Matyjaszewski, K. Adv. Polym. Sci. 2002, 159,
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increase in the order Cu Br/2dNbpy < Cu Br/PMDETA
30-106.