Highly efficient "click" functionalization of poly(3-azidopropyl methacrylate) prepared by ATRP

Article abstract of DOI:10.1021/ma0511245

To prepare polymers with pendant functionality capable of participating in highly efficient Cu^I-catalyzed 1,3-dipolar cycloaddition of azide and alkynes, monomers with acetylene or azido groups were polymerized via controlled radical polymerization. Atom transfer radical polymerization (ATRP) of propargyl methacrylate (PgMA) resulted in high polydispersities (M _w/M_n > 3), multimodal molecular weight distributions, and cross-linked networks at moderate to high conversion. The poor results obtained with this monomer were presumably due to addition of the propagating radicals to the acetylene group, transfer reactions, and/or interference with the catalyst. A novel monomer, 3-azidopropyl methacrylate (AzPMA), was polymerized via ATRP with good control of the polymer molecular weight distribution and retention of chain functionality. Poly(3-azidopropyl methacrylate) was coupled with propargyl alcohol, propargyl triphenylphosphonium bromide, propargyl 2-bromoisobutyrate, and 4-pentynoic acid via a highly efficient "click" reaction in the presence of a Cu^I catalyst. The azido-functionalized polymer demonstrated enhanced reactivity as compared to small molecules with comparable structures. The ability of the coupling reactions to be conducted at room temperature without significant excess of reagents makes this an attractive alternative to preparing (co)polymers with high degrees of functionalization.

Full text of DOI:10.1021/ma0511245

7540
Macromolecules 2005, 38, 7540-7545
Articles
Highly Efficient “Click” Functionalization of Poly(3-azidopropyl
methacrylate) Prepared by ATRP
Brent S. Sumerlin, Nicolay V. Tsarevsky, Guillaume Louche, Robert Y. Lee, and
Krzysztof Matyjaszewski*
Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue,
Pittsburgh, Pennsylvania 15213
Received May 31, 2005; Revised Manuscript Received June 30, 2005
ABSTRACT: To prepare polymers with pendant functionality capable of participating in highly efficient
CuI-catalyzed 1,3-dipolar cycloaddition of azide and alkynes, monomers with acetylene or azido groups
were polymerized via controlled radical polymerization. Atom transfer radical polymerization (ATRP) of
propargyl methacrylate (PgMA) resulted in high polydispersities (Mw/Mn > 3), multimodal molecular
weight distributions, and cross-linked networks at moderate to high conversion. The poor results obtained
with this monomer were presumably due to addition of the propagating radicals to the acetylene group,
transfer reactions, and/or interference with the catalyst. A novel monomer, 3-azidopropyl methacrylate
(AzPMA), was polymerized via ATRP with good control of the polymer molecular weight distribution
and retention of chain functionality. Poly(3-azidopropyl methacrylate) was coupled with propargyl alcohol,
propargyl triphenylphosphonium bromide, propargyl 2-bromoisobutyrate, and 4-pentynoic acid via a
highly efficient “click” reaction in the presence of a CuI catalyst. The azido-functionalized polymer
demonstrated enhanced reactivity as compared to small molecules with comparable structures. The ability
of the coupling reactions to be conducted at room temperature without significant excess of reagents
makes this an attractive alternative to preparing (co)polymers with high degrees of functionalization.
Introduction
called “click” reactions, has gained a great deal of
attention due to its high specificity, quantitative yields,
and near-perfect fidelity in the presence of most func-
tional groups.12-15
Controlled/living radical polymerization (CRP) tech-
niques facilitate the preparation of a broad variety of
polymeric materials with predetermined molecular
weights, narrow molecular weight distributions, and
high degrees of chain end functionalization.1 When
compared to their ionic counterparts, CRP methods
provide comparable control while having the advantage
of enhanced functional group tolerance and the ability
to be conducted under less stringent conditions. The
most widely investigated CRP methods are atom trans-
fer radical polymerization (ATRP),2-6 reversible addi-
tion-fragmentation chain transfer (RAFT) polymeriza-
tion,7 and nitroxide-mediated polymerization (NMP).8,9
ATRP has emerged as one of the most widely used CRP
methods due to the facile experimental setup and the
use of readily accessible and inexpensive initiators and
catalysts.
Despite the progress made in the field of CRP toward
the direct polymerization of functional monomers, post-
polymerization modification remains a viable means of
incorporating functionality that is potentially incompat-
ible with synthetic, characterization, or processing
conditions.10,11 A drawback of such a method of func-
tionalization is the possibility of relatively low yields
and side reactions with other groups within the polymer.
Efficient and specific reactions are desirable in order
for postpolymerization modification to be highly suc-
cessful. Recently, one such group of reactions, generally
Initially, NMP was employed to prepare block copoly-
mers that were then modified to contain azido or
acetylene groups to be further coupled in subsequent
click reactions that led to fluorescently labeled copoly-
mers or shell-cross-linked micelles.16,17 Recently, there
have been reports of using click chemistry reactions in
combination with ATRP to prepare block copolymers18
as well as functional telechelic19 and chain-extended
polystyrene.20 Polymers prepared by ATRP are particu-
larly well-suited to subsequent end-group modification
via CuI-catalyzed azide-alkyne coupling because the
halogen terminal groups that result from the polymer-
ization can be easily converted to azido groups.21,22
Additionally, pendant moieties were modified by click
functionalization of acrylonitrile (co)polymers with so-
dium azide, which resulted in well-defined polymeric
tetrazoles.23
Herein, we further extend the application of click
chemistry toward the modification of side-chain func-
tional groups for polymers prepared by ATRP. A novel
azido-containing monomer was directly polymerized and
subsequently modified with model alkynes to efficiently
prepare functional (co)polymers.
Experimental Section
Materials. Propargyl methacrylate was purchased from
Polysciences Inc. and purified by passing through basic
* Corresponding author. E-mail: km3b@andrew.cmu.edu.
10.1021/ma0511245 CCC: $30.25 © 2005 American Chemical Society
Published on Web 08/04/2005

Macromolecules, Vol. 38, No. 18, 2005
“Click” Functionalization of PgMA 7541
alumina. N,N-dimethyaminoethyl methacrylate (DMAEMA;
Aldrich) was purified in the same fashion. All other reagents
and solvents were purchased from Aldrich or Acros and used
as received unless otherwise noted. Deoxygenation of the
solvents and liquid reagents was accomplished by bubbling
with nitrogen.
at complete conversion was lower (100), the amounts of
catalyst and initiator were decreased 2-fold.
Synthesis of PolyAzPMA-b-poly(N,N-dimethylamino-
ethyl methacrylate). A mixture of polyAzPMA (Mn ) 18 400,
Mw/Mn ) 1.33) (1.0 g, 0.054 mmol), DMAEMA (0.85 g, 5.0
mmol), CuCl2 (3 mg, 0.02 mmol), and acetone (2.7 mL) in a 10
mL Schlenk tube was degassed by three freeze-pump-thaw
cycles, and CuCl (11 mg, 11 mmol) was added under nitrogen
flow. The tube was closed, evacuated, and backfilled with
nitrogen several times, and the flask was placed in a 40 °C oil
bath. 1,1,4,7,10,10-Hexamethyltriethylenetetraamine (HMTE-
TA) (35 µL, 0.022 mmol) was added via syringe to begin the
polymerization, and after 3 h, the flask was removed from heat
and opened to expose the catalyst to air. The resulting solution
was diluted with chloroform, passed through a neutral alumina
column to remove the catalyst, and precipitated into methanol
to give polyAzPMA-b-polyDMAEMA (conversion ) 71%, Mn
) 30 200 g/mol; Mw/Mn ) 1.37).
Synthesis of 3-Azidopropanol (AzPOH). 3-Chloropro-
panol (30 mL, 33.93 g, 0.358 mol) was added to a mixture of
water (40 mL), sodium azide (47 g, 2 equiv), and tetrabuty-
lammonium hydrogen sulfate (1 g). The mixture was stirred
at 80 °C for 24 h and then at room temperature for 13-14 h.
The product was extracted with ether (3 × 80 mL), the
resulting solution was dried over sodium sulfate, the solvent
was removed on a rotary evaporator, and after vacuum
distillation, 3-azidopropanol was obtained (yield: 30.8 g, 85%).
1H NMR in CDCl3 (δ, ppm): 3.76 (t, 2H, CH2O), 3.46 (t, 2H,
CH2N3), and 1.84 (tt, 2H, CCH2C). No unreacted 3-chloropro-
panol was detected by NMR (in CDCl3: δ ) 3.80 (t, 2H, CH2O),
3.68 (t, 2H, CH2Cl), and 2.01 ppm (tt, 2H, CCH2C)). IR
Click Functionalization of PolyAzPMA. Homopolymers
and block copolymers of AzPMA were reacted with various
functional alkynes (propargyl alcohol (PgOH); propargyl triph-
enylphosphonium bromide (PgPPh3Br); 4-pentynoic acid (PA);
propargyl 2-bromoisobutyrate20 (PgBriBu), Scheme 1) in the
presence of a CuI catalyst. The general reaction conditions
involved polyAzPMA (1 equiv of -N3, 0.05 M), alkyne (1.1
equiv), and CuBr (0.5 equiv) being dissolved in deoxygenated
DMF-d7 (PgOH, PA, PgBriBu) or DMSO-d6 (PgPPh3Br). 1,8-
Diazabicyclo[5.4.0]undec-7-ene (DBU) (1.1 equiv) was included
in the reactions of PgPPh3Br. The reactions were allowed to
proceed at room temperature under a nitrogen atmosphere,
spectrum (neat liquid, NaCl plates): 3368 cm-1 (broad, νO-H
)
and 2103 cm-1 (νN ). The density of the alcohol was determined
3
as 1.09 g/mL.
Synthesis of 3-Azidopropyl Methacrylate (AzPMA). A
solution of 3-azidopropanol (23.5 mL, 0.253 mol), triethylamine
(45 mL, 0.323 mol, dried over sodium sulfate), hydroquinone
(0.1 g), and methylene chloride (100 mL, dried over sodium
sulfate) was cooled in an ice-water bath. Methacryloyl chloride
(29 mL, 0.3 mol) was added dropwise over a period of 20 min,
and the mixture was stirred in the cooling bath for 1 h and
then at room temperature for 14 h. Methylene chloride (100
mL) was added, and the mixture was extracted with an
aqueous solution of hydrochloric acid (1/10 v/v, 2 × 100 mL),
water (2 × 100 mL), 10 wt % aqueous NaOH (2 × 100 mL),
and again with water (2 × 100 mL). The methylene chloride
solution was mixed with hydroquinone (0.1 g) and dried over
sodium sulfate. The organic solvent was removed under
vacuum, and the resulting liquid was distilled under reduced
pressure (yield: 49%). (Caution: special care should be taken
not to heat the azide compound above 75-80 °C because it
1
and conversion was monitored by H NMR spectroscopy.
Analyses. Monomer conversion was determined with a
Shimadzu GC 14A gas chromatograph with a flame ionization
detector and a J & W Scientific 30 m DB608 column (injector
temperature ) 250 °C; detector temperature ) 270 °C; column
initial temperature ) 50 °C; initial time ) 2 min; heat ramp
) 40 °C/min; column final temperature ) 170 °C; final time
) 3 min). Apparent molecular weights were determined by size
exclusion chromatography (SEC) (Waters microstyragel col-
umns (guard, 105, 103, and 102 Å) calibrated with poly(methyl
methacrylate) standards) at a flow rate of 1 mL/min in THF
eluent at 35 °C for the AzPMA homopolymerization samples
and in DMF, containing 50 mM LiBr at 50 °C for the
polyAzPMA macroinitiator and polyAzPMA-b-polyDMAEMA
copolymer. 1H NMR spectroscopy was conducted in CDCl3,
DMF-d7, or DMSO-d6 using a Bruker Avance 300 MHz
spectrometer.
1
becomes shock-sensitive at elevated temperatures.) H NMR
in CDCl3 (δ, ppm): 6.11 (m, 1H, dCH), 5.58 (m, 1H, dCH),
4.24 (t, 2H, CH2O), 3.52 (t, 2H, CH2N3), and 1.91-2.02 (m,
5H, overlapping CH3C) and CCH2C). IR spectrum (neat liquid,
NaCl plates): 2100 cm-1 (νN ) and 1721 cm-1 (νCdO). The
density of the monomer was d3etermined as 1.07 g/mL.
ATRP of PgMA. A mixture of acetone (3 mL) and diphenyl
ether (0.2 mL) was deoxygenated in a Schlenk flask by five
freeze-pump-thaw cycles. The contents were again frozen,
and the flask was filled with nitrogen. CuBr (16.6 mg, 0.115
mmol) and 2,2′-bipyridyl (bpy) (36.1 mg, 0.230 mmol) were
added to the frozen mixture, and the flask was evacuated and
backfilled with nitrogen several times. The deoxygenated
monomer, PgMA (3.0 mL, 23 mmol), was added via a nitrogen-
purged syringe, and the resulting solution was heated in an
oil bath to 50 °C. Deoxygenated ethyl 2-bromoisobutyrate
(EtBriBu) (17 µL, 1/200 equiv vs monomer) was injected, and
samples were withdrawn periodically for analysis.
Synthesis of Poly(AzPMA). The typical procedure for the
ATRP of AzPMA is as follows. A mixture of AzPMA (2.0 mL,
13 mmol), acetone (2 mL), and diphenyl ether (0.15 mL) in a
10 mL Schlenk tube was degassed by five freeze-pump-thaw
cycles, and CuBr (9.3 mg, 0.065 mmol) and 2,2′-bipyridine (bpy,
20.2 mg, 0.129 mmol) were added to the frozen mixture under
a nitrogen flow. The tube was closed, evacuated, and backfilled
with nitrogen several times, and the reaction mixture was
heated to 50 °C. After dissolving the complex, deoxygenated
EtBriBu (9.5 µL, 0.065 mmol) was injected. Samples were
withdrawn periodically to monitor molecular weight evolution
and conversion. After 8 h, the flask was removed from heat
and opened to expose the catalyst to air. The resulting solution
was diluted with chloroform, passed through a neutral alumina
column to remove the catalyst, and precipitated into methanol
to give polyAzPMA (Mn ) 12 300; Mw/Mn ) 1.44). In another
experiment, in which the targeted degree of polymerization
Results and Discussion
The CuI-catalyzed Huisgen24 1,3-dipolar cycloaddi-
tions are excellent candidates to functionalize polymeric
materials due to their high yields and specificity. To
facilitate direct functionalization via azide-alkyne cou-
pling, an acetylene- or azido-containing monomer can
be polymerized, and the resulting polymer can be
reacted with a compound containing the appropriate
complementary functionality. Both routes were consid-
ered for the current study.
ATRP of PgMA. Initially, ATRP of the commercially
available propargyl methacrylate was attempted at 50
°C in acetone with [PgMA]:[EtBriBu]:[CuBr]:[bpy] )
200:1:1:2. While first-order kinetics and relatively good
agreement between theoretical and experimental mo-
lecular weights were observed (Figure 1), the molecular
weight distributions of the resulting polymers were
bimodal and broad (Mw/Mn > 3.3 at 50% monomer
conversion) (Figure 2).
The poor control observed for the ATRP of PgMA may
be due, in part, to radical addition to the acetylene
groups, which can lead to branching and cross-linking
at high conversion. Indeed, insoluble gels were observed
for polymerizations that reached >80% conversion.

7542 Sumerlin et al.
Macromolecules, Vol. 38, No. 18, 2005
Scheme 1. Synthesis of AzPMA and the Subsequent ATRP and Postpolymerization Modification with Various
Functional Alkynes
Transfer reactions to the monomer or polymer similar
to the case of radical polymerization of allyl monomers25
may also take place and lead to poor control. Further
complications can be caused by coordination of monomer
and polymer acetylene groups with the ATRP catalyst.
Vinyl monomer coordination to CuI complexes used as
ATRP catalysts has already been reported;26,27 because
of the strong coordination of alkynes to copper ions, the
complexation of monomers or polymers with acetylene
groups to copper-based ATRP catalysts is expected to
be especially pronounced.28-30 Though protection of
acetylene monomers and subsequent postpolymerization
deprotection is possible, an alternate approach toward
the synthesis of a click reactive polymer is direct
polymerization of an azido-functional monomer.
ATRP of AzPMA. The novel monomer AzPMA was
prepared from 3-azidopropanol and methacryloyl chlo-
ride and was polymerized via ATRP as outlined in
Scheme 1. Good control was observed, as indicated by
the semilogarithmic kinetic plot and the linear increase
Figure 2. Molecular weight distributions as a function of
monomer conversion (labeled on each trace) for the ATRP of
PgMA ([PgMA]:[EtBriBu]:[CuBr]:[bpy] ) 200:1:1:2, 50 vol %
acetone, T ) 50 °C).
Figure 1. (a) Semilogarithmic kinetic plot and (b) Mn and
Mw/Mn vs conversion for the ATRP of PgMA ([PgMA]:[Et-
BriBu]:[CuBr]:[bpy] ) 200:1:1:2, 50 vol % acetone, T ) 50 °C).

Macromolecules, Vol. 38, No. 18, 2005
“Click” Functionalization of PgMA 7543
Figure 4. Molecular weight distributions for the polymeri-
zation of DMAEMA with a polyAzPMA macroinitiator (Mn )
18 400 g/mol, Mw/Mn ) 1.33) to yield polyAzPMA-b-polyD-
MAEMA (Mn ) 30 200 g/mol, Mw/Mn ) 1.37). Obtained by SEC
in DMF with a PMMA calibration ([DMAEMA]:[polyAzPMA]:
[CuCl]:[CuCl2]:[HMTETA] ) 92:1:2:0.4:2.4, T ) 40 °C, 3 h).
By employing postpolymerization modification, func-
tionality that is potentially incompatible with the po-
lymerization conditions can be incorporated. As an
example of the advantageous nature of such a modifica-
tion route, the 2-bromoisobutyrate moiety could lead to
hyperbranched polymers if incorporated pendantly into
the monomer structure prior to polymerization.32-34 The
conversion of greater than 95% for the reaction of
PgBriB with polyAzPMA indicates that this method
successfully introduced functionality that is potentially
capable of initiating ATRP to yield graft or macromo-
lecular brush copolymers.35,36 Potentially, the free or
clicked PgBriB could have been activated by the CuI
catalyst to yield radicals capable of termination by
coupling or disproportionation; however, the reaction
solution remained soluble, and no vinyl peaks were
observed by 1H NMR spectroscopy, indicating that CuBr
complexed or solvated by DMF was insufficiently active
alkyl bromide activator.
Figure 3. (a) Semilogarithmic kinetic plot and (b) Mn and
Mw/Mn vs conversion for the ATRP of AzPMA with [AzPMA]:
[EtBriBu]:[CuBr]:[bpy] ) 100:1:1:2 (circles) or [AzPMA]:[Et-
BriBu]:[CuBr]:[bpy] ) 200:1:1:2 (squares). 50 vol % acetone,
T ) 50 °C. Theoretical Mn dependence on conversion repre-
sented by the dotted lines.
in Mn with conversion for two polymerizations with
varying [AzPMA]:[EtBriBu] ratios (Figure 3). SEC
analysis indicated the molecular weight distributions
were slightly broader than typical for ATRP due to a
slight amount of low molecular tailing or small degree
of potential side reactions that are known to occur with
azide moieties via either thermal or photochemical
pathways. Nonetheless, the traces were unimodal, and
Mw/Mn remained less than 1.5 below 75% conversion.
The controlled nature of the polymerization and re-
tained end-group functionality was further confirmed
by an isolated polyAzPMA homopolymer (Mn ) 18 400
g/mol, Mw/Mn ) 1.33) being successfully employed as a
macroinitiator to prepare a block copolymer with DMAE-
MA (Mn ) 30 200 g/mol, Mw/Mn ) 1.37) (Figure 4).
Functionalization of PolyAzPMA. The polyAz-
PMA homopolymer was isolated, purified, and subse-
quently reacted with several model alkynes. Previous
reports from our group20 and others31 have indicated
that click reactions are efficient in the absence of an
additionally added ligand provided the solvent facili-
tates sufficient solubility for the CuI catalyst. The model
alkynes PgBriB, PgPPh3Br, PgOH, and PA were suc-
cessfully coupled to polyAzPMA in DMF or DMSO with
a CuBr catalyst (Scheme 1). Conversions of greater than
95% in less than 2 h were observed at room temperature
for the reactions with all of the functional alkynes with
the only precaution being the removal of oxygen to
prevent oxidation of the catalyst.
Coupling of PgPPh3Br with polyAzPMA resulted in
efficient transformation to yield cationic polyelectro-
lytes. Because of poor solubility of this alkyne species
in DMF, the reaction was conducted in DMSO. While
the reactions of most of the alkynes considered here
demonstrated an appreciable rate in the absence of
DBU, the base was essential for the reaction with
PgPPh3Br in order to increase the relative rate of azide-
alkyne coupling with respect to the propargyl-allenyl
isomerization.37 Coupling with PA was nearly quantita-
tive as well, which resulted in the preparation of a
water-soluble polyanion in basic aqueous media. The
success observed for this system establishes coupling
of PA, or other acid-containing alkynes, to polymeric
azides as an alternative for introducing carboxylic acid
groups that are incompatible with the conditions typi-
cally employed for ATRP. So far, the major way to
prepare poly(carboxylic acid)s by ATRP is to directly
polymerize protected polymers that can be converted to
the corresponding acids after the polymerization. Pro-
tecting groups include tert-butyl,38 benzyl,39,40 tetrahy-
dropyranyl,39,40 4-nitrophenyl,41 and 1-ethoxyethyl.42
A
postpolymerization modification, namely the reaction of
hydroxy group-containing polymers with succinic an-
hydride, has also been employed to introduce the
carboxylic acid groups in polymers prepared by ATRP.43
The click chemistry route proposed herein is a highly

7544 Sumerlin et al.
Macromolecules, Vol. 38, No. 18, 2005
nation for the discrepancy in rates. Moreover, the reac-
tion of PgOH with 3-azidopropanol resulted in similar
kinetic profiles as those observed for the monomer.
The accelerated rate of reaction with the polymer was
somewhat unexpected but can potentially be explained
by anchimeric assistance.44 Previous reports have shown
that polytriazoles can sufficiently solubilize CuI.45 In the
absence of additional ligand, triazoles formed along the
polyAzPMA backbone can complex CuI, leading to an
effective higher local catalyst concentration in the
immediate vicinity of neighboring unreacted azido
groups. Similar autocatalytic results were observed by
Rodionov et al.31 during the coupling of alkynes to
diazido compounds.
Figure 5. 1H NMR spectra as a function of time for the
coupling of PAzPMA and PgOH ([-N3] ) 0.05 M, [PgOH] )
0.05 M, [CuCl] ) 0.0025 M, DMF-d7, rt). δ ) 1.98 ppm:
-COOCH2CH2CH2-N3; δ ) 2.35 ppm: -COOCH2CH2CH2-
triazole.
Conclusions
ATRP of PgMA resulted in high polydispersities,
multimodal molecular weight distributions, and cross-
linked networks at moderate to high conversion. The
poor results obtained with this monomer were presum-
ably due to interference of the acetylene group with the
catalyst or propagating radicals.
AzPMA was polymerized via ATRP with good control
of the polymer molecular weight and molecular weight
distribution. Retention of chain functionality was con-
firmed by chain extension with DMAEMA to yield a
diblock copolymer. PolyAzPMA was coupled with func-
tional alkynes via CuI-catalyzed 1,3-dipolar cycloaddi-
tion and demonstrated enhanced reactivity as compared
to small molecules with comparable structures. The
ability of the coupling reactions to be conducted at room
temperature without significant excess of reagents
makes this an attractive alternative to preparing (co)-
polymers with high degrees of functionalization.
Acknowledgment. The authors are grateful for the
funding provided by members of the CRP Consortium
at Carnegie Mellon University (CMU) and the National
Science Foundation under Grant DMR0090409. N.V.T.
acknowledges financial support from the Harrison
Legacy Dissertation Fellowship at CMU.
Figure 6. Conversion vs time for the reaction of PgOH with
PAzPMA (Mn ) 18 400, Mw/Mn ) 1.33), AzPMA, and AzPOH
as determined by 1H NMR spectroscopy. ([-N3] ) 0.05 M,
[PgOH] ) 0.05 M, [CuCl] ) 0.0025 M, DMF-d7, rt).
efficient alternative approach to the mentioned methods
of preparation of well-defined polyacids.
References and Notes
To gain an increased understanding regarding the
kinetics of click reactions of polyAzPMA, the coupling
(1) Matyaszewski, K., Davis, T. P., Eds.; Handbook of Radical
Polymerization; Wiley: New York, 2002.
1
(2) Wang, J.-S.; Matyjaszewski, K. J. Am. Chem. Soc. 1995, 117,
reaction with PgOH was monitored by H NMR spec-
5614-5615.
troscopy. To facilitate more reliable kinetic character-
ization, the concentration of CuI was reduced to 0.05
equiv with respect to PgOH in order to slow the rate of
reaction. By monitoring the methylene protons of un-
reacted (-COOCH2CH2CH2-N3, δ ) 1.98 ppm) and
reacted (-COOCH2CH2CH2-triazole, δ ) 2.35 ppm)
polyAzPMA, conversion was determined as a function
of time (Figure 5). With an equimolar amount of PgOH
and azido groups, 90% functionalization was observed
in less than 2 h at room temperature. Because of steric
constraints and inaccessibility of functional groups
along polymer chains, postpolymerization modification
reactions are often slower and less efficient than the
analogous reaction between two low molecular weight
species. However, the rate of azide-alkyne coupling of
polyAzPMA was observed to be significantly higher than
that for AzPMA monomer (Figure 6). Although vinyl
monomers are known to coordinate to CuI,26,27 which
could potentially affect the activity of the catalyst,
taking into account that methacrylate coordination is
relatively weak, it is unlikely that this is the sole expla-
(3) Matyjaszewski, K.; Xia, J. Chem. Rev. 2001, 101, 2921-2990.
(4) Kato, M.; Kamigaito, M.; Sawamoto, M.; Higashimura, T.
Macromolecules 1995, 28, 1721-1723.
(5) Kamigaito, M.; Ando, T.; Sawamoto, M. Chem. Rev. 2001, 101,
3689-3745.
(6) Matyaszewski, K.; Wang, J. S. US 5,763,548, 1998.
(7) Chiefari, J.; Chong, Y. K.; Ercole, F.; Krstina, J.; Jeffery, J.;
Le, T. P. T.; Mayadunne, R. T. A.; Meijs, G. F.; Moad, C. L.;
Moad, G.; Rizzardo, E.; Thang, S. H. Macromolecules 1998,
31, 5559-5562.
(8) Georges, M. K.; Veregin, R. P. N.; Kazmaier, P. M.; Hamer,
G. K. Macromolecules 1993, 26, 2987-2988.
(9) Hawker, C. J.; Bosman, A. W.; Harth, E. Chem. Rev. 2001,
101, 3661-3688.
(10) Schulz, D. N.; Patil, A. O. ACS Symp. Ser. 1998, 704, 1-14.
(11) Coessens, V.; Pintauer, T.; Matyjaszewski, K. Prog. Polym.
Sci. 2001, 26, 337-377.
(12) Kolb, H. C.; Finn, M. G.; Sharpless, K. B. Angew. Chem., Int.
Ed. 2001, 40, 2004-2021.
(13) Rostovtsev, V. V.; Green, L. G.; Fokin, V. V.; Sharpless, K.
B. Angew. Chem., Int. Ed. 2002, 41, 2596-2599.
(14) Wu, P.; Feldman, A. K.; Nugent, A. K.; Hawker, C. J.; Scheel,
A.; Voit, B.; Pyun, J.; Frechet, J. M. J.; Sharpless, K. B.;
Fokin, V. V. Angew. Chem., Int. Ed. 2004, 43, 3928-3932.

Macromolecules, Vol. 38, No. 18, 2005
“Click” Functionalization of PgMA 7545
(15) Diaz, D. D.; Punna, S.; Holzer, P.; McPherson, A. K.;
Sharpless, K. B.; Fokin, V. V.; Finn, M. G. J. Polym. Sci.,
Part A: Polym. Chem. 2004, 42, 4392-4403.
(16) O’Reilly, R. K.; Hawker, C. J.; Wooley, K. L. Polym. Prepr.
2004, 45, 780.
(31) Rodionov, V. O.; Fokin, V. V.; Finn, M. G. Angew. Chem., Int.
Ed. 2005, 44, 2-6.
(32) Matyjaszewski, K.; Gaynor, S. G.; Kulfan, A.; Podwika, M.
Macromolecules 1997, 30, 5192-5194.
(33) Matyjaszewski, K.; Gaynor, S. G.; Mueller, A. H. E. Macro-
molecules 1997, 30, 7034-7041.
(34) Matyjaszewski, K.; Gaynor, S. G. Macromolecules 1997, 30,
7042-7049.
(17) O’Reilly, R. K.; Joralemon, M. J.; Nugent, A. K.; Matson, J.
B.; Hawker, C. J.; Wooley, K. L. Polym. Prepr. 2004, 45,
292.
(18) Opsteen, J. A.; van Hest, J. C. M. Chem. Commun. 2005, 57-
59.
(35) Beers, K. L.; Gaynor, S. G.; Matyjaszewski, K.; Sheiko, S. S.;
Moeller, M. Macromolecules 1998, 31, 9413-9415.
(36) Sumerlin, B. S.; Neugebauer, D.; Matyjaszewski, K. Macro-
molecules 2005, 38, 702-708.
(19) Lutz, J. F.; Borner, H. G.; Weichenhan, K. Macromol. Rapid
Commun. 2005, 26, 514-518.
(20) Tsarevsky, N. V.; Sumerlin, B. S.; Matyjaszewski, K. Mac-
romolecules 2005, 38, 3558-3561.
(37) Schweizer, E. E.; DeVoe Goff, S.; Murray, W. P. J. Org. Chem.
1977, 42, 200-205.
(21) Coessens, V.; Nakagawa, Y.; Matyjaszewski, K. Polym. Bull.
(Berlin) 1998, 40, 135-142.
(38) Davis, K. A.; Matyjaszewski, K. Macromolecules 2000, 33,
4039-4047.
(22) Coessens, V.; Matyjaszewski, K. J. Macromol. Sci., Pure Appl.
Chem. 1999, A36, 667-679.
(39) Zhang, X.; Xia, J.; Matyjaszewski, K. Polym. Prepr. 1999, 40,
440.
(23) Tsarevsky, N. V.; Bernaerts, K. V.; Dufour, B.; Du Prez, F.
E.; Matyjaszewski, K. Macromolecules 2004, 37, 9308-9313.
(24) Huisgen, R. Proc. Chem. Soc. 1961, 357.
(25) Volodina, V. I.; Tarasov, A. I.; Spasskiy, S. S. Usp. Khim.
1970, 39, 276.
(40) Butun, V.; Vamvakaki, M.; Billingham, N. C.; Armes, S. P.
Polymer 2000, 41, 3173.
(41) Liu, Y.; Wang, L.; Pan, C. Macromolecules 1999, 32, 8301-
8305.
(42) Van Camp, W.; Du Prez, F. E.; Bon, S. A. F. Macromolecules
2004, 37, 6673-6675.
(26) Braunecker, W. A.; Pintauer, T.; Tsarevsky, N. V.; Kickelbick,
G.; Matyjaszewski, K. J. Organomet. Chem. 2005, 690, 916-
924.
(27) Braunecker, W. A.; Tsarevsky, N. V.; Pintauer, T.; Gil, R. G.;
Matyjaszewski, K. Macromolecules 2005, 38, 4081-4088.
(28) Bennett, M. A. Chem. Rev. 1962, 62, 611-652.
(29) Nast, R. Coord. Chem. Rev. 1982, 47, 89.
(30) Osakada, K.; Yamamoto, T. Trends Organomet. Chem. 1999,
3, 219-225.
(43) Cai, Y.; Armes, S. P. Macromolecules 2005, 38, 271-279.
(44) Streitwieser, A.; Heathcock, C. H.; Kosower, E. M. Introduc-
tion to Organic Chemistry, 4th ed.; MacMillan: New York,
1992.
(45) Chan, T. R.; Hilgraf, R.; Sharpless, K. B.; Fokin, V. V. Org.
Lett. 2004, 6, 2853-2855.
MA0511245