Synthesis of Comblike Poly(butyl methacrylate) Using Reversible Addition-Fragmentation Chain Transfer and an Activated Ester

Article abstract of DOI:10.1021/ma035302a

Comblike polymers of poly(n-butyl methacrylate) were prepared using an activated ester-type comonomer (N-acryloxysuccinimide, NAS) to generate branch points. The conventional solution free-radical copolymerization kinetics of n-butyl methacrylate (BMA) and NAS were first investigated by following individual monomer consumption rates by ¹H NMR spectrometry and reactivity ratios of BMA and NAS determined using the terminal model. The reactivity ratios so obtained are both close to 0.2; the joint confidence interval is also determined. Reversible addition - fragmentation chain transfer (RAFT) was then used to grow polymers with controlled backbone and branch chain length. Because both reactivity ratios have similar values, this implies that the copolymer will have a random distribution of NAS and hence of branch points. RAFT-mediated polymerization was first used to synthesize linear poly(BMA-co-NAS) chains. Primary hydroxy-functionalized RAFT agents were then immobilized on this linear poly(BMA-co-NAS) through nucleophilic substitution on the activated ester units of the NAS. From these immobilized RAFT agents, branches were grown upon addition of a further aliquot of monomer (BMA) and initiator (AIBN). The amount of NAS in the starting BMA/NAS composition was varied without adversely affecting the uniformity of the NAS distribution along the resulting linear poly(BMA-co-NAS) backbone. This results in branched polymers whose molecular weight, branching density, and degree of polymerization of branches are all relatively narrow and controlled.

Full text of DOI:10.1021/ma035302a

Macromolecules 2004, 37, 2371-2382
2371
Synthesis of Comblike Poly(butyl methacrylate) Using Reversible
Addition-Fragmentation Chain Transfer and an Activated Ester
J oh a n n es J . Vosloo,† Ma tth ew P . Ton ge, Ch r istop h er M. F ellow s,
,‡
‡
†
§
‡
,†
F r a n ck D’Agosto, Ron a ld D. Sa n d er son , a n d Rober t G. Gilber t*
Key Centre for Polymer Colloids, School of Chemistry F11, University of Sydney, NSW 2006, Australia;
UNESCO Associated Centre for Macromolecules and Materials, Department of Chemistry and Polymer
Science, University of Stellenbosch, Private Bag X1, De Beers Street, Matieland, 7602, South Africa;
and LCPP CPE/ CNRS, B aˆ t 308 F, 43 Blvd du 11 Novembre 1918, BP 2077,
6
9616 Villeurbanne Cedex, France
Received September 4, 2003; Revised Manuscript Received J anuary 22, 2004
ABSTRACT: Comblike polymers of poly(n-butyl methacrylate) were prepared using an activated ester-
type comonomer (N-acryloxysuccinimide, NAS) to generate branch points. The conventional solution free-
radical copolymerization kinetics of n-butyl methacrylate (BMA) and NAS were first investigated by
1
following individual monomer consumption rates by H NMR spectrometry and reactivity ratios of BMA
and NAS determined using the terminal model. The reactivity ratios so obtained are both close to 0.2;
the joint confidence interval is also determined. Reversible addition-fragmentation chain transfer (RAFT)
was then used to grow polymers with controlled backbone and branch chain length. Because both reactivity
ratios have similar values, this implies that the copolymer will have a random distribution of NAS and
hence of branch points. RAFT-mediated polymerization was first used to synthesize linear poly(BMA-
co-NAS) chains. Primary hydroxy-functionalized RAFT agents were then immobilized on this linear poly-
(BMA-co-NAS) through nucleophilic substitution on the activated ester units of the NAS. From these
immobilized RAFT agents, branches were grown upon addition of a further aliquot of monomer (BMA)
and initiator (AIBN). The amount of NAS in the starting BMA/NAS composition was varied without
adversely affecting the uniformity of the NAS distribution along the resulting linear poly(BMA-co-NAS)
backbone. This results in branched polymers whose molecular weight, branching density, and degree of
polymerization of branches are all relatively narrow and controlled.
In tr od u ction
polymerization techniques, make the free radical route
an appealing option. Reversible addition-fragmentation
Gaining control over polymer architecture is an al-
luring prospect since it enables control over resulting
material properties. Control at a molecular level would
enable the synthesis of polymers made up of the same
chemical repeat unit, yet potentially with different
mechanical properties with a wide range of possible
applications. Different architectures and microstruc-
tures include linear chains, various copolymers (e.g.,
gradient, alternating, and random), block copolymers
1
2
chain transfer (RAFT), atom transfer radical polym-
1
3
erization (ATRP), and nitroxide-mediated radical po-
1
4
lymerization (NMP) offer simple and efficient routes
to polymers of comblike structure.
Apart from the polymerization technique used, there
exist three general approaches to synthesizing polymers
that exhibit branched architectures.
The first approach (Scheme 1a) comprises the syn-
thesis of macromonomers. Some of the approaches used
to synthesize macromonomers include the catalytic
(AB, ABA, etc.), stars, dendrites, combs, and pom-poms.
Molecular architectures related to branched struc-
1
5-17
tures and the resulting mechanical properties have
generated considerable interest.1-5 Creating a palette
of polymers with (say) identical chemical composition
and backbone chain length, but where branching den-
sity and branch molecular weight can be systematically
varied, opens the way to test theories of these mechan-
ical properties.
chain transfer (CCT) technique,
conventional or-
18,19
ganic routes,
addition-fragmentation reaction tech-
niques, conventional chain transfer to polymer, and
20
21
22-25
ATRP.
All of these techniques yield low molecular
weight oligomers with terminal vinyl end groups or
other terminal functional end groups capable of being
polymerized. These macromonomers can subsequently
be copolymerized with other monomers in various ratios
Various polymerization techniques can be used to
prepare branched structures, including polycondensa-
22,26-28
to yield branched polymers.
Macromonomers are
6
,7
8-10
tion, ionic polymerization,
and free radical polym-
most useful when very short branches are required.
1
1
erization. While condensation polymerization reactions
are relatively simple, ionic techniques require very
stringent reaction conditions. Alternatively, the indus-
trial importance and robustness of free radical polym-
erization, relatively mild reaction conditions and the
continued improvement of various controlled free radical
The second approach (Scheme 1b) involves the syn-
thesis of a linear polymer containing functional monomer-
(s) distributed along the polymer chain. In a separate
step, polymers that have been end-functionalized are
prepared. These end-functionalized polymers are sub-
sequently reacted covalently with the functional groups
distributed along the original polymer backbone.1
This approach allows the chains that eventually serve
as branches to be characterized extensively before
incorporation into the backbone and is often called the
“grafting onto” approach.
0,29-32
†
University of Sydney.
University of Stellenbosch.
LCPP CPE/CNRS.
‡
§
*
Corresponding author: Fax +61-2-9351 8651, e-mail gilbert@
chem.usyd.edu.au.
1
0.1021/ma035302a CCC: $27.50 © 2004 American Chemical Society
Published on Web 03/04/2004

2
372 Vosloo et al.
Macromolecules, Vol. 37, No. 7, 2004
Sch em e 1. Differ en t Ap p r oa ch es for Syn th esizin g P olym er s w ith Con tr olled Br a n ch ed Str u ctu r es: (a ) Use of
Ma cr om on om er s, (b) “Gr a ftin g On to” Ap p r oa ch , a n d (c) “Gr a ftin g F r om ” Ap p r oa ch ; M ) Mon om er , A, X, Y a n d I
Ap p r op r ia te F u n ction a l Gr ou p s
)
Sch em e 2. Str u ctu r es of N-Acr yloxysu ccin im id e
NAS) (1), n -Bu tyl Meth a cr yla te (BMA) (2),
mers to impart a range of desired properties and
capabilities.
(
44-52
2
-{[(Dod ecylsu lfa n yl)ca r bon oth ioyl]su lfa n yl}-
p r op a n oic Acid (3), Ben zyl
To ensure a truly random distribution of branches
along a poly(BMA-co-NAS-graft-BMA) molecule, a ran-
dom distribution of potential branch points must be
present in the “parent” chain. To achieve this, the free
radical copolymerization kinetics of BMA and NAS were
investigated and reactivity ratios for the BMA- and
NAS-terminated polymer radicals determined, assum-
2
-(2-Hyd r oxyeth yla m in o)-1-m eth yl-2-oxoeth yl
Tr ith ioca r bon a te (4), 2-P h en ylp r op yl
P h en yld ith ioa ceta te (5), a n d 2-Cya n op r op yl
Dith ioben zoa te (6)
5
3-55
ing the terminal model.
The data so obtained permit
conditions to be chosen so as to maintain a constant
copolymer composition throughout the course of a po-
lymerization and thus a random distribution along a
poly(BMA-co-NAS) chain throughout the course of a
reaction. The incorporation of BMA and NAS into a
propagating chain was investigated by monitoring
changes in individual free monomer concentrations by
1
H NMR spectrometry.
As controlled radical techniques do not significantly
affect reactivity ratios when compared to conventional
5
6-58
free radical systems,
RAFT was employed to control
The third approach (Scheme 1c) also requires the
synthesis of a linear polymer backbone incorporating a
functional monomer. The functional monomer must
contain a chemical group which either directly or after
chemical modification is capable of participating in
initiating a polymerization reaction. These functional
monomers act as sites from which branches can grow
upon addition of monomer (and an appropriate initiator,
backbone length. RAFT-mediated copolymerization of
BMA and NAS in the feed region of interest was
investigated. The presently accepted mechanism for the
RAFT process is as follows.12
Initiator-derived primary
radicals react with monomer units to form oligomeric
radicals, which undergo addition to the carbon-sulfur
double bond of the dithioester chain transfer agents. The
resulting radical then loses a good homolytic leaving
group, as a radical capable of either initiating a polym-
erization reaction or, in the case of a polymeric leaving
species, propagating further. Equilibrium is established
between active (propagating) and dormant polymer
chains via the subsequent addition and fragmentation
steps. The RAFT mechanism has been discussed in
1
9,33-36
if required).
In some cases the formed branches
can be chemically cleaved from the backbone and
3
7
characterized. This approach is often referred to as
the “grafting from” approach.
In this study the “grafting from” approach was
employed. n-Butyl methacrylate (BMA (2), Scheme 2)
was the main monomer, and N-acryloxysuccinimide
12,59,60
detail elsewhere.
(NAS (1), Scheme 2) was selected as the functional
monomer to be incorporated into the poly(BMA) back-
Exp er im en ta l Section
3
8-43
bone. NAS is an activated ester-type monomer:
the
Ch em ica ls. N-Hydroxysuccinimide (NHS, Aldrich, 97%),
presence of the electron-withdrawing succinimide moi-
ety renders the carbonyl carbon of the ester susceptible
to nucleophilic substitution reactions. NAS has been
employed as a functional monomer in various copoly-
acryloyl chloride (Aldrich, 96%), triethylamine (Et
9.5%), 4-(dimethylamino)pyridine (DMAP, Aldrich, 99+%),
and 1,3,5-trioxane (Fluka AG, 97%) were used as received. 1,4-
Dioxane was distilled over LiAlH to remove any traces of
3
N, Aldrich,
9
4

Macromolecules, Vol. 37, No. 7, 2004
Synthesis of Comblike Poly(butyl methacrylate) 2373
Sch em e 3. Syn th esis of N-Acr yloxysu ccin im id e (NAS)
degassed in the same manner for an additional 10 min. The
sample cavity of the NMR instrument was heated to 60 °C
(after accurate temperature calibration), and the sample was
lowered into the cavity. Instantaneous individual monomer
concentrations were measured every 3 min using a single scan
only, employing the technique described earlier.
Molecu la r Weigh t An a lyses. Molecular weights were
determined using size exclusion chromatography (SEC).
Samples were prepared for SEC analysis by drying the
polymer in vacuo and redissolving ca. 5 mg of the polymer in
1 mL of THF. The SEC instrument consisted of a Waters
717plus autosampler, a Waters 600E system controller, and a
Waters 610 fluid unit. A Waters 410 differential refractometer
was used at 35 °C as detector. Tetrahydrofuran (THF, HPLC-
grade) sparged with IR-grade helium was used as eluent at a
water and other impurities. Chloroform was distilled prior to
use. Butyl methacrylate (BMA, Aldrich, 99%) was extracted
with two equal aliquots of a 0.3 M aqueous KOH solution to
remove inhibitors and distilled at reduced pressure. The
middle fraction was collected and stored over molecular sieves
(4 Å) at 2 °C for later use. Azobis(isobutyronitrile) (AIBN, Delta
-
1
Scientific, 98%) was recrystallized from methanol. The water
was distilled and deionized (DDI).
flow rate of 1 mL min and 60 min per sample. The column
oven was kept at 35 °C, and the injection volume was 100 µL.
Four Phenogel columns (300 mm × 7.80 mm) with respective
The following RAFT agents were used. 2-{[(Dodecylsulfanyl)-
carbonothioyl]sulfanyl}propanoic acid (3): The synthesis of
3
4
5
pore sizes of 100, 10 , 10 , and 10 Å were used in series. The
system was calibrated using six narrow polystyrene molecular
weight standards in the range 4000-2000 000, supplied by
Pressure Chemical. All molecular weights were calculated
relative to polystyrene.61
6
1
this RAFT agent is described elsewhere. Benzyl 2-(2-hy-
droxyethylamino)-1-methyl-2-oxoethyl trithiocarbonate (4): This
RAFT agent was supplied by the Key Centre for Polymer
Colloids with the permission of Dulux, Australia. The synthetic
procedure will be disclosed in a forthcoming patent. Benzyl
P oly(BMA-co-NAS) Syn th esis. NAS content was varied.
A typical reaction mixture contained BMA (5.028 g, 3.511 ×
2
-(2-hydroxyethylamino)-1-methyl-2-oxoethyl trithiocarbonate
-
2
-3
(4) was selected for immobilization on the poly(BMA-co-NAS)
10 mol), NAS (1.190 g, 7.036 × 10 mol), AIBN (0.007 g,
-5
backbone since the compound contained a primary hydroxy
functionality needed for nucleophilic substitution reactions
with NAS units.
4.3 × 10 mol), 2-{[(dodecylsulfanyl)carbonothioyl]sulfanyl}-
-4
propanoic acid (3, 0.072 g, 2.1 × 10 mol), 1,3,5-trioxane (0.082
-
4
g, 9.1 × 10 mol), and 1,4-dioxane (22.0 mL). The reaction
NAS Syn th esis. NAS was synthesized by reacting acryloyl
mixture was purged with N for 30 min before heating to the
2
-
1
chloride (11.71 g, 1.29 × 10 mol) and N-hydroxysuccinimide
reaction temperature of 80 °C. Individual monomer conver-
sions were determined by withdrawing samples at regular
-
1
(
NHS, 15.15 g, 1.32 × 10 mol) in the presence of triethy-
-1
3
1
lamine (14.40 g, 1.42 × 10 mol) at 0 °C in CHCl
(200 mL),
intervals for analysis by H NMR spectrometry as described
as shown in Scheme 3. Details of the synthesis and purification
earlier, without any precipitation or purification. The final
resulting polymer was precipitated in an excess amount of
cyclohexane and/or hexane, washed, and dried in vacuo.
Methanol was not used for precipitation of the resulting
polymer to prevent any substitution reactions of methanol with
the activated ester units. The final yield for the example above
was 90%.
4
4 1
procedures have been reported elsewhere. H NMR was used
to verify that the product was free of any side products as
described in detail by d’Agosto et al. The final yield was 57%.
6
2
1
NMR Sp ectr om etr y An a lysis. H NMR spectra were
recorded on a Bruker AVANCE DPX300 spectrometer. The
instrument frequency was 300 MHz with the default number
of scans being eight. CDCl
3
and 1,4-dioxane-d
8
were used as
Im m obiliza tion of RAF T Agen t on to P oly(BMA-co-
NAS). Benzyl 2-(2-hydroxyethylamino)-1-methyl-2-oxoethyl
trithiocarbonate (4) was immobilized on the poly(BMA-co-NAS)
solvents. TMS was used as internal reference. Accurate high-
temperature calibration was done using an ethylene glycol
6
3
sample.
backbone by refluxing in CHCl
3
for 48 h in the presence of a
Deter m in a tion of Rea ctivity Ra tios. BMA/NAS copo-
lymerization reactions were conducted in 1,4-dioxane at 60 °C
using AIBN as initiator. The reaction mixture was purged with
catalytic amount of 4-(dimethylamino)pyridine (DMAP) (Scheme
4). The resulting polymer was precipitated in an excess amount
of methanol, after which the sample was filtered and washed
with additional methanol to remove formed byproducts. The
sample was redissolved in chloroform, and the filtering and
washing procedure was repeated. The material was dried in
vacuo to remove residual solvent. The immobilization yield was
2
N for 30 min before heating the mixture to the reaction
temperature. Samples were removed and individual monomer
1
concentrations followed using H NMR spectrometry. Monomer
concentrations were calibrated by comparing the signals of the
vinylic protons corresponding to the different monomers with
determined by monitoring the decrease of the succinimide-CH
2
4
4
1
that of an inert internal reference, 1,3,5-trioxane. For each
signal (4 H at ca. δ ) 2.80 ppm, CDCl
spectrum, using a methylene group in the BMA alkyl-ester
) as an internal reference.
3
) in the H NMR
1
different BMA/NAS starting composition, a H NMR spectrum
of the entire reaction mixture was recorded before the start of
the reaction and after running the reaction for 30 min. The
ratio of the integrated signals of the vinylic protons for each
monomer to the integrated signal of the internal reference,
before and after reaction, was used to calculate the individual
monomer consumption during the course of the copolymeri-
zation reaction.
chain (2 H at ca. δ ) 3.95 ppm, CDCl
3
A typical reaction mixture contained poly(BMA-co-NAS) (2.00
g, ca. 20% NAS), benzyl 2-(2-hydroxyethylamino)-1-methyl-2-
-3
oxoethyl trithiocarbonate (4, 1.183 g, 3.750 × 10 mol), DMAP
-
4
(0.034 g, 2.8 × 10 mol), and CHCl
3
(50.0 mL). The final
immobilization yield for this example was 83%.
Syn th esis of P oly(BMA-co-NAS-gr a ft-BMA). Poly(BMA-
co-NAS) with immobilized RAFT agent (4) on the NAS units
was dissolved in CHCl . AIBN was used as free radical
3
Reactivity ratios were determined applying a least-squares
nonlinear fitting procedure to eq 1 using code developed and
6
4
discussed by van Herk. Further refining of the reactivity
initiator (Scheme 4) in the molar ratio [immobilized RAFT
agent]:[AIBN] ) 10:1. BMA was used as monomer for the
branches in a stoichiometric quantity that targeted a branch
molar mass of ∼6000. The reaction mixture was purged with
6
5
ratios was done using the Tidwell-Mortimer method. The
9
5% confidence interval was also obtained using van Herk’s
6
4
1
code. In situ H NMR spectrometry data were obtained by
conducting a BMA/NAS copolymerization reaction starting
from a ∼50/50 (BMA/NAS) ratio in the NMR instrument. A
2
N for 30 min before heating to the reaction temperature of
60 °C. The resulting polymer was precipitated in an excess
amount of methanol and conversion was determined gravi-
metrically. A typical reaction mixture contained poly(BMA-
co-NAS-graft-RAFT agent) (1.365 g, i.e., containing ca. 20%
-
4
reaction mixture containing BMA (0.069 g, 4.8 × 10 mol),
-4
-5
NAS (0.076 g, 4.5 × 10 mol), AIBN (0.007 g, 4.3 × 10 mol),
-
4
1
,3,5-trioxane (0.013 g, 1.5 × 10 mol), and 1,4-dioxane (3.0
mL) was prepared and degassed by purging with N for 30
min. Ca. 800 µL of this mixture was transferred to an NMR
spectrometer tube containing 3 drops of 1,4-dioxane-d and
-
2
2
immobilized RAFT agent), BMA (9.691 g, 6.767 × 10 mol),
-4
3
AIBN (0.026 g, 1.6 × 10 mol), and CHCl
(40.0 mL). The
8
final yield for this example was 77%.

2
374 Vosloo et al.
Macromolecules, Vol. 37, No. 7, 2004
F igu r e 1. 1H NMR spectrum (CDCl
) of a BMA/NAS (40/60) copolymerization reaction mixture showing the region of interest.
3
The spectrum shows the signals corresponding to the vinylic protons of the two respective monomers relative to 1,3,5-trioxane.
Sch em e 4. Im m obiliza tion of P r im a r y Hyd r oxy-F u n ction a lized RAF T Agen ts (Ben zyl
-(2-Hyd r oxyeth yla m in o)-1-m eth yl-2-oxoeth yl Tr ith ioca r bon a te (4)) on a P oly(BMA-co-NAS) Ba ck bon e a n d
2
Su bsequ en t Br a n ch Syn th esis
Resu lts a n d Discu ssion
where F1 is the fraction of monomer M1 in the copoly-
mer, f1 and f2 ) 1 - f1 the fractions of monomer M1 and
monomer M2 in the feed, respectively, and r1 and r2 the
reactivity ratios.
BMA/NAS Cop olym er iza tion Kin etics. In this
study individual monomer conversions were determined
1
by H NMR spectrometry before reaction and after
1H NMR analysis (as described earlier) enabled the
stopping conventional free radical BMA/NAS copolym-
erization reactions at low conversions for a number of
different BMA/NAS starting compositions. Nonlinear
determination of F
BMA
and fBMA values. An example of
1
a H NMR spectrum for a typical BMA/NAS copolym-
erization reaction mixture is shown in Figure 1. It was
assumed that all monomer not present in the reaction
mixture as free monomer had been incorporated into
the polymer chain. FNAS and fNAS values were obtained
in the same manner. The reactivity ratios obtained by
least-squares fitting to eq 1 were rBMA ) 0.98 (+0.51,
(
least-squares) fitting to eq 1 was used to determine the
6
6,67
reactivity ratios:
2
r f + f f
1
1
1 2
F )
(1)
1
2
2
r f + 2f f + r f
2 2
1
1
1 2

Macromolecules, Vol. 37, No. 7, 2004
Synthesis of Comblike Poly(butyl methacrylate) 2375
F igu r e 3. 95% confidence interval associated with the
obtained final values for the reactivity ratios for the copolym-
erization of BMA and NAS in 1,4-dioxane at 60 °C using AIBN
as initiator.
0
-
.241 (+0.089, -0.060) and rNAS ) 0.221 (+0.037,
0.024). These reactivity ratios enabled the construction
of a compositional diagram as shown in Figure 2b. Error
bars on the initial data points were calculated by
assuming a 5% uncertainty in integration values ob-
1
tained from H NMR spectra and calculating the total
uncertainty as the sum of these individual uncertainties.
Although a slight compositional drift can be seen in
Figure 2b, the copolymer composition remains relatively
close to the azeotrope. Figure 2 illustrates the care that
should be taken when using data points obtained from
a single experimental run. Figure 2b shows discarded
outliers observed at each of the two optimum feed
compositions which could have been taken as valid data
points, had repeated runs not been done. Repeated runs
at identical feed compositions (as was done in Figure
F igu r e 2. Copolymer composition vs feed composition for the
conventional free radical copolymerization of BMA and NAS
conducted in 1,4-dioxane at 60 °C using AIBN as initiator (a)
using the initial estimates for the reactivity ratios and (b) after
refinement of the reactivity ratios using the Tidwell-Mortimer
approach. The diagrams show the azeotrope (dashed) and the
experimentally obtained data points (/, for initial estimate;
O, for Tidwell-Mortimer experiments; +, for outliers in the
Tidwell-Mortimer series) to which the fitting (solid) was done.
2
b) ensured that eventual data points were trustworthy.
The 95% confidence interval associated with the final
values of the reactivity ratios is shown in Figure 3. The
behavior predicted by the compositional diagram in
Figure 2b is supported by the data in Figure 4, which
show the decrease in individual monomer concentra-
tions of BMA and NAS for an approximately equimolar
starting ratio. The individual BMA and NAS concentra-
tions decreased at similar rates. This was expected since
an equimolar feed composition lies very close to the
predicted azeotrope. Starved-feed protocols were con-
sidered unnecessary to ensure a uniform distribution
of NAS units along the poly(BMA-co-NAS) backbone,
since copolymer composition remained in the vicinity
of the azeotrope through the feed range.
-
0.36) and rNAS ) 0.39 (+0.57, -0.17). The composi-
tional diagram constructed using the reactivity ratios
so calculated is shown as Figure 2a. These values in
turn served as the good estimate needed to employ the
Tidwell-Mortimer method,65 which uses a good first
estimation of a set of reactivity ratios to predict the two
feed compositions at which the errors are at a minimum.
This leads to a set of reactivity ratios having the
smallest possible confidence interval. A number of
experiments are consequently conducted at each of these
compositions. The two feed compositions were deter-
mined using the following expressions:
P oly(BMA-co-NAS) Syn th esis. RAFT was used to
control backbone poly(BMA-co-NAS) synthesis. Figures
5
-8 show conversion data as functions of time for the
solution RAFT copolymerization of BMA and NAS
starting from different (BMA/NAS) molar ratios for
different [AIBN]:[RAFT agent] ratios. These data com-
prise individual monomer conversions as obtained using
2
rNAS
1
H NMR spectrometry, and ln([M]0/[M]t), where [M]t )
f ′BMA ≈ 2
and f ′′BMA
≈
+ rBMA
2 + rNAS
monomer concentration at time t. If ideal free radical
kinetics were obeyed, ln([M]0/[M]t) would be linear in t.
It is clear from the data in Figures 5 and 7 that both
monomers were consumed at a comparable rate (with
respect to relative individual starting concentrations)
throughout the course of the copolymerization reaction.
A slight preference was shown toward NAS, as predicted
The two optimum feed compositions were calculated
to be f ′BMA ) 0.67 and f ′′BMA ) 0.16. Experiments done
at these feed compositions were done exactly as those
described earlier; results are shown in Table 1. The
reactivity ratios obtained from these data were rBMA )

2
376 Vosloo et al.
Macromolecules, Vol. 37, No. 7, 2004
Ta ble 1. H NMR Sp ectr om etr y Resu lts for BMA/NAS Cop olym er iza tion Rea ction sa
1
composition
(BMA/NAS)
I(NAS)b
at t ) 0 min
I(NAS)b
at t ) 30 min
I(BMA)e
at t ) 0 min
c
[NAS]td (M)
reaction ID
[NAS]0 (M)
1
2
3
4
5
6
7
16/84
16/84
16/84
67/33
67/33
67/33
67/33
0.967
0.967
0.967
0.982
0.982
0.982
0.982
0.945
0.941
0.947
0.961
0.969
1.007
0.960
0.252
0.252
0.252
0.099
0.099
0.099
0.099
0.211
0.202
0.198
0.087
0.091
0.077
0.087
0.222
0.222
0.222
1.897
1.897
1.897
1.897
I(BMA)e
at t ) 30 min
I(trioxane)h
at t ) 0 min
I(trioxane)h
at t ) 30 min
f
[BMA]tg (M)
FBMAi
FNASi
reaction ID
[BMA]0 (M)
1
2
3
4
5
6
7
0.152
0.131
0.141
1.945
1.937
2.066
1.938
0.049
0.049
0.049
0.201
0.201
0.201
0.201
0.029
0.024
0.025
0.184
0.191
0.165
0.184
0.242
0.242
0.242
1.054
1.054
1.054
1.054
0.283
0.294
0.301
1.178
1.128
1.394
1.175
0.33
0.33
0.31
0.57
0.55
0.61
0.58
0.67
0.67
0.69
0.43
0.45
0.39
0.42
a
All reactions were done in 1,4-dioxane at 60 °C using AIBN as initiator. For all reactions: [BMA + NAS] ) 0.3 M, [AIBN]/[monomer]
b
c
d
)
0.005. Normalized integrals of vinylic protons of NAS. Initial monomer concentration. Final monomer concentration. e Normalized
integrals of vinylic protons of BMA. Initial monomer concentration. g Final monomer concentration. h Normalized integrals of vinylic
f
protons of trioxane. i Copolymer composition.
F igu r e 4. Monomer concentration (M) vs time (s) for the conventional free radical solution copolymerization of BMA and NAS
(
50/50) in 1,4-dioxane at 60 °C, as obtained using in situ 1H NMR spectrometry measurements.
by the reactivity ratios. Theoretical composition values
were well within range of observed composition values,
as determined using free monomer concentrations. Now,
the reactivity ratios were determined at 60 °C compared
to 80 °C for the rate data shown in these figures. The
effect of temperature on reactivity ratios, as described
elsewhere, is to increase the randomness of incorpora-
tion; i.e., reactivity ratios approach 1 as the reaction
temperature increases.68 Since the reactivity ratios do
not differ by a significant amount, no detrimental
impact on the uniformity of the NAS distribution is
expected. The polymerization reaction proceeded rap-
idly, as expected of systems employing trithio-type
tive incorporation rates of BMA and NAS, however,
remained largely unchanged with changing initiator
concentration.
Figures 6 and 8 illustrate the relationship between
reaction rate for the individual monomers and reaction
time for different initiator concentrations (while main-
taining a constant RAFT agent concentration) in the
RAFT solution copolymerization of BMA and NAS for
different BMA/NAS starting compositions. No evidence
to suggest significant autoacceleration at higher conver-
sion was observed, although a slight decrease in reaction
rate with increasing conversion can be seen for the 90/
10 (BMA/NAS) starting composition. The consumption
rates for both BMA and NAS also indicate that the
incorporation of both monomers proceeded in an even
and controlled manner, with the expected minor prefer-
ence toward NAS. Even at relatively extreme feed
compositions such as 80/20 and 90/10 (BMA/NAS), no
6
9,70
RAFT agents.
Figures 5 and 7 also show the
decrease in consumption rates as the ratio of AIBN to
RAFT agent was changed from 1:5 to 1:10 by decreasing
the amount of AIBN. This change is the expected result
of a lower propagating radical concentration. The rela-

Macromolecules, Vol. 37, No. 7, 2004
Synthesis of Comblike Poly(butyl methacrylate) 2377
F igu r e 5. Monomer conversion vs time for the RAFT solution BMA/NAS (80/20) copolymerization reaction for different [RAFT
agent]:[AIBN] ratios conducted in 1,4-dioxane at 80 °C.
0 t
F igu r e 6. ln([M] /[M] ) vs time for the RAFT solution BMA/NAS (80/20) copolymerization for different [RAFT agent]:[AIBN]
ratios conducted in 1,4-dioxane at 80 °C.
significant drift in relative consumption rates was
observed. This observation suggests a relatively random
distribution of NAS units along the backbone, which is
critical for a random distribution of branches in the
target comblike molecules.
Molecular weight distributions of poly(BMA-co-NAS)
showed a degree of tailing toward the low molecular
weight end, as can be seen in Figure 9. Increasing low
molecular weight tailing corresponding to an increasing
NAS content observed during the SEC of poly(BMA-co-
NAS) can also be seen in Figure 9. A possible explana-
tion is the formation of low molecular weight species
due to termination events occurring early during the
RAFT process. This type of tailing was also observed in
the synthesis of BMA homopolymer throughout the
course of the polymerization reaction. The low molecular
weight tail gave rise to higher than expected polydis-
persities (1.5 < Mh w/ Mh n). The data presented in Figure
10 show the molecular weight distributions of poly-
(BMA-co-NAS) prepared under identical conditions,
apart from the type of RAFT agent used. Moving
through the different families of RAFT agentssfrom the
RAFT agent giving the fastest reaction rate to the RAFT
agent giving the slowest reaction rate in going from 3
to 5 to 6 (Scheme 2)sthe troublesome low molecular
weight tailing decreases. This suggests that this specific
system might be sensitive toward termination events
occurring or lack of efficiency either during the initial

2
378 Vosloo et al.
Macromolecules, Vol. 37, No. 7, 2004
F igu r e 7. Monomer conversion vs time for the RAFT solution BMA/NAS (90/10) copolymerization reaction for different [RAFT
agent]:[AIBN] ratios conducted in 1,4-dioxane at 80 °C.
0 t
F igu r e 8. ln([M] /[M] ) vs time for the RAFT solution BMA/NAS (90/10) copolymerization for different [RAFT agent]:[AIBN]
ratios conducted in 1,4-dioxane at 80 °C.
preequilibrium in the RAFT process or during normal
chain propagation throughout the polymerization reac-
tion.
decrease in intensity of the succinimide-CH2 signal from
the NAS units (4 H at ca. δ ) 2.80 ppm, CDCl3) in the
1
H NMR spectrum, relative to a methylene group signal
Im m obiliza tion of RAF T Agen ts on P oly(BMA-
co-NAS). Once a desired NAS distribution and content
were obtained, primary hydroxy-functionalized RAFT
agents (benzyl 2-(2-hydroxyethylamino)-1-methyl-2-oxo-
ethyl trithiocarbonate (4), Scheme 2) were reacted with
the polymer. The reaction was catalyzed using 4-(dim-
ethylamino)pyridine (DMAP). The immobilization yield
of benzyl 2-(2-hydroxyethylamino)-1-methyl-2-oxoethyl
trithiocarbonate (4) onto NAS units in the poly(BMA-
co-NAS) backbone was determined by monitoring the
from the BMA alkyl-ester chain (2 H at ca. δ ) 3.95
ppm, CDCl3) as an internal reference (Figure 11). The
intensity of the succinimide-CH2 signal decreased rela-
tive to the intensity of the alkyl-ester methylene signal,
indicating that reaction between 4 and the succinimide
moiety (resulting in substitution of the succinimide
group) took place through the course of the substitution
reaction. Integration of the benzyl peak (5 H at ca. δ )
7.4 ppm, CDCl3) and subsequent comparison with the
alkyl-ester reference signal, as an alternative to obtain

Macromolecules, Vol. 37, No. 7, 2004
Synthesis of Comblike Poly(butyl methacrylate) 2379
RAFT agents added as pendant side groups to a linear
chain would not impact greatly on the molecular weight
distribution of the poly(BMA-co-NAS) as determined
prior to RAFT agent immobilization. The molecular
weight distribution of poly(BMA-co-NAS) was consid-
ered to be an accurate reflection of the molecular weight
distribution of the corresponding poly(BMA-co-NAS-
graft-RAFT agent). The evolution of shoulders in mo-
lecular weight distributions during the process of im-
mobilizing RAFT agents (due to suggested molecular
coupling reactions as a result of peroxides present as
impurities in ether solvent acting as radical sources)
3
4
have been reported elsewhere. In our case the im-
mobilization reaction was conducted in CHCl3, a solvent
in which a minimal amount of peroxides are expected
(as opposed to an ether), thereby avoiding this problem.
The orientation of the immobilized RAFT agents on the
poly(BMA-co-NAS-graft-RAFT agent) were such that
any propagating radical would always propagate as a
growing side chain in a direction that is away from the
backbone. This resulted in the trithio moiety always
being situated on the chain ends of the side chains. This
is beneficial as it allows subsequent removal of the
trithio moieties if desired and decreasing steric hin-
drance around the propagating radical as the polymer-
F igu r e 9. Molecular weight distributions of poly(BMA-co-
NAS) containing different amounts of NAS prepared using
RAFT agent (3): (a) Mh
n
) 35 600, PDI ) 1.98; (b) Mh ) 45 200,
n
PDI ) 1.67; (c) Mh ) 45 600, PDI ) 1.75.
n
3
4
ization reaction proceeds. This scenario also lowers the
probability of homopolymer formation during branch
propagation since this orientation of the RAFT agent
will result in few unbound free radicals. The only mobile
free radicals would be generated from the primary free
radical source, short oligomeric radicals formed from the
first few propagation steps before addition, and possible
unwanted transfer reactions.
P oly(BMA-co-NAS-gr a ft-BMA) Syn th esis. Poly-
(BMA-co-NAS-graft-RAFT agent) chains with immobi-
lized RAFT agents along the length of the polymer
backbone were obtained in good yield. Upon addition of
a primary free radical source and monomer, chain
growth commenced from these points, resulting in
comblike structures, shown in Scheme 4. The use of
RAFT agents with benzyl groups as leaving groups has
been reported in the literature, but in all reported cases
symmetrical trithiocarbonates such as S,S′-dibenzyl
F igu r e 10. Molecular weight distributions of poly(BMA-co-
NAS) containing 10% NAS prepared using different RAFT
7
0,71
agents: (a) Mh
n
) 45 200, PDI ) 1.67; (b) Mh
n
) 38 300, PDI )
trithiocarbonate were employed.
This necessarily
1
.56; (c) Mh ) 26 300, PDI ) 1.64.
n
leads to benzyl groups acting as initiating species.
During branch growth from poly(BMA-co-NAS-graft-
RAFT agent) described in this study, there is competi-
tion between a secondary radical (segment of immobi-
lized RAFT agent attached to polymer backbone) and a
primary radical (benzyl group) leaving. As a secondary
radical is more stable than a primary radical, it would
be expected that a secondary radical will preferentially
act as leaving group. Any significant BMA insertion
between the sulfur and benzyl group will cause the
immobilization yield, showed excellent agreement with
the result obtained from following the decrease in
intensity of the succinimide-CH2 signal. Immobilization
of 4 became progressively more difficult with decreasing
NAS content in the poly(BMA-co-NAS). Poly(BMA-co-
NAS) containing 20% NAS was reacted to ∼90% graft-
ing efficiency in less than 24 h, but poly(BMA-co-NAS)
containing 10% and 5% NAS respectively appeared to
reach a ceiling grafting yield of 50-60%. Residual,
unreacted NAS units in the polymer backbone should
not have any detrimental effect on the behavior of the
resulting polymers when subjected to the subsequent
free radical polymerization steps. The activated-ester
moiety only undergoes substitution-type reactions and
is therefore not expected to react with primary free
radicals originating from AIBN or other propagating
radicals. The presence of the immobilized RAFT agents
on the poly(BMA-co-NAS) backbone rendered the mate-
rial only partially soluble in THF, making accurate SEC
analysis of the poly(BMA-co-NAS-graft-RAFT agent)
impossible. It is, however, expected that immobilized
1
benzylic -CH2- singlet in the H NMR spectrum
(Figure 11) to shift upfield and increase in multiplicity.
1
Comparison of the H NMR spectra of pure (benzyl 2-(2-
hydroxyethylamino)-1-methyl-2-oxoethyl trithiocarbon-
ate (4) and poly(BMA-co-NAS-graft-RAFT agent) showed
that the chemical shift and multiplicity of the benzylic
-CH2- signal (2 H at ca. δ ) 4.61 ppm, CDCl3)
remained unchanged. This indicates that no significant
insertion of BMA units between the sulfur and benzyl
group had occurred. Branch growth proceeded to high
conversions: 77% and 64% for poly(BMA-co-NAS) con-
taining 20% NAS and 10% NAS, respectively. The
branch Mh n was calculated by means of the percentage

2
380 Vosloo et al.
Macromolecules, Vol. 37, No. 7, 2004
F igu r e 11. 1H NMR spectrum of a poly(BMA-co-NAS) chain activated by reacting ca. 83% of the NAS units with RAFT agent
(
4). The BMA alkyl ester -CH O- group, used as internal reference to calculate grafting yield, is shown by the peak labeled 4
2
and residual NAS units (not explicitly shown in accompanying figure) by the peak labeled 5. The relative integration values of
peaks 4 and 5 are also shown.
F igu r e 12. Comparison of the (apparent) molecular weight
distributions (PSt equivalents) of poly(BMA-co-NAS) (Mh
5 200, PDI ) 1.67) containing 10% NAS (∼50% activated)
with the resulting poly(BMA-co-NAS-graft-BMA) (comb Mh
1 900, PDI ) 2.09, calculated branch Mh
∼ 3800).
F igu r e 13. Comparison of the (apparent) molecular weight
distributions (PSt equivalents) of poly(BMA-co-NAS) (Mh
35 300, PDI ) 1.65) containing 20% NAS (∼83% activated)
with the resulting poly(BMA-co-NAS-graft-BMA) (comb Mh
56 200, PDI ) 1.93, calculated branch Mh
∼ 4700).
n
)
n
)
4
n
)
n
)
5
n
n
conversion of targeted branch Mh n (6000 in this case):
calculated branch Mh n ) (% conversion obtained during
branch growth step) × 6000. SEC analysis of nonlinear
polymers, including the present comb architecture,
results in separation based on hydrodynamic volume,
which of course is not simply related to molecular
weight. With this caveat, the SEC chromatograms now
discussed are presented as apparent molecular weight
distributions, where it is understood that the abscissa
is in fact the molecular weight of a linear polystyrene
chain with the same hydrodynamic volume as that of
the polymer being eluted. Figures 12 and 13 compare
the molecular weight distribution for the poly(BMA-co-
NAS) that served as backbone with the apparent mo-
lecular weight distribution of the resulting poly(BMA-
co-NAS-graft-BMA). The increase in apparent molecular
weight in going from linear backbone to final comblike
polymer is more evident in Figure 13 than is the case
in Figure 12. This could be because in the polymer in
Figure 12, the linear chain containing 10% NAS was
only activated to a ∼50% grafting yield in terms of
RAFT agent immobilization. This would lead to a much
lower branch number (and subsequent molecular weight)
than in the case depicted in Figure 13. No significant
broadening of the apparent molecular weight distribu-
tion or secondary distributions at either lower (new,

Macromolecules, Vol. 37, No. 7, 2004
Synthesis of Comblike Poly(butyl methacrylate) 2381
unbound polymer chains) or higher molecular weight
(BMA-co-NAS), and the distribution of the resulting
poly(BMA-co-NAS-graft-BMA) in terms of equivalent
hydrodynamic volume, were similar, with no significant
broadening occurring. This is consistent with the sup-
position that homopolymer formation and molecular
cross-linking were minimized during the second stage
polymerization. This suggests that the procedure used
here results in comb polymers whose backbone and
branch molecular weight distributions are well con-
trolled and that the distribution of branch points is
random.
(
coupled products) were observed, in contrast to other
controlled syntheses of comb polymers reported else-
where.3
4,72,73
Significant amounts of free homopolymer
formed during the synthesis of the side chains would
be expected to be clearly visible as humps in the low
molecular weight regions, while intra- or intermolecular
cross-linking products arising from radical-radical
coupling between propagating branches would be ex-
pected to be shown in the form of humps or shoulders
in the high molecular weight regions. The data in
Figures 12 and 13 suggest that the formation of free
homopolymer in the second-stage polymerization was
largely circumvented and that significant intra- or
intermolecular cross-linking was largely avoided. Even
though the comb branches could not be cleaved off and
characterized separately, Figures 12 and 13 show that
the resulting apparent molecular weight distributions
remained relatively narrow and monomodal. This sup-
ports the supposition that the comb polymers have well-
controlled molecular weight of the branches: comb
polymers composed of branches where the branches
exhibited a broad molecular weight distribution would
show broader global apparent molecular weight distri-
butions than the parent polymer, due to the major
Ack n ow led gm en t. The support of an ARC Discov-
ery grant is gratefully acknowledged. Dr. Simone Von-
willer kindly synthesized the benzyl 2-(2-hydroxyethy-
lamino)-1-methyl-2-oxoethyl trithiocarbonate and gave
highly appreciated assistance with other synthetic
procedures. Dr. Ian Luck kindly provided assistance
with NMR spectrometer operation and analyses. Dulux
Australia is gratefully acknowledged for the supply of
2-{[(dodecylsulfanyl)carbonothioyl]sulfanyl}propanoic
acid. The Key Centre for Polymer Colloids is established
and supported under the Australian Research Council’s
Research Centres Program.
3
4
differences in subsequent hydrodynamic volumes. The
supposition that the branch polydispersities are low is
supported by the data for BMA homopolymers in Figure
Refer en ces a n d Notes
(
1) Former, C.; Castro, J .; Fellows, C. M.; Tanner, R. I.; Gilbert,
R. G. J . Polym. Sci., Polym. Chem. 2002, 40, 3335-3349.
1
0. The narrow polydispersities of those polymers,
(2) Gownder, M. J . Plast. Film Sheeting 2001, 17, 53-61.
(3) Romm, F.; Figovsky, O. Macromol. Theory Simul. 2002, 11,
synthesized with similar trithiocarbonate RAFT agents
under similar conditions, imply that the branch chains
would exhibit similar (low) polydispersity.
9
3-101.
(
4) Xu, X. R.; Xu, J . T.; Feng, L. X.; Chen, W. J . Appl. Polym.
Sci. 2000, 77, 1709-1715.
(
(
5) Yan, D.; Wang, W. J .; Zhu, S. Polymer 1999, 40, 1737-1744.
6) Niimi, L.; Serita, K.; Hiraoka, S.; Yokozawa, T. J . Polym. Sci.,
Polym. Chem. 2002, 40, 1236-1242.
Con clu sion s
(
7) Brenner, A. R.; Schmaljohann, D.; Voit, B. I.; Wolf, D.
Macromol. Symp. 1997, 122, 217-222.
Terminal-model reactivity ratios in the conventional
free radical copolymerization of BMA and NAS were
determined by monitoring the decrease in individual
(
8) Hadjichristidis, N.; Xenidou, M.; Iatrou, H.; Pitsikalis, M.;
Poulos, Y.; Avgeropoulos, A.; Sioula, S.; Paraskeva, S.; Velis,
G.; Lohse, D. J .; Schulz, D. N.; Fetters, L. J .; Wright, P. J .;
Mendelson, R. A.; Garc ´ı a-Franco, C. A.; Sun, T.; Ruff, C. J .
Macromolecules 2000, 33, 2424-2436.
1
free monomer concentrations using H NMR spectrom-
etry. A simple least-squares nonlinear fit procedure to
the copolymer equation (eq 1) was used to determine
the values of the reactivity ratios. Initial rough esti-
mates of the values of the reactivity ratios were deter-
mined after which the Tidwell-Mortimer method was
employed to refine the values. The final values of the
reactivity ratios were calculated as rBMA ) 0.24 (+0.089,
(
9) Pi, Z.; Kennedy, J . P.; Summers, J . W. J . Polym. Sci., Polym.
Chem. 2002, 40, 3644-3651.
(10) Hirao, A.; Kawano, H.; Ryu, S. W. Polym. Adv. Technol. 2002,
13, 275-284.
(
11) Hua, F. J .; Liu, B.; Hu, C. P.; Yang, Y. L. J . Polym. Sci.,
Polym. Chem. 2002, 40, 1876-1884.
(
12) Chiefari, J .; Chong, Y. K.; Ercole, F.; Krstina, J .; J effery, J .;
Le, T. P. T.; Mayadunne, R. T. A.; Meijs, G. F.; Moad, C. L.;
Moad, G.; Rizzardo, E.; Thang, S. H. Macromolecules 1998,
-0.060) and rNAS ) 0.22 (+0.037, -0.024); the numbers
in parentheses represent the extremes of the joint
confidence interval for these reactivity ratios, given in
Figure 3. These reactivity ratios suggest that, with a
slight drift with feed composition, BMA/NAS copolymer
composition should remain relatively close to the azeo-
trope, implying that the distribution of branch points
in the final comb polymer should be random.
3
1, 5559-5562.
(
(
(
(
(
(
13) Wang, J .; Matyjaszewski, K. J . Am. Chem. Soc. 1995, 117,
5
614-5615.
14) Georges, M. K.; Hamer, G. K.; Listigovers, N. A. Macromol-
ecules 1998, 31, 9087-9089.
15) Haddleton, D. M.; Maloney, D. R.; Suddaby, K. G. Macro-
molecules 1996, 29, 481-483.
16) Haddleton, D. M.; Maloney, D. R.; Suddaby, K. G.; Clarke,
A.; Richards, S. N. Polymer 1997, 38, 6207-6217.
17) Kukulj, D.; Heuts, J . P. A.; Davis, T. P. Macromolecules 1998,
Copolymers of BMA and NAS were polymerized by
RAFT-mediated free radical polymerization, resulting
in a main backbone showing controlled molecular weight
distribution, while the distribution of NAS functionality
along the backbone should be random. The immobiliza-
tion of the primary hydroxy-functionalized RAFT agents
onto the poly(BMA-co-NAS) backbone took place through
substitution reactions of the primary hydroxy function-
alities with the activated ester groups. The presence of
3
1, 6034-6041.
18) Berlinova, I. V.; Dimitrov, I. V.; Vladimirov, N. G.; Samichkov,
V.; Ivanov, Y. Polymer 2001, 42, 5963-5971.
(19) B o¨ rner, H. G.; Matyjaszewski, K. Macromol. Symp. 2002, 177,
1-15.
(
20) Bon, S. A. F.; Morsley, D. R.; Waterson, C.; Haddleton, D.
M. Macromolecules 2000, 33, 5819-5824.
(21) Chiefari, J .; J effery, J .; Mayadunne, R.; Moad, G.; Rizzardo,
E.; Thang, S. Macromolecules 1999, 32, 7700-7702.
the immobilized RAFT agents on the poly(BMA-co-NAS)
(22) Mecerreyes, D.; Pomposo, J . A.; Bengoetxea, M.; Grande, H.
backbone was shown by 1H NMR spectrometry. The
Macromolecules 2000, 33, 5846-5849.
23) Zeng, F.; Shen, Y.; Zhu, S.; Pelton, R. Macromolecules 2000,
(
growing of side chains in the synthesis of poly(BMA-
co-NAS-graft-BMA) proceeded to high conversions. The
molecular weight distribution profiles of backbone poly-
3
3, 1628-1635.
(
24) Coessens, V.; Pintauer, T.; Matyjaszewski, K. Prog. Polym.
Sci. 2001, 26, 337-377.

2
382 Vosloo et al.
Macromolecules, Vol. 37, No. 7, 2004
(
(
(
(
(
25) Matyjaszewski, K.; Beers, K. L.; Kern, A.; Gaynor, S. G. J .
(49) Yoshida, M.; Asano, M.; Yokota, T.; Kumakura, M. Polymer
1990, 31, 371-378.
Polym. Sci., Polym. Chem. 1998, 36, 823-830.
26) Roos, S. G.; M u¨ ller, A. H. E.; Matyjaszewski, K. Macromol-
ecules 1999, 32, 8331-8335.
(50) Monji, N.; Cole, C. A.; Hoffman, A. S. J . Biomater. Sci., Polym.
Ed. 1994, 5, 407-420.
27) Cacioli, P.; Hawthorne, D. G.; Laslett, R. L.; Rizzardo, E.;
Solomon, D. H. J . Macrom. Sci., Chem. 1986, A23, 839-852.
28) Sprong, E.; De Wet-Roos, D.; Tonge, M.; Sanderson, R. D. J .
Polym. Sci., Polym. Chem. 2003, 41, 223-235.
(51) Cole, C. A.; Schreiner, S. M.; Priest, J . H.; Monji, N.; Hoffman,
A. S. ACS Symp. Ser. 1987, 350, 245-254.
(52) Chen, J . P.; Chiu, S. H. Enzyme Microb. Technol. 2000, 26,
359-367.
29) Penn, L. S.; Hunter, T. F.; Lee, Y.; Quirk, R. P. Macromol-
ecules 2000, 33, 1105-1107.
(
(
(
(
53) Mayo, F. R.; Lewis, F. M. J . Am. Chem. Soc. 1944, 66, 1594-
1
601.
(
30) Hou, S.; Kuo, P. Polymer 2001, 42, 2387-2394.
54) Stevens, M. P. Polymer Chemistry-An Introduction, 3rd ed.;
(31) Tong, J .-D.; Du Prez, F. E.; Goethals, E. J . Macromolecules
Oxford University Press: Oxford, 1999.
2
001, 34, 761-767.
55) O’Driscoll, K. F.; Reilly, P. M. Makromol. Chem., Macromol.
Symp. 1987, 10/ 11, 355-374.
56) Moineau, G.; Minet, M.; Dubois, P.; Teyssi e´ , P.; Senninger,
T.; J e´ r oˆ me, R. Macromolecules 1999, 32, 27-35.
(
32) (a) D’Agosto, F.; Charreyre, M.-T.; M e´ lis, F.; Mandrand, B.;
Pichot, C. J . Appl. Polym. Sci. 2003, 88, 1808-1816. (b)
Charreyre, M.-T.; D’Agosto, F.; Favier, A.; Pichot, C.; Man-
drand, B. Biocompatible polymers for fixing biological ligands,
WO 092361, 2001.
(57) Matyjaszewski, K. Macromolecules 1998, 31, 4710-4717.
58) Arehart, S. V.; Matyjaszewski, K. Macromolecules 1999, 32,
(
(
(
(
(
(
(
(
33) Li, Z.; Du, Q. G.; Yang, Y. L.; Lin, M. D. Macromol. Chem.
2
221-2231.
Phys. 2001, 202, 2314-2320.
(
(
(
59) Hawthorne, D. G.; Moad, G.; Rizzardo, E.; Thang, S. H.
Macromolecules 1999, 32, 5457-5459.
60) Calitz, F. M.; Tonge, M. P.; Sanderson, R. D. Macromolecules
34) Quinn, J . F.; Chaplin, R. P.; Davis, T. P. J . Polym. Sci., Polym.
Chem. 2002, 40, 2956-2966.
35) Guo, X. P.; Li, Z. A.; Du, Q. G.; Yang, Y. L.; Lin, M. D. J .
Appl. Polym. Sci. 2002, 84, 2318-2326.
2
003, 36, 5-8.
61) Ferguson, C. J .; Hughes, R. J .; Pham, B. T. T.; Hawkett, B.
36) Mart ´ı nez, G.; de Santos, E.; Mill a´ n, J . L. Macromol. Chem.
Phys. 2001, 202, 2377-2386.
S.; Gilbert, R. G.; Serelis, A. K.; Such, C. H. Macromolecules
2
002, 35, 9243-9245.
37) B o¨ rner, H. G.; Beers, K. L.; Matyjaszewski, K.; Sheiko, S. S.;
M o¨ ller, M. Macromolecules 2001, 34, 4375-4383.
38) Lee, A. H. F.; Chan, A. S. C.; Li, T. H. Tetrahedron 2003, 59,
(
(
(
62) D’Agosto, F.; Charreyre, M.-T.; Pichot, C. Macromol. Biosci.
2
001, 1, 322-328.
63) Braun, S.; Kalinowski, H.-O.; Berger, S. 150 and More Basic
8
33-839.
NMR Experiments; Wiley-VCH: Weinheim, 1998.
64) Van Herk, A. J . Chem. Educ. 1995, 72, 138-140.
39) Lewis, M. R.; Boswell, C. A.; Laforest, R.; Buettner, T. L.;
Ye, D.; Connett, J . M.; Anderson, C. J . Cancer Biother.
Radiopharm. 2001, 16, 483-494.
(65) Tidwell, P. W.; Mortimer, G. A. J . Polym. Sci., Polym. Chem.
(
(
(
40) Loiseau, N.; Cavelier, F.; Noel, J . P.; Gomis, J . M. J . Pept.
1965, 3, 369-387.
Sci. 2002, 8, 335-346.
(66) Brar, A. S.; Kumar, R. J . Mol. Struct. 2002, 616, 37-47.
(67) Ito, H.; Dalby, C.; Pomerantz, A.; Sherwood, M.; Sato, R.;
Sooriyakumaran, R.; Guy, K.; Breyta, G. Macromolecules
2000, 33, 5080-5089.
41) Luo, Y.; Prestwich, G. D. Bioconjugate Chem. 2001, 12, 1085-
1
088.
42) Takei, Y. G.; Matsukata, M.; Aoki, T.; Sanui, K.; Ogata, N.;
Kikuchi, A.; Sakurai, Y.; Okano, T. Bioconjugate Chem. 1994,
(68) O’Driscoll, K. F. J . Macrom. Sci., Chem. 1969, A3, 307-309.
(69) Lai, J . T.; Filla, D.; Shea, R. Macromolecules 2002, 35, 6754-
6756.
(70) Mayadunne, R. T. A.; Rizzardo, E.; Chiefari, J .; Krstina, J .;
Moad, G.; Postma, A.; Thang, S. H. Macromolecules 2000,
33, 243-245.
(71) Quinn, J . F.; Barner, L.; Davis, T. P.; Thang, S. H.; Rizzardo,
E. Macromol. Rapid Commun. 2002, 23, 717-721.
5
, 577-582.
(
(
(
(
(
(
43) Zhang, H. T.; Guo, Z. R.; Huang, J . L. J . Polym. Sci., Polym.
Chem. 2002, 40, 4398-4403.
44) D’Agosto, F.; Charreyre, M.-T.; Veron, L.; Llauro, M.-F.;
Pichot, C. Macromol. Chem. Phys. 2001, 202, 1689-1699.
45) Erout, M. N.; Ela ¨ı ssari, A.; Pichot, C.; Llauro, M.-F. Polymer
1
996, 37, 1157-1165.
46) Erout, M. N.; Troesch, A.; Pichot, C.; Cros, P. Bioconjugate
Chem. 1996, 7, 568-575.
(
72) Fern a´ ndez-Garc ´ı a, M.; De la Fuente, J . L.; Cerrada, M. L.;
Madruga, E. L. Polymer 2002, 43, 3173-3179.
47) Yang, H. J .; Cole, C. A.; Monji, N.; Hoffman, A. S. J . Polym.
Sci., Polym. Chem. 1990, 28, 219-226.
(73) Wang, Z.; He, J .; Tao, Y.; Yang, L.; J iang, H.; Yang, Y.
Macromolecules 2003, 36, 7446-7452.
48) Yoshida, M.; Asano, M.; Yokota, T.; Chosdu, R.; Kumakura,
M. J . Polym. Sci., Polym. Lett. 1989, 27, 437-442.
MA035302A