Nitroxide-mediated controlled radical polymerizations of styrene derivatives

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Nitroxide-Mediated Controlled Radical Polymerizations

of Styrene Derivatives

Patrick J. M. Stals,^1,2Trang N. T. Phan,³Didier Gigmes,³

Tim F. E. Paffen,²E. W. Meijer,^1,2Anja R. A. Palmans^1,2

¹Institute for Complex Molecular Systems, Eindhoven University of Technology, PO Box 513,

5600 MB Eindhoven, The Netherlands

²Laboratory of Macromolecular and Organic Chemistry, Eindhoven University of Technology,

PO Box 513, 5600 MB Eindhoven, The Netherlands

³UMR 6264 Laboratoire Chimie Provence, Aix-Marseille Universite´, Avenue Escadrille Normandie-Niemen,

Case 542, 13397 Marseille Cedex 20, France

Correspondence to: A. R. A. Palmans (E-mail: a.palmans@tue.nl)

Received 29 September 2011; accepted 29 October 2011; published online 28 November 2011

DOI: 10.1002/pola.25833

ABSTRACT: Several (protected) amine and alcohol functional-

ized styrene monomers were synthesized via readily accessible

synthetic routes. The controlled radical copolymerization of

these functionalized styrene monomers with styrene was per-

formed using two alkoxyamines, namely N-(2-methylpropyl)-N-

(1-diethylphosphono-2,2-dimethylpropyl)-O-(2-carboxylprop-2-yl)

hydroxylamine (MAMA-SG1) and N-tert-butyl-N-(2-methyl-1-

phenylpropyl)-O-(1-phenylethyl)hydroxylamine. The copolymers

obtained showed low polydispersities, controlled molecular

weights, and a random topology. The thermal properties of the

polymers were determined with differential scanning calorime-

try. All polymers were amorphous and showed glass transition

temperatures between 40 and 111 ^ꢀC. Deprotection of the

copolymers afforded amine or alcohol pendant polystyrenes

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which were readily functionalized with isocyanates.

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KEYWORDS: copolymerization; functionalization of polymers;

glass transition; nitroxide-mediated polymerization; polystyrene

INTRODUCTION Controlled radical polymerizations (CRPs)

are highly attractive polymerization techniques and widely

used to obtain polymers with defined end-groups, controlled

topologies, and narrow polydispersity indices (PDIs).^1–6In

the last two decades, several CRP techniques have been

developed, the most important being single-electron transfer

mediated living radical polymerization,¹atom transfer radical

polymerization (ATRP),²reversible addition fragmentation

chain transfer (RAFT),³and nitroxide-mediated polymeriza-

tion (NMP).^4,5,6Of these techniques, NMP is particularly

interesting, as no metals are required and NMP agents can

act both as controlling agent as well as unimolecular initia-

tor, simplifying polymerization and work up. NMP is success-

ful in the controlled polymerization of styrene, affording

polystyrene of low polydispersity (PDI < 1.10).⁵In addition,

the development of bifunctional NMP agents allowed easy

access to block copolymers using two inherently different

polymerization techniques in a one-pot procedure.⁷

als,^2,9and catalytically active nanoparticles.¹⁰To circumvent

problems, such as limited solubility of monomers at high

concentrations and unwanted side reactions under polymer-

ization conditions, postfunctionalization of polymers contain-

ing pendant functional groups is an attractive option. Pend-

ant functional groups such as alkynes, alkenes, and thiols,

have been reacted with ‘‘click"-reactions such as Huisgen-1,3-

dipolar cycloadditions,¹¹Diels–Alder reactions,¹²and thiol-

ene additions.¹³The polymerization of isocyanate-based

monomers and subsequent postfunctionalization with alco-

hols, thiols, and amines to form urethanes, thioureas, and

ureas, respectively, has been evaluated in recent years.^14–16

However, a problem with isocyanate pendant polymers is

their sensitivity to every nucleophile (e.g. water).

We are interested in amine/alcohol pendant polystyrenes of

controlled molecular weight and narrow PDI that can be

quantitatively reacted with a variety of electrophiles. The

advantage of this approach is that one does not suffer from

problems with instability of the pendant functionalities on

these backbones and it is easy to get rid of the excess of

electrophile. Surprisingly, the controlled (co)polymerization

Lately, there has been a lot of interest in controlled (co)poly-

merizations of vinyl monomers for a variety of applications,

such as supramolecular-polymeric constructs,⁸biomateri-

Additional Supporting Information may be found in the online version of this article

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SCHEME 1 Chemical structures of monomers 2–9.

of (protected) amine or alcohol functionalized styrenes has

received little attention to date; Fukuda and coworkers¹⁷dis-

cussed the (co)polymerization of N-(p-vinylbenzyl)phthali-

mide using 2,2,6,6-tetramethylpiperidinyl-1-oxy. Several pro-

polymerizations.²¹Finally, the versatility of our postfunction-

alization strategy is demonstrated by reacting a model-iso-

cyanate with the pendant alcohols or amines of the obtained

copolymers.

tected

alcohol-functionalized

styrenes

have

been

polymerized using anionic techniques,¹⁸whereas block poly-

mers have been prepared with tert-butyldimethyl(4-vinyl-

phenoxy)silane using NMP.¹⁹

RESULTS AND DISCUSSION

Monomer Design and Synthesis

We designed a set of styrene-based monomers which com-

prise a (protected) amine or alcohol functionality, so that a

variety of molecules can be readily attached via reactions

with isocyanates to the final polymer (Scheme 1). All mono-

mers contained either a short or a longer aliphatic spacer

between the (protected) amine or alcohol functionality and

the styrene to minimize differences in the electronic proper-

ties of the vinyl group. The latter may result in a nonrandom

polymer topology on copolymerizing the functional mono-

mers with styrene. The monomers with longer spacers

between the (protected) amine or alcohol and vinylphenyl

functionality are expected to increase the solubility of the

resulting copolymers. Most of the polymerizations were con-

ducted on monomers with protected amine (monomers 2, 3,

and 8) or protected alcohol (monomers 5, 6, and 9) groups.

Herein, we present an efficient strategy for both the synthe-

sis of several (protected) amine and alcohol functional styr-

enes as well as the synthesis of random copolymers of these

monomers with styrene. We copolymerized our library of

functional styrene monomers using two of the most widely

used NMP agents. The first one, N-tert-butyl-N-(2-methyl-1-

phenylpropyl)-O-(1-phenylethyl) hydroxylamine (CTA-1) was

popularized by Hawker et al. in the late 1990s and has been

used extensively in (co)polymerizations of styrene.^5,20The

second one is a commercially available diethoxyphosphoryl-

based alkoxy-amine, N-(2-methylpropyl)-N-(1-diethylphos-

phono-2,2-dimethylpropyl)-O-(2-carboxylprop-2-yl)hydroxylamine

(MAMA-SG1, CTA-2) that has been studied in recent years

because of its high activity and excellent control in styrene

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the three monomers indicating a random built in of the

monomers.

Monomers 2, 3, and 5–9 were subsequently copolymerized

with styrene in a 10/90 ratio using CTA-1 with the aim to

produce well-defined polymers with number average molec-

ular weights of around 25 kDa. To ensure a moderate load-

ing of functional groups, a loading of 10% of functional styr-

enes was chosen. After optimization of the polymerization

conditions, polymerizations using CTA-1 yielded polymers

with PDI ranging from 1.07 to 1.72 and number average

molecular weights M_nranging from 18 to 27 kDa as deter-

mined by gel permeation chromatography (GPC). The results

are summarized in Table 1. Copolymers with very narrow

PDIs (PDI ꢂ 1.11, Table 1, entries 1, 2, 5, and 10) were pro-

cured from monomers 2, 3, 5, and 8, whereas the polymers

obtained from monomers 6 and 7 showed a slightly higher

PDI ꢂ 1.25 (Table 1, entries 7 and 8). The terpolymer p(10-

co-st) with a total incorporation of 20% monomers 3 and 5

was also well-defined (entry 12, Table 1, M_nꢁ 22,000, PDI

¼ 1.25). In all the polymerization reactions tested, no signifi-

cant differences were observed between the feed ratio of the

monomers and the observed ratio after isolation of the poly-

mer. These results, together with those obtained by GC–FID,

indicate that CTA-1 is an excellent NMP agent for copolymer-

izing functional styrenes with styrene and that the designed

monomers are randomly incorporated into the copolymers.

SCHEME 2 Molecular structures of N-tert-butyl-N-(2-methyl-1-

phenylpropyl)-O-(1-phenylethyl)hydroxylamine (CTA-1, left), N-

(2-methylpropyl)-N-(1-diethylphosphono-2,2-dimethylpropyl)-O-

(2-carboxylprop-2-yl)hydroxylamine (CTA-2, middle), and the

free nitroxide SG1 (right).

We used both esters and ethers as a linking group; esters

(monomer 6 and 8) are more prone to hydrolysis, but are

synthetically more easily accessible, whereas ethers (mono-

mer 2 and 9) are chemically more stable, but need harsher

conditions to prepare.

All monomers were readily prepared starting from 4-vinyl-

benzylchoride 1. Monomers 2 and 9 were synthesized via a

straightforward Williamson-ether synthesis of 4-vinylbenzyl-

chloride with the corresponding alcohols using sodium

hydride as a base. Esters 6 and 8 were prepared using a

substitution of 4-vinylbenzylchloride with the appropriate

acids and potassium carbonate as a base. Monomers 3 and 4

were prepared via a Gabriel synthesis on 4-vinylbenzylchlor-

ide (monomer 3) and subsequent hydrazinolysis (monomer

4). Monomer 7 was prepared by hydrolysis of 4-vinylbenzy-

lacetate, which can also be prepared from 1.²²Last, mono-

mer 5 was prepared by silyl-protection of monomer 7 with

t-butyl dimethylsilylchloride. The yields of the monomers

varied between 15 and 93% and all were prepared in high

purity as evidenced by NMR, GC–MS, and ESI–MS.

As a comparison, selected monomers were also polymerized

under similar, separately optimized, conditions using CTA-2.

Monomer 3 and 5 were selected because these two mono-

mers gave the two copolymers with the narrowest PDIs with

CTA-1, whereas monomer 7 was chosen because it gave a rel-

atively large PDI with CTA-1. The polymerizations applying

CTA-2 (Table 1, entries 3, 4, 6, and 9), resulted in copolymers

NMP Co-Polymerization of Monomers 2–3 and 5–9 with

Styrene using CTA-1 and 3, 5, and 7 Using CTA-2

Our library of monomers was tested in a controlled polymer-

ization process using N-tert-butyl-N-(2-methyl-1-phenyl-

propyl)-O-(1-phenylethyl)hydroxylamine (CTA-1, Scheme 2)

and N-(2-methylpropyl)-N-(1-diethylphosphono-2,2-dimethyl-

propyl)-O-(2-carboxylprop-2-yl)hydroxylamine (MAMA-SG1,

CTA-2, Scheme 2).

The electronic properties of the vinyl group are expected to

be unaffected by the various functional groups in monomers

2–9, so that random copolymers are expected when mono-

mers 2, 3, and 5–9 are copolymerized with styrene in NMP-

conditions. To test this, selected monomers and styrene

were copolymerized in a polymerization reaction with a feed

of ꢁ 10/90 mol % functional styrene/styrene using CTA-1

(see Supporting Information, Figs. S1–S3). Monomer 4 was

excluded from these tests, since a large reactivity difference

with styrene has been reported previously.²³The conversion

of the monomers during the polymerization was quantified

using gas chromatography (GC–FID). As an example, the con-

version 3/5/styrene in a feed of 10/10/80 mol % is shown

in Figure 1. The increase in conversion is almost equal for

FIGURE 1 Conversion of the monomers in the synthesis of a

terpolymer of 80% styrene with 10% monomer 3 and 10%

monomer 5, closed squares: styrene, open triangles: monomer

3, open circles: monomer 5. Conditions: monomers 50% w/w

in toluene at 95 ^ꢀC using CTA-1 (target DP ꢁ 250).

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TABLE 1 Results of the Copolymerizations of Monomer 2–9 (StA and StB) with Styrene (St) and Corresponding Thermal Properties

of the Resulting Copolymers^a

Obs. Ratio

Feed-Ratio

Conv.

(%)

(St/StA/

StB)

M_n,exp

T_g

(^ꢀC)

i

Entry

Copolymer

StA

StB

NMP-Agent

(St/StA/StB)

M_n,th(Da.)

(Da.)

PDI

1

p(2-co-st)

p(3-co-st)

p(5-co-st)

p(6-co-st)

p(7-co-st)

p(8-co-st)

p(9-co-st)

p(10-co-st)

p(4-co-st)

p(11-co-st)

p(12-co-st)

p(13-co-st)

p(14-co-st)

p(15-co-st)

p(16-co-st)

2

3

–

7

–

CTA-1

CTA-2

CTA-2^b

CTA-1

CTA-2

CTA-1

CTA-2

CTA-1

–

92/8

90/10

91/9

90/10

95/5

80/10/10

–

76

77

69

56

63

47

58

91

47

74

n.d.

76

–

92/8

90/10

n.d.

88/12

90/10

93/7

92/8

88/12

95/5

93/7

80/10/10^h

–

17,100

20,200

24,100

28,600

15,900

11,600

19,400

27,000

28,000

20,200

n.d.

19,100

18,300

20,900

29,000

19,000

8,400

1.11

1.09

1.27

1.15

1.08

1.25

1.21

1.25

1.31

1.10

1.72

1.25

n.d.^c

1.56

n.d.^c

1.09

1.08

77.0

2

98.4

3

–

4

3

5

84.9

43.7

6

5

–

7

6

21,400

26,800

29,600

18,100

27,500

22,100

n.d.^c

8

7

101.1

–

9

7

10

11

12

13

14

15

16

17

18

19

8

81.5

51.6

95.7

111.4

91.5

94.0

87.0

88.9

80.2

104.3

9

5

26,000

–

4^e

2^d

8^f

–

n.d.^c

–

25,300

n.d.^c

–

7^g

–

20,100

18,400

–

d

e

f

n.d. ¼ not determined.

Deprotected polymer p(2-co-st).

Deprotected polymer p(3-co-st).

Deprotected polymer p(8-co-st).

deprotected polymer p(5-co-st).

As determined by GC–FID.

a

All GPC measurements were measured on a THF system using a poly-

styrene calibration after isolation of the polymer. Conversions and

observed ratios determined by ¹H NMR. The thermal properties were

derived from the second heating run.

g

h

i

b

2.5 mol % of free SG-1 was added to increase the control.

Based on conversion.

c

These polyamines/ureas showed too much interaction with the GPC-

column.

showing low PDIs as well. Copolymer p(3-co-st) (Table 1,

entry 3) showed a PDI of 1.27 which was further reduced to

1.15 by addition of 2.5 mol % of the free nitroxide of CTA-2

(Table 1, entry 4). Additional nitroxide increases the concen-

tration of free nitroxide in the polymerization mixture and

decreases the number of active, growing chains present at any

given time.²⁴This amount of excess of nitroxide is certainly

not an optimized one, but gives a good compromise between

kinetics and polymerization control. P(5-co-st) (Table 1, entry

6) showed a low PDI of 1.25. The PDI of p(7-co-st) was

slightly higher at 1.34 (Table 1, entry 9). These results indi-

cate that CTA-2 is also an excellent NMP agent for copolymer-

izing functional styrenes with styrene.

tive other figures, including results for CTA-2). As expected,

CTA-2 proved to be considerably faster than CTA-1: while

the ‘‘controlled’’ polymerization of functional monomers

using CTA-1 usually required 6–7 days to reach 60–70%

conversion, 1 day sufficed for CTA-2 (see Supporting Infor-

mation) under almost similar conditions.²⁵

Although most copolymers show good to excellent PDIs in

the NMP polymerization, in some cases there is broadening

of the molecular weight distribution. In the case of p(7-co-

st) and p(9-co-st) the slightly higher PDIs can be related to

a pronounced shoulder observed in the high molar mass

side of the GPC traces, particularly, when the polymerization

time increases. This shoulder was also observed for p(2-co-

st), but was absent in other copolymers such as p(3-co-st)

(Figure 3). The shoulder is rationalized by the molecular

structure of the starting monomers: the protons at the ben-

zylic position in the corresponding styrene monomers 2, 7,

and 9 have a relatively weak bond and are rather labile and

sensitive toward radical abstraction and other transfer reac-

tions,²⁶a phenomenon that has been studied in detail for

the ATRP of 4-vinylbenzylchloride.²⁷We could suppress the

lability of the benzylic position using esters instead of ethers

In addition to the low polydispersities obtained for the

copolymerization of monomers 2–3 and 5–9, the kinetic

plots show behavior typical for a CRP for both CTA-1 and

CTA-2. An almost linear relationship is found when plotting

the natural logarithm of the conversion versus time and the

molecular weight versus overall conversion of the mono-

mers. As an example, the kinetic results of the copolymeriza-

tion of 3 and styrene using CTA-1 are shown in Figure 2

(see Supporting Information, Figures S4–S5 for representa-

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FIGURE 2 Conversion versus time (left) and molecular weight versus conversion (right) for the copolymerization of monomer 3

and styrene 50% w/w in toluene at 95 ^ꢀC using CTA-1. Conversions and M_nwere determined from the crude reaction mixtures.

as a linker. This combination of a donor and an acceptor for

radicals stabilizes the radical on the benzylic position and,

thus, decreases its reactivity (polymer p(5-co-st) and p(8-

co-st)), an effect which is similar to the high stability of radi-

cals formed in AIBN. A second possibility to reduce side-

reactions is using a phthalimide containing monomer (mono-

mer 3, polymer p(3-co-st)). This results in delocalized radi-

cals on the isoindoline-1,3-dione, thus, decreasing the chance

for further polymerization on the radical or recombination of

the radical. As a third possibility, introducing a t-butyl dime-

thylsilyl protecting group (monomer 5, polymer p(5-co-st))

on the alcohol sterically hinders the availability of the ben-

zylic position for radical abstraction, which also results in

well-defined polymers.

the functionalization reaction. This yielded copolymers p(14-

co-st) and p(13-co-st), respectively, (Scheme 3, entries 17

and 16 in Table 1). In addition, we reacted a hydroxyl-func-

tional [the silyl-deprotected p(5-co-st)] with nonylisocyanate

to afford p(15-co-st) (Scheme 3, entry 18 in Table 1).

All copolymers were readily functionalized with nonylisocya-

nate after overnight reaction, as evidenced by ¹H NMR. For

functionalization of the alcohol, a catalyst (dibutyltin dilaur-

eate) and reflux conditions were necessary. The ¹H NMR

spectrum of amine functional p(11-co-st) is compared to

that of p(13-co-st) in Figure 4. The appearance of the CH₂

protons next to the urea group at 3.2 ppm together with the

disappearance of the CH₂protons next to the amine indicate

that the amine-pendant groups are fully converted into urea

groups. No obvious influence of the length of the spacer was

observed on the reactivity of the amines or alcohols, a result

of the very reactive electrophile that was used. GPC-traces of

the urethane containing polymers showed the narrow PDIs

in line with those of the starting polymers (Table 1, entry 18

The protected polymers p(2-co-st), p(3-co-st), p(5-co-st),

and p(8-co-st) (Table 1, entries 1, 2, 5, and 10) were subse-

quently deprotected; p(2-co-st) and p(3-co-st) via hydrazi-

nolysis of the phthalimide yielding free amine copolymers

(Table 1, entries 13 and 14, respectively). Free alcohols were

obtained starting from p(5-co-st) via a silyl-deprotection

with tetrabutylammonium fluoride (TBAF). Last, p(8-co-st)

was deprotected via acidolysis with TFA to yield p(12-co-st)

(Table 1, entry 15). All the deprotections were quantitative

after overnight reaction and the free alcohol or amine pend-

ant polystyrenes were obtained pure after precipitation in

1

methanol. As an example, the H NMR spectra of phthalimide

containing p(2-co-st) and the reduced polymer p(11-co-st)

are given in Figure 4. The disappearance of the phthalimide

protons around 7.8 ppm after and the shift of methylene

next to the nitrogen from 3.7 to 3.5 ppm indicate the re-

moval of the protective group.

Postfunctionalization of Alcohol and Amine

Pendant Polystyrenes

To illustrate the reactivity of the free alcohols and amines of

the prepared copolymers with isocyanates in a postfunction-

alization reaction, several copolymers were reacted with

nonylisocyanate, which acts as a model for other electro-

philes. We selected p(4-co-st) and p(11-co-st) comprising

free amines to examine the influence of the spacer length in

FIGURE 3 Representative GPC-curves for polymers p(3-co-st)

(top, Table 1, entry 2), p(9-co-st) (middle, Table 1, entry 11),

p(7-co-st) (bottom, Table 1, entry 8).

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FIGURE 4 Proton NMR of p(2-co-st) (entry 1, Table 1, bottom), the reduced polymer p(11-co-st) (entry 14, Table 1, middle) and

final, functionalized polymer p(13-co-st) (entry 16, Table 1, top).

SCHEME 3 Urea and urethane functional polystyrenes p(13-co-st) (left), p(14-co-st) (middle), and p(15-co-st) (right).

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and Supporting Information, Fig. S7). The introduction of

urea groups decreases the solubility of the copolymers.

Although protected p(2-co-st) and p(3-co-st) were readily

analyzed with GPC using THF as the eluent, polymer p(14-

co-st) could not be analyzed with GPC using either THF,

CHCl₃, or DMF as eluent and p(13-co-st) gave a broad PDI

(Table 1, entries 17 and 16, respectively, and Supporting In-

formation, Fig. S7), presumably due to interactions with the

column.

TMS using the resonance of the deuterated solvent as inter-

nal standard. Abbreviations used are s: singlet, d: doublet,

dd: double doublet, t: triplet, q: quartet, m: multiplet. Deu-

terated solvents were obtained from Cambridge Isotope Lab-

oratories. Manual column chromatography was performed

using Merck 60 Å pore size silica gel (particle size: 63–200

lm). Flash column chromatography was performed on a

Biotage SP-1 Flash Chromatography system, with KP-SILTM

Silica Gel SNAP columns. GC–MS measurements were per-

formed on a Shimadzu GC–MS system equipped with an

autosampler with a Zebron ZB-35 column of 30 m ꢃ 0.25

mm with a 0.25 lm coating and using_ꢀthe fo_ꢀllowing temper-

Thermal Properties of Polystyrenes with

Pendant Groups

The thermal properties of all polymers were investigated

using differential scanning calorimetry (DSC), the results are

summarized in Table 1. The thermal properties of polystyr-

enes are strongly affected by the presence of substituents on

the phenyl ring.²⁸In our case, the T_gof the copolymers is

strongly affected by the nature of the side-group of the

comonomer, showing that changing the comonomer allows

tuning of the thermal properties of the polymer. Although

the T_gof unfunctionalized polystyrene in the molecular range

of 20 kDa is around 90 ^ꢀC (89 ^ꢀC for 22 kDa),²⁹the T_gof

polystyrenes comprising 10 mol % of functional monomer

varies between 44 and 111 ^ꢀC. Polymers with spacers

between the functionality and the styrene in general show a

lower T_gthan polystyrene: the T_gdropped to 77 ^ꢀC in the

case of p(2-co-st), 44 ^ꢀC for p(6-co-st) and 52 ^ꢀC for p(9-

co-st). Most likely, this drop in T_gis caused by the flexibility

of these side-chains. Incorporating a phthalimide directly

linked to the polymer (p(3-co-st)), a silyl-protected alcohol

directly linked to the polymer (p(5-co-st)) or a terpolymer

with these two monomers (p(10-co-st)) resulted in T_g’s sim-

ilar to that of polystyrene. Reducing the phthalimide in p(3-

co-st) to the free amine containing p(4-co-st) caused a re-

ꢀ

ature program: 80 C | 1 min ! 330 C, 30 C/min | 3 min.

GC–FID measurements were performed on a Shimadzu GC-

2010 system equipped with an autosampler with a Chrom-

pack CP-Sil 5CB-M5 column of 25 m ꢃ 0.32 mm with a 0.25

lm_ꢀcoating and using_ꢀthe following temperature program:

80 C | 1 min ! 320 C, 20 ^ꢀC/min | 5 min. ESI–MS meas-

urements were recorded with a Perkin-Elmer SCIEX API 165

single quadrupole LC/MS instrument. GPC-measurements

were performed on a Shimadzu-system with two Polymer-

Labs columns in serie (PLgel 5 lm mixed C [200–2,000,000

Da] and PLgel 5 lm mixed D [200–40,000 Da]) and

equipped with a RI (Shimadzu RID-10A) and a PDA detector

(Shimadzu SPD-M10A), with THF as eluent at a constant

flow rate of 1.0 mL/min. Number averaged molecular

weights and molecular weight distribution (M_w/M_n) were

obtained relative to polystyrene standards (Polymer Labora-

tories, molecular weight range: 580–100,000 g mol^ꢄ1). The

system used for entries 3, 4, 6, and 9 in Table 1 was oper-

ated at 30 ^ꢀC and equipped with a Waters 515 liquid chro-

matograph pump, a guard column, and two Nucleogel (HR4

and HR5) columns in series. Detection systems were a differ-

ential refractive index detector (Waters Model 410) and an

ultraviolet (UV) detector (Waters Model 468). The mobile

phase was THF at a constant flow rate of 1.0 mL/min. Num-

ber averaged molecular weights and molecular weight distri-

bution (M_w/M_n) were obtained relative to polystyrene stand-

ards (Polymer Laboratories, molecular weight range: 580–

377,400 g mol^ꢄ1). GPC measurements were performed on

precipitated polymers, unless otherwise noted. The thermal

transitions were determined with DSC using a TA Q2000

DSC under a nitrogen atmosphere with heating and cooling

rates of 40 K/min. In all the cases, the second heating run

was used to determine transitions.

ꢀ

markable increase in T_gfrom 98.4 to 111 C. Similarly, p(11-

co-st) shows an increase of 15 ^ꢀC in T_gafter reduction of

the phthalimide of p(2-co-st). In addition, the T_gof p(5-co-

st) is 16 ^ꢀC lower than that of the corresponding alcohol

functionalized p(7-co-st). Apparently, the additional hydro-

gen bonding interactions between the amines or alcohols in

the solid state cause a further rigidification of the polymer

structure compared to the protected version of the polymer,

thus increasing the T_g. A similar effect was observed for the

T_gof urea/urethane containing polymers p(13-co-st), p(14-

co-st), and p(15-co-st) (T_gbetween 80 and 90 ^ꢀC). The

hydrogen bonds between the ureas and urethanes cause a

rigidification of the polymer structure, and thus an increase

in T_g, compared to that of polymers that had long tails with-

out the possibility of additional noncovalent interactions

(p(2-co-st), p(6-co-st), and p(9-co-st)).

Materials

All solvents were obtained from Biosolve, all other chemicals

were obtained from Aldrich or Acros unless otherwise noted.

Dry, degassed toluene, THF and dichloromethane were tapped

off a solvent purification column. Chloroform was dried over

molecular sieves and triethylamine was stored over KOH pel-

lets. Styrene was purified before use by distillation under

reduced pressure. Other monomers were additionally purified

by filtration over a short plug with basic alumina or with col-

umn chromatography. Aminomethylated polystyrene resin was

obtained from NovaBioChem. 2-({tert-Butyl[1-(diethoxyphos-

phoryl)-2,2-dimethylpropyl] amino} oxy)-2-methylpropanoic

EXPERIMENTAL

Instrumentation

¹H NMR and ¹³C NMR spectra were recorded on a Varian

Mercury Vx 400 MHz and/or a Varian 400MR 400 MHz (400

1

MHz for H NMR and 100 MHz for ¹³C NMR). Proton chemi-

cal shifts are reported in ppm downfield from tetramethylsi-

lane (TMS) and carbon chemical shifts in ppm downfield of

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acid (MAMA-SG1) and {tert-butyl[1-(diethoxyphosphoryl)-2,2-

dimethylpropyl]amino}oxyl radical (SG1) were kindly provided

by Arkema. All other chemicals were used as received. 2-(6-

Bromohexyl)isoindoline-1,3-dione was synthesized in accord-

ance with published procedures.³⁰

combined organic layers were washed with brine (50 mL),

dried with MgSO₄and the solvent was removed in vacuo to

yield 4 as a yellow oil (0.23 g, 89%).

¹H NMR (CDCl₃): d ¼ 7.38 (d, J ¼ 8.1 Hz, 2H, ArAH), 7.28

(d, J ¼ 8.1 Hz, 2H, ArAH), 6.71 (dd, J ¼ 17.6 Hz, 10.9 Hz,

1H, ArACH¼¼C), 5.73 (d, 1H, J ¼ 17.6, 1H, ArACH¼¼CH₂),

5.22 (d, J ¼ 10.9 Hz, 1H, ArACH¼¼CH₂), 3.85 (s, 2H,

ArACH₂), 1.64–1.25 (s, broad, 2H, NH₂). ¹³C NMR: d ¼

141.9, 135.5, 135.1, 126.6, 125.9, 112.4, 45.0. GC/MS t_R¼

3.808; m/z: 133 (M^þ).

Synthesis

Synthesis of 2-(6-(4-Vinylbenzyloxy)hexyl)

isoindoline-1,3-dione (2)

In a 100-mL three-necked round bottom flask, (4-vinylphe-

nyl)methanol (0.50 g, 3.7 mmol) in 5 mL of dry DMF was

added to a solution of sodiumhydride (60% dispersion in

mineral oil, 0.95 eq, 0.14 g, 3.5 mmol) in 25 mL of dry DMF,

while cooling the solution to 0_ꢀ^ꢀC under an Ar atmosphere.

The solution was heated to 60 C for 2 h, where after it was

cooled to 0 ^ꢀC. To this solution, 2-(6-bromohexyl)isoindoline-

1,3-dione (0.51 g, 3.3 mmol) was added in 4 mL of DMF. The

Synthesis of Tert-butyldimethyl(4-vinylbenzyloxy)

silane (5)

A 250-mL round-bottom flask was charged with (4-vinylphe-

nyl)methanol (5.30 g, 39.5 mmol), tert-butylchlorodimethylsi-

lane (0.95 eq, 5.65 g, 37.5 mmol), imidazole (1.9 eq, 5.10 g,

75.1 mmol), and 100 mL of DMF. The mixture was stirred for

48 h under an Ar atmosphere. The DMF was removed in vacuo

and the resulting crude solid was dissolved in water (50 mL)

and chloroform (50 mL), the layers were separated and the

water layer was extracted with chloroform (2 ꢃ 50 mL). The

combined organic layers were washed with brine (100 mL)

and the solvent was removed in vacuo. The crude product was

purified by column chromatography (ethylacetate/heptane;

20:80), to yield 5 as a colorless liquid (8.03 g, 86%).

ꢀ

mixture was subsequently heated at 50 C for 24 h. After this,

the reaction was quenched with water (20 mL). The mixture

was transferred to a separation funnel filled with water (150

mL), extracted with diethylether (3 ꢃ 50 mL), and the com-

bined organic layers were washed with 1 M HCl (2 ꢃ 50 mL)

and were dried with MgSO₄. The solvent was removed in

vacuo and the resulting crude product was purified by column

chromatography (ethylacetate/chloroform; 5:95), to yield com-

pound 2 as a slightly yellow solid (0.28 g, 21%).

¹H NMR (CDCl₃): d ¼ 7.38 (d, J ¼ 8.1 Hz, 2H, ArAH), 7.28

(d, J ¼ 8.1 Hz, 2H, ArAH), 6.71 (dd, J ¼ 17.6, 10.9 Hz, 1H,

ArACH¼¼C), 5.72 (d, 1H, J ¼ 17.6 Hz, 1H, ArACH¼¼CH₂), 5.27

(d, J ¼ 10.9 Hz, 1H, ArACH¼¼CH₂), 4.73 (s, 1H, ArACH₂),

0.95 (s, 9H, SiACACH₃), 0.10 (s, 6H, SiACH₃). ¹³C NMR

(CDCl₃): 141.1, 136.7, 136.3, 126.2, 126.1, 113.3, 64.8, 26.0,

18.4, ꢄ5.2. GC/MS t_R¼ 4.605; m/z: 191 (M^þ).

¹H NMR (CDCl₃): d ¼ 7.83 (m, 2H, NCOAArAH), 7.70 (m,

2H, NCOAArAH), 7.37 (d, J ¼ 8.1 Hz, 2H, ArAH), 7.28 (d, J

¼ 8.1 Hz, 2H, ArAH), 6.70 (dd, J ¼ 17.6 Hz, 10.9 Hz, 1H,

ArACH¼¼C), 5.74 (d, 1H, J ¼ 17.6 Hz, 1H, ArACH¼¼CH₂), 5.24

(d, J ¼ 10.9 Hz, 1H, ArACH¼¼CH₂), 4.47 (s, 2H, ArACH₂),

3.68 (t, 2H, NACH₂), 3.44 (t, 2H, OACH₂), 1.77–1.30 (m, 8H,

CH₂), traces of starting bromide. ¹³C NMR (CDCl₃): d ¼

168.4, 136.6, 133.9, 133.8, 132.2, 127.8, 126.2, 123.2, 123.1,

113.6, 72.5, 70.2, 38.0, 29.6, 28.6, 26.7, 25.8. ESI–MS (posi-

tive mode): m/z: 386.5 (MþNa^þ).

Synthesis of 4-Vinylbenzyl

6-(tert-butyldimethylsilyloxy)hexanoate (6)

A 500-mL round-bottom flask was charged with e-caprolac-

tone (8.0 mL, 72 mmol), sodium hydroxide (5.4 g, 0.13 mol),

and water (250 mL). The solution was stirred overnight at

room temperature and subsequently the pH was adjusted to

a value of 2 using 1 M HCl. The solution was transferred to

a separating funnel and was extracted with diethyl ether (3

ꢃ 200 mL). The ether fractions were combined and dried

over MgSO₄, filtered and subsequently the ether was

removed in vacuo to yield 6-hydroxyhexanoic acid as a white

solid (6.3 g, 66%).

Synthesis of 2-(4-Vinylbenzyl)isoindoline-1,3-dione (3)

2-(4-Vinylbenzyl)isoindoline-1,3-dione was synthesized in ac-

cordance with published procedures.³¹Monomer 3 was

obtained as a white solid (12.6 g, 68%).

¹H NMR (CDCl₃): d ¼ 7.83 (m, 2H, NCOAArAH), 7.70 (m, 2H,

NCOAArAH), 7.39 (d, J ¼ 8.2 Hz, 2H, ArAH), 7.35 (d, J ¼ 8.3

Hz, 2H, ArAH), 6.67 (dd, J ¼ 17.6, 10.9 Hz, 1H, ArACH¼¼C),

5.71 (d, J ¼ 17.6 Hz, 1H, ArACH¼¼CH₂), 5.22 (d, J ¼ 10.9 Hz,

1H, ArACH¼¼CH₂), 4.83 (s, 2H, ArACH₂). ¹³C NMR (CDCl₃): d

¼ 168.0, 137.2, 136.3, 135.8, 134.0, 132.1, 128.8, 126.5,

123.3, 114.1, 41.3. GC/MS t_R¼ 10.175; m/z: 263 (M^þ).

¹H NMR (CDCl₃): d ¼ 3.65 (t, 2H, HOACH₂A), 2.37 (t, 2H,

CH₂ACOOH), 1.69–1.36 (m, 6H, CH₂).

A 50-mL round-bottom flask was charged with 6-hydroxy-

hexanoic acid (3.97 g, 30.1 mmol), t-butyldimethylsilylchlor-

ide (1.1 eq, 4.97 g, 33.0 mmol), imidazole (2.25 eq, 4.60 g,

67.6 mmol), and DMF (25 mL). The solution was stirred

overnight at 50 ^ꢀC under an Ar atmosphere. The reaction

mixture was poured into a separating funnel containing

brine (60 mL) and was extracted with diethyl ether (3 ꢃ 60

mL). The ether fractions were combined and dried over

MgSO₄, filtered and subsequently the solvent was removed

Synthesis of (4-Vinylphenyl)methanamine (4)

A 50-mL three-necked round bottom flask was charged with

2-(4-vinylbenzyl)isoindoline-1,3-dione (0.48 g, 1.9 mmol) in

20 mL of ethanol. Methylhydrazine (0.37 g, 8.0 mmol) was

added and the mixture was stirred overnight at room tem-

perature. The solvent was removed in vacuo and the result-

ing crude product was dissolved in chloroform (30 mL) and

4 M NaOH (30 mL). The layers were separated and the

water layer was extracted with chloroform (25 mL). The

in vacuo to yield

a crude mixture containing 6-(tert-

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butyldimethyl)siloxyhexanoic acid, which was used without

further purification (2.18 g, 57%).

rated in vacuo and the residue was dissolved in water (100

mL) followed by extraction with diethyl ether (3 ꢃ 100 mL).

The organic layers were combined, dried over MgSO₄and

the solvent was removed in vacuo. The crude product was

purified by column chromatography (ethylacetate/heptane;

20:80) to yield 8 as a white solid (5.97 g, 95%).

¹H NMR (CDCl₃): d ¼ 3.57 (t, 2H, HOACH₂A), 2.30 (t, 2H,

CH₂ACOOH), 1.66–1.31 (m, 6H, CH₂), 0.85 (s, 9H, SiACA

(CH₃)₃), 0.06 (s, 6H, SiA (CH₃)₂).

A 250-mL round-bottom flask was charged with the crude

mixture of 6-(tert-butyldimethyl)siloxyhexanoic acid (2.18 g,

8.85 mmol), 4-vinylbenzylchloride (1.7 eq, 1.94 g, 15.0

mmol), potassium carbonate (5 eq, 6.40 g, 46.0 mmol), and

DMF (100 mL). The solution was stirred overnight at 60 ^ꢀC

under an Ar atmosphere. The solvent was evaporated

in vacuo, the residue was dissolved in water (100 mL), and

was extracted with diethyl ether (3 ꢃ 100 mL). The ether

layers were combined and the ether was removed in vacuo.

The crude product was purified by column chromatography

(ethylacetate/heptane; 20:80), to yield 6 as a colorless oil

(1.37 g, 43%).

¹H NMR (CDCl₃): d ¼ 7.40 (d, J ¼ 8.1 Hz, 2H, ArAH), 7.30

(d, J ¼ 8.2 Hz, 2H, ArAH), 6.71 (dd, J ¼ 17.6, 10.9 Hz, 1H,

ArACH¼¼C), 5.75 (d, 1H, J ¼ 17.6, 1H, ArACH¼¼CH₂), 5.27 (d,

J ¼ 10.9 Hz, 1H, ArACH¼¼CH₂), 5.09 (s, 2H, ArACH₂AOACO),

4.48 (s, 1H, NAH), 3.09 (t, 2H, COANHACH₂), 2.35 (t, 2H,

OACOACH₂), 1.76–1.18 (m, 15H, CH₂, CA(CH₃)₃). ¹³C NMR

(CDCl₃): d ¼ 173.4, 155.9, 137.6, 136.3, 135.5, 128.5, 126.4,

114.3, 66.4, 50.1, 40.4, 34.2, 29.7, 28.4, 26.3, 24.6. ESI–MS

(positive mode): m/z: 370.4 (MþNa^þ).

Synthesis of Tert-butyldimethyl(6-(4-vinylbenzyloxy)

hexyloxy)silane (9)

¹H NMR (CDCl₃): d ¼ 7.37 (d, J ¼ 8.1 Hz, 2H, ArAH), 7.30

(d, J ¼ 8.1 Hz, 2H, ArAH), 6.71 (dd, J ¼ 17.6, 10.9 Hz, 1H,

ArACH¼¼C), 5.75 (d, 1H, J ¼ 17.6 Hz, 1H, ArACH¼¼CH₂), 5.24

The procedure was adapted from published procedures.³²

A

dry 250-mL three-necked round bottom flask was charged

with imidazole (15.3 g, 0.112 mol), tert-butyldimethylsilyl

chloride (16.9 g, 0.112 mol), and hexane-1,6-diol (12.0 g,

0.102 mol) in 150 mL of DMF, while cooling the solution to 0

^ꢀC. The mixture was then stirred for 18 h at room tempera-

ture under an Ar atmosphere. The solvent was evaporated in

vacuo and the resulting oil was dissolved in diethylether (150

mL). To this suspension, H₂O (200 mL) was added and it was

transferred to a separation funnel. The layers were separated

and the water layer was extracted with diethylether (2 ꢃ 150

mL). The organic layers were then collected, dried with

MgSO₄, concentrated in vacuo and the resulting yellowish liq-

uid was purified with column chromatography (hexane/dieth-

ylether; 50/50 v/v) to yield 6[(t-butyl)-dimethylsiloxy]-1-hex-

anol as a slightly yellow liquid (6.91 g, 29.4%).

(d,

J

¼

10.9 Hz, 1H, ArACH¼¼CH₂), 5.09 (s, 2H,

COAOACH₂AAr), 3.58 (t, 2H, SiAOACH₂A), 2.35 (t, 2H,

CH₂ACOO), 1.70–1.21 (m, 6H, CH₂), 0.88 (s, 9H, SiACA

(CH₃)₃), 0.03 (s, 6H, SiA (CH₃)₂). ¹³C NMR (CDCl₃): d ¼

173.7, 137.6, 136.5, 135.7, 128.6, 126.5, 114.4, 66.0 63.1,

34.5, 32.6, 26.1, 25.6, 24.9, 18.5, ꢄ5.1. ESI–MS (positive

mode): m/z: 363.3 (MþH^þ).

Synthesis of (4-Vinylphenyl)methanol (7)

In a 100-mL round-bottom flask, 4-vinylbenzylacetate (8.0 g,

46 mmol) and potassiumhydroxide (8.6 g, 0.15 mol) were

dissolved in 40 mL of methanol and 10 mL of water and the

resulting mixture was refluxed overnight. After the reaction

was completed, the dark-yellow reaction mixture was con-

centrated in vacuo, then water (100 mL) was added, and the

water layer was extracted with diethylether (3 ꢃ 100 mL).

The combined organic layers were washed with saturated

ammoniumchloride (2 ꢃ 50 mL) and water (1 ꢃ 50 mL).

The organic layer was then dried with Na₂SO₄and the sol-

vent was removed in vacuo to yield (4-vinylphenyl)methanol

as a yellowish liquid (5.7 g, 93%).

¹H NMR (CDCl₃): d ¼ 3.58 (t, 2H, HOACH₂), 1.60 (m, 1H,

HOACH₂ACH), 1.51–1.08 (m, 10H, CH₂), 0.91–0.86 (m, 6H,

CH₃). GC/MS t_R¼ 4.85; m/z: 162 (M^þ-C₅H₁₁).

A

three-necked round bottom flask was charged with

sodiumhydride (60% dispersion in mineral oil, 0.39 g, 9.8

mmol) in 25 mL of dry DMF. To this solution, 6[(t-butyl)-

dimethylsiloxy]-1-hexanol (0.76 g, 3.3 mmol) in 3 mL of

DMF was added, while retaining the solution at 0 ^ꢀC under

¹H NMR (CDCl₃): d ¼ 7.35 (d, J ¼ 8.2 Hz, 2H, ArAH), 7.27

(d, J ¼ 8.3 Hz, 2H, ArAH), 6.70 (dd, J ¼ 17.6, 10.9 Hz, 1H,

ArACH¼¼C), 5.74 (d, 1H, J ¼ 17.6 Hz, 1H, ArACH¼¼CH₂), 5.24

(d, J ¼ 10.9 Hz, 1H, ArACH¼¼CH₂), 4.60 (s, 1H, ArACH₂),

2.34 (s, broad 1H, ArACH₂AOH). ¹³C NMR (CDCl₃): d ¼

140.4, 136.8, 136.5, 127.2, 126.4, 113.8, 64.9. GC/MS t_R¼

4.605; m/z: 134 (M^þ).

ꢀ

an Ar atmosphere. The solution was heated to 60 C for 1 h,

and then it was cooled to 0 ^ꢀC. To this solution, 4-vinylben-

zylchloride (0.51 g, 3.3 mmol) in 4 mL of DMF was added.

The mixture was subsequently heated at 50 ^ꢀC for 24 h.

After this, the reaction was quenched with water (20 mL).

The mixture was transferred to a separation funnel filled

with water (150 mL), extracted with ethylacetate (3 ꢃ

75 mL) and the combined organic layers were dried with

MgSO₄. The solvent was removed in vacuo and the crude

product was purified by column chromatography (ethylace-

tate/chloroform; gradient from 4% to 10% ethylacetate) to

yield 9 as a slightly yellow oil (0.15 g, 13%).

Synthesis of 4-Vinylbenzyl

6-(tert-butoxycarbonylamino)hexanoate (8)

A 500-mL three-necked round bottom flask was charged

with 6-(tert-butoxycarbonylamino)hexanoic acid (4.18 g, 18.1

mmol), 4-vinylbenzylchloride (0.98 eq, 2.70 g, 17.7 mmol),

potassiumcarbonate (3 eq, 7.50 g, 54.2 mmol), and DMF

(180 mL). The resulting suspension was heated overnight

under an Ar atmosphere at 60 ^ꢀC. The solvent was evapo-

¹H NMR (CDCl₃): d ¼ 7.39 (d, J ¼ 8.1 Hz, 2H, ArAH), 7.31

(d, J ¼ 8.2 Hz, 2H, ArAH), 6.71 (dd, J ¼ 17.6, 10.9 Hz, 1H,

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ArACH¼¼C), 5.74 (d, 1H, J ¼ 17.6, 1H, ArACH¼¼CH₂), 5.23 (d,

J ¼ 10.9 Hz, 1H, ArACH¼¼CH₂), 4.49 (s, 2H, ArACH₂AO),

3.60 (t, 2H, SiAOACH₂), 3.45 (t, 2H, ArACH₂AOACH₂),

1.70–1.22 (m, 8H, CH₂), 0.89 (s, 9H, SiACA(CH₃)₃), 0.04 (s,

6H, SiA(CH₃)₂).GC/MS t_R¼ 9.015; m/z: 117 (C₉H₈^þ).

p(10-co-st). ¹H NMR (CDCl₃):

NCOAArAH), 7.65 (s, broad, NCOAArAH), 7.31–6.10 (m,

ArAH), 4.65 (s, broad, ArACH₂), 2.22–1.09 (m, CH, CH₂),

d

¼

7.83 (s, broad,

0.94 (s, SiACA(CH₃)₃), 0.07 (s, SiA(CH₃)₂)._ꢀGPC: M_n

¼

22,100, PDI ¼ 1.25. DSC transitions: T_g¼ 95.7 C.

General Procedure for Polymerizations Using CTA-2

General Procedure for Polymerizations Using CTA-1

In a Schlenck-tube, styrene (0.90 g, 8.6 mmol) and functional

styrene monomers (0.96 mmol) dissolved in 1 mL of toluene

were added. To this solution, CTA-1 was added (1/250 eq to

total amount of styrene, 12.5 mg, 3.84 ꢃ 10^ꢄ5mol). The

mixture was subjected to five consecutive freeze–pump–

thaw cycles, backfilled with argon and placed in a preheated

oil-bath at 95 ^ꢀC. In kinetic studies, samples were collected

from the reaction mixture at given time intervals by a sy-

ringe. Monomer conversion was determined by ¹H NMR in

CDCl₃. Average molar mass and molecular weight distribu-

tion were determined by size exclusion chromatography. The

polymerization was stopped by quenching the reactor in an

ice bath. The polymer was purified by precipitation in

MeOH, filtered and dried under high vacuum at room tem-

perature to a constant weight.

The monomers and CTA-2 were dissolved in toluene to gen-

erate a solution containing 60–70% weight fraction of the

monomers. This solution was placed in a three-neck flask

equipped with a reflux condenser and a magnetic stir bar.

The mixture was purged for 25 min with argon at room tem-

ꢀ

perature to remove oxygen and then heated to 100 C. In ki-

netic studies, samples were collected from the reaction mix-

ture at given time intervals by a syringe through a septum.

Monomer conversion was determined by ¹H NMR in CDCl₃.

Average molar mass and molecular weight distributions

were determined by size exclusion chromatography. The po-

lymerization was stopped by quenching the reactor in an ice

bath. The polymer was purified by precipitation in MeOH, fil-

tered and dried under high vacuum at room temperature to

a constant weight.

The obtained polymers showed similar characteristics as

those obtained with CTA-1.

p(2-co-st). ¹H NMR (CDCl₃):

d

¼

7.83 (s, broad,

NCOAArAH), 7.68 (s, broad, NCOAArAH), 7.32–6.22 (m,

ArAH), 4.38 (s, broad, ArACH₂), 3.69 (s, NACH₂), 3.41 (t,

OACH₂), 2.37–1.20 (m, CH, CH₂). GPC: M_n¼ 19,100, PDI ¼

TFA-Deprotection of Polymer p(8-co-st) to p(12-co-st)

In a 25-mL two-necked round-bottom flask, 0.120 g of p(8-

co-st) was dissolved in 10 mL of dry CHCl₃, TFA (0.2 mL)

was added and the mixture was stirred overnight at room

temperature under an Ar atmosphere. The solvent was

removed in vacuo to yield the polymer as a white powder.

ꢀ

1.11. DSC transitions: T_g¼ 77.0 C.

p(3-co-st). ¹H NMR (CDCl₃):

d

¼

7.84 (s, broad,

NCOAArAH), 7.70 (s, broad, NCOAArAH), 7.27–6.16 (m,

ArAH), 4.74 (s, broad, ArACH₂), 2.16–1.06 (m, CH, CH₂).

GPC: M_n¼ 18,300, PDI ¼ 1.09. DSC transitions: T_g¼ 98.4

^ꢀC.

¹H NMR (CDCl₃): d ¼ 7.85 (s, broad, NH₃^þ), 7.45–6.23 (m,

ArAH), 4.98 (s, broad, ArACH₂), 3.05 (m, CH₂ANH₂), 2.37

(m, CH₂ACO), 2.13–1.10 (m, CH, CH₂). DSC transitions: T_g¼

p(5-co-st). ¹H NMR (CDCl₃): d ¼ 7.33–6.18 (m, ArAH), 4.61

(s, broad, ArACH₂), 2.21–1.19 (m, CH, CH₂), 0.94 (s, SiACA

(CH₃)₃), 0.07 (s, SiA (CH₃)₂). GPC: M_n¼ 19,000, PDI ¼ 1.08.

ꢀ

94.0 C.

ꢀ

Silyl-deprotection of Polymer p(5-co-st) to p(16-co-st)

In a 50-mL round-bottom flask, 1.00 g of p(5-co-st) was dis-

solved in 20 mL of THF, and then TBAF (1 M in THF, 6 mL)

was added and the mixture was stirred overnight at room

temperature under an Ar atmosphere. After the reaction was

completed, the solvent was removed in vacuo. The polymer

was purified by precipitation in MeOH (twice) to yield the

DSC transitions: T_g¼ 84.9 C.

p(6-co-st). ¹H NMR (CDCl₃): d ¼ 7.30–6.11 (m, ArAH), 5.01

(s, ArACH₂), 3.59 (s, broad, SiAOACH₂), 2.34 (s, broad,

CH₂ACOO), 2.04–1.13 (m, CH, CH₂). 0.89 (s, SiACA(CH₃)₃),

0.05 (s, SiA(CH₃)₂). GPC: M_n¼ 21,400, PDI ¼ 1.21. DSC

ꢀ

transitions: T_g¼ 43.7 C.

1

p(7-co-st). ¹H NMR (CDCl₃): d ¼ 7.30–6.28 (m, ArAH), 4.55

polymer as a white powder. H NMR (CDCl₃): d ¼ 7.20–6.24

(m, ArAH), 4.57 (s, broad, ArACH₂), 2.19–1.15 (m, CH, CH₂).

(s, broad, ArACH₂), 2.22–1.15 (m, CH, CH₂). GPC: M_n

¼

ꢀ

GPC: M_n¼ 18,400, PDI ¼ 1.08. DSC transitions: T_g

¼

26,800, PDI ¼ 1.25. DSC transitions: T_g¼ 101.1 C.

ꢀ

104.3 C.

p(8-co-st). ¹H NMR (CDCl₃): d ¼ 7.20–6.24 (m, ArAH), 4.97

(s, ArACH₂AOACO), 4.45 (s, NAH), 3.05 (s, broad,

COANHACH₂), 2.32 (s, broad, OACOACH₂), 2.16–1.20 (m,

CH, CH₂). GPC: M_n¼ 18,100, PDI ¼ 1.10. DSC transitions: T_g

Hydrazinolysis of Polymer p(3-co-st) to p(4-co-st)

In a 25-mL round-bottom flask, 0.33 g of p(3-co-st) was dis-

solved in 5 mL of THF. Hydrazine (0.2 mL, 4 mmol) was

added and the mixture was refluxed for 48 h. The solvent

was removed in vacuo, where after the polymer was dis-

solved in chloroform (25 mL) and 3 M NaOH (25 mL). The

mixture was separated, the solvent was removed in vacuo

and the polymer was purified by precipitation in MeOH

(twice) to yield the polymer as a white powder.

ꢀ

¼ 81.5 C.

p(9-co-st). ¹H NMR (CDCl₃): d ¼ 7.28–6.24 (m, ArAH), 4.40

(s, ArACH₂AOACO), 3.61 (s, broad, 2H, SiAOACH₂), 3.46 (s,

broad, 2H, ArACH₂AOACH₂), 2.25–1.20 (m, CH, CH₂). 0.91

(s, SiACA(CH₃)₃), 0.07 (s, SiA(CH₃)₂). GPC: M_n¼ 27,500,

ꢀ

PDI ¼ 1.72. DSC transitions: T_g¼ 51.6 C.

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¹H NMR (CDCl₃): d ¼ 7.21–6.24 (m, ArAH), 3.75 (s, broad,

formed are useful in elucidating folding pathways in

single chain polymeric nanoparticles and constructing cata-

lytically active single chain nanoparticles with tunable

properties.^8,10,33

ArACH₂), 2.17–1.21 (m, CH, CH₂). DSC transitions: T_g

¼

ꢀ

111.4 C.

Hydrazinolysis of Polymer p(2-co-st) to p(11-co-st)

The authors thank J.A.J.M. Vekemans for insightful discussions.

The European Research Council (ERC Advanced Grant No.

246829) is acknowledged for funding.

The procedure was identical to that described for p(3-co-st).

¹H NMR (CDCl₃):

¼ 7.22–6.20 (m, ArAH), 4.41 (t,

ArACH₂), 3.55–3.26 (m, ArACH₂AOACH₂, CH₂ANH₂), 2.64

d

(s, broad, NH₂), 2.32–1.17 (m, CH₂). DSC transitions: T_g

91.5 C.

¼

ꢀ

REFERENCES AND NOTES

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d

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d

¼ 7.36–6.17 (m, ArAH), 5.02 (t,

ArACH₂), 3.16 (t, COANHACH₂), 2.27–1.10 (m, CH₂), 0.88 (t,

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Article Doi

Nitroxide-mediated controlled radical polymerizations of styrene derivatives

DOI: 10.1002/pola.25833

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