Sabrina Paillet, † Armelle Roncin, † Gérald Clisson, † Gaëlle Pembouong, ‡ Laurent Billon, †
Christophe Derail † and Maud Save †
† IPREM Equipe de Physique et Chimie des Polymères, UMR 5254 CNRS - Université de Pau et des Pays de L’Adour, Hélioparc, 2 Avenue du Président Angot, 64053 Pau Cedex, France
‡ UPMC Univ. Paris 6 and CNRS, Laboratoire de Chimie des Polymères, UMR 7610, 3 rue
Galilée, 94200 Ivry, France.
Electronic Supporting Information
Synthesis of the trifunctional initiator (A
3
in scheme 1) from reference 1
A solution of BlocBuilder® (4.7g, 12.3 mmol) and trimethylolpropane triacrylate (1.02g, 3.44 mmol) in tert-butanol (13mL) was introduced in a round-bottom flask, deoxygenated by nitrogen bubbling and heated at 100°C for 1h under stirring. The reaction mixture was concentrated under reduced pressure. The alkoxyamine obtained was precipitated in fresh pentane. The yield was
15.7 % with good purity (see proton NMR spectrum in Figure SI-3). 1 H NMR (CDCl
3
): δ 0.8-1.6 ppm (95H), 2-2.8 ppm (6H), 3.2-4.7 ppm (18H). The tri-alkoxyamine was obtained as a white powder which was kept refrigerated.

Synthesis of the acryloyloxyethyl 2-Bromoisobutyrate (AEBrIB) co-monomer from reference 2.
2-Hydroxyethyl acrylate (9.99 g, 86.0 mmol), anhydrous dichlorometane (100 mL), and triethylamine (9.60 g, 94.8 mmol) were added to a dry 250 mL round-bottom flask. The flask was immersed in an ice bath under stirring. 2-Bromo-isobutyryl bromide (21.81g, 94.8 mmol) was added dropwise to the flask via syringe over 30 min. The mixture was stirred at 0°C for 1h and then at 20°C for 4h. The resulting reaction solution was filtered to remove the insoluble amine hydrobromide salt and washed three times with 4% sodium carbonate aqueous solution? The combined organic solution was dried over anhydrous magnesium sulphate and passes through a silica column using dichloromethane as an eluent. This solvent was removed under vacuum to afford a light yelow liquid. The yield was 80%. Purity was > 99% by NMR.
1
H NMR (CDCl
3
): δ
6.5-5.8 ppm (3H, CH
2
=CHCOO), 4.4 ppm (4H, COOCH
2
CH
2
OCO), 2 ppm (6H, C(CH
3
)Br). The purified product was stored in a refrigerator at -20°C prior to use.
Synthesis of the Me
6
TREN ligand from references 3-4
To prepare the salt (ClNH
3
CH
2
)
3
NHCl, 60 mL of 3.0 M HCl in methanol was added dropwise to
8.mL or 0.053 mol of tris(2-aminoethyl) amine in 100 mL of methanol. After stirring at room temperature for 1h, the precipitate was filtered and washed with 100 mL methanol thrice to yield
12.4g or 0.048 mol of product in 90% yield.
To prepare Me
6
TREN, 12.4g of (ClNH
3
CH
2
)
3
NHCl, 20 mL of deionized water, 110g of formic acid and 90g of a formaldehyde aqueous solution were mixed. The mixture was heated under stirring in a 120°C oil bath for 6h. Volatile components were removed by rota-evaporation.
NaOH aqueous solution was added until pH equal 10. After shaking, the aqueous phase was extracted with diethyl ether at 200 mL each time for three times. The organic phase was combined, dried over anhydrous magnesium sulfate, and evaporated to produce a yellow oil. The yield was 73 %. Purity was 90% by NMR. Proton NMR (CDCl3): δ 2.2 ppm (18H, CH3-N-),
2.4ppm (6H, -CH
2
-N-), 2.6 ppm (6H, -CH
2
-N-)

(A)
0.7
0.6
0.5
0.4
0.3
0.2
0.1
1
0.9
0.8
0.7
0.6
10
0
0.2
0.1
0.5
0.4
0.3
0
0 2 4
Time (h)
6 8
(B)
160000
140000
120000
100000
80000
60000
40000
20000
2.4
2.2
2
1.8
1.6
1.4
1.2
0 1
0 0.1
0.2
0.3
Conversion
0.4
0.5
Figure SI-1. Comparison of (A) kinetic plots and (B) evolution of M n
(plain symbols, extracted from LS detector) and M w
/ M n
(empty symbols) versus conversion for the polymerization of n BA
(

, expt 1 in Table 1) and the copolymerization of n BA with BIEA (

, expt 2 in Table 1) initiated by the mono-alkoxyamine in bulk at 111 °C. The straight line corresponds to the

theoretical M n
. [M]
0
/[BlocBuilder]
0
= 2400, [AEBrIB]
0
/[ n BA]
0
= 0.0038.

n
n
CH
2
CH
C O
O
CH
2
CH
2
CH
2
CH
3 n
H
C C
H
H
C
O
CH
2
CH
2
O
C O
O
CH
3
C
Br
CH
3
P(nBA) n
P(BIEA)
Figure SI-2.
Proton NMR spectrum (in CDCl
3
) of the crude solution for the copolymerization of n BA and BIEA monomers by NMP.

CH
3
CH
2
C
CH
3
CH
3
CH
3
O
CH
2
C
C
N
O
CH
CH
3
CH
C
CH
3
CH
3
O
P O CH
2
O CH
2
CH
2
O
C
CH
3
CH
3 C O
O H
CH
3
CH
3
24H
3H 18H 3H
Vinylic (3H)
3H
6H
95H
9 8 7 6 5 4 3 2 1 ppm
Figure SI-3 : Proton NMR of A3 alkoxyamine

0.25
0.2
0.15
0.1
0.05
0
0 y = 3.296E-02x
R² = 9.950E-01
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
2 4
Time (h)
6
Figure SI-4.
Conversion (  ) and ln[M]
0
/[M] (  ) versus time for the copolymerization of n BA with BIEA (Expt 8, Table 2) initiated by the trifunctional alkoxyamine in bulk at 111 °C.

0.2
0.18
0.16
0.14
0.12
0.1
0.08
0.06
15 20 25 30
Figure SI-5. SEC traces (LS signal, 90°) of the star-branched P n BA synthesized from the A3 trifunctional alkoxyamine (black line, expt 4 from Table 3) and of the corresponding P( n BAco -
BIEA)
3
star macro-initator (blue line, expt 8 from Table 2).

1 a b
1
2 c
4
3
4 c
(CH
2 b
CH)
C O co
O a
H
3
C
Br
O c
CH
3
3
(CH
2
2
CH)
C O
O
1
3
4
2
65 60 55 50 45 40 35 30 25 20 15 ppm
Figure SI-6 .
13
C DEPT135 NMR, overlay of spectra: P( n BAco -BIEA)-2 (top) and P n BA of M n
= 204 000 g/mol synthesized by SET-LRP from P( n BAco -BIEA)-2 macroinitiator (below)

0.65
0.6
0.55
0.5
0.45
0.4
0.35
0.8
0.7
0.6
0.5
0
-0.1
-0.2
-0.3
-0.4
-0.5
y = 1.7013x + 0.0845
R² = 0.9822
0.4
0.3
-0.6
0.3
0.25
0.2
0.2
-0.7
-0.45
-0.4
-0.35
-0.3
-0.25
-0.2
5.8
6 6.2
6.4
6.6
6.8
LogM
Log(g)
Figure SI-7.
Evolution of g’
(red, below) and g (blue, top) with LogM (left) and Flory-Fox relationship (right) for the star-branched P n BA (Expt 4 in Table 3).
The value of g (g = (< R g
> br
/< R g
> linear
)
M
) was calculated using the experimental value of < R g
> br
of the branched P n BA and the experimental value of < R g
> linear
of the linear PS (see blue curve in
Figure SI-7) at constant M. This was possible as Figure SI-7 showed a comparative behavior in
THF between P n BA and PS.

9
8
7
6
5
4
3
12
11
10
2
4.5
5 5.5
Log (g.M
w
)
6 6.5
Figure SI-8.
Evolution of zero-shear viscosity as a function of the product between molar mass and the branching factor. The plain line corresponds to the theoretical variation of zero-shear viscosity for the linear samples and doted one to the star polymers (guide for eyes). All points correspond to the experimental measurements on the star-branches samples. One can clearly observed that, in the range of molar mass explored, the zero-shear viscosity of star-branched polymers is lower than linear species. To obtain a higher zero-shear viscosity for star-branched the molar mass must be higher than about 5

10 6 g.mol
-1 .
References
1. Dufils, P. E.; Chagneux, N.; Gigmes, D.; Trimaille, T.; Marque, S. R. A.; Bertin, D.; Tordo, P.
Polymer 2007, 48, 5219-5225.
2. Cai, Y. L.; Armes, S. P. Macromolecules 2005, 38, 271-279.
3. Ciampoli.M; Nardi, N. Inorganic Chemistry 1966, 5, 41-&.
4. Feng, L.; Hu, J. W.; Liu, Z. L.; Zhao, F. B.; Liu, G. J. Polymer 2007, 48, 3616-3623.