Domino Synthesis of Star-Shaped Polymers Based on Monomer Selective Living
Cationic Polymerization: Highly Controlled Star Polymer Formation
Shokyoku Kanaoka, Mayuka Yamada, Jun Ashida, Arihiro Kanazawa,
and Sadahito Aoshima
Department of Macromolecular Science, Graduate School of Science, Osaka University,
Toyonaka, Osaka 560-0043, Japan
Tel & Fax: +81-6-6850-5448
E-mail: aoshima@chem.sci.osaka-u.ac.jp
Supporting Information
I. Materials……………………………………………………………………………….S1
II. Characterization………………………………………………………………………S2
III. Domino Synthesis of Block Copolymers……………………………………………S2
IV. Domino Synthesis of Star-Shaped Polymers………………………………………...S4
V. Reference……………………………………………………………………………..S6
I. Materials
Isobutyl vinyl ether [IBVE (TCI; >99%)], p-tert-butoxystyrene [tBOS (Wako; 98.0%)],
1,4-cyclohexanedimethanol divinyl ether [DVE (Aldrich; 99%)], and 1,4-diisopropenyl benzene [DIPB (TCI;
>98.0%)] were washed with 10% aqueous sodium hydroxide solution and then water, dried overnight over
potassium hydroxide pellets, and distilled twice over calcium hydride before use. Ethyl acetate (Wako;
>99.5%), heptane (TCI; >99.0%), and 2,6-di-tert-butylpyridine [DTBP (Wako; 97.0%)] were distilled twice
over
calcium
hydride
before
use.
A
divinyl
compound
with
two
alkoxystyryl
moieties
[1,3-bis(4-vinylphenoxy)propane; BVP] was prepared from p-acetoxystyrene and 1,3-dibromopropane as
previously reported.1 BVP was purified by recrystallization from methanol and then from ethyl acetate, and
vacuum-dried for over 3 h prior to use. Toluene (Wako; 99.5%) and dichloromethane (Nacalai Tesque; 99%)
were purified by passage through solvent purification columns (Glass Contour). 1-(Isobutoxy)ethyl acetate
S1
[IBEA; CH3CH(OiBu)OCOCH3; IBEA] was prepared by the reaction of acetic acid with the corresponding
vinyl ethers as previously reported.2 Commercially available SnCl4 (Aldrich; 1.0 M solution in heptane),
EtAlCl2 (Wako; 1.0 M solution in hexane) and TiCl4 (Aldrich; 1.0 M solution in toluene) were used without
further purification. All materials except for dichloromethane, toluene and BVP were stored in brown ampules
under dry nitrogen.
II. Characterization
The molecular weight distribution (MWD) of the polymers was measured by gel permeation
chromatography (GPC) in chloroform at 40 ºC with three polystyrene gel columns [Tosoh; TSK gel
G-4000HXL, G-3000HXL, and G-2000HXL (exclusion limit molecular weight = 4 × 105, 6 × 104, and 1 × 104,
respectively; bead size = 5 μm; column size = 7.8 mm internal diameter × 300 mm) or TSK gel
MultiporeHXL-M × 3 (exclusion limit molecular weight = 2 × 106; bead size = 4 μm; column size = 7.8 mm
internal diameter × 300 mm); flow rate = 1.0 mL/min] connected to a Tosoh DP-8020 pump, a CO-8020
column oven, a UV-8020 ultraviolet detector, and an RI-8020 refractive-index detector. The number-average
molecular weight (Mn) and polydispersity ratio [weight-average molecular weight/number-average molecular
weight (Mw/Mn)] were calculated from the chromatographs with respect to 16 polystyrene standards (Tosoh;
Mn = 291– 1.09 × 106, Mw/Mn ≤1.1). The weight-average molecular weights (Mw) of the star polymers were
determined by GPC coupled with multi-angle light scattering (GPC–MALS) in chloroform at 40 ºC on a
DAWN HELEOS (Wyatt Technology; Ga-As laser, = 690 nm). Based on the Mw values, the average number
of arms of star-shape polymers was calculated by the following equation:
The number of arms =
M w of star polymer ´ weight fraction of linear segments
M w of linear polymer
The refractive index increment (dn/dc) values were measured in chloroform on differential refractometer
(Otsuka Electronics DRM-3000; = 633 nm). NMR spectra were recorded using a JEOL JNM-LA 500
spectrometer (500 MHz for 1H).
III. Domino Synthesis of Block Copolymers
Synthesis of block copolymers was conducted at 0 ºC under dry nitrogen atmosphere in a glass
tube with a three-way stopcock baked over 300 ºC for 10 min before use. Domino synthesis of block
S2
copolymers in toluene at 0 ºC is as follows: IBVE, tBOS, toluene, ethyl acetate as an added base, and IBEA as
an initiator were added sequentially to glass tube. Then an EtAlCl2 solution in toluene was added the
monomer solution at 0 ºC to produce an initiating species (IBVE-HCl) quantitatively. The reaction was
initiated by the addition of a prechilled SnCl4 solution in toluene into the mixture at 0 ºC. The polymerization
was terminated by adding prechilled methanol containing a small amount of an aqueous ammonia solution.
The reaction mixture was washed with water to remove the initiator residues. The solvent and other volatile
ingredients were evaporated under reduced pressure, and then a product polymer was vacuum-dried overnight.
Conversion of IBVE was determined from its residual concentration measured by gas chromatography with
heptane as an internal standard. The monomer compositions of the obtained polymers were measured by 1H
NMR.
1
H NMR
b, c
a, d
e
i
a, d, f, g
h
Figure S1. 1H NMR spectra of the products in the copolymerization of IBVE and tBOS recorded in CDCl3 at
30 ºC; [IBVE]0 = 0.38 M, [tBOS]0 = 0.40 M, [IBEA]0/[EtAlCl2]0 = 4.0 mM/2.5 mM, [SnCl4]0 = 10 mM,
[CH3COOEt] =1.0 M, [heptane] = 5 vol%, in toluene at 0 ºC.
S3
Figure S2. MWD curves of the products in the copolymerization of IBVE and tBOS; [IBVE]0 = 0.38 M,
[tBOS]0 = 0.40 M, [IBEA]0/[EtAlCl2]0 = 4.0 mM/2.5 mM, [SnCl4]0 = 10 mM, [CH3COOEt] =1.0 M, [heptane]
= 5 vol%, in toluene at 0 ºC.
IV. Domino Synthesis of Star-Shaped Polymers
Star polymer synthesis was conducted in the same way as that for block copolymerization. IBVE,
a divinyl compound (BVP, DVE, or DIPB), toluene, CH2Cl2, ethyl acetate as an added base, and IBEA as an
initiator were mixed in a glass tube. To the solution an EtAlCl2 or TiCl4 solution in toluene was added at 0 ºC
to produce an initiating species quantitatively. The reaction was initiated by the addition of a prechilled SnCl4
solution in toluene into the mixture at 0 ºC. The polymerization was terminated by adding prechilled methanol
containing a small amount of an aqueous ammonia solution. The reaction mixture was washed with water to
remove the initiator residues. The solvent and other volatile ingredients were evaporated under reduced
pressure, and then a product polymer was vacuum-dried overnight. Conversion of IBVE was determined by
gravimetry.
S4
1
H NMR spectra
Core
b, c
a, d
e
a, d, f, g, j
h
i
Figure S3. 1H NMR spectra of poly(IBVE) (A) and star-shaped poly(IBVE) (B) recorded in CDCl3 at 30 ºC;
[IBVE]0 = 0.57 M, [BVP]0 = 40 mM, [IBEA]0/[EtAlCl2]0 = 4.0 mM/2.5 mM, [SnCl4]0 = 10 mM,
[CH3COOEt] =1.0 M, in toluene/CH2Cl2 (9/1 v/v) at 0 ºC.
S5
1
H NMR
b, c
a, d, f, g, j
e
h
i
Figure S4. 1H NMR spectra of the lower molecular weight fraction products in the copolymerization of IBVE
and BVP using EtAlCl2 alone recorded in CDCl3 at 30 ºC; [IBVE]0 = 0.57 M, [BVP]0 = 40 mM,
[IBEA]0/[EtAlCl2]0 = 4.0 mM/20 mM, [CH3COOEt] =1.0 M, in toluene/CH2Cl2 (9/1 v/v) at 0 ºC.
Figure S5. MWD of the products in the copolymerization of IBVE and BVP using EtAlCl2 alone in
toluene/CH2Cl2= (9/1 v/v) at 0 ºC: RI detection (
), UV absorption at 254 nm (- - -).
VI. References
(1) Ericsson, J.; Hult, A. Polym. Bull. 1987, 18, 295-302.
(2) Aoshima, S.; Higashimura, T. Macromolecules 1989, 22, 1009-1013.
S6