Synthesis of amphiphilic diblock copolymers of isotactic polystyrene-block-isotactic poly(p-hydroxystyrene) using a titanium complex with an [OSSO]-type bis(phenolate) ligand and sequential monomer addition

Article abstract of DOI:10.1039/C7RA01450C

A series of isotactic diblock copolymers of polystyrene-block-poly(p-tert-butyldimethylsilyloxystyrene) (iPS-b-iP(p-TBDMSOS)) were successfully synthesized using living coordination polymerization techniques with a kind of titanium dichloro complex contai

Full text of DOI:10.1039/C7RA01450C

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Synthesis of amphiphilic diblock copolymers of
isotactic polystyrene-block-isotactic poly(p-
hydroxystyrene) using a titanium complex with an
[OSSO]-type bis(phenolate) ligand and sequential
monomer addition†
Cite this: RSC Adv., 2017, 7, 19885
QiHua Zhou,a HuaQing Liang,a WanChu Wei,a ChunFeng Meng,b YongJiang Longa
ac
*
and FangMing Zhu
A series of isotactic diblock copolymers of polystyrene-block-poly(p-tert-butyldimethylsilyloxystyrene) (iPS-b-
iP(p-TBDMSOS)) were successfully synthesized using living coordination polymerization techniques with
a kind of titanium dichloro complex containing a 1,4-dithiabutandiyl-linked [OSSO]-type bis(6-cumyl-4-
methyl phenolato) ligand (complex 1) activated by methylaluminoxane (MAO) as a catalyst. Nuclear magnetic
resonance (NMR), gel permeation chromatography (GPC), infrared spectroscopy (IR), and differential scanning
calorimetry (DSC) were used to characterize the copolymers. iPS-b-iP(p-TBDMSOS) had a higher molecular
weight than that of the iPS prepolymer, and a narrow molecular weight distribution below 1.35. The diblock
copolymers displayed two glass transition temperatures (Tg) at ꢀ97 and ꢀ117 ꢁC, originating from iPS and
iP(p-TBDMSOS) blocks, respectively. Furthermore, a novel well-defined amphiphilic diblock copolymer
consisting of iPS (nonpolar block) and isotactic poly(p-hydroxystyrene) (iP(p-HOS), polar block), was achieved
through hydrolysis of iP(p-TBDMSOS) block of iPS-b-iP(p-TBDMSOS) in the presence of hydrochloric acid.
The obtained amphiphilic diblock copolymers self-assembled into spherical micelles with size of
approximately 70 nm in methanol.
Received 4th February 2017
Accepted 28th March 2017
DOI: 10.1039/c7ra01450c
rsc.li/rsc-advances
It is well known that the synthesis of diblock copolymers was
based on living/control polymerizations to minimize undesired
termination and/or transfer reactions.12 Three methods have been
Introduction
Stereospecic living diblock copolymerization of nonpolar
monomers with polar monomers has attracted great interest
due to its capability to form amphiphilic diblock copolymers
with well-dened stereochemistry and comonomer composi-
tion, controlled molecular weight as well as narrow molecular
weight distribution.1,2 The interest stems from the unique
features of the copolymers synthesized to be used as compati-
bilizers for polymer blends and their ability to self-assemble
into ordered nanostructures that can be applied in various
elds including nanoreactors, nanotemplates, nanocarriers,
and drug delivery.3–11
developed for the synthesis of diblock copolymers: (a) sequential
addition of monomers; (b) macroinitiator methods and (c)
coupling of two end-functionalized chains. A widely used method
is the sequential addition of monomers, living polymerization of
the rst monomer, followed by polymerization of the second
monomer. However, this method requires that the same catalytic
or initiating species can initiate the living polymerization of
both monomers, and that the conversion of the rst monomer
must be quantitative.13–21 Macroinitiators were prepared from
end-functionalized polymers available, which initiate or catalyze
living polymerizations of desired monomers to obtain well-
dened diblock copolymer.22–26 Moreover, click coupling reac-
tion of two end-functionalized macromolecular chains has been
employed to synthesize diblock copolymers in recent years.27,28
Our group has reported the synthesis of amphiphilic diblock
copolymers of polyethylene-block-poly(ethylene oxide), syndiotac-
tic polypropylene-block-poly(ethylene oxide) and isotactic poly-
styrene-block-poly(ethylene oxide) via click coupling reactions.29–31
Nevertheless, such coupling reaction is inefficient when long
polymer blocks (Mw > 104) are used because of wrapping of the
reactive ends by polymer chains. Post-modication including
aKey Lab for Polymer Composite and Functional Materials of Ministry of Education,
School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou,
510275, China. E-mail: ceszfm@mail.sysu.edu.cn; Fax: +86-20-84114033; Tel: +86-
20-84113250
bSchool of Material Science and Engineering, Jiangsu University, Zhenjiang, Jiangsu,
212003, China
cGDHPRC Lab, School of Chemistry and Chemical Engineering, Sun Yat-Sen
University, Guangzhou, 510275, China
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c7ra01450c
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hydrogenation,32–39 hydrolysis,34,35 hydroboration,36 and hydro-
silylation,37–39 are also used to synthesize diblock copolymers.
Group IV metal complexes containing tetradentate [OSSO]-
type bis(phenolate) ligands have been recently developed by
Okuda and co-workers.40–46 They demonstrated that group IV
complexes with 1,4-dithiabutandiyl-linked [OSSO]-type bis(6-tert-
butyl-4-tert-butyl phenolato) ligands could be used as a highly
active pre-catalysts for styrene isospecic polymerizations.40
A
titanium complex bearing tetradentate [OSSO] bis(phenolate)
ligand activated by [PhNMe2H]-[B(C6F5)4] in the presence of
Al(nOct)3 at 25 ꢁC was rst used for styrene living polymerization
with perfect isotacticity (mmm > 95%).43 Subsequently, the
styrene stereospecic living polymerization catalyzed by titanium
dichloro complex of 1,4-dithiabutandiyl-linked [OSSO]-type bis(6-
cumyl-4-methyl phenolato) ligand (complex 1, Scheme 1) acti-
vated by MAO was fullled to produce highly isotactic polystyrene
(iPS) with narrow molecular weight distribution.46 Styrene
stereospecic living polymerization with other olens such as
butadiene, 4-methyl-1,3-pentadiene (4MPD),46 4-methylstyrene
(PMS),47 and 4-tert-butylstyrene (PTBS)47 was carried out by using
[OSSO] titanium complexes having two cumyl bulky groups in the
ortho positions.46–48 The mechanism of isospecic styrene poly-
merization was depicted in Scheme 2. The active species were
formed from the dichloro complex as a result of methyl exchange
between aluminum and titanium.40 The insertion of monomers
into the Ti–CH3 bond occurred in a 2, 1- or secondary fashion,
and the polymerization was highly regioselective in either the
initiation step or the propagation step. The b-hydrogen reaction
did not represent an irreversible termination reaction, and the
unsaturated polymer chain represented a resting state.47
Scheme 2
block-isotactic poly(p-hydroxystyrene) (iPS-b-iP(p-HOS)) was
obtained.
Experimental
Materials
All manipulations of air- and moisture-sensitive compounds
were performed under an inert atmosphere of nitrogen using
a VAC glovebox or standard Schlenk-line techniques. Toluene
and hexane were reuxed over sodium/benzophenone under
high-pure-nitrogen. Styrene was stirred over CaH2 for about
24 h and then distilled under vacuum over CaH2. MAO (1.5 M)
was purchased from Akzo-Nobel. All solvents, if not specied,
were purchased from Sinopharm Chemical Reagent Co. Ltd.
and used as received. Titanium tetrachloride and all other
chemicals were purchased from J&K Chemicals and were used
as received. Complex 1 was prepared as previously reported.40
It is difficult to use directly transition metal catalysts for
coordination polymerization of hydroxystyrene monomers,
owing to the fact that hydroxyl groups coordinate with the
Synthesis of p-TBDMSOS
transition metals and poison the catalysts.49 Consequently, The p-TBDMSOS was prepared according to procedure reported
these monomers were generally protected using bulky groups by Kim et al.34 12.6 mL (90 mmol) of triethylamine were added to
before polymerization. Syndiospecic living coordination poly- a suspension of 10.98 g (90 mmol) of p-hydroxybenzaldehyde in
merization of p-tert-butyldimethylsilyloxy styrene (p-TBDMSOS) 150 mL of CH2Cl2, and the mixture was stirred at room
has been succeed using transition metal catalysts.50–52 However, temperature for 30 min. A solution of tert-butyldimethylsilyl
the stereospecic living polymerization of p-TBDMSOS base on chloride (13.56 g, 90 mmol) in 150 mL of CH2Cl2 was then
transition metal catalysts is unprecedented. Herein we reported added dropwise. The mixture was kept at room temperature
the rst example of isospecic living polymerization of p- under stirring for 3 h, and the reaction was quenched with
TBDMSOS and the synthesis of diblock copolymer of iPS-b-iP(p- water. The organic phase was separated, washed repeatedly with
TBDMSOS) via sequential monomer addition using complex 1/ water and brine, dried over anhydrous MgSO4, ltered and
MAO as a catalyst. Aer hydrolysis of the iP(p-TBDMSOS) block concentrated to yield 20.8 g (98%) of a yellow oily product as p-
by hydrochloric acid, an amphiphilic diblock copolymer of iPS- tert-butyldimethylsilyloxybenzaldehyde (p-TBDMSOB).
n-BuLi (1.6 M solution in hexane, 14 mL, 22.4 mmol) was
added dropwise to a stirred, cold (0 ꢁC) solution of methyl-
triphenylphosphonium bromide (8.19 g, 22.8 mmol) in 50 mL of
ꢁ
THF. The suspension was stirred and kept at 0 C for 15 min,
a solution of p-TBDMSOB (5.69 g, 24 mmol) in 50 mL of THF
was added dropwise via needle. The yellow suspension was
stirred for 4 h and treated with NH4Cl. The solution was ltered
and concentrated under vacuum. The resultant viscous liquid
was puried by column chromatography using hexane as the
solvent. The product was obtained as a colorless oil in a yield of
4.50 g (90%) and used immediately. 1H NMR (400 MHz, CDCl3):
Scheme 1
d ¼ 7.33 (d, 2H, C6H4), 6.85 (d, 2H, C6H4), 6.70 (q, 1H, –CH]
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CH2), 5.65 (d, 1H, –CH]CH2), 5.17 (d, 1H, –CH]CH2), 1.04 (s, mixture was reuxed for 5 h. The resultant hydroxylated homo-
9H, C(CH3)3), 0.25 (s, 6H, Si(CH3)2).
or diblock co-polymers were concentrated and recovered by
precipitation with cold diethyl ether and dried to constant
weigh under vacuum at 50 C.
ꢁ
Styrene polymerization
A 100 mL Schlenk ask equipped with a magnetic stirrer was
dried more than 3 h by infrared light under vacuum and then
Self-assembly of iPS-b-iP(p-HOS)
cooled to room temperature. Aer replacement with high-pure- Typically, 3 mg of iPS-b-iP(p-HOS) and 9.0 mL of THF were
ꢁ
nitrogen three times, the ask was charged with high-pure- placed into a 20 mL ask. The mixture was stirred at 60 C for
nitrogen to atmospheric pressure. Toluene, MAO solution in 3 h to ensure that iPS-b-iP(p-HOS) dissolved completely to form
toluene, and complex 1 solution in toluene were charged a molecular solution. Aer the solution was added into meth-
sequentially by syringe under high-pure-nitrogen pressure. Aer anol under stirring, the mixture was volatilized at room
equilibration of the solution at the polymerization temperature, temperature for several days to remove THF entirely.
the reaction was started by styrene. The run was terminated aer
the desired time by injection of ethanol (2 mL). The polymer was
coagulated in ethanol (200 mL) acidied with aqueous HCl
(ethanol/HCl, 90/10). The precipitated polymer was collected by
ltration, washed several times with ethanol, and dried under
vacuum at 60 ꢁC to a constant weight.
Measurements
Nuclear magnetic resonance (1H NMR, 13C NMR) spectra of
organic compounds and polymer were recorded on a Varian
Unity Inova 400 spectrometer, operating at 400 MHz for 1H
NMR and 100 MHz for 13C NMR, respectively. Using 5 mm NMR
tubes, polymer samples (30–50 mg) were dissolved in CDCl3,
deuterated terahydrofuran (THF-d8) or CH3OD and analyzed at
p-TBDMSOS polymerization
A 100 mL Schlenk ask equipped with a magnetic stirrer was 25 ꢁC. Chemical shis were referenced to tetramethylsilane
dried more than 3 h by infrared light under vacuum and then (TMS) or the residual solvent peak.
cooled to room temperature. Aer replacement with high-pure-
The differential scanning calorimetry (DSC) analyses were
nitrogen three times, the ask was charged with high-pure- performed using a PerkinElmer DSC-4000 instrument with the
nitrogen to atmospheric pressure. Toluene, MAO solution in samples placed under a nitrogen atmosphere 2.0–4.0 mg of
toluene and complex 1 solution in toluene were charged samples. Step-scan method for homopolymers: heating from
sequentially by syringe under high-pure-nitrogen pressure. 30 ꢁC to 310 ꢁC at a rate of 10 ꢁC minꢂ1; hold for 5 min at 310 ꢁC;
Polymerization was initiated by injecting p-TBDMSOS. The cooling to 30 C at a rate of 10.0 C minꢂ1; hold for 5 min at
reactions were kept at 25 ꢁC under stirring for the required length 30 ꢁC and reheating from 30 ꢁC to 310 ꢁC at a rate of 10 ꢁC
of time. Polymerization was terminated by adding methanol. The minꢂ1. Step-scan method for diblock copolymers: heating from
polymers coagulated in methanol were recovered by ltration 30 ꢁC to 310 ꢁC at a rate of 10 ꢁC minꢂ1; hold for 5 min at 310 ꢁC;
aer washing several times with methanol, and the ltrate was cooling to 30 ꢁC at a rateꢁof 1.0 ꢁC minꢂ1; hold for 5 min at 30ꢂꢁ1C
ꢁ
ꢁ
ꢁ ꢁ
and reheating from 30 C to 310 C at a rate of 10 C min .
dried to constant weight under vacuum at 60 ꢁC.
Glass transition temperature (Tg) and melting temperature (Tm)
were recorded on the second heating scan. The infrared (IR)
spectra were obtained on a Thermo Nicolet Nexus 670 instru-
Block copolymerization of styrene with p-TBDMSOS via
sequential monomer addition
ment with a measurement range of 400–4000 cmꢂ1
.
A 100 mL Schlenk ask equipped with a magnetic stirrer was
dried more than 3 h by infrared light under vacuum and then
cooled to room temperature. Aer replacement with high-pure-
nitrogen three times, the ask was charged with high-pure-
nitrogen to atmospheric pressure. Toluene, MAO solution in
toluene and complex 1 solution in toluene were charged
sequentially by syringe under high-pure-nitrogen pressure.
Polymerization was initiated by injecting styrene. Aer 2 h of
polymerization, p-TBDMSOS was then rapidly added to this
ask. The copolymerization continuously proceeded for an
additional time, and then was terminated by introducing
methanol. The polymers coagulated in methanol were recov-
ered by ltration aer washing several times with methanol,
and the ltrate was dried to constant weight under vacuum at
Gel permeation chromatography (GPC) analysis of the
molecular weights and molecular weight distributions of the
polymer were performed at 150 C on a Varian PL-220 HTGPC
ꢁ
instrument equipped with a triple-detection array, including
a differential refractive-index detector, a two-angle light-
scattering detector, and a four-bridge capillary viscometer that
use narrow molecular weight distribution polystyrene as stan-
dards. The detection angles of the LS detector were 15 and 90ꢁ,
and the laser wavelength was 658 nm. 1,2,4-Trichlorobenzene
(TCB) was used as the eluent at a ow rate of 1.0 mL minꢂ1
.
The morphological observation of the self-assembled
micelles in methanol was performed using scanning electron
microscopy (SEM) observations (Hitachi S-4800) with an accel-
erating voltage of 10.0 kV. A drop from the previously prepared
micelle solution was deposited onto a cover glass. The cover
glass was dried at room temperature for several hours before
examination by SEM.
ꢁ
60 C.
Deprotection of silylated homo- or block co-polymers
Silylated homo- or diblock co-polymers (0.2 g) were dissolved in
Dynamic light scattering (DLS) measurements were con-
THF (30 mL), acidied with concentrated HCl (5 mL), and the ducted on a Brookhaven BI-2005M apparatus with a BI-9000AT
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digital correlator and a He–Ne laser at 532 nm. The angle was conversion (Fig. 1(a)), showing a typical living polymerization
xed to be 90ꢁ. The samples were placed in an index-matching characteristics. The molecular weight distribution of iPS was
decaline bath with temperature control within ꢃ2 ꢁC. Each below 1.30, verifying the living characteristics of the polymeri-
solution passed through a 0.45 mm polytetrauoroethene zation. The isospecic living coordination polymerization of
(PTFE) lter to remove dust. The data were analyzed by CONTIN styrene was quick, and reached a full conversion in 2 h.46
algorithm, while the hydrodynamic diameter (Dh) and size The coordination polymerization of styrene derivates such as
polydispersity of the particles were obtained by a cumulant p-tert-butyldimethylsilyloxy styrene (p-TBDMSOS) was further
analysis of the experimental correlation function.
checked using the identical catalyst system. The linear depen-
dence of the molecular weight of poly(p-TBDMSOS) on the
conversion of p-TBDMSOS was observed again (Fig. 1(b) and
Table 1). The narrow molecular weight distribution of poly(p-
TBDMSOS) was comparable to that of iPS. This suggested that
the induction of silyloxy moiety had little inuence on the
coordination polymerization. Representatively, the addition of
2.2 g of p-TBDMSOS with 5.0 mmol of complex 1 and 1500 equiv.
of MAO yielded 0.80 g poly(p-TBDMSOS) (Mn ¼ 6.4 ꢄ 105 and
PDI ¼ 1.15) at 25 min. 13C NMR spectrum of the poly(p-
Results and discussion
Isospecic living coordination polymerization of styrene and
p-TBDMSOS
Living coordination polymerization of styrene was carried out
using complex 1 as catalyst activated by MAO at 25 ꢁC. The
number-average molecular weight (Mn) of isospecc polystyrene
synthesized (iPS) increased linearly with increasing monomer
TBDMSOS) synthesized was shown in Fig.
2 peaks at
Table 1 Homopolymerization results of p-TBDMSOS with complex 1/
MAOa
t
Conv.
(%)
[mmmm]d
(%)
c
c
Run
(min)
Act.b
Mn ꢄ 10ꢂ5
Mw/Mn
1
2
3
4
5
6
5
10
28
40
48
55
62
4.8
4.4
3.8
3.6
3.2
2.7
3.08
4.84
6.43
6.96
7.56
7.84
1.07
1.10
1.15
1.20
1.26
1.30
>95
>95
>95
>95
>95
>95
15
25
35
45
60
a
Polymerization conditions: complex 1, 5.0 mmol; [Al]/[Ti], 1500; toluene,
20 mL; p-TBDMSOS (2.2 g, 9.40 mmol); polymerization temperature,
25 ꢁC. 105 g (polymer) (mol per catalyst) per h. Determined by GPC.
b
c
d
Determined by 13C NMR.
Fig.
1 Plots of Mn (:) and Mw/Mn (-) of polystyrene, poly(p-
TBDMSOS) and block copolymer versus conversion of styrene (a), p- Fig. 2 13C NMR spectrum of the iP(p-TBDMSOS) in CDCl3 at 25 ꢁC.
TBDMSOS (b) and comonomer (c). Polymerization conditions: styrene Polymerization conditions: p-TBDMSOS, 9.40 mmol; complex 1, 5.0
and p-TBDMSOS, 9.40 mmol; complex 1, 5.0 mmol; toluene, 20 mL; mmol; toluene, 20 mL; Al/Ti ¼ 1500; polymerization temperature,
Al/Ti ¼ 1500; polymerization temperature, 25 ꢁC.
25 ꢁC.
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Fig. 4 GPC profiles of iPS (Table 2, Run 2), iPS-b-iP(p-TBDMSOS)
(Table 2, Run 2) and iP(p-TBDMSOS) in THF at 25 ꢁC.
Isospecic living block copolymerization of styrene with p-
TBDMSOS via sequential monomer addition
Fig. 3 13C NMR spectrum of the iP(p-HOS) (in CD3OD at 25 ꢁC)
obtained from hydrolysis of iP(p-TBDMSOS) with complex 1, 5.0
mmol; toluene, 20 mL; Al/Ti ¼ 1500; polymerization temperature,
25 ꢁC.
The main results of isospecic living block copolymerization via
sequential monomer addition of styrene (rst monomer) and p-
TBDMSOS (second monomer) using complex 1/MAO were
summarized in Table 2. As in Fig. 1c, Mn of iPS with narrow
molecular weight distribution (Mw/Mn < 1.35) also increased
linearly as the conversion increased. This further veried that
the polymerization was living. The activity decreased slightly
with time.
The obtained diblock copolymers were characterized by
GPC, NMR and DSC. The results displayed that the relative
length of the blocks in the diblock copolymer of iPS-b-iP(p-
TBDMSOS) can be ne-tuned by changing the feed ratio of
monomers. The representative GPC proles of iPS prepolymer
that was removed from the same polymerization mixture before
feeding p-TBDMSOS, the second step diblock copolymer (Table
2, Run 2) and homopolymer of iP(p-TBDMSOS) under identical
conditions were shown in Fig. 4. A unimodal and quite
symmetric peak for iPS-b-iP(p-TBDMSOS) showed the molecular
weight (Mn ¼ 5.30 ꢄ 105) was higher than that of the iPS pre-
polymer (Mn ¼ 3.71 ꢄ 105). The conversion of styrene reached
100% before adding p-TBDMSOS, and molecular weight distri-
bution of the diblock copolymer was narrow, Mw/Mn ¼ 1.29.
This indicated the formation of iPS-b-iP(p-TBDMSOS). The 13C
NMR spectrum of iPS-b-iP(p-TBDMSOS) showed characteristic
153.43 ppm (C4), 139.51 ppm (C1 ipso-phenyl carbon),
128.17 ppm (C2), 119.57 ppm (C3), 43.25 ppm (the methylene
carbons C6), and 39.78 ppm (the methine carbons C5) were
observed. According to the literature data of syndiotacic poly(p-
TBDMSOS) (sP(p-TBDMSOS)), the C1 singlet at 139.50 ppm in the
13C NMR was a characteristic peak of isotactic poly(p-TBDMSOS)
(iP(p-TBDMSOS)) ([mmmm] > 95%).50 This showed that living
isospecc coordination polymerization of p-TBDMSOS using
catalyst system of complex 1 was successful.
Herein, we demonstrate rst p-TBDMSOS isospecic
living coordination polymerization with [OSSO]-type tita-
nium catalyst (complex 1) activated by MAO and the forma-
tion of iP(p-TBDMSOS) with high isotacticity ([mmmm] >
95%). Consequently, isotactic poly(p-hydroxystyrene) (iP(p-
HOS)) was readily acquired through hydrolyzing the iP(p-
TBDMSOS) in the presence of hydrochloric acid. The depro-
tection of tert-butyldimethylsilyl to hydroxyl group gave rise
to small chemical shi comparing to iP(p-TBDMSOS), as
shown Fig. 3.
Table 2 The results of isospecific living block copolymerization of styrene with p-TBDMSOS via sequential monomer addition by complex 1/
MAOa
c
d
d
e
e
Run
Feed (M1 : M2)
M2Conv. (%)
Act.b
XS
Mn ꢄ 10ꢂ5
Mw/Mn
Mn ꢄ 10ꢂ5
Mw/Mn
1
2
3
4
5
6
0.00 : 2.05
4.35 : 4.27
4.35 : 2.05
4.35 : 1.03
2.17 : 4.27
0.87 : 4.27
72
38
60
82
55
70
0.70
0.37
0.37
0.38
0.26
0.27
0.00
0.73
0.78
0.82
0.52
0.23
—
—
3.54
5.30
4.82
4.54
5.65
7.60
1.26
1.29
1.33
1.32
1.32
1.35
3.71
3.71
3.71
2.20
1.00
1.24
1.24
1.24
1.23
1.23
a
Polymerization conditions: complex 1, 5.0 mmol; [Al]/[Ti], 1500; toluene, 20 mL; M1, styrene (mmol); M2, p-TBDMSOS (mmol); polymerization
temperature, 25 ꢁC; rst step, styrene, 120 min; second step, p-TBDMSOS, 60 min. 105 g (polymer) (mol per catalyst) per h. Styrene molar
b
c
fraction in iPS-b-iP(p-TBDMSOS), determined by 1H NMR spectra. Relative to the iPS block before feeding p-TBDMSOS monomer determined
d
by GPC. e Relative to the iPS-b-iP(p-TBDMSOS), determined by GPC.
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Fig. 5 13C NMR spectra of iPS-b-iP(p-TBDMSOS) (Table 2, Run 2), iPS
and iP(p-TBDMSOS) in CDCl3 at 25 ꢁC.
peak of 146.52 ppm (C1 ipso-phenyl carbon) of iPS and char-
acteristic peak of 153.43 ppm (C4), 139.51 ppm (C1 ipso-phenyl
carbon) of iP(p-TBDMSOS) as shown in Fig. 5, showing the
existence of iPS and iP(p-TBDMSOS) blocks. As the existence of
chain transfer (b-hydrogen reaction) effect, the Mn of the block
copolymer was not a simple sum of the Mn of the two
homopolymers.
In addition, IR spectrometry was used to characterize the
homopolymers and block copolymers, as shown in Fig. 6. The
peak at ꢀ1450 cmꢂ1 which was attributed to CH2 bending vibra-
tion, and the peaks at 2840–3060 cmꢂ1 ascribing to stretching
vibration of C–H bonds indicated that the polymerizations were
successful. The peak at ꢀ1601 cmꢂ1 for iPS can be attributed to
C]C stretching vibration of benzene rings, and peaks at ꢀ699
cmꢂ1 and ꢀ759 cmꢂ1 were characteristic absorption peaks of
mono-substituted benzene rings. For iP(p-TBDMSOS), peak at
ꢀ1257 cmꢂ1 derived from the stretching vibration of Si–CH3 band,
ꢀ1170 cmꢂ1 derived from the stretching vibration of C–O band,
and ꢀ839 cmꢂ1 was characteristic absorption peak of 1,4-
substituted benzene rings. In Fig. 6c, the peaks at 2840–3060
cmꢂ1, ꢀ1460 cmꢂ1,ꢀ1170 cmꢂ1, ꢀ839 cmꢂ1, ꢀ759 cmꢂ1, ꢀ699
cmꢂ1 indicated that iPS-b-iP(p-TBDMSOS) block copolymer was
successfully synthesized.
The thermal properties of the iPS-b-iP(p-TBDMSOS) obtained
by complex 1/MAO were investigated by DSC, and compared with
those of iPS and iP(p-TBDMSOS). As the complicated crystalli-
zation of the block copolymer, cooling cycle was conducted at
1.0 ꢁC minꢂ1. Typical DSC curves of the synthesized iPS, iP(p-
TBDMSOS) and iPS-b-iP(p-TBDMSOS) of Run 6 in Table 2 were
ꢁ
displayed in Fig. 7 iP(p-TBDMSOS) showed higher Tg at 117 C
and Tm at 294 ꢁC than those of iPS (Tg ¼ 97 ꢁC, Tm ¼ 223 ꢁC). A
bulky group in the para position of styrene restricted segmental
dynamics and lead to an increase in Tg.53 iPS-b-iP(p-TBDMSOS)
ꢁ
displayed two glass transition temperatures (ꢀ97 and ꢀ117 C)
and a wide overlapped melting temperature from 267 to 275 ꢁC
originating from the iPS and iP(p-TBDMSOS) blocks. These
results demonstrated that the iPS-b-iP(p-TBDMSOS) was double
crystalline diblock copolymer.
Fig. 6 IR spectra of iPS (a), iP(p-TBDMSOS) (b), iPS-b-iP(p-TBDMSOS)
(c), and iPS-b-iP(p-HOS) (d) samples.
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Fig. 7 DSC curves of the second heating scan of iPS, iP(p-TBDMSOS)
and iPS-b-iP(p-TBDMSOS) samples obtained in Table 2, Run 6.
Preparation and solution self-assembly of iPS-b-iP(p-HOS)
iPS-b-iP(p-TBDMSOS) was hydroxylated to produce amphiphilic
diblock copolymer of iPS-b-iP(p-HOS) in the presence of
hydrochloric acid. iPS-b-iP(p-HOS) was characterized by 13C
NMR in THF-d8 at 25 ꢁC, as depicted in Fig. 8. The characteristic
peaks at 146.57 ppm (C1 ipso-phenyl carbon) for iPS, and at
155.40 ppm (C4), 137.53 ppm (C1 ipso-phenyl carbon) for iP(p-
HOS), conrmed the formation of iP(p-HOS) block. IR spectrum
of iPS-b-iP(p-HOS) in Fig. 6d showed no peak at ꢀ1257 cmꢂ1 and
a broad peak at 3200–3500 cmꢂ1, which also affirmed the
formation of iP(p-HOS) block.
THF is a common solvent for both iPS and iP(p-HOS) blocks,
while methanol is a selective solvent for the iP(p-HOS) block but
poor solvent for the iPS block. A THF solution of the iPS-b-iP(p-
HOS) was added dropwise to methanol to form a light blue
solution, implying the self-assembly process of the iPS-b-iP(p-
HOS). Aer the mixture solution was volatilized at room
temperature for several days to remove THF, the self-assembled
Fig. 9 SEM image of the self-assembled micelles of iPS-b-iP(p-HOS)
obtained from the hydrolysis of iPS-b-iP(p-TBDMSOS) (Table 2, Run 2)
in methanol solution (0.03 mg mLꢂ1).
micelles were observed using SEM, as displayed as in Fig. 9. The
SEM images of a self-assembled iPS-b-iP(p-HOS) showed
spherical nanoparticles with a diameter of approximately
Fig. 10 The Dh distribution of the self-assembled micelles of iPS-b-
Fig. 8 13C NMR spectrum (in THF-d8 at 25 ꢁC) of iPS-b-iP(p-HOS) iP(p-HOS) obtained from the hydrolysis of iPS-b-iP(p-TBDMSOS)
obtained from hydrolysis of iPS-b-iP(p-TBDMSOS) (Table 2, Run 2).
(Table 2, Run 2) in methanol solution (0.03 mg mLꢂ1) at 25 ꢁC.
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70 nm. Hydrodynamic diameter of iPS-b-iP(p-HOS) micelles in 15 S. Tanaka, R. Goseki, T. Ishizone and A. Hirao,
methanol were further measured using DLS, as shown in Macromolecules, 2014, 47, 2333–2339.
Fig. 10. The hydrodynamic diameter of iPS-b-iP(p-HOS) micelles 16 Z. Q. Wu, Y. Chen, Y. Wang, X. Y. He, Y. S. Ding and N. Liu,
was about 74 nm, constant with SEM results.
Chem. Commun., 2013, 49, 8069–8071.
17 J. X. Yang, Y. Y. Long, L. Pan, Y. F. Men and Y. S. Li, ACS Appl.
Mater. Interfaces, 2016, 8, 12445–12455.
18 J. Wu, H. Jiang, L. Zhang, Z. Cheng and X. Zhu, Polym. Chem.,
2016, 7, 2486–2491.
Conclusions
A
series of isospecic diblock copolymers of iPS-b-iP(p-
TBDMSOS) with well-controlled molecular weights, narrow 19 Y. Ren, Z. Wei, X. Leng, Y. Wang and Y. Li, Polymer, 2015, 78,
molecular weight distribution, and tunable block ratios, have
51–58.
been successfully synthesized using sequent living coordination 20 A. D. Todd and C. W. Bielawski, ACS Macro Lett., 2015, 4,
polymerization of styrene and p-TBDMSOS monomers with 1254–1258.
complex 1/MAO as a catalyst. iPS-b-iP(p-TBDMSOS) displays two 21 R. Goseki, S. Onuki, S. Tanaka, T. Ishizone and A. Hirao,
glass transition temperatures (ꢀ97 and ꢀ117 ꢁC), originating
Macromolecules, 2015, 48, 3230–3238.
from the iPS and iP(p-TBDMSOS) blocks, respectively. Further- 22 S. J. Buwalda, A. Amgoune and D. Bourissou, J. Polym. Sci.,
more, a novel amphiphilic diblock copolymer of iPS-b-iP(p-HOS)
is prepared through the hydrolysis of the p(p-TBDMSOS) block 23 J. F. Reuther, M. P. Bhatt, G. Tian, B. L. Batchelor, R. Campos
in the presence of hydrochloric acid. iPS-b-iP(p-HOS) self
and B. M. Novak, Macromolecules, 2014, 47, 4587–4595.
assembles into spherical micelles with size of approximately 24 T. C. Chung, Prog. Polym. Sci., 2002, 27, 39–85.
Part A: Polym. Chem., 2015, 54, 1222–1227.
70 nm in methanol.
25 T. Shiono, Y. Akino and K. Soga, Macromolecules, 1994, 27,
6229–6231.
26 Y. J. Chen, B. J. Wu, F. S. Wang, M. H. Chi, J. T. Chen and
C. H. Peng, Macromolecules, 2015, 48, 6832–6838.
Acknowledgements
This work was supported by the National Natural Science 27 H. C. Kolb, M. Finn and K. B. Sharpless, Angew. Chem., Int.
Foundation of China (21174167, 51573212) and the NSF of
Guangdong Province (S2013030013474, 2014A030313178).
Ed., 2001, 40, 2004–2021.
28 W. H. Binder and R. Sachsenhofer, Macromol. Rapid
Commun., 2007, 28, 15–54.
29 T. Li, W. J. Wang, R. Liu, W. H. Liang, G. F. Zhao, Z. Y. Li,
Q. Wu and F. M. Zhu, Macromolecules, 2009, 42, 3804–3810.
Notes and references
1 L. Sung, J. F. Douglas, C. C. Han and A. Karim, J. Polym. Sci., 30 Z. Y. Li, R. Liu, B. Y. Mai, S. Feng, Q. Wu, G. D. Liang,
Part B: Polym. Phys., 2003, 41, 1697–1700. H. Y. Gao and F. M. Zhu, Polym. Chem., 2013, 4, 954–960.
2 H. K. Jeon, B. J. Feist, S. B. Koh, K. Chang, C. W. Macosko and 31 R. Liu, Z. Y. Li, B. Y. Mai, Q. Wu, G. D. Liang, H. Y. Gao and
R. P. Dion, Polymer, 2004, 45, 197–206. F. M. Zhu, J. Polym. Res., 2013, 20, 1–11.
3 A. Blanazs, S. P. Armes and A. J. Ryan, Macromol. Rapid 32 Q. H. Zhou, Z. Y. Li, H. Q. Liang, Y. J. Long, Q. Wu, H. Y. Gao,
Commun., 2009, 30, 237–266.
G. D. Liang and F. M. Zhu, Chin. J. Polym. Sci., 2015, 33, 646–
4 G. Pandav and V. Ganesan, Macromolecules, 2015, 73, 16–22.
651.
5 J. Rodriguez-Hernandez, F. Checot, Y. Gnanou and 33 X. L. He, W. Li, A. M. Liang, J. J. Chen, A. D. Wang, B. L. Hu,
S. Lecommandoux, Prog. Polym. Sci., 2005, 30, 691–724.
6 B. A. Rozenberg and R. Tenne, Prog. Polym. Sci., 2008, 33, 40–
112.
J. W. Shi and A. M. Chen, China Synth. Rubber Ind., 2011, 34,
8–12.
34 Y. Kim and Y. Do, Macromol. Rapid Commun., 2000, 21, 1148–
7 N. Tomczak, D. Jancsewski, M. Han and G. J. Vancso, Prog.
Polym. Sci., 2009, 34, 393–430.
1155.
´
35 M. Franco, F. J. Rabagliati, A. A. Rodrıguez, M. I. Antxon and
´
M.-G. Sebastian, Polymer, 2007, 48, 4646–4652.
8 A. Meristoudi, G. Mountrichas and S. Pispas, Encyclopedia of
nanoscience and nanotechnology, American Scientic 36 C. Bae, US Pat., US7671157,2010.
Publishers, 2010.
37 S. Andre, F. Guida-Pietrasanta, A. Rousseau and B. Boutevin,
9 N. Nishiyama and K. Kataoka, Pharmacol. Ther., 2006, 112,
630–648.
10 N. Nishiyama and K. Kataoka, Adv. Polym. Sci., 2006, 193, 67–
101.
11 J. H. Park, S. Lee, J.-H. Kim, K. Park, K. Kim and I. C. Kwon,
Prog. Polym. Sci., 2008, 33, 113–137.
J. Polym. Sci., Part A: Polym. Chem., 2001, 39, 2414–2425.
38 B. C. Auman, V. Percec, H. A. Schneider and H. J. Cantow,
Polymer, 1987, 28, 1407–1417.
39 B. N. Gacal, V. Filiz, S. Shishatskiy, S. Rangou, S. Neumann
and V. Abetz, J. Polym. Sci., Part B: Polym. Phys., 2013, 51,
1252–1261.
12 N. Hadjichristidis, M. Pitsikalis and H. Iatrou, Adv. Polym. 40 C. Capacchione, A. Proto, H. Ebeling, R. Mulhaupt,
Sci., 2005, 189, 1–124.
13 G. Leone, Polym. Chem., 2012, 3, 1987–1990.
K. Moller, T. P. Spaniol and J. Okuda, J. Am. Chem. Soc.,
2003, 125, 4964–4965.
14 A. Anastasaki, C. Waldron, P. Wilson, C. Boyer, 41 C. Capacchione, R. Manivannan, M. Barone, K. Beckerle,
P. B. Zetterlund, M. R. Whittaker and D. Haddleton, ACS
Macro Lett., 2013, 2, 896–900.
R. Centore, L. Oliva, A. Proto, A. Tuzi, T. P. Spaniol and
J. Okuda, Organometallics, 2005, 24, 2971–2982.
19892 | RSC Adv., 2017, 7, 19885–19893
This journal is © The Royal Society of Chemistry 2017

View Article Online
Paper
RSC Advances
42 K. Beckerle, C. Capacchione, H. Ebeling, R. Manivannan, 47 C. Capacchione, D. Saviello, R. Ricciardi and A. Proto,
R. MVulhaupt, A. Proto, T. P. Spaniol and J. Okuda, J.
Organomet. Chem., 2004, 689, 4636–4641.
43 K. Beckerle, R. Manivannan, T. P. Spaniol and J. Okuda,
Organometallics, 2006, 25, 3019–3026.
Macromolecules, 2011, 44, 7940–7947.
48 M. Loria, A. Proto and C. Capacchione, Polym. Int., 2017, 66,
144–150.
49 A. Grassi, P. Longo, A. Proto and A. Zambelli,
Macromolecules, 1989, 22, 104–108.
44 K. Beckerle, R. Manivannan, B. Lian, G.-J. M. Meppelder,
G. Raabe, T. P. Spaniol, H. Ebeling, F. Pelascini, 50 Y. J. Kim and Y. K. Do, Macromol. Rapid Commun., 2000, 21,
¨
R. Mulhaupt and J. Okuda, Angew. Chem., Int. Ed., 2007,
1148–1155.
46, 4790–4793.
51 M. Kawabe and M. Murata, Macromol. Chem. Phys., 2002,
203, 24–30.
45 G.-J. M. Meppelder, K. Beckerle, R. Manivannan, B. Lian,
G. Raabe, T. P. Spaniol and J. Okuda, Chem.–Asian J., 2008, 52 M. Kawabe and M. Murata, Macromol. Chem. Phys., 2001,
3, 1312–1323. 202, 3157–3164.
46 A. Proto, A. Avagliano, D. Saviello, R. Ricciardi and 53 Y. S. Xu and H. B. Li, Chem. Ind. Eng. Prog., 2000, 19, 35–37.
C. Capacchione, Macromolecules, 2010, 43, 5919–5921.
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