Synthesis of block copolymers and asymmetric star-branched polymers comprised of polyacetylene and polystyrene segments via ionic bond formation

Article abstract of DOI:10.1007/s00706-006-0482-4

Novel ion-bonded AB diblock copolymers and three-arm AB₂ asymmetric star-branched polymers comprised of polyacetylene (A) and polystyrene (B) segments have been synthesized by the stoichiometric reaction of tert-amine-chain-end-functionalized p

Full text of DOI:10.1007/s00706-006-0482-4

Monatshefte f€ur Chemie 137, 869–880 (2006)
DOI 10.1007/s00706-006-0482-4
Synthesis of Block Copolymers
and Asymmetric Star-Branched Polymers
Comprised of Polyacetylene and Polystyrene
Segments via Ionic Bond Formation
ꢀ
Youling Zhao, and Akira Hirao
Kenji Sugiyama , Yasunori Karasawa, Tomoya Higashihara,
Department of Organic and Polymeric Materials, Graduate School of Science and Engineering,
Tokyo Institute of Technology, Ohokayama, Meguro-ku, Tokyo, Japan
Received July 1, 2005; accepted January 23, 2006
Published online July 3, 2006 # Springer-Verlag 2006
Summary. Novel ion-bonded AB diblock copolymers and three-arm AB2 asymmetric star-branched
polymers comprised of polyacetylene (A) and polystyrene (B) segments have been synthesized by the
stoichiometric reaction of tert-amine-chain-end-functionalized poly(phenyl vinyl sulfoxide)s with
either chain-end- or in-chain-carboxylated polystyrenes to link the two polymer segments via ionic
bond, followed by thermal treatment to convert their poly(phenyl vinyl sulfoxide)s to polyacetylene
segments. Periodic lamellar morphologies were observed in the cast films of such polymers by TEM
measurement. The isolation of the nano-size sheet consisting of polyacetylene lamellar layers was
attempted.
Keywords. Anions; Carbanions; End-functionalized polymer; Interactions; Polymerizations.
Introduction
Block copolymers comprised of conducting conjugated polymer segments such as
polyacetylenes, polyphenylenes, and poly(phenylenevinylene)s are receiving in-
creasing attention because of their potential applications in the areas of electronic
and optical devices [1–3]. These polymers are also expected to exhibit unique
physical and mechanical properties in bulk and solution originating from the rigid
rod-like structures of the conjugated polymer segments. These block copolymers
were generally synthesized by the linking reaction of living anionic polymers with
conjugated polymers or well-defined oligomers synthesized by stepwise reactions
[4–7]. As an alternative route, several research groups proposed a ‘‘soluble pre-
cursor’’ method, in which soluble precursor polymer segments were in advance
ꢀ
Corresponding author. E-mail: ksugiyam@polymer.titech.ac.jp

870
K. Sugiyama et al.
incorporated into the block copolymers obtainable by sequential living polymer-
ization, followed by conversion to the corresponding conjugated polymer segments
[8–15]. In practice, polystyrene-block-polyphenylene and polystyrene-block-poly-
acetylene were synthesized by this method.
Recently, we have proposed a promising methodology for the synthesis of block
copolymers comprised of polyacetylene segments [16]. The methodology involves
two synthetic steps: (a) the synthesis of ion-bonded block copolymer by the stoichio-
metric reaction of chain-end-carboxylated polystyrenes with tert-amine-chain-end-
functionalized poly(phenyl vinyl sulfoxide)s, and (b) the complete conversion of
poly(phenyl vinyl sulfoxide)s to polyacetylene segments by subsequent thermal
treatment. Similarly, the synthesis of new asymmetric star-branched polymers
comprised of polyacetylene segments has been reported.
Herein, we report on more detailed synthetic studies of block copolymers and
asymmetric star-branched polymers by the above-mentioned methodology with use
of different chain-functionalized polymers. The morphological study and attempts
to isolate the nano-size sheet consisting of polyacetylene lamellar layers are also
described.
Results and Discussions
Our synthetic approach herein used for the synthesis of ion-bonded block copoly-
mers and asymmetric star-branched polymers comprised of polyacetylene and
polystyrene segments is illustrated in Scheme 1. The synthesis of block copolymers
is achieved by stoichiometrically reacting poly(phenyl vinyl sulfoxide) having tert-
amine terminus with chain-end-carboxylated polystyrene to link the two polymer
chains via ionic bond, followed by converting the poly(phenyl vinyl sulfoxide)
chain to a polyacetylene segment by thermal treatment. The asymmetric star-
branched polymers are synthesized by the following two routes: The first synthetic
route involves the stoichiometric reaction of chain-end-functionalized poly(phenyl
vinyl sulfoxide) with two tert-amine functionalities with chain-end-carboxylated
polystyrene, followed by thermal treatment. In the second route, the star-branched
polymers are synthesized by the reaction of poly(phenyl vinyl sulfoxide) with one
Scheme 1

Synthesis of Block Copolymers
871
tert-amine functionality with in-chain-carboxylated polystyrene. In order to realize
such ion-bonded polymer syntheses, chain-end- and in-chain-carboxylated poly-
styrenes as well as poly(phenyl vinyl sulfoxide)s with one and two tert-amine
functionalities are required as starting chain-functionalized polymers.
Preparation of tert-Amine-Chain-End-Functionalized
Poly(phenyl vinyl sulfoxide)s
The anionic polymerization of phenyl vinyl sulfoxide was first reported in 1990 by
Hogen-Esch and his coworkers [14, 15]. They demonstrated that the polymeriza-
tion proceeds in a living manner to afford the polymers with controlled molecular
weights and relatively narrow molecular weight distributions (Mw=Mn ¼ 1.2 ꢁ 1.4).
A series of well-defined block copolymers of phenyl vinyl sulfoxide with styrene
was also synthesized. They also successfully demonstrated that the resulting poly-
mer could be quantitatively converted into a polyacetylene segment only by ther-
mal treatment. By this success, the poly(phenyl vinyl sulfoxide)s obtained by the
living anionic polymerization become advantageous polyacetylene precursors solu-
ble in organic solvents and well-controlled in chain length. Furthermore, a variety
of molecular designs accessible through living polymerization become possible.
Subsequently, the synthesis and application of structural similar block copolymers
comprised of polyacetylene segments have been reported by several other research
groups [17–19].
In general, molecular weight distributions of the polymers obtained by the anio-
nic polymerization have been reported to be relatively but not extremely narrow,
the Mw=Mn values being in between 1.2 and 1.4, or higher values [20]. Very
recently, we have found that the addition of a 10-fold or more excess of LiCl
can be effective to narrow the molecular weight distribution. For example, the
Mw=Mn value of the resulting polymer was reduced considerably from 1.45 to
1.12 in the polymerization in THF at ꢂ78ꢃC with 3-methyl-1,1-diphenylpentyl-
lithium (sec-BuLi=DPE) as an initiator. Therefore, the objective tert-amine-chain-
end-functionalized polymers used in this study were prepared in the presence of a
large excess of LiCl. In order to introduce the dimethylaniline moiety of tert-
aromatic amine functionality at the initiating chain-end, the initiator was prepared
from sec-BuLi and 1-(4-N,N-dimethylaminophenyl)-1-phenylethylene (1). A new
anionic initiator was also prepared from sec-BuLi and 1-(4-(3-N,N-diethylamino-
propyl)phenyl)-1-phenylethylene (2) and used in the polymerization to introduce
aliphatic tert-amine functionality.
The results are summarized in Table 1. As can be seen, polymers (Mn<20 K)
with Mw=Mn values of less than 1.2 are usually obtained by the polymerization
carried out in the presence of a large excess of LiCl. The additive effect of LiCl is
thus evident. In the case of a high molecular weight polymer (Mn ¼ 36 K), the
Mw=Mn value was found to be 1.33. However, the addition of LiCl was still effec-
tive, since a multimodal distribution was observed in the polymer obtained without
LiCl. The resulting polymers all possessed near predictable Mn values based on the
ratios of [monomer] to [initiator]. Deviation of the Mn values between observed
and predicted was observed when the target molecular weight was 20 K or higher,
possibly due to impurities in phenyl vinyl sulfoxide difficult to be removed and=or

872
K. Sugiyama et al.
Table 1. Anionic polymerization of phenyl vinyl sulfoxide in THF at ꢂ78ꢃC for 1–15 ha
Initiatorb
LiCl
Monomer
mmol
Mnꢄ10ꢂ3
Obsdc
mmol
mmol
d
Calcd
Mw=Mn
sec-BuLi=DPE, 0.124
sec-BuLi=DPE, 0.0923
sec-BuLi=1, 0.103
sec-BuLi=1, 0.0943
sec-BuLi=1, 0.115
sec-BuLi=2, 0.148
sec-BuLi=2, 0.125
Cumyl K=3, 0.0981
–
5.85
8.19
6.60
7.45
12.9
12.1
15.9
6.07
7.40
13.7
10.0
12.3
17.4
12.8
19.8
9.83
9.01
18.9
9.46
18.0
36.0
11.6
20.6
7.75
1.45
1.12
1.24
1.10
1.33
1.17
1.29
1.33
2.37
0.523
2.08
1.75
1.80
1.91
–
a
b
Yields of polymer were quantitative; 1: 1-(4-N,N-dimethylaminophenyl)-1-phenylethylene, 2:
1-(4-(3-N,N-diethylaminopropyl)phenyl)-1-phenylethylene, 3: 1,1-bis(4-N,N-dimethylaminophenyl)
ethylene, Cumyl K: cumyl potassium; end-group analysis by 1H NMR (see Experimental);
d
c
determined by SEC
unavoidable ꢀ-proton abstraction of monomer and the polymer. In each sample,
dimethylanilino or 3-N,N-diethylaminopropyl group was quantitatively introduced
1
as confirmed by H NMR analysis.
Similarly, two dimethylanilino groups could be introduced at the initiating
chain-end by the anionic polymerization with the initiator prepared from sec-BuLi
and 1,1-bis(4-N,N-dimethylaminophenyl)ethylene (3) in THF at ꢂ78ꢃC. The tert-
amine-chain-end-functionalized poly(phenyl vinyl sulfoxide)s thus synthesized are
referred to as PPVS–ArNMe2, PPVS–C3H6NEt2, and PPVS–(ArNMe2)2, respec-
tively.
Preparation of Chain-End- and In-Chain-Carboxylated Polystyrenes
Chain-end-carboxylated polystyrenes (PS-COOH) were prepared by the reaction of
polystyryllithiums (PSLi) with CO2 according to the method reported previously
by Quirk and his coworkers [21]. The degrees of end-functionalization were deter-
mined by TLC-FID to be 91–98%. The synthesis of in-chain-carboxylated poly-
styrene (PS–(COOH)–PS) could be achieved by the addition reaction of a 1.1-fold
excess of PSLi to chain-end-functionalized polystyrene with 1,1-diphenylethylene
moiety, followed by treatment with CO2 as illustrated in Scheme 2.
Scheme 2

Synthesis of Block Copolymers
873
Table 2. Chain-end- and in-chain-functionalized polystyrenesa
Typec
Mnꢄ10ꢂ3
Obsdd
Functionalityb
%
Calcd
Mw/Mne
PS–COOH
6.75
12.4
15.4
27.7
20.9
20.1
24.8
10.0
7.10
13.0
15.2
29.3
20.0
22.6
24.1
10.0
1.02
1.02
1.04
1.05
1.04
1.05
1.04
1.04
97
98
PS–COOH
PS–COOH
91
PS–COOH
93
PS–(COOH)–PS
PS–(COOH)–PS
PS–ArNMe2
PS–(ArNMe2)2
94
93
ꢁ100
ꢁ100
a
Yields of polymers were always quantitative; b determined by TLC-FID; c PS–COOH: chain-end-
carboxylated polystyrene, PS–(COOH)–PS: in-chain-carboxylated polystyrene, PS–ArNMe2: chain-
end-functionalized polystyrene with N,N-dimethylaniline moiety, PS–(ArNMe2)2: chain-end-functio-
d
1
nalized polystyrene with two N,N-dimethylaniline moieties; end-group analysis by H NMR (see
e
Experimental); determined by SEC
SEC profile of the reaction mixture showed two distinct sharp single peaks
corresponding to the objective PS–(COOH)–PS and the deactivated PSLi (pre-
sumably PS–COOH) used in excess in the reaction. The higher molecular weight
fraction was isolated in 80% yield by fractional precipitation. The molecular weight
measured by SEC agreed with that calculated. The degree of in-chain func-
tionalization was determined to be 94% by TLC-FID analysis. The results are sum-
marized in Table 2.
In order to use in the model reaction, tert-amine-chain-end-functionalized poly-
styrenes were also prepared by end-capping reaction of PSLi with either of 1 or 3.
They are referred to as PS–ArNMe2 and PS–(ArNMe2)2, respectively. The results
are also listed in Table 2.
Synthesis of Block Copolymers and Asymmetric Star-Branched
Polymers via Ionic Bonds
Approaches to the synthesis of block copolymers by means of ionic bond formation
between the terminal groups of two chain-end-functionalized polymers have been
reported by several research groups [22–29]. Furthermore, Hadjichristidis and his
coworkers have recently demonstrated the possible synthesis of four-arm asymmetric
star-branched polymers by the similar ionic interaction of chain-end-functionalized
polyisoprene with a SO3H group and polystyrene having three dimethylamino ter-
mini [30]. However, they couldn’t have the strong evidence of the quantitative
ionic bond formation of three functional groups at one chain-end, although the
higher-order structure was observed by SAXS and TEM. To the best of our knowl-
edge, no synthetic example of ion-bonded block copolymers and asymmetric stars
containing poly(phenyl vinyl sulfoxide) and polyacetylene segments has been re-
ported so far.
Recently, we have reported the synthesis of new AB diblock copolymer and
three-arm AB2 asymmetric star-branched polymer comprised of conductive poly-

874
K. Sugiyama et al.
þ
acetylene (A) and polystyrene (B) segments linked via ionic bond ðNHðMeÞ2
ꢂOCO) by the stoichiometric reaction of either PPVS–ArNMe2 or PPVS–(ArNMe2)2
with PS–COOH [16]. Herein, the synthesis of such polymers is investigated in
more detail in order to establish the methodology used for the synthesis as a more
general procedure.
As previously reported, it was found that PPVS–NMe2 was stoichiometrically
reacted with PS–COOH to link the two polymer chains via ionic bond to afford the
AB diblock copolymer. The block copolymer formation (Mw ¼ 13 K) was evi-
1
denced by H NMR, FT-IR, and SLS analyses. In this study, the synthesis of a
higher molecular weight block copolymer has been carried out by the same reac-
tion of PPVS–NMe2 (Mw ¼ 48 K) with PS–COOH (Mw ¼ 31 K, COOH content ¼
93%) under the identical condition. SEC profile of the reaction mixture exhibited
only overlapping two peaks corresponding to the starting chain-end-functionalized
polymers. No peak for the expected diblock copolymer was observed at all in the
same SEC profile. Thus, SEC was not effective for detecting the formation of this
kind of ion-bonded block copolymer. This result is consistent with the previous
result. On the other hand, the formation of block copolymer was strongly indicated
1
by H NMR and IR analyses, respectively. More indicatively, the Mw value of the
resulting polymer was determined by SLS to be 69 K, but not 40 K of an average
Mw value ((31 K þ 48 K)=2). This value is very close to the target value of 70 K
assuming that the two chain-end-functionalized polymers were linked to quantita-
tively form an AB block copolymer. Thus obviously, the higher molecular weight
AB block copolymer could be formed via ionic bond without any difficulty.
A similar ion-bonded AB block copolymer was obtained by the reaction using
PPVS–C3H6NEt2 (Mw ¼ 14 K) and PS–COOH (Mw ¼ 31 K, COOH content ¼ 93%).
The Mw value of the resulting polymer determined by SLS was 44 K that agreed
well with the expected value of 42 K. Thus, the aliphatic tert-amine functionality
also works satisfactorily for the synthesis of ion-bonded block copolymer. All
results are summarized in Table 3.
Table 3. Block and AB2 star-branched polymers synthesized via ionic bond formation
Type
A
B
ABn, Mwꢄ10ꢂ3
Polymer
Mwꢄ10ꢂ3
Polymer
Mwꢄ10ꢂ3
Calcd
Obsda
AB
PPVS–ArNMe2
PPVS–ArNMe2
9.34
47.9
13.6
9.34
7.76
13.8
25.1
19.8
47.9
13.6
26.6
PS–COOH
PS–COOH
PS–COOH
PS–COOH
PS–COOH
PS–COOH
7.24
30.8
30.8
7.24
30.8
15.8
20.8
20.8
20.8
20.8
23.7
16
70
42
23
63
40
42
38
65
32
47
13
69
44
22
42
24
43
28
49
32
54
AB
AB
PPVS–C3H6NEt2
PPVS–(ArNMe2)2
PPVS–(ArNMe2)2
PS–(ArNMe2)2
PS–ArNMe2
AB2
AB2
A3
A3
PS–(COOH)–PS
PS–(COOH)–PS
PS–(COOH)–PS
PS–(COOH)–PS
PS–(COOH)–PS
AB2
AB2
AB2
AB2
PPVS–ArNMe2
PPVS–ArNMe2
PPVS–C3H6NEt2
PPVS–C3H6NEt2
a
Determined by SLS in THF

Synthesis of Block Copolymers
875
We also reported that a three-arm AB2 asymmetric star-branched polymer was
synthesized by the reaction of PPVS–(ArNMe2)2 (Mw ¼ 9.3 K) with PS–COOH
(Mw ¼ 7.2 K, COOH content ¼ 97%). Very unfortunately, however, the synthesis
of the star-branched polymer could not be reproduced at all, although the reason is
not clear at the present. Instead, the AB diblock copolymer (Mw ¼ 16 K) was
always obtained nearly quantitatively. Higher molecular weight chain-end-car-
boxylated polystyrene, PS–COOH (Mw ¼ 31 K, COOH content ¼ 93%), was also
reacted with PPVS–(ArNMe2)2 (Mw ¼ 7.8 K) under the same conditions. In this
case, the Mw value of the resulting polymer was determined by SLS to be 42 K.
Again, this value was far from the molecular weight of the expected three-arm star
(Mw ¼ 63 K), but nearly equal to that of the AB block copolymer (Mw ¼ 38 K) com-
prised of one poly(phenyl vinyl sulfoxide) segment and one polystyrene segment.
Since the incompatibility of two polymer segments can possibly be influenced
in the reaction between polymer chains, a newly synthesized PS–(ArNMe2)2
(Mw ¼ 14 K) was reacted with PS–COOH (Mw ¼ 16 K, COOH content ¼ 91%) as
a model reaction under the same conditions. The resulting polymer was found to
have 24 K in Mw value determined by SLS. This is close to the Mw value (28 K) of
the polymer formed by linking the two polystyrene segments. Thus, the result of
model reaction also indicates the formation of block copolymer, but not the ex-
pected three-arm star-branched polymer. One more polymer segment seems to be
no longer able to link to the block copolymer once formed. As often mentioned,
SEC is not effective to detect the ion-bonded polymer and, therefore, the informa-
tion on the real product(s) formed in the reaction is not available at the present
time. In addition, the isolation of the product(s) by fractional precipitation was not
successful. It is of course possible to speculate that the product is a mixture of a
three-arm AB2 star, an AB diblock copolymer, and two starting chain-end-functio-
nalized polymers. However, we consider that the block copolymer may possibly be
quantitatively formed in the reaction of PPVS–(ArNMe2)2 with PS–COOH, since
the Mw value of the resulting polymer always agreed well with that of the block
copolymer in each instance under various conditions.
Since it seems difficult to synthesize the objective three-arm star by the reac-
tion of PPVS–(ArNMe2)2 with PS–COOH, we have designed a new combination
of PPVS–ArNMe2 and in-chain-carboxylated polystyrene (PS–(COOH)–PS) for
the synthesis of the AB2 asymmetric star-branched polymers as illustrated in the
above-mentioned Scheme 1. Prior to the synthesis of star-branched polymer, the
model reaction was carried out between PS–ArNMe2 (Mw ¼ 25 K) and PS–
(COOH)–PS (Mw ¼ 21 K, COOH content¼ 94%). Again, a direct evidence for the
star-polymer formation was not provided by the SEC analysis of the reaction mix-
ture. On the other hand, the Mw value of the resulting polymer determined by SLS was
43 K which is the same as that (Mw ¼ 42 K) of the expected three-arm star-branched
polymer formed by completely linking the two polystyrene chains. Accordingly, the
synthesis of star was successfully achieved by the above-mentioned reaction.
On the basis of the success of the model reaction, two reactions were carried
out between either PPVS–ArNMe2 (Mw ¼ 20 K) or PPVS–ArNMe2 (Mw ¼ 48 K)
and PS–(COOH)–PS (Mw ¼ 21 K, COOH content ¼ 94%) under the same condi-
tions. However, the observed Mw values of the resulting polymers obtained by both
reactions were 28 and 49 K, respectively. These values were a little bit higher than

876
K. Sugiyama et al.
21 and 35 K which are the average Mw values of the starting polymers, but con-
siderably smaller than 38 and 65 K which are the Mw values of the expected stars.
Estimating from these Mw values, the three-arm AB2 star-branched polymers were
formed only in 43–48% yields. Thus, these results were not consistent with the
result obtained by the model reaction and were unsatisfactory in terms of yield of
star-branched polymer.
Next, we reacted PPVS–C3H6NEt2 (Mw ¼ 14 K) having a more basic amine
terminus with the same in-chain-functionalized polystyrene, PS–(COOH)–PS
(Mw ¼ 21 K, COOH content ¼ 94%). In this case, the Mw value of the resulting
polymer was determined by SLS to be 32 K and was consistent with 32 K of the
expected three-arm star-branched polymer. This may happen because the basicity
of the terminal aliphatic tert-amine is much higher than that of the terminal
dimethylaniline functionality, thus interacting more strongly with carboxylic acid
to form a stable ionic bond. The effectiveness of the terminal aliphatic tert-amine
was also demonstrated by the successful formation of another star-branched poly-
mer with Mw value of 54 K. The star was obtained from PPVS–C3H6NEt2 (Mw ¼
27 K) with PS–(COOH)–PS (Mw ¼ 24 K, COOH content ¼ 93%). Thus, we were
successful in synthesizing the objective three-arm AB2 asymmetric star-branched
polymer by using PPVS–(CH2)3NEt2 in place of PPVS–ArNMe2 in the reaction
with PS–(COOH)–PS.
Synthesis and Morphological Studies of Block Copolymer and AB2
Asymmetric Star-Branched Polymer Comprised of Polyacetylene
and Polystyrene Segments
Both the block copolymer (Mw ¼ 44 K) and the three-arm AB2 star-branched poly-
mer (Mw ¼ 32 K) newly synthesized in this study were cast into films, followed by
heating at 150ꢃC for 5 h. Their poly(phenyl vinyl sulfoxide) (PPVS) chains were
converted to the corresponding polyacetylene (PA) segments by this thermal treat-
ment as reported previously by several research groups [14, 15]. It was observed
that the color of each film gradually changed from pale yellow to black character-
istic to PA. The films were washed with toluene to remove by-products and char-
acterized by FT-IR and TGA, respectively.
The strong IR absorption band at 1032 cmꢂ1 due to the S¼O stretching was
observed in the starting polymer films and disappeared after thermal treatment, in-
dicating the complete conversion of the PPVS chains to PA segments. Weight losses
by such conversion to PA segments could be clearly detected by TGA measurement.
As expected, the observed weight losses were in good agreement with those calcu-
lated. Thus, new ion-bonded AB diblock copolymer as well as three-arm AB2 asym-
metric star comprised of PA and polystyrene segments were obtained.
Their PA segments were selectively stained with iodine vapor to clarify the mor-
phological structures by TEM measurement. Similar to our results reported pre-
viously, periodic lamellar structures were observed in both films. As illustrated in
Scheme 3, we attempted to isolate the nano-size sheet consisting of PA lamellar layers
from the film by treatment with HCl in THF. The film of the block copolymer was
similarly cast on mica, followed by thermal treatment. The resulting film on mica was
washed several times with THF solution containing HCl. By this treatment, the ionic

Synthesis of Block Copolymers
877
Scheme 3
þ
bond between PA and polystyrene segments may be cleaved from PA–C3H6NHEt2
þ
ꢂOCO–PS to PA–C3H6NHEt2 Clꢂ and PS–COOH. The polystyrene microdomain
was removed from the film by washing with THF and, on the other hand, the PA layer
might remain on mica due to its insolubility in THF. Although it was suggested by
AFM measurement that the PA layer, that is nano-size sheet, shown in Scheme 3 was
present in part, clear images could not be obtained by the interference from residual
polystyrene segments which remained on the film. Since the methodology for the
synthesis of ion-bonded block copolymers and asymmetric star-branched polymers
has been established, morphological studies of the resulting polymers, followed by
the isolation of their specially shaped nano-objects are now undertaken.
Conclusions
A series of AB diblock copolymers were quantitatively synthesized by the stoi-
chiometric reaction of either PPVS–ArNMe2 (A) or PPVS–C3H6NEt2 (A) with
PS–COOH (B) to link the two polymer chains via ionic bond. Similarly, the
synthesis of three-arm AB2 asymmetric star-branched polymers was successfully
achieved by the reaction of PPVS–C3H6NEt2 with PS–(COOH)–PS. The resulting
polymers all possessed predictable Mw values of the expected block copolymers
and asymmetric stars. Furthermore, novel ion-bonded AB block copolymers and
AB2 asymmetric star-branched polymers comprised of polyacetylene and polystyr-
ene segments have been obtained by thermal treatment of the resulting polymers at
150ꢃC for 5 h to convert their PPVS chains to PA segments. The lamellar morphol-
ogies with PA layers were observed in the cast films of such block copolymers and
asymmetric star-branched polymers. Unfortunately, the attempt to isolate the nano-
size sheet consisting of polyacetylene layers by treatment with HCl in THF was not
successful, although the formation was suggested by AFM.
The synthesis of ion-bonded asymmetric star-branched polymers having more
arms and hyperbranched polymers consisting of polyacetylene segments is now
undertaken. Furthermore, their morphological studies and isolation of specially
shaped nano-objects derived from morphologies are also under way.
Experimental
Materials
THF was refluxed over sodium wire, distilled over LiAlH4 under a nitrogen atmosphere, and then
distilled from its sodium naphthalenide solution on the vacuum line (10ꢂ6 Torr). sec-Butyllithium

878
K. Sugiyama et al.
(sec-BuLi) was used as received. Cumylpotassium was prepared by the reaction of cumyl methyl ether
with K–Na alloy in THF according to the previous method [31]. Styrene was purified by usual
methods. Phenyl vinyl sulfoxide (PVS) was synthesized by the oxidation of phenyl vinyl sulfide
prepared from benzenethiol and dibromoethane according to the method reported by Paquette and
Carr [32]. It was purified by silica gel column chromatography (hexane=ethyl acetate ¼ 9=1 v=v),
followed by distillation three times over CaH2. Finally, styrene and PVS were distilled on the vacuum
line over dibutylmagnesium and CaH2, respectively. 1,1-Diphenylethylene (DPE) was distilled over
CaH2 under reduced pressure and finally distilled from its BuLi solution on the vacuum line. Lithium
chloride was dried at 110ꢃC overnight under high vacuum conditions. 1-(4-N,N-Dimethylaminophenyl)-
1-phenylethylene (1) and 1,1-bis(4-N,N-dimethylaminophenyl)ethylene (3) were synthesized according
to our previous method [16].
Measurements
Both 1H and 13C NMR spectra were measured on a Bruker DPX300 in CDCl3. Chemical shifts were
recorded in ppm downfield relative to (CH3)4Si (ꢁ ¼ 0) for 1H NMR and relative to CDCl3 (ꢁ ¼ 77.1)
for 13C NMR as standards. Size exclusion chromatography (SEC) was measured by Tosoh HLC-8020
at 40ꢃC with refractive index detection using THF as a carrier solvent at a flow rate of 1.0 cm3=min.
Static light scattering (SLS) measurement was performed on a Photal DLS-2000 equipped with a
He–Ne laser source (633 nm) at 25ꢃC. The refractive index increment (dn=dc) was determined on an
Otsuka Electronics DRM-1020. Thin-layer chromatography coupled with flame ionization detector
(TLC-FID) was performed on an Iatron Iatroscan new MK-5 equipped with Iatrocorder TC-21 using
sintered quartz rods (150 mmꢄ2.0mm) with silica gel. Infrared spectra were recorded on a JASCO
FT=IR-460 spectrometer. Transmission electron microscope (TEM) observation was carried out on a
JEOL JEM-200CX.
Synthesis of 4-(3-Bromopropyl)benzophenone
To a solution of benzoyl chloride (30.2 g, 214 mmol) and aluminum chloride (21.1g, 159 mmol) pre-
stirred at 60ꢃC for 20 min was added dropwise 3-bromopropylbenzene (25.0 g, 126mmol) at 60ꢃC for
30min. The reaction mixture was kept at 60ꢃC with stirring for 4 h. The reaction mixture was poured
into 2 N HCl aq (50 cm3) and extracted with dichloromethane (50 cm3) three times. The organic layer
was washed with 5% NaOH aq (50 cm3, three times) and water (50 cm3, three times) and dried over
MgSO4. After removal of solvent, the crude product was purified by column chromatography (hexane=
ethyl acetate ¼ 9=1 v=v) and dried under vacuum to afford 4-(3-bromopropyl)benzophenone (26.4g)
as yellowish oil in 70% yield [33]. 1H NMR (CDCl3, 300 MHz): ꢁ ¼ 2.24 (p, 2H, CH2CH2CH2), 2.88
(t, 2H, ArCH2), 3.39 (t, 2H, CH2Br), 7.28–7.78 (m, 9H, Ar) ppm.
Synthesis of 1-(4-(3-Bromopropyl)phenyl)-1-phenylethylene
We have reported the synthesis of 1-(4-(3-bromopropyl)phenyl)-1-phenylethylene by a Grignard
coupling reaction of 1-(4-bromophenyl)-1-phenylethylene with 1-bromo-3-chloropropane followed
by a Finkelstein halogen exchange reaction [34]. However, the overall yield was not sufficient. Here
we report a preferable synthetic route for the title compound in better yield as shown below. To a
solution of methyltriphenylphosphonium bromide (26.1 g, 73.1mmol) and potassium tert-butoxide
(8.27 g, 73.7mmol) in THF (100 cm3) was added dropwise 4-(3-bromopropyl)benzophenone (18.0 g,
59.4mmol) in THF (50 cm3) at 0ꢃC for 20min under a nitrogen atmosphere. The reaction mixture was
kept at 25ꢃC with stirring for 12 h. The reaction mixture was poured into water (100cm3) and extracted
with ether (50 cm3) three times. The ethereal layer was washed with aq NaHCO3 solution, with
saturated aq NaCl solution, and dried over MgSO4. After filtration, the condensed ethereal layer was
poured into hexane to precipitate triphenylphosphine oxide. Flash column chromatography (hexane=
1
ethyl acetate ¼ 100=1 v=v) gave the title compound in 68% yield (12.2g) as colorless oil. H NMR
(CDCl3, 300 MHz): ꢁ ¼ 2.20 (p, 2H, CH2CH2CH2), 2.81 (t, 2H, ArCH2), 3.43 (t, 2H, CH2Br), 5.45
(d, 2H, J ¼ 7.4 Hz, CH2¼), 7.16–7.37 (m, 9H, Ar) ppm; 13C NMR (CDCl3, 75MHz): ꢁ ¼ 33.1

Synthesis of Block Copolymers
879
(CH2CH2CH2), 33.7 (ArCH2), 34.1 (CH2Br), 114.0 (CH2¼), 127.7, 128.0, 128.2, 128.3, 128.4, 139.4,
140.2, 141.6 (Ar), 149.8 (¼C) ppm.
Synthesis of 1-(4-(3-N,N-Dimethylaminopropyl)phenyl)-1-phenylethylene (2)
To a solution of 1-(4-(3-bromopropyl)phenyl)-1-phenylethylene (9.20 g, 30.5 mmol) and diethylamine
(11.2g, 153 mmol) in acetonitrile (150 cm3) was added in portions potassium carbonate (21.1g,
153 mmol) and the reaction mixture was refluxed for 30h. After filtering the salt off, the organic layer
was washed with brine (50 cm3). The objective product was quaternarized with 2N HCl aq to dissolve in
water. The aqueous layer was washed with hexane to remove unreacted starting materials and neutralized
with 10% NaOH aq to neutralize the product. The organic layer was extracted with ethyl acetate (50 cm3)
three times and dried over MgSO4. After filtration and condensation, the crude product was purified by
silica gel column chromatography (pre-treated with 3% triethylamine in hexane, hexane=ethyl acetate ¼
9=1 v=v) and dried under vacuum to afford 1-(4-(3-N,N-dimethylaminopropyl)phenyl)-1-phenylethylene
1
(7.15 g, 24.4 mmol) as colorless oil in 80% yield. H NMR (CDCl3, 300MHz): ꢁ ¼ 0.98 (t, 6H, J ¼
10.0Hz, CH3), 1.79 (p, 2H, J ¼ 7.8 Hz, CH2CH2CH2), 2.41–2.56 (m, 6H, NCH2), 2.62 (t, 2H, ArCH2),
5.42 and 5.68 (2d, 2H, J ¼ 11.4Hz, CH2¼), 6.90–7.56 (m, 9H, Ar) ppm. 13C NMR (CDCl3, 75MHz):
ꢁ ¼ 11.8 (CH3), 28.7 (CH2CH2CH2), 33.6 (ArCH2), 46.9 (NCH2CH3), 52.5 (CH2CH2N), 113.7 (CH2¼),
127.7, 128.1, 128.2, 128.3, 138.9, 141.7, 142.1 (Ar), 149.9 (¼C) ppm; IR (KBr): ꢂꢀ¼ 1246 (C–N), 1608
(C¼C) cmꢂ1; Anal: calcd for C21H27N C 85.95, H 9.27, N 4.77; found C 85.91, H 9.29, N 4.80.
Anionic Polymerization of Phenyl Vinyl Sulfoxide
The anionic polymerization of PVS was carried out under high vacuum conditions (10ꢂ6 Torr) in the
all glass apparatus equipped with break-seals. The functionalized initiators were usually prepared from
the reaction of sec-BuLi with a 1.2-fold excess of DPE derivatives in THF at ꢂ78ꢃC for 0.5 h. LiCl was
added to this initiator before the polymerization. The polymerization was carried out by adding a THF
solution of PVS into the functionalized initiator system with vigorous shaking and was terminated with
degassed methanol. The polymer was precipitated into a large amount of hexane or methanol. The
precipitated polymer was collected by filtration, purified by reprecipitation from THF solution to
1
methanol, and dried under vacuum. The molecular weight of the polymer was determined by H
NMR signal ratio of aromatic protons of main chain (6.9–7.7ppm) to methyl protons of sec-Bu
group (0.5–0.8 ppm). Similarly, the molecular weights of functionalized polystyrenes were determined
by end-group analysis comparing the signals of aromatic protons (6.3–7.3 ppm) and methyl protons
(0.6–0.8 ppm). The functionality of carboxylated polystyrenes was determined by TLC-FID peak area
ratio of carboxylated-polystyrene (Rf ¼ 0) to polystyrene (Rf ¼ 0.68) developed with toluene.
Preparation of Block Copolymers and Star-Branched Polymers via Ionic Bond Formation
The title polymers were prepared by mixing dimethylaniline- or diethylpropylamine-chain-end-func-
tionalized poly(phenyl vinyl sulfoxide)s with chain-end- or in-chain-carboxylated polystyrenes in THF
at 25ꢃC for 1 h. The amino and carboxyl groups were exactly adjusted at one to one molar ratio. The
solution was used for SLS measurement to determine the molecular weight. FT-IR, 1H NMR, and SEC
measurements were carried out with the dried polymer after evaporation and drying under vacuum.
The film sample for TEM observation was prepared by casting a THF solution of the polymer onto
carbon membrane on copper mesh sheet and drying at 25ꢃC overnight under nitrogen atmosphere. The
PPVS segments in the block copolymer and star-branched polymer films were converted into con-
ducting PA segments by heating the films at 150ꢃC for 5 h under high vacuum condition. After washing
with toluene, the film was stained with iodine vapor at 25ꢃC for 24h.
Acknowledgements
This work is supported by a Grand-in-Aid for Scientific Research (No. 15310085) from the Ministry of
Education, Culture, Sports, Science and Technology. T.H. is grateful for support from the Japan Society

880
K. Sugiyama et al.: Synthesis of Block Copolymers
of the Promotion of Science Research Fellowships for Young Scientists. Y.Z. gratefully thanks for the
support from the Japan Society of the Promotion of Science Research Fellowships for Foreign
Researchers.
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