Three mechanisms of asymmetric polymerization of phenylacetylenes having an l-amino ether residue and two hydroxy groups

Article abstract of DOI:10.1021/ma101424x

Three novel chiral phenylacetylenes having an octyloxyethanolamine residue derived from a l-aminoalcohol and two hydroxymethyl groups were synthesized and polymerized by two achiral catalysts ((nbd) Rh⁺[I?⁶-(C₆H₅)B ^-(C₆H₅)₃] and [Rh(nbd)Cl] ₂/triethylamine (TEA)) and a chiral catalytic system ([Rh(nbd)Cl]₂/(S)- or (R)-phenylethylamine ((S)- or (R)-PEA)). All of the resulting polymers showed Cotton effects at wavelengths around 430 nm. This observation indicated that they had an excess of one-handed helical backbones. Positive and negative Cotton effects were observed for the polymers having an l-valinol residue produced by using (S)- and (R)-PEA as a cocatalyst, respectively, although the monomers had the same chirality. The two polymers having an l-alaninol or l-phenylalaninol residues obtained by using (S)- and (R)-PEA as a cocatalyst showed CD absorptions with identical signs. Therefore, we found that the chiral monomer having an l-valinol residue was suitable for both modes of asymmetric polymerization, that is, helix-sense-selective polymerization (HSSP) with the chiral catalytic system and asymmetric-induced polymerization (AIP) with the achiral catalysts. However, the other two monomers having an l-alaninol or l-phenylalaninol residue were not suitable for HSSP because the helix sense could not be controlled by the chirality of PEA. To explain the unexpected behaviors in the asymmetric polymerizations of the two chiral monomers having a chiral bidentate ligand, a novel third mechanism of asymmetric polymerization, that is, self-helix-sense-selective polymerization (SHSSP), is proposed in this Article. This Article discusses the contribution of the three mechanisms (AIP, HSSP, and SHSSP) in asymmetric polymerizations of the three monomers.

Full text of DOI:10.1021/ma101424x

Macromolecules 2010, 43, 8353–8362 8353
DOI: 10.1021/ma101424x
Three Mechanisms of Asymmetric Polymerization of Phenylacetylenes
Having an -Amino Ether Residue and Two Hydroxy Groups
L
Hongge Jia,†,^ Masahiro Teraguchi,†,‡,§ Toshiki Aoki,*,†,‡,§, Yunosuke Abe,†
Takashi Kaneko,‡,§ Shingo Hadano,§, Takeshi Namikoshi,§, and Tomoyuki Ohishi§,
†Department of Chemistry and Chemical Engineering, Graduate School of Science and Technology,
‡Center for Education and Research on Environmental Technology, Materials Engineering, Nanochemistry,
§Center for Transdisciplinary Research, and Venture Business Laboratory, Niigata University, Ikarashi
2-8050, Nishi-Ku, Niigata 950-2181, Japan, and ^Department of Polymeric Material and Engineering,
Qiqihaer University, Wenhua Street 42, Qiqihaer, China
Received December 17, 2009; Revised Manuscript Received August 22, 2010
ABSTRACT: Three novel chiral phenylacetylenes having an octyloxyethanolamine residue derived from a
L-aminoalcohol and two hydroxymethyl groups were synthesized and polymerized by two achiral catalysts
((nbd)Rhþ[η6-(C6H5)B-(C6H5)3] and [Rh(nbd)Cl]2/triethylamine (TEA)) and a chiral catalytic system
([Rh(nbd)Cl]2/(S)- or (R)-phenylethylamine ((S)- or (R)-PEA)). All of the resulting polymers showed Cotton
effects at wavelengths around 430 nm. This observation indicated that they had an excess of one-handed
helical backbones. Positive and negative Cotton effects were observed for the polymers having an L-valinol
residue produced by using (S)- and (R)-PEA as a cocatalyst, respectively, although the monomers had
the same chirality. The two polymers having an L-alaninol or L-phenylalaninol residues obtained by using
(S)- and (R)-PEA as a cocatalyst showed CD absorptions with identical signs. Therefore, we found that the
chiral monomer having an L-valinol residue was suitable for both modes of asymmetric polymerization, that
is, helix-sense-selective polymerization (HSSP) with the chiral catalytic system and asymmetric-induced
polymerization (AIP) with the achiral catalysts. However, the other two monomers having an L-alaninol or
L-phenylalaninol residue were not suitable for HSSP because the helix sense could not be controlled by the
chirality of PEA. To explain the unexpected behaviors in the asymmetric polymerizations of the two chiral
monomers having a chiral bidentate ligand, a novel third mechanism of asymmetric polymerization, that is,
self-helix-sense-selective polymerization (SHSSP), is proposed in this Article. This Article discusses the
contribution of the three mechanisms (AIP, HSSP, and SHSSP) in asymmetric polymerizations of the three
monomers.
Introduction
during polymerization, several oligosiloxanylphenylacetylenes
having one or two bulky chiral pinanyl groups at the one-,
Conjugated polymers like polyacetylenes have gained interest
because of their noteworthy physical properties such as conduc-
tivity, organomagnetism, and optical nonlinear susceptibility.
Recently, chiral polyacetylenes have received much attention
because the chiral structure can enhance the unique properties
and add new functions.
three-, and five-positions of an oligosiloxane chain were poly-
merized with a Rh complex to produce high-molecular-weight
polymers.2g The polymers with a chiral pinanyl group at the one-
position of an oligosiloxanyl group showed high molar ellipticity
in the main-chain region in the CD spectra. The polymers from
monomers with a chiral pinanyl group at the three- or five-
positions of an oligosiloxanyl group showed almost no CD
absorptions. Therefore, to realize the AIP, the chiral group
should be substituted at a position close to the polymerizable
group in the monomers. In this AIP, the sign of the chirality of the
formed main-chain was strongly affected by the sign of the
chirality of the chiral group. Therefore, only two kinds of chiral
polymers, that is, the enantiomers, PD and ML (or PL and MD),4
could be obtained from the enantiomeric monomers by AIP. In
other words, it was impossible to synthesize their diastereomers.
The authors have also found a simple and novel synthetic
method for obtaining such a chiral polymer from an achiral
substituted acetylene monomer by using a chiral catalytic
system.5 In addition, the helical conformation was stable in
solution. This is the first example of helix-sense-selective poly-
merization (HSSP) of substituted acetylenes whose chiral helicity
is stable in solution without the aid of other chiral substituents or
other small molecules. The authors polymerized an achiral
phenylacetylene having two hydroxyl groups and a dodecyl
group (DoDHPA) (Chart 1) by using a chiral catalytic system
In 1993, the authors accidentally found an asymmetric-
induced polymerization (AIP) that induced a one-handed helical
chirality in the main-chain during polymerization of a phenyl-
acetylene having a bulky chiral L
-menthoxycarbonyl group.1 After
this finding, the authors synthesized and polymerized many other
phenylacetylenes and diphenylacetylenes having a chiral substi-
tuent to check whether a main-chain chirality was induced.2 As a
result, many chiral monomers were found to be suitable for the
AIP. For example, the homopolymers of (-)-p-(dimethyl(10-
pinanyl)silyl)phenylacetylene2a and (þ)-p-(10-pinanyloxycarbonyl)-
phenylacetylene2g obtained with an Rh complex showed strong CD
absorptions similar to that of p-{ -(-)-menthoxycarbonyl}phenyl-
L
acetylene.1 Similar results were also reported by other researchers.3
To investigate the effects of the position of the chiral groups in
the monomers on the induction of chirality in the main chain
*Corresponding author. Address: Department of Chemistry and
Chemical Engineering, Graduate School of Science and Technology,
Niigata University, Ikarashi2-8050, Nishi-Ku, Niigata 950-2181, Japan.
Tel/Fax: þ81 25 262 7280. E-mail: toshaoki@eng.niigata-u.ac.jp.
r 2010 American Chemical Society
Published on Web 09/23/2010
pubs.acs.org/Macromolecules

8354 Macromolecules, Vol. 43, No. 20, 2010
Jia et al.
Chart 1. Chemical Structure of DoDHPA in Our Previous Study
Chart 3. Chemical Structures of the Monomers Having a Bidentate
Ligand (ORDHPA) in This Study8
Chart 2. Chemical Structures of the Monomers (RDHPA) in Our
Previous Study
zation (SHSSP), for the first time in this Article. The contribu-
tion of the three mechanisms, AIP, HSSP, and SHSSP, to
asymmetric polymerizations is discussed.
Experimental Part
Materials. All of the solvents used for synthesis and poly-
merizations of the monomers were distilled as usual. The poly-
merization initiator, [Rh(nbd)Cl]2 (nbd = 2,5-norbornadiene),
purchased from Aldrich Chemical was used as received. According
to the literature procedures, (nbd)Rhþ[η6-(C6H5)B-(C6H5)3]9 and
DoDHPA5a were prepared. L-Alanine (Ala, [R]2D0 = þ14.3 ∼
þ15.2ꢀ (c 10 g/dL, 6 mol/L HCl)), L-valine (Val, [R]D20 = þ27.6
consisting of a rhodium dimeric complex, [Rh(nbd)Cl]2, as a
catalyst, and a chiral amine, (R)-phenylethylamine ((R)-PEA), as
a cocatalyst. The polymer showed Cotton effects at wavelengths
around 430 and 310 nm, where there are no UV absorptions of
DoDHPA and (R)-PEA.5a,5b No HSSPs occurred in the case of
the corresponding monomers having no hydroxy groups. There-
fore, two hydroxy groups were found to be necessary to realize
the HSSP. In this polymerization, the sense of the main-chain
helicity was governed by the sign of the chirality of the cocatalyst
used. In thiscase, alsoonly the pair of the enantiomers (M and P)4
could be produced.
∼ þ28.7ꢀ (c 8 g/dL, 6 mol/L HCl)), L-phenylalanine (Phe, [R]2D0
=
-33.5 ∼- 35.0ꢀ (c 2 g/dL, H2O)), and 2-aminoethanol (4)
purchased from Junsei Chemical were used as received. 1-Bro-
mooctane purchased from Tokyo Chemical was used as received.
Synthetic Procedures and Characterization of the Monomers
(OADHPA, OVDHPA, OPDHPA, and OEDHPA) (Scheme 1).
All of the following reaction procedures were conducted under
dry nitrogen.
These monomers described above were suitable only for
the AIP or the HSSP. There had been no monomers that
were suitable for both asymmetric polymerizations. We recently
1. L-Alaninol (1).10 A mixture of Ala (5.00 g, 56.1 mmol) in
dry THF (40 mL) was added slowly to a mixture of lithium
aluminum hydride (3.20 g, 84.2 mmol) in dry THF (40 mL) at
0 ꢀC. After the mixture was refluxed for 12 h, water (5 mL) was
slowly added. The mixture was filtered, and the solvent was
removed. The crude product was purified by vacuum distillation
to give 1 as colorless liquid. Yield: 51.1% (2.11 g). bp 55 ꢀC (6.8
reported a novel chiral phenylacetylene having an L-valinol
residue and two hydroxymethyl groups (VDHPA) (Chart 2).6
The monomer was suitable for both the HSSP with an chiral
catalytic system and the AIP with an achiral catalyst.6 This was
the first example of such a monomer. Positive and negative
Cotton effects were observed for the polymers obtained by using
(R)-PEA and (S)-PEA, respectively in HSSP. The handedness of
the main chain was controlled not by the chiral substituent but by
the chiral cocatalyst. For all asymmetric polymerizations (AIP)
of chiral acetylenes reported,1-3 the chiralities of the main chain
and the chiralities of the monomer substituent were not indepen-
dent. Therefore, only their enantiomers PD and ML (or PL and
MD)4 could be synthesized. We obtained the diastereomers (ML
and PL)4 first from the monomer VDHPA, as described in our
previous communication.6 However, the [θ] values and solubil-
ities of the poly(VDHPA) were not high.
mmHg). [R]2D0 = 8.5ꢀ (c 0.10 g/dL, THF). H NMR (CDCl3,
1
TMS, δ): 3.52 and 3.24 (2dd, 2H, CH2OH), 3.01 (m, 1H, NH2-
CH), 2.51 (b, 3H, NH2 and OH), 1.06 (d, 3H, J=6.2 Hz, CH3).
2. L-Valinol (2).6,10 According to the literature procedure,
2 was prepared. Yield: 57.5%. bp 42 ꢀC (0.32 mmHg). Appear-
ance: colorless liquid [R]2D0 = þ11ꢀ (c 0.10 g/dL, THF). 1H NMR
(CDCl3, TMS, δ): 3.60 and 3.25 (2dd, 2H, CH2OH), 2.52
(m, 1H, NH2CH), 1.87 (b, 3H, NH2 and OH), 1.55 (m, 1H,
CH(CH3)2), 0.87 and 0.90 (2d, 6H, J=3.4 Hz, CH(CH3)2).
3. L-Phenylalaninol (3).10 A similar procedure as described for
1 was employed. After the reaction, the mixture was filtered, and
the solution was concentrated to give a solid residue. The crude
product was dissolved in ethyl acetate, and the solution was
washed with brine. The water layer was extracted with ethyl
acetate. The organic layer was dried over MgSO4 and concen-
trated to give 3 as yellow solid. Yield: 46.1%. [R]2D0=-28ꢀ (c 0.10
We also studied the synthesis and polymerization of two other
RDHPAs (ADHPA and PDHPA) containing two hydroxy
groups and a chiral group, an L-alaninol residue and L-phenyla-
laninol residue, respectively, as shown in Chart 2.7 However,
because most of the resulting polymers were insoluble or partially
soluble in nonpolar solvents such as THF, chloroform, and so on
because of their high polarity, it was difficult to obtain a one-
handed helical backbone that was maintained by hydrogen bonds
in polar solvents, such as methanol, DMF, DMSO, and so on.
Therefore, we needed new monomers that may yield polymers
soluble in nonpolar solvents. As such monomers, we designed
three new ORDHPAs (OADHPA, OVDHPA, and OPDHPA),8
as shown in Chart 3. To enhance the solubility of the resulting
polymers, an octyl group was introduced to the hydroxyl group
of the amino alcohol residue in the corresponding RDHPA
(Chart 2). Here we discuss which monomer is suitable for both
HSSP and AIP. In addition, we propose a new mechanism of
asymmetric polymerization, self-helix-sense-selective polymeri-
1
g/dL, THF). H NMR (CDCl3, TMS, δ): 7.34-7.17 (m, 5H,
phenyl), 3.64 and 3.38 (2dd, 2H, CH2OH), 3.10 (m, 1H,
NH2CH), 2.80 and 2.52 (2dd, 2H, PhCH2), 2.10 (b, 3H, NH2
and OH).
4. (-)-2-Octyloxy-1-methylethylamine (Octyl Ether of L-Alaninol)
(5).11 A mixture of sodium hydride dispersion in paraffin (1.23 g,
28.1 mmol, content: 55%) in dry THF (25 mL) was added slowly to
asolutionof1(2.11g, 28.1mmol) indryTHF(25mL) at0ꢀC. After
the mixture was refluxed for 30 min, 1-bromooctane (4.45 mL, 25.6
mmol) was added at room temperature. After the mixture was
refluxed for 7 h, water (2 mL) was slowly added. The mixture was
filtered, and the solvent was removed. The crude product was
purified by silica-gel column chromatography to give 5 as a yellow

Article
Macromolecules, Vol. 43, No. 20, 2010 8355
Scheme 1. Synthetic Route to ORDHPAs (OADHPA, OVDHPA, OPDHPA, and OEDHPA)
Scheme 2. Synthetic Route to Compound 9
liquid. Yield: 64.2% (3.07 g). Rf = 0.13 (ethyl acetate/methanol
2:1). [R]2D0 =-7.0ꢀ (c0.10 g/dL, THF). 1HNMR(CDCl3, TMS, δ):
3.45 and 3.10 (m, 5H, OCH2CHN, OCH2CH2, and NH2CH), 1.55
(m, 2H, OCH2CH2), 1.43 (b, 2H, NH2), 1.27 (b, 10H, (CH2)5CH3),
1.02 (d, 3H, J = 6.2 Hz, NH2CHCH3), 0.85 (t, 3H, J = 6.8 Hz,
CH2CH3).
on p-bromophenol): 25.0%. Appearance: yellow liquid. Rf =
0.69 (ethyl acetate: hexane =2:1). 1H NMR (CDCl3, TMS, δ):
10.04 (s, 1H, CHO), 7.92 (d, 2H, J = 8.3 Hz,
5. (-)-2-Octyloxy-1-isopropylethylamine (Octyl Ether of
L-Valinol) (6).11 A similar procedure as that described for 5
was applied. Yield: 66.0%. Appearance: yellow liquid. Rf=0.33
(ethyl acetate/methanol 2:1). [R]2D0=-10ꢀ (c 0.10 g/dL, THF). 1H
NMR (CDCl3, TMS, δ): 3.48 (m, 3H, OCHaCHNH2 and
OCH2CH2), 3.18 (dd, 1H, OCHbCHNH2), 2.71 (m, 1H,
NH2CH), 1.56 (m, 3H, CH(CH3)2 and OCH2CH2), 1.26 (b,
10H, (CH2)5CH3), 0.90 (m, 9H, CH(CH3)2 and CH2CH3).
6. (-)-2-Octyloxy-1-benzylethylamine (Octyl Ether of L-Phenyl-
alaninol) (7).11 A similar procedure as that described for 5 was
applied. Yield: 64.0%. Appearance: yellow liquid. Rf=0.12 (ethyl
acetate/hexane 2:1). [R]2D0=-20ꢀ (c 0.10 g/dL, THF). 1H NMR
(CDCl3, TMS, δ): 7.32-7.18 (m, 5H, phenyl), 3.45 and 3.23 (m,
5H, OCH2CHN, OCH2CH2, and NH2CH), 2.78 and 2.54 (2dd,
2H, PhCH2), 1.55 (m, 4H, OCH2CH2 and NH2), 1.27 (b, 10H,
(CH2)5CH3), 0.88 (t, 3H, J = 6.8 Hz, CH3).
), 7.61 (d, 2H, J = 8.3 Hz,
), 7.51 (s, 2H,
7. 2-Octyloxyethylamine (8).11 A similar procedure as that
described for 5 was applied. Yield: 48.2%. Appearance: yellow
liquid. Rf=0.10 (ethyl acetate/ methanol 7:3). 1H NMR (CDCl3,
TMS, δ): 3.42 and 3.37 (2t, 4H, OCH2CH2N and OCH2CH2-
CH2), 2.81 (t, 2H, J = 5.1 Hz, NH2CH2CH2), 1.54 (m, 4H,
OCH2CH2CH2 and NH2), 1.22 (b, 10H, (CH2)5CH3), 0.83
(t, 3H, J = 6.8 Hz, CH3).
), 5.07 (s, 2H, PhOCH2Ph), 4.67 (d, 4H, J = 5.9 Hz, Ph-
(CH2OH)2), 1.88 (t, 2H, J = 5.9 Hz, Ph(CH2OH)2), 0.24 (s,
9H, Si(CH3)3).
9. (þ)-4-[4-{(2-Octyloxy-1-methyl)ethylaminomethyl}benzyloxy]-
3,5-bis(hydroxymethyl)-phenylacetylene (OADHPA)6,12,13 A solu-
tion of 5 (254 mg, 1.36 mmol) and 9 (500 mg, 1.36 mmol) in dry
methanol (10 mL) was stirred in the presence of molecular sieves
˚
8. 4-{4-Trimethylsilylethynyl-2,6-(bishydroxymethyl)-1-phe-
noxymethyl}benzaldehyde (9) (Scheme 2).5,6 According to the
method we reported before, 9 was prepared. Total yield (based
4 A (2.0 g) for 24 h at room temperature. Sodium tetrahydroborate
(51.6 mg, 1.36 mmol) was added to the solution, which was stirred
for 36 h again. After the solution was filtered, the solvent was

8356 Macromolecules, Vol. 43, No. 20, 2010
Jia et al.
removed. The crude product was purified by silica-gel column
chromatography to give OADHPA as a yellow liquid. Yield:
75.0% (476 mg). Appearance: yellow liquid. Rf = 0.35 (ethyl
acetate/methanol 8:1). [R]2D0 = 5.0ꢀ (c 0.10 g/dL, THF). 1H NMR
(CDCl3, TMS, δ): 7.51 (s, 2H,
Yield: 50.0%. Appearance: yellow liquid. Rf = 0.31 (ethyl
acetate/methanol 4:1). 1H NMR (CDCl3, TMS, δ): 7.51 (s, 2H,
), 7.35 (b, 4H,
), 7.35 (b, 4H,
), 4.92 (s, 2H, PhOCH2Ph), 4.62 (s, 4H, Ph(CH2OH)2), 3.82 (s,
2H, PhCH2NH), 3.56 (t, 2H, OCH2CH2N), 3.43 (t, 2H, OCH2-
CH2CH2), 3.05 (s, 1H, HCtC), 2.80 (t, 2H, NHCH2CH2), 2.14
(b, 3H, (OH)2 and NH), 1.57 (m, 2H, OCH2CH2CH2), 1.27 (b,
10H, (CH2)5CH3), 0.87 (t, 3H, J = 6.8Hz, CH3). IR(cm-1, KBr):
3301, 2927, 2860, 1738, 1603, 1458, 1367, 1207, and 1122. Anal.
Calcd for C28H39NO4: C, 74.14; H, 8.67; N, 3.09. Found: C, 73.90;
H, 8.95; N, 3.08.
), 4.91 (s, 2H, PhOCH2Ph), 4.61 (s, 4H, Ph(CH2OH)2), 3.89 (2d,
2H, J = 13 Hz, PhCH2NH), 3.40 and 3.29 (m, 4H, OCH2CHN
and OCH2CH2), 3.04 (s, 1H, HCtC), 2.92 (m, 1H, NHCH),
2.12 (b, 3H, (OH)2 and NH), 1.56 (m, 2H, OCH2CH2), 1.26
(b, 10H, (CH2)5CH3), 1.06 (d, 3H, J = 6.2 Hz, CHCH3), 0.86
(t, 3H, J = 6.8 Hz, CH2CH3). IR (cm-1, KBr): 3279, 2925, 2858,
1595, 1459, 1368, 1203, 1117, 974, and 891. Anal. Calcd for
C29H41NO4: C, 74.48; H, 8.84; N, 3.00. Found: C, 74.38; H, 9.04;
N, 2.87.
Polymerizations5,6 Asymmetric polymerizations were carried
out by two achiral catalysts, (nbd)Rhþ[η6-(C6H5)B-(C6H5)3]
and [Rh(nbd)Cl]2/triethylamine (TEA), and a chiral catalytic
system, [Rh(nbd)Cl]2/(R)- or (S)-PEA, respectively.
1. Polymerization of OADHPA. A typical polymerization
procedure was as follows: A solution of [Rh(nbd)Cl]2 (0.490 mg,
1.07 μmol) and (R)-PEA (68.0 μL, 535 μmol) in THF (0.53 mL)
was added to a solution of monomer OADHPA (50.0 mg,
107 μmol) in THF (0.54 mL). The reaction solution was stirred
at room temperature for 4 h. The formed polymer was purified
by precipitation of the THF solution in a large amount of ethyl
acetate/hexane 2:1 and dried in vacuum to give a red poly-
(OADHPA). Yield: 11.2% (5.60 mg). Mw = 85 000. Mw/Mn =
10. (-)-4-[4-{(2-Octyloxy-1-isopropyl)ethylaminomethyl}ben-
zyloxy]-3,5-bis(hydroxymethyl)-phenylacetylene (OVDHPA)6,12,13
A similar procedure as that described for OADHPA was applied.
Yield: 80.1%. Appearance: yellow liquid. Rf = 0.60 (ethyl acetate/
1
methanol 4:1). [R]2D0 = -27ꢀ (c 0.10 g/dL, THF). H NMR
(CDCl3, TMS, δ): 7.50 (s, 2H,
1
2.4 (Table 1, no. 4). H NMR (THF-d8/DMSO-d6 9:1 (V/V),
TMS, δ): 7.28 (b, 4.30H,
), 7.35 (b, 4H,
and
), 4.94 (s, 2H, PhOCH2Ph), 4.64 (s, 4H, Ph(CH2OH)2), 3.82 (s, 2H,
PhCH2NH), 3.48 and 3.34 (m, 4H, OCH2CHN, OCH2CH2), 3.05
(s, 1H, HCtC), 2.57 (m, 1H, NHCH), 1.90 (b, 3H, (OH)2 and
NH), 1.57 (m, 3H, OCH2CH2CH2 and CH(CH3)2), 1.26 (b, 10H,
), 6.95 (b, 2H,
(CH2)5CH3), 0.90 (m, 9H, CH(CH3)2 and CH2CH3). IR (cm-1
,
KBr): 3305, 2927, 2862, 1603, 1460, 1367, 1203, 1110, and 1076.
Anal. Calcd for C31H45NO4: C, 75.11; H, 9.15; N, 2.83. Found: C,
74.93; H, 9.34; N, 2.80.
11. (-)-4-[4-{(2-Octyloxy-1- benzyl)ethylaminomethyl}benzyloxy]-
3,5-bis(hydroxymethyl)-phenylacetylene (OPDHPA)6,11,12 A similar
procedure as that described for OADHPA was applied. Yield:
79.0%. Appearance: yellow liquid. Rf = 0.35 (chloroform/methanol
4:1). [R]2D0=-38ꢀ (c 0.10 g/dL, THF). 1H NMR (CDCl3, TMS, δ):
7.50-7.14 (m, 11H, phenyl), 4.95 (s, 2H, PhOCH2Ph), 4.64 (s, 4H,
Ph(CH2OH)2), 3.85 (s, 2H, PhCH2NH), 3.46-3.32 (m, 4H,
OCH2CHN and OCH2CH2), 3.02 (m, 2H, HCtC and NHCH),
2.84 and 2.75 (2dd, 2H, PhCH2CH), 2.09 (b, 3H, (OH)2 and
NH), 1.52 (m, 2H, OCH2CH2), 1.23 (b, 10H, (CH2)5CH3), 0.84
(t, 3H, J = 6.8 Hz, CH3). IR (cm-1, KBr): 3269, 3029, 2925, 2858,
1454, 1368, 1245, 1200, 1127, 1069, 1029, and 992. Anal. Calcd
for C35H45NO4: C, 77.31; H, 8.34; N, 2.58. Found: C, 77.35; H, 8.32;
N, 2.56.
), 5.97 (b, 0.70H,
), 4.71 (b, 2H, PhOCH2Ph), 4.41 (b, 4H, Ph(CH2OH)2), 3.76 (b,
PhCH2NH), 3.38 and 3.29 (2b, 4H, OCH2CHN and
OCH2CH2), 2.82 (b, NHCH, (OH)2 and NH), 1.53 (b, 2H,
OCH2CH2), 1.28 (b, 10H, (CH2)5CH3), 1.02 (b, 3H, CHCH3),
0.88 (b, 3H, CH2CH3). cis % = 70%. The other polymerizations
were also conducted similarly.
2. Polymerization of OVDHPA. Similar procedures as those
described for polymerizations of OADHPA were applied. The
formed polymer was purified by precipitation of the THF
solution into a large amount of methanol and dried in vacuum
12. 4-{4-(2- Octyloxyethylaminomethyl)benzyloxy}-3,5-bis-
(hydroxymethyl)phenylacetylene (OEDHPA)6,11,12 A similar
procedure as that described for OADHPA was applied.

Article
Macromolecules, Vol. 43, No. 20, 2010 8357
a
Table 1. Polymerizations of ORDHPAs by Using Achiral or Chiral Catalytic Systems Based On [Rh(nbd)Cl]2
[cocatalyst]
b
no.
monomer
cocatalyst
mol/L
vol %
yield (%)
Mw (ꢀ104)b
Mw/Mn
[θ]430 (ꢀ103)c
1d
2
3
4
OADHPA
none
TEA
TEA
(R)-PEA
(S)-PEA
(S)-PEA
none
TEA
TEA
(R)-PEA
(S)-PEA
none
TEA
TEA
(R)-PEA
(S)-PEA
(S)-PEA
none
TEA
(R)-PEA
(S)-PEA
(0.1)e
0.5
2.4
0.5
0.0
6.7
33.3
5.9
5.9
33.3
0.0
6.7
33.3
5.9
5.9
0.0
6.7
33.3
5.9
5.9
33.3
0.0
6.7
5.9
55.2
56.2
34.8
11.2
5.2
13.5
14.8
2.8
8.5
6.9
3.9
10.1
6.5
2.5
9.2
10.5
25.7
17.8
2.5
11.5
6.7
1.9
1.2
2.2
2.5
1.8
2.4
1.5
2.1
3.8
4.1
2.0
2.9
2.8
7.7
5.4
1.7
2.3
2.7
1.7
1.1
1.1
1.2
1.1
5.1
4.3
1.9
9.6
5
0.5
1.2
6
2.5
12.5
36.1
43.1
42.1
14.1
14.1
85.1
42.6
44.5
25.4
12.4
20.7
29.2
23.1
14.2
8.8
-2.8
-1.9
-1.5
-2.8
2.0
-2.3
-5.4
2.7
7d
8
OVDHPA
OPDHPA
(0.1)e
0.5
9
2.4
0.5
10
11
12 d
13
14
15
16
17
18d
19
20
21
0.5
(0.1)e
0.5
2.4
0.5
0.5
3.2
-2.8
-3.3
-2.7
0.0
0.0
0.4
2.5
OEDHPA
(0.1)e
0.5
1.1
3.2
1.2
0.5
0.5
5.9
-0.3
a At room temperature in THF, [monomer] = 0.1 mol/L, [catalyst] = 1 ꢀ 10-3 mol/L, [monomer]/[catalyst] = 100. b Determined by GPC correlating
polystyrene standard with THF eluent. c In deg cm2/dmol, 1.0 mmol/L, in THF. d By using (nbd)Rhþ[η6-(C6H5)B-(C6H5)3] as a catalyst. e Concentra-
tion of the monomer working as a cocatalyst also.
3
to give a red poly(OVDHPA). Yield: 14.1%. Mw = 92 000. Mw/
Mn = 2.9 (Table 1, no. 10). H NMR (THF-d8/DMSO-d6 9:1
), 5.97 (b, 0.77H,
1
v/v, TMS, δ): 7.30 (b, 4.24H,
), 4.73 and 4.45 (2b, 6H, PhOCH2Ph and Ph(CH2OH)2), 3.76
(b, PhCH2NH), 3.32 and 3.28 (2b, 4H, OCH2CHN and
OCH2CH2), 2.84 (b, NHCH, (OH)2 and NH) 1.51 (b, 2H,
OCH2CH2), 1.26 (b, 10H, (CH2)5CH3), 0.86 (b, 3H, CH3). cis
% = 77%.
and
4. Polymerization of OEDHPA. Similar procedures as those
described for polymerizations and purifications of OADHPA
were applied. Yield: 14.2%. Mw = 32 000. Mw/Mn = 1.2(Table 1,
1
no. 20). H NMR (THF-d8/DMSO-d6 9: 1 (v/v), TMS, δ): 7.29
(b, 6.28H, phenyl and
), 6.98 (b, 2H,
), 5.97 (b, 0.72H,
), 5.98 (b, 0.76H,
), 4.89-4.41 (b, 6H, PhOCH2Ph and Ph(CH2OH)2), 3.79 (b,
PhCH2NH), 3.47 (b, 2H, OCH2CH2N), 3.39 (b, 2H,
OCH2CH2CH2), 2.82 (b, NHCH, (OH)2 and NH), 1.53 (b, 2H,
OCH2CH2CH2), 1.28 (b, 10H, (CH2)5CH3), 0.88 (b, 3H, CH3). cis
% = 72%.
), 4.95-4.43 (b, 6H, PhOCH2Ph and Ph(CH2OH)2), 3.80 (b,
PhCH2NH), 3.39 (b, 4H, OCH2CHN and OCH2CH2), 2.86 (b,
(OH)2 and NH), 2.50 (b, NHCH), 1.87 (b, CH(CH3)2), 1.54 (b,
2H, OCH2CH2CH2), 1.28 (b, 10H, (CH2)5CH3), 0.91 (b, 9H,
CH(CH3)2 and CH2CH3). cis % = 76%.
3. Polymerization of OPDHPA. Similar procedures as those
described for polymerizations of OADHPA were applied. The
formed polymer was purified by precipitation of the THF
solution into a large amount of methanol and dried in
For the other data such as Mw and CD, see Tables 1 and 2,
Figures 1-7, and Figures S1-S4 (Supporting Information).
Measurements. H NMR (270 MHz) spectra were recorded
1
on a JEOL LEOLEX-270 spectrometer. The average molecular
weights (Mn and Mw) were evaluated by gel permeation chro-
matography (GPC) by using JASCO liquid chromatograph
instruments with PU-2080, DG-2080-53, CO-2060, UV-2070,
CD-2095, and two polystyrene gel columns (Shodex KF-807 L,
THF eluent, polystyrene calibration). We recorded CD spectra
by using a JASCO J-720WI spectropolarimeter with a Peltier
controller for temperatures at 20 ꢀC (a quartz cell of 1 mm path
length; sample concentration: 0.10 to 2.0 mM based on the
monomer unit). The specific rotations were recorded with
vacuum to give a red poly(OPDHPA). Yield: 85.1%. Mw
=
1
257 000. Mw/Mn = 7.7 (Table 1, no. 12). H NMR (THF-d8/
DMSO-d6 9:1 (v/v), TMS, δ): 7.69-7.20 (3b, 11.23H, phenyl
and

8358 Macromolecules, Vol. 43, No. 20, 2010
Jia et al.
Table 2. Solubility of Poly(ORDHPA)s and Poly(RDHPA)sa
polymer
CHCl3
THF
methanol
DMF
DMSO
poly(OADHPA)
poly(OVDHPA)
poly(OPDHPA)
poly(OEDHPA)
poly(ADHPA)b
poly(VDHPA)b
þþ
þþ
þþ
þþ
-
þþ
þþ
þþ
þþ
-
þ
þ
þ
-
-
-
-
-
-
þ
þ
þ
þþ
þ
þþ
þ
þþ
þ
-
þ
poly(PDHPA)b
-
-
þþ
þþ
þþ
þþ: soluble, þ: partially soluble, -: insoluble. b From ref 6.
a
Figure 4. CD spectra of poly(DoDHPA)s in THF prepared by using
octyl ethers of L-amino alcohols as a chiral cocatalyst (Table 3, nos.
1-3).
Figure 1.þCD spectra of poly(ORDHPA)s in THF prepared by using
(nbd)Rh [η6-(C6H5)B-(C6H5)3] (Table 1, nos. 1, 7, 12, and 18).
Figure 5. CD spectra of poly(DoDHPA)s in THF prepared by using a
1:1 (v/v) mixture of (R)- or (S)-PEA and octyl ether of -alaninol
-phenylalaninol as cocatalysts (Table 3, nos. 6, 7, 10,
L
or octyl ether of
and 11).
L
Figure 2. CD spectra of poly(ORDHPA)s in THF prepared by using
[Rh(nbd)Cl]2/TEA (Table 1, nos. 2, 8, 13, and 19).
Figure 6. CD spectra of poly(DoDHPA)s in THF prepared by using a
1:1 (v/v) mixture of (R)- or (S)-PEA and octyl ether of -valinol as
L
cocatalysts (Table 3, nos. 8 and 9), and by using (R)- or (S)-PEA as
cocatalysts (Table 3, nos. 4 and 5).
Figure 3. CD spectra of poly(ORDHPA)s in THF prepared by using
[Rh(nbd)Cl]2/(R)- or (S)-PEA (Table 1, nos. 4, 5, 10, 11, 15, 16, 20,
and 21).
Polarimeter SEPA-200 (Horiba). The infrared spectra were
recorded on FT/IR-4200 (JASCO).
Results and Discussion
Asymmetric Polymerization and Solubility of the Formed
Polymers. The results of polymerizations are shown in
Table 1. Except for the two polymers of an achiral OEDHPA
Figure 7. Effect of monomer concentration on CD of poly-
(ORDHPA)s by using an achiral catalytic system (Table 4, nos. 1-6).

Article
Macromolecules, Vol. 43, No. 20, 2010 8359
(Chart 3) prepared by using two achiral catalysts (Table 1,
nos. 18 and 19), all of the new resulting polymers (ORDHPA
in Chart 3) showed CD absorptions assigned to their main
chains (Figures 1-3).5 The absorption band at 430 nm is
assigned to the conjugated main chain, and the peaks at 310
nm may arise from a chiral position between adjacent
pendant groups. They indicated that the polymers had a
one-handed helical structure in their main chains.
As shown in Table 2, all of the polymers having octyl
groups (ORDHPA in Chart 3) in this study were soluble in
chloroform and THF and insoluble or partially soluble in
polar solvents such as methanol, DMF, and DMSO. By
introducing an octyl group to the corresponding RDHPAs
(Chart 2) in our previous study,6 the resulting polymers
changed from being insoluble in chloroform and THF and
soluble in polar solvents to being soluble in chloroform and
THF, in which the hydrogen bonds in the resulting polymers
were maintained. This is a very important point because
intramolecular hydrogen bonds are needed to maintain the
one-handed helicity.5
Effect of the Catalytic Systems on the Asymmetric Poly-
merizations. Asymmetric-Induced Polymerization Using the
Achiral Catalysts ((nbd)Rhþ[η6-(C6H5)B-(C6H5)3] or [Rh(nbd)-
Cl]2/TEA). As shown in Figures 1 and 2, chiral ORDHPAs
(OADHPA, OVDHPA, and OPDHPA) were polymerized by
the achiral catalysts (nbd)Rhþ[η6-(C6H5)B-(C6H5)3] or
[Rh(nbd)Cl]2/TEA to give chiral polymers showing CD absorp-
tions assignable to the main chains (Table 1, nos. 1, 7, 8, 12, and
13). Despite the long distance between the chiral group and the
polymerizable group, one-handed helicity was induced. There-
fore, the three chiral monomers having an L-amino ether residue
seemed to be suitable for AIP, where the chiral source is the
L-amino ether residue.
In general, monomers having a bulkier chiral substituent
tend to give polymers showing larger CD absorption at the
main-chain region. However, in these polymerizations (AIP)
mentioned above, some unexpected results were observed.
The absolute [θ] values of poly(OADHPA) and poly-
(OPDHPA) were similar (Table 1, nos. 1, 2, 12, and 13),
and the sign of the [θ] value for poly(OPDHPA) prepared by
using (nbd)Rhþ[η6-(C6H5)B-(C6H5)3] was opposite to that
prepared by using [Rh(nbd)Cl]2/TEA (Table 1, nos. 12 and
13). To explain these unexpected phenomena, we propose the
existence of a third mechanism for the asymmetric polymer-
ization of ORDHPAs other than AIP and HSSP. In the case
of polymerization of chiral ORDHPAs (OADHPA, OVDH-
PA, and OPDHPA) having a chiral bidentate ligand, their
chiral ligand can coordinate to the rhodium catalyst, and the
formed complex can work as a chiral catalytic system in
HSSP. We call it SHSSP.
Helix-Sense-Selective Polymerization Using [Rh(nbd)Cl]2/
(R)- or (S)-PEA. The results of polymerization of ORDH-
PAs by using a chiral catalytic system, [Rh(nbd)Cl]2/
(R)- or (S)-PEA, are shown in Table 1 and Figure 3. Poly-
(OVDHPA)s (Table 1, nos. 10 and 11) and poly(OEDHPA)s
(Table 1, nos. 20 and 21) prepared by using this catalyst
showed CD absorptions having opposite signs for (R)- and
(S)-PEA. Poly(OADHPA)s (Table 1, nos. 4 and 5) and
poly(OPDHPA)s (Table 1, nos. 15 and 16) showed CD
absorptions having the same signs when (R)- or (S)-PEA
was used (Figure 3). The sense of the helicity of the main
chains of poly(OVDHPA) and poly(OEDHPA) can be con-
trolled by the chirality of the cocatalysts, but the helical sense
of poly(OADHPA) and poly(OPDHPA) cannot be con-
trolled in this way. Therefore, we concluded that OVDHPA
and OEDHPA were suitable for HSSP, whereas OADHPA
and OPDHPA were not.
However, in the case of OEDHPA, the [θ] values were
much smaller (Table 1, nos. 20 and 21, and Figure 3) than
those in the case of DoDHPA (Chart 1) (Table 3, nos. 4 and 5,
and Figure 6) . This may also be because the achiral amino
ether residues in OEDHPA coordinated to the rhodium
preferentially compared with chiral PEAs. As a result, the
amino ether ligands suppressed HSSP by chiral PEAs. A
detailed discussion appears in the following section.
Self-Helix-Sense-Selective Polymerization. Why is it that
only in the case of OVDHPA the helical sense of the polymer
was controlled by the chirality of PEA as a cocatalyst? Why is
it that a similar degree of control to OVDHPA was not
possible for OADHPA and OPDHPA? Furthermore, why
were the [θ] values of poly(OEDHPA)s prepared by HSSP so
small? To explain these unexpected behaviors in asymmetric
polymerizations (AIP and HSSP) of ORDHPAs, we present
here details of the third mechanism briefly mentioned above,
SHSSP.
We have already reported that (R)- or (S)-PEA coordi-
nated to the rhodium catalyst acted as a cocatalyst and
controlled the helix sense in the HSSP of the achiral mono-
mer, DoDHPA (Chart 1).5 In this study, the chiral amino
ether residues in the monomer and the resulting polymer
were thought to work as a ligand and cocatalyst of HSSP
instead of (R)- and (S)-PEA.14
To obtain supporting evidence of the possibility of the
existence of the new SHSSP mechanism, a model HSSP
experiment was carried out as follows: an achiral monomer
DoDHPA (Chart 1) was polymerized by using octyl ethers of
L-alaninol, L-valinol, or L-phenylalaninol as cocatalysts. The
results are listed in Table 3. It shows that these L-amino
ethers also are effective for HSSP (Table 3, nos. 1-3, and
Figure 4). Judging from the [θ] values of the formed poly-
mers, the abilities for asymmetric induction of octyl ethers of
L-alaninol (Table 3, no. 1) and L-phenylalaninol (Table 3, no. 3)
are similar to each other, and much better than that of octyl
ether of L-valinol (Table 3, no. 2). These findings were con-
sistent with the results that OADHPA and OPDHPA pro-
duced unexpected behavior in polymerization and OVDHPA
did not. Therefore, they support some contribution of SHSSP
to the asymmetric polymerization of OADHPA and OPDH-
PA having octyl ethers of L-alaninol and L-phenylalaninol,
respectively.
We suppose that the decreasing order of coordination
ability to the rhodium of the L-amino ether residues in
ORDHPA is OADHPA > TEA > OPDHPA, judging from
the following experimental results. Because both poly-
(OADHPA)s prepared by two kinds of achiral catalysts
showed similar [θ] values (Table 1, nos. 1 and 2), the effect
of TEA added as a cocatalyst was thought to be small.
Because both poly(OPDHPA)s prepared by two kinds of
achiral catalysts showed completely different [θ] values
(Table 1, nos. 12 and 13), in the case of polymerization of
OPDHPA by using [Rh(nbd)Cl]2/TEA, TEA may preferen-
tially coordinate to rhodium compared with the bidentate
ligand in OPDHPA; therefore, SHSSP was thought to be
suppressed. In other words, when TEA was used, mainly AIP
occurred, and when TEA was not used, mainly SHSSP
occurred. A detailed discussion of this point will be presented
in a later section.
In addition, DoDHPA was polymerized by using 1:1 molar
ratio mixtures of octyl ethers of L-alaninol, L-valinol, or
L-phenylalaninol and (R)- or (S)-PEA as cocatalysts (Table 3,
nos. 6-11). In the case of mixtures containing octyl ether of
L-alaninol or octyl ether of L-phenylalaninol, the signs of the [θ]
values of the formed polymers were the same irrespective of
the chirality of PEA used (Table 3, nos. 6, 7, 10, and 11 and

8360 Macromolecules, Vol. 43, No. 20, 2010
Jia et al.
Table 3. Polymerizations (HSSP) of DoDHPA by Using [Rh(nbd)Cl]2 As a Catalyst and Octyl Ethers of L-Amino Alcohols (5-7) As
Cocatalystsa,b
Mw (ꢀ106)c
Mw/Mn
[θ]430 (ꢀ103)d
c
no.
cocatalyst
yield (%)
1
2
3
4
octyl ether of L-alaninol (5)
octyl ether of L-valinol (6)
octyl ether of L-phenylalaninol (7)
(R)-PEA
(S)-PEA
(R)-PEA/octyl ether of L-alaninol (5)
(S)-PEA/octyl ether of L-alaninol (5)
(R)-PEA/octyl ether of L-valinol (6)
(S)-PEA/octyl ether of L-valinol (6)
(R)-PEA/octyl ether of L-phenylalaninol (7)
(S)-PEA/octyl ether of L-phenylalaninol (7)
58.3
55.6
37.2
5.36
68.2
81.6
78.5
79.2
79.5
42.3
75.2
1.6
3.5
1.2
3.2
3.5
1.9
2.3
1.3
1.5
1.1
1.1
3.1
2.7
2.3
2.3
1.7
3.2
3.8
2.8
3.1
2.3
2.4
6.9
0.8
11.0
-4.0
4.1
1.9
4.9
-3.1
3.0
3.0
5
6e
7e
8e
9e
10e
e
11
5.5
a See Scheme 1. b At room temperature in toluene, [monomer] = 0.1 mol/L, [monomer]/[catalyst] = 100, [cocatalyst]/[catalyst] = 100. c Determined
by GPC correlating polystyrene standard with THF eluent. d In deg cm2/dmol, 1.0 mmol/L, in THF. e Molar ratio is 1: 1.
3
Figure 5). In the case of the mixtures containing octyl ether of
L-valinol, the signs of the [θ] values of the formed polymers were
opposite (Table 3, nos. 8 and 9, and Figure 6), like the case of
HSSP of DoDHPA by (R)- or (S)-PEA, where the absolute
values of [θ] of the resulting polymers were the same and the
signs were opposite5 (Table 3, nos. 4 and 5, and Figure 6).
Therefore, abilities of octyl ethers of L-alaninol and L-phenyl-
alaninol for asymmetric induction were higher than those of
octyl ether of L-valinol and (R)- or (S)-PEA, and that of octyl
ether of L-valinol was lower than that of PEA. These findings
can also explain the unexpected phenomena observed in the
asymmetric polymerization of OADHPA and OPDHPA
described above.
We supposed that the observed differences in asymmetric
induction ability were mainly caused by the coordinating
ability of the ligands to rhodium. We expect the order of
coordinating ability to decrease as follows: OADHPA >
OPDHPA > (R)- or (S)-PEA > OVDHPA. In other words,
we concluded that in the case of asymmetric polymerization
of OADHPA and OPDHPA, the preferred mechanism was a
combination of SHSSP and AIP. In the case of asymmetric
polymerization of OVDHPA, the preferential mechanism
was HSSP. In the case of OADHPA and OPDHPA, the
resulting one-handed helicity was caused by their L-amino
alcohol residues. Therefore, the sign of the [θ] values of the
formed polymers were the same (Table 1, nos. 4, 5, 15, and
16); therefore, they were not suitable for HSSP. Only the
main chain helicity of poly(OVDHPA) could be controlled
by PEA; therefore, OVDHPA was suitable for HSSP in
addition to AIP. The extent of contribution of the three
mechanisms will be discussed in the last section.
tion. The contribution of AIP may be small because of
the small size of the methyl group at the chiral center of the
L-amino ether residues.
Asymmetric Polymerization Behavior of OVDHPA. Poly-
(OVDHPA)s prepared by using the chiral catalytic system,
[Rh(nbd)Cl]2/(R)- and (S)-PEA, showed CD absorptions
having opposite signs; therefore, they had one-handed
helixes whose senses were opposite (Figure S2 of the Sup-
porting Information and Table 1, nos. 10 and 11). In addi-
tion, poly(OVDHPA)s prepared by using the two achiral
catalytic systems showed CD absorptions (Figure S2 of the
Supporting Information and Table 1, nos. 7-9); therefore,
they also had one-handed helicities. These findings indicated
that OVDHPA was suitable for both HSSP and AIP. In this
case, the ability of PEA for asymmetric induction was thought
to be higher than that of L-valinol residue in OVDHPA
because the coordination ability of PEA was higher than that
of OVDHPA. In other words, the degree of contribution of
HSSP was higher than that of SHSSP. The contribution of
AIP was thought to be small but present.
Asymmetric Polymerization Behavior of OPDHPA. The
two poly(OPDHPA)s prepared by using (R)- or (S)-PEA
showed CD absorptions having the same signs; therefore, the
senses of the helix were found to be the same (Figure S3 of the
Supporting Information and Table 1, nos. 15 and 16). This
unexpected finding indicated that OPDHPA was not suit-
able for HSSP, and the coordination ability of a L-phenyl-
alaninol residue in OPDHPA was thought to be larger than
that of (R)- or (S)-PEA. In the polymerization of OPDHPA,
the main mechanism was some combination of SHSSP and
AIP.
Asymmetric Polymerization Behavior of ORDHPA.
Asymmetric Polymerization Behavior of OADHPA. When
OADHPA was polymerized by using two achiral catalysts,
(nbd)Rhþ[η6-(C6H5)B-(C6H5)3] and [Rh(nbd)Cl]2/TEA,
and a chiral catalytic system, [Rh(nbd)Cl]2/(R)- or (S)-
PEA, the signs of the [θ] values of all the resulting polymers
were unexpectedly the same except for no. 6 (Table 1, nos.
1-5 and Figure S1 of the Supporting Information). There-
fore, SHSSP was thought to be the preferential mechanism
in the asymmetric polymerizations of this monomer by any
catalytic systems by using cocatalysts because the order of
the coordinating ability to the rhodium was thought to be
OADHPA > TEA > PEA.
However, when the concentration of (S)-PEA was high
(no. 6 in Table 1), the sign of the [θ] values was opposite to
that of the others. Therefore, the one-handed helicities (nos.
4-6) may be caused not only by the L-amino ether residues
but also by (R)- or (S)-PEA. The main mechanism of the
asymmetric polymerization was SHSSP, but HSSP also
contributed to the asymmetric induction in the polymeriza-
The sign of [θ] for poly(OPDHPA) prepared by using
(nbd)Rhþ[η6-(C6H5)B-(C6H5)3] was opposite to that by
using [Rh(nbd)Cl]2/TEA (Table 1 and Figure S3 of the
Supporting Information). The coordination ability of TEA
is likely to be higher than that of L-phenylalaninol residue
in OPDHPA. Therefore, in the case of polymerization of
OPDHPA by using [Rh(nbd)Cl]2/TEA, SHSSP was sup-
pressed and AIP dominated. Therefore, AIP had a relatively
large contribution in this polymerization. In summary,
the coordination ability decreases as TEA > OPDHPA >
(R)- or (S)-PEA. Both AIP and SHSSP have larger contribu-
tion than HSSP by PEA in the polymerization of OPDHPA.
Order of the Coordinating Ability to the Rhodium and the
Extent of Contribution of SHSSP. We have discussed above
the order of the coordinating ability of the cocatalysts and
ligand moieties in the monomers judging from the results of
asymmetric polymerizations of the four new monomers by
using four catalytic systems. Finally, we will discuss the order
again this time based on the chemical structures of the
cocatalysts and ligand moieties in the monomers. Because

Article
Macromolecules, Vol. 43, No. 20, 2010 8361
Figure 8. Three mechanisms (HSSP, SHSSP, and AIP) ofasymmetric polymerizations of ORDHPAs having a chiral bidentate ligand by using achiral
and chiral catalytic systems. (a) HSSP by using (R)-PEA. (b) SHSSP by using no cocatalysts. (c) AIP by using TEA.
Table 4. Effect of the Monomer Concentration on Polymerizations of ORDHPAs by Using an Achiral Catalytic System, [Rh(nbd)Cl]2/TEAa
Mw (ꢀ104)b
Mw/Mn
[θ]430 (ꢀ103)c
b
no.
monomer
[monomer] (mol/L)
yield (%)
1
2
3
4
5
6
OADHPA
0.1
56.2
47.5
37.5
43.1
32.8
32.5
14.8
1.8
1.8
6.5
1.9
1.9
2.5
1.1
1.2
4.1
1.3
1.2
4.3
2.8
2.0
-1.5
-1.6
-1.4
0.04
0.02
0.1
0.04
0.02
OVDHPA
a At room temperature in THF, [catalyst]/[TEA(cocatalyst)] = 500, [monomer]/[catalyst] = 100. b Determined by GPC correlating polystyrene
standard with THF eluent. c In deg cm2/dmol, 1.0 mmol/L, in THF.
3
TEA, ORDHPAs, and PEA are tertiary, secondary, and
primary amines, respectively, the decreasing order of the
basicity is TEA > ORDHPA > PEA. The order of the coordi-
nating ability is probably the same. Because the R-carbon
of the asymmetric carbons of OADHPA, OPDHPA, and
OVDHPA are primary, secondary, and tertiary, respectively,
the increasing order of the bulkiness should be OADHPA <
OPDHPA < OVDHPA. Therefore, the decreasing order of
the coordinating ability may be OEDHPA > OADHPA >
OPDHPA > OVDHPA.
extent of the contribution of SHSSP could be controlled by
the concentration of TEA and OADHPA. In addition, the
sign of [θ] could be changed by enhancing [(S)-PEA], that is,
HSSP was realized (Table 1, no.6). Therefore, in the case of
polymerization of OADHPA, SHSSP had large contribu-
tion and AIP had only small contribution. In summary, in
asymmetric polymerization of OADHPA, the contribution
of three mechanisms could be controlled by changing [TEA],
[OADHPA], and [(S)-PEA] because of the small contribu-
tion of AIP (Figure 8a-c)).
Judging from the above discussion and the facts that
ORDHPAs contain a bidentate ligand and TEA and PEA
are monodentate ligands, we expect the coordination ability
to decrease in the order OEDHPA > OADHPA > TEA >
OPDHPA>PEA>OVDHPA. This order reasonably
explains the relative contributions of the three mechanisms
of the asymmetric polymerizations discussed above.
In the case of asymmetric polymerization of OVDHPA by
achiral catalysts, when [TEA] increased (Table 1, nos. 8 and 9,
and Figure S4 of the Supporting Information) or [OADHPA]
decreased (Table 4, nos. 4-6, and Figure 7), the [θ] values did
not decrease. This observation may indicate that the contribu-
tion of SHSSP was originally small. As described above,
OVDHPA was suitable to HSSP (Table 1, nos. 10 and 11).
In summary, in asymmetric polymerization of OVDHPA, the
contribution of AIP and HSSP could be controlled because of
the small contribution of SHSSP (Figure 8a,c)).
In the case of asymmetric polymerization of OPDHPA by
achiral catalysts, the sign of [θ] could be changed by adding
[TEA] (Table 1, nos. 12 to 13, and Figure S3 of the Support-
ing Information). This fact may indicate that the transfor-
mation of SHSSP to AIP occurred. However, the signs of [θ]
could not be changed by enhancing [(S)-PEA] (Table 1, nos.
16 to 17). Therefore, HSSP could not be realized because the
contribution of AIP was too large. In summary, in asym-
metric polymerizations of OPDHPA, the contribution of
AIP and SHSSP could be controlled (Figure 8b,c).
Extent and Control of Contribution of the Three Mecha-
nisms by Changing the Concentrations of TEA, the Mono-
mers, and PEA (Figure 8). As described above in the case of
asymmetric polymerizations of the chiral monomers by
achiral catalysts, two mechanisms, that is, AIP and SHSSP,
were thought to operate. However, the extent of both con-
tributions was not clear. To obtain information on the
extent, we planned to eliminate SHSSP. For this purpose,
we planned to suppress coordination of the chiral ligands in
the monomers to the rhodium by increasing [TEA] or decreas-
ing [monomer]. When [TEA] is higher or [monomer] is lower,
some of the ligands in the monomers coordinating to the
rhodium may be exchanged with TEA. As a result, the extent
of the contribution of SHSSP must be lowered (Figure 8b,c).
In the case of asymmetric polymerization of OADHPA by
achiral catalysts, when [TEA] increased or [OADHPA]
decreased, the [θ] values decreased (Table 1, nos. 2 and 3,
or Figure S4 of the Supporting Information and Table 4, nos.
1-3, and Figure 7). This fact indicated that the asymmetric
polymerization proceeded by both AIP and SHSSP and the
Conclusions
Three mechanisms for the asymmetric polymerizations of four
new monomers were discussed, HSSP, AIP, and SHSSP, the
latter being proposed for the first time in this Article. To
illuminate the contribution of the three mechanisms to each

8362 Macromolecules, Vol. 43, No. 20, 2010
Jia et al.
asymmetric polymerization, the order of coordination ability was
investigated. The following order was postulated: OEDHPA >
OADHPA> TEA > OPDHPA > PEA > OVDHPA. As a
result of the differing coordination abilities, the contributions to
the three mechanisms were different in each polymerization. In
the case of polymerization of OADHPA, SHSSP was the
preferential mechanism. In the case of polymerization of OVDH-
PA, HSSP was the preferential mechanism with some contribu-
tion from AIP, whereas the contribution of SHSSP was small. In
the case of polymerization of OPDHPA, AIP was thought to be
the main mechanism, but the contribution of SHSSP was
significant. Therefore, only OVDHPA was suitable for both
HSSP and AIP. VDHPA (Chart 2) was also suitable for both
HSSP and AIP, as previously reported. In addition, by changing
the concentrations of the cocatalysts and the monomers, the
extent of the contribution of the three mechanisms could be
controlled to some extent.
(3) (a) Suzuki, Y.; Tabei, J.; Shiotsuki, M.; Inai, Y.; Sanda, F.;
Masuda, T. Macromolecules 2008, 41, 1086. (b) Nakako, H.;
Nomura, R.; Tabata, M.; Masuda, T. Macromolecules 1999, 32,
2861. (c) Ohsawa, S.; Maeda, K.; Yashima, E. Macromolecules
2007, 40, 9244. (d) Yashima, E.; Maeda, Y.; Okamoto, Y. J. Am.
Chem. Soc. 1998, 120, 8895. (e) Otsuka, I.; Hongo, T.; Nakade, H.;
Narumi, A.; Sakai, R.; Satoh, T.; Kaga, H.; Kakuchi, T. Macromole-
cules 2007, 40, 8930. (f) Otsuka, I.; Sakai, R.; Kakuchi, R.; Satoh, T.;
Kakuchi, T. Eur. Polym. J. 2008, 44, 2971. (g) Liu, J. H.; Yan, J. J.;
Chen, E. Q.; Lam, J. W. Y.; Dong, Y. P.; Liang, D. H.; Tang, B. Z.
Polymer 2008, 49, 3366. (h) Lam, J. W. Y.; Dong, Y.; Cheuk, K. K. L.;
Tang, B. Z. Macromolecules 2003, 36, 7927. (i) Lam, J. W. Y.; Dong,
Y.; Cheuk, K. K. L.; Law, C. C. W.; Lai, L. M.; Tang, B. Z. Macro-
molecules 2004, 37, 6695. (j) Gao, G.; Sanda, F.; Masuda, T. Macro-
molecules 2003, 36, 3932. (k) Gao, G.; Sanda, F.; Masuda, T.
Macromolecules 2003, 36, 3938. (l) Sanda, F.; Araki, H.; Masuda,
T. Macromolecules 2004, 37, 8510. (m) Sanda, F.; Terada, K.; Masuda,
T. Macromolecules 2005, 38, 8149. (n) Sanda, F.; Araki, H.; Masuda, T.
Macromolecules 2005, 38, 10605.
(4) P and M mean a right- and left-handed helicity of main chains,
respectively. D and L mean the chirality of the substituents in the
monomers.
Acknowledgment. Partial financial support through a Grant-
in-Aid for Scientific Research (B) (nos. 16350061 and 19350054)
from the Japan Society for the Promotion of Science and a Grant-
in-Aid for Scientific Research in a Priority Area “Super-
Hierarchical Structures” (nos. 18039011 and 19022009) from the
Ministry of Education, Culture, Sports, Science and Technology,
Japan, through the Asahi Glass Foundation, through the Iketani
Science and Technology Foundation, and through a Grant for
Promotion of Niigata University Research Projects is gratefully
acknowledged.
(5) (a) Aoki, T.; Kaneko, T.; Maruyama, N.; Sumi, A.; Takahashi, M.;
Sato, T.; Teraguchi, M. J. Am. Chem. Soc. 2003, 125, 6346.
(b) Hadano, S.; Kishimoto, T.; Hattori, T.; Tanioka, D.; Teraguchi,
M.; Aoki, T.; Kaneko, T.; Namikoshi, T.; Marwanta, E. Macromol.
Chem. Phys. 2009, 210, 717. (c) Sato, T.; Aoki, T.; Teraguchi, M.;
Kaneko, T.; Kim, S. Y. Polymer 2004, 45, 8109. (d) Umeda, Y.;
Kaneko, T.; Teraguchi, M.; Aoki, T. Chem. Lett. 2005, 34, 854.
(e) Kaneko, T.; Umeda, Y.; Yamamoto, T.; Teraguchi, M.; Aoki, T.
Macromolecules 2005, 38, 9420. (f) Aoki, T.; Kaneko, T. Polym.
J. 2005, 37, 717. (g) Aoki, T.; Kaneko, T.; Teraguchi, M. Polymer 2006,
47, 4867. (h) Kaneko, T.; Umeda, Y.; Honge, J.; Hadano, S.; Teraguchi, M.;
Aoki, T. Macromolecules 2007, 40, 7098. (i) Hadano, S.; Teraguchi, M.;
Kaneko, T.; Aoki, T. Chem. Lett. 2007, 36, 220. (j)Katagiri, H.;Kaneko, T.;
Teraguchi, M.; Aoki, T. Chem. Lett. 2008, 37, 390. (k) Liu, L.; Oniyama,
Y.; Zang, Y.; Hadano, S.; Aoki, T.; Teraguchi, M.; Kaneko, T.; Namikoshi,
T.; Marwanta, E. Polymer 2010, 51, 2460–2464.
Supporting Information Available: CD spectra for the
polymers prepared and a CD spectrum for the chiral catalytic
system. The material is available free of charge via the Internet at
http://pubs.acs.org.
(6) Jia, H.; Teraguchi, M.; Aoki, T.; Abe, Y.; Kaneko, T.; Hadano, T.;
Namikoshi, T.; Marwanta, E. Macromolecules 2009, 42, 17.
(7) Our unpublished data. Submitted for publication.
References and Notes
(8) In ORDHPA, DH and PA mean dihydroxy groups and phenyl-
acetylene, respectively. In OADHPA, OVDHPA, and OPDHPA,
OA, OV, and OP mean the residue of the octyl ether of L-alaninol,
L-valinol, and L-phenylalaninol, respectively.
(9) Schrock, R. R.; Osborn, J. A. Inorg. Chem. 1970, 9, 2339.
(10) Dickman, D. A.; Meyers, A. L.; Smith, G. A.; Gawley, R. E. Org.
Synth. 1990, 530.
(11) Telfer, S. G.; Sato, T.; Kuroda, R.; Lefebvre, J.; Leznoff, D. B.
Inorg. Chem. 2004, 43, 421.
(12) Wieland, H. Ber. 1907, 40, 1676.
(13) Blackburn, L.; Taylor, R. J. K. Org. Lett. 2001, 3, 1637.
(14) The formation of a chiral complex of rhodium from the chiral
catalytic system, [Rh(nbd)Cl]2 and octyl ether of L-valinol
was supported by UV-CD spectrum (Figure S5 in Supporting
Information).
(1) Aoki, T.; Kokai, M.; Shinohara, K.; Oikawa, E. Chem. Lett. 1993,
2009.
(2) (a) Aoki, T.; Shinohara, K.; Kaneko, T. Polymer 1995, 36, 2403. (b)
Aoki, T.; Shinohara, K.; Kaneko, T.; Oikawa, E. Macromolecules 1996,
29, 4192. (c) Aoki, T.; Kobayashi, Y.; Kaneko, T.; Oikawa, E.;
Yamamura, Y.; Fujita, Y.; Teraguchi, M.; Nomura, R.; Masuda, T.
Macromolecules 1999, 32, 79. (d) Kaneko, T.; Yamamoto, T.; Aoki, T.;
Oikawa, E. Chem. Lett. 1999, 623. (e) Shinohara, K.; Aoki, T.;
Kaneko, T. J. Polym. Sci., Part A: Polym. Chem. 2002, 40, 1689.
(f) Teraguchi, M.; Suzuki, J.; Kaneko, T.; Aoki, T.; Masuda, T.
Macromolecules 2003, 36, 9694. (g) Aoki, T.; Fukuda, T.; Shinohara,
K.; Kaneko, T.; Teraguchi, M.; Yagi, M. J. Polym. Sci., Part A: Polym.
Chem. 2004, 42, 4502. (h) Teraguchi, M.; Mottate, K.; Kim, S. Y.; Aoki,
T.; Kaneko, T.; Hadano, S.; Masuda, T. Macromolecules 2005, 38,
6367.