Molecular design of the polymer forming the complex with metal. Part IV. Complexation of pyridine-containing polyisoprene with zinc

Article abstract of DOI:10.1016/S0022-2860(00)00961-3

Two types of polyisoprenes modified by N-pyrid-2-ylmethyl amide (MPY) group were synthesized, and their complexation with ZnCl₂ and the thermal property of complexes were investigated. Although these polymers are viscous liquid, the complex is solid at room temperature. MPY modified polyisoprene in which MPY connected a main chain without a spacer (MPYIP) shows the non-stoichiometric complexation, so that the melting temperature of the complex is low (105°C). On the other hand, MPY modified polyisoprene with a C5 spacer (MPYC5IP) shows the high melting temperature (143°C). It is surprising that the glass-transition temperatures of the complexes are almost as same as that of polyisoprene. These results indicate that the presence of the spacer effectively enhances the aggregation of polymers. As a result, MPY is a novel functional structure, since MPY-ZnCl₂ complex functions as an excellent hard-segment in various flexible polymers.

Full text of DOI:10.1016/S0022-2860(00)00961-3

Journal of Molecular Structure 562 (2001) 205±213
www.elsevier.nl/locate/molstruc
Molecular design of the polymer forming the complex with metal.
Part IV. Complexation of pyridine-containing polyisoprene
with zinc
*
N. Moriguchi, T. Tsugaru, S. Amiya
Analytical Research Center, Kuraray Co. Ltd, 2045-1 Sakazu, Kurashiki, Okayama 710-8691, Japan
Received 25 October 2000; accepted 22 November 2000
Abstract
Two types of polyisoprenes modi®ed by N-pyrid-2-ylmethyl amide (MPY) group were synthesized, and their complexation
with ZnCl2 and the thermal property of complexes were investigated. Although these polymers are viscous liquid, the complex
is solid at room temperature. MPY modi®ed polyisoprene in which MPY connected a main chain without a spacer (MPYIP)
shows the non-stoichiometric complexation, so that the melting temperature of the complex is low (1058C). On the other hand,
MPY modi®ed polyisoprene with a C5 spacer (MPYC5IP) shows the high melting temperature (1438C). It is surprising that the
glass-transition temperatures of the complexes are almost as same as that of polyisoprene. These results indicate that the
presence of the spacer effectively enhances the aggregation of polymers. As a result, MPY is a novel functional structure, since
MPY±ZnCl2 complex functions as an excellent hard-segment in various ¯exible polymers. q 2001 Elsevier Science B.V. All
rights reserved.
Keywords: Thermoplastic elastomers; Polyisoprene; Metal coordination; Complexation
1. Introduction
organic polymer and an inorganic substance have
been of interest as novel functionalized and high-
performance polymer materials [3].
New polymer materials have been developed by
the invention of new monomers or catalysts of the
polymerization [1]. The chemical modi®cation and
functionalization of a polymer have also been
performed. The technology of polymer blends is
especially an excellent strategy for the effective
development of advanced polymer materials [2].
Therefore numerous researches in this ®eld have
been reported so far. Most of these investigations
were performed with the combination of different
types of organic polymers. Recently, blends of an
A metal-containing polymer is the unique material
consisting of the organic polymer with a functiona-
lized group as a ligand [4,5]. The functionalized group
forms the complex with a metal. The metal coordina-
tion interactions and crystallization of metal
complexes obtained by complexation have been
recently reported as a new type of the driving force
of hard-segment aggregation in thermoplastic
elastomers [6±12]. The degree of aggregation of
hard-segments and phase-separation rate of hard and
soft segments essentially in¯uence on their mechan-
ical and thermal properties [13]. Therefore the high-
performance thermoplastic elastomers should be
* Corresponding author.
E-mail address: shigetoshi_amiya@kuraray.co.jp (S. Amiya).
0022-2860/01/$ - see front matter q 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-2860(00)00961-3

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N. Moriguchi et al. / Journal of Molecular Structure 562 (2001) 205±213
obtained by the enhancement of the hard-segment
aggregation.
(100 g) in an autoclave, and stirred at 1808C for 15 h.
After the reaction mixture was cooled to 808C,
methanol (2.7 ml) was added and stirred for 15 h.
The unreacted methanol was evaporated under
vacuum, then the product was obtained as clear liquid
(yield .99%). The degree of substitution was 0.032
(3.2 mol% per isoprene unit) by the 1H-NMR
In the previous papers [14±16], we found that the
N-pyrid-2-ylmethyl amide (MPY) group, which was
introduced to poly(dimethyl siloxane) with the substi-
tution degree of 1.6±9.0 mol% (MPYSI), formed the
stoichiometric 1:1 complex with zinc chloride
(ZnCl2). Although the uncomplexed MPYSI was
liquid at room temperature, the MPYSI-ZnCl2
complex had the high melting temperature at about
1408C. The elastic and thermoplastic properties were
also observed in this MPYSI±ZnCl2 complex [15]. By
means of the X-ray crystal analysis and EXAFS spec-
troscopy, we con®rmed that the structure of the
MPY±Zn complex formed the chelate ring, so that
the structure was rigid and planar. In addition, the
complex structure had the large dipole moment.
Consequently we concluded that the remarkable
strong aggregation came from these unique character-
istics of the MPY±Zn complex [16].
In the present paper, we synthesized two types of
MPY-modi®ed polyisoprene. The complexation of
the MPY group and ZnCl2 in these polymers and the
thermal properties of the polymer were investigated.
The purpose of this study is to clarify the steric in¯u-
ence on the aggregation of the MPY±Zn complex, and
to con®rm the validity of the new type of hard-
segment, that is MPY, to various polymer systems
other than poly(dimethyl siloxane).
1
measurements. H-NMR (CDCl3): d1.3±1.65 (yCH
±CH2±, ±CHyCHC(CH3)±, ±C(CH3)yCH2), d2.0
(±CHyC(CH3)CH2±), d2.2±3.0 (±CH(C(yO)OCH3)
±CH(C(yO)OH)±), d3.60 (s, CH3OCyO).
2.3. Synthesis of MPY-branched polyisoprene
(MPYIP) (2)
Carboxylic acid-branched polyisoprene (31 g) and
DMF (0.5 ml) were dissolved in THF (150 ml). In this
solution, excess thionyl chloride was added, and
stirred under a N2 atmosphere at room temperature
for 2 h. After the unreacted thionyl chloride and the
solvent were evaporated, the residue was dissolved in
THF (200 ml). Excess of 2-aminomethyl pyridine and
triethylamine (18 ml) were added to this solution, and
stirred under a N2 atmosphere at 08C overnight. The
product was precipitated with methanol and dried
under vacuum, then obtained as clear liquid (yield
96%). The degree of substitution was 0.031 (3.1 mol%
1
1
per isoprene unit) by the H-NMR measurements. H-
NMR (CDCl3): d1.3±1.65 (yCH±CH2±, ±CHy
C(CH3)±, ±C(CH3)yCH2), d2.0 (±CHyC(CH3)CH2±
), d2.2±3.0 (±CH(C(yO)OCH3)±CH(C(yO)OH)±),
d3.60 (s, CH3OCyO), d4.52 (d, ±CH2±Py), d4.70
(CH2yC(CH3)±), d5.10 (±CHyC(CH3)±), d6.7±7.0
(±NH±CH2±Py), d7.18, d7.28 (t 1 d, PyH-3, 5),
d7.62 (t, PyH-4), d8.52 (d, PyH-6).
2. Experimental
2.1. Materials
Zinc chloride (99.9%) was purchased from Wako
Chemical Co. and used as received. Polyisoprene (the
number-average molecular weight 20 000) was
produced by Kuraray Co. and used as received.
Tetrahydrofuran (THF), N, N-dimethylformaide
(DMF) and triethylamine were dried with calcium
hydride, distilled and then stored over molecular
sieves 4A. All other solvents and reagents were used
as received from the commercial distributors.
2.4. Synthesis of 6-(tert-butoxycarbonylamino)-
hexanoic acid (3)
6-aminohexanoic acid (12 g) and triethylamine
(19.3 ml) were dissolved in water (60 ml). In this
solution, 2-(tert-butoxycarbonyloxyimino)-2-pheny-
lacetonitorile (25 g) in dioxane solution (60 ml) was
added, and stirred at room temperature for 5 h. The
product was extracted with ethyl acetate and the
solvent was evaporated, then the product was obtained
as clear liquid (yield 23 g). 1H-NMR (DMSO-d6):
d1.2±1.6 (±NH±CH2±CH2CH2CH2±CH2C(yO)OH,
(CH3)3CO±), d2.20 (t, ±CH2C(yO)OH), d2.90
2.2. Synthesis of carboxylic acid-branched
polyisoprene (1)
Maleic anhydride (5 g) was added to polyisoprene

N. Moriguchi et al. / Journal of Molecular Structure 562 (2001) 205±213
207
(m, ±CH2NH±), d6.75 (t, ±CH2NH±), d12.05 (s, ±
CH2C(yO)OH).
were used as starting materials, and a procedure
similar to that of MPY-branched polyisoprene
(MPYIP) was used. The product was obtained as
clear liquid (yield 91%). The degree of substitution
was 0.030 (3.0 mol% per isoprene unit) by the H-
NMR measurements. 1H-NMR (CDCl3): d1.3±1.8
2.5. Synthesis of 1-(N-pyrid-2-ylmethyl)-6-(tert-
butoxycarbonylamino)-hexanamide (4)
1
6-(tert-butoxycarbonylamino)-hexanoic acid (22 g)
and 2-aminomethylpyridine (9.7 g) were dissolved in
ethyl acetate (150 ml). In this solution, triethylamine
(13.3 ml) and 1,3-dicyclohexylcarbodiimide (DCC,
19.6 g) in ethyl acetate solution (100 ml) were
added at 08C, stirred at room temperature for 48 h.
The reaction mixture was poured into the sodium
bicarbonate aqueous solution, and the product was
extracted to an organic phase. The product was puri-
®ed by crystallization from ethyl acetate/hexane, and
obtained as white crystals (yield 83%). 1H-NMR
(DMSO-d6): d1.2±1.6 (±NH±CH2±CH2CH2CH2±
CH2C(yO)±, (CH3)3CO±), d2.19 (t, ±CH2C(yO)±),
d2.90 (m, ±CH2NH±), d4.38 (d, ±CH2±Py), d6.75 (t,
±CH2CH2NH±), d7.25 (t 1 d, PyH-3, 5), d7.76 (t,
PyH-4), d8.40, d8.50 (t 1 d, ±NHCH2±Py, PyH-6).
(yCH±CH2±, ±CHyC(CH3)±, ±C(CH3)yCH2,
±
NH±CH2CH2CH2CH2CH2±C(yO)±), d2.0 (±CHyC
(CH3)CH2±), d2.30 (t, ±NH±CH2CH2CH2CH2CH2±
C(yO)±), d3.10 (m, ±NH±CH2CH2CH2CH2CH2±C
(yO)±), d3.60 (s, CH3OCyO), d4.52 (d, ±CH2±
Py), d4.70 (CH2yC(CH3)±), d5.10 (±CHyC (CH3)±),
d5.6±6.2 (m, ±NH±CH2CH2CH2CH2CH2±C(yO)±),
d6.87 (±NH±CH2±Py), d7.18, d7.28 (t 1 d, PyH-3,
5), d7.62 (t, PyH-4), d8.52 (d, PyH-6).
2.8. Preparation of zinc complex
An appropriate amount of zinc chloride in methanol
solution was mixed to MPYIP or MPYC5IP in THF
solution. The solvents were evaporated, then the
complex was obtained. The MPYIP±ZnCl2 complex
with the mole ratio (MPY group)/ZnCl2 ˆ 1:2 was
coded MPYIP±ZnCl2 1:2.
2.6. Synthesis of 1-(N-pyrid-2-ylmethyl)-6-amino-
hexanamide (5)
2.9. General procedure
1-(N-pyrid-2-ylmethyl)-6-(tert-butoxycarbonyla-
mino)-hexanamide (22 g) was added to tri¯uoroacetic
acid (58 ml) and water (4.3 ml), and the reaction
mixture was stirred at 08C for 1 h. After the solvent
was evaporated, the reaction mixture was neutralized
with the sodium bicarbonate aqueous solution. The
product was extracted with ethyl acetate and the
solvent was evaporated, then the mixture of 1-(N-
pyrid-2-ylmethyl)-6-amino-hexanamide and sodium
tri¯uoroacetate was obtained as white powder (yield
26 g). The purity of 1-(N-pyrid-2-ylmethyl)-6-amino-
The FT-IR measurements were performed on a
JEOL JIR-5500. The IR spectrum was obtained
directly (liquid sample) or from powders in potassium
bromide medium (solid sample). Each spectrum was
generated by signal averaging 10 scans at a resolution
of 2.0 cm21
.
The differential scanning calorimetry (DSC)
measurements were performed on a Perkin±Elmer
DSC-7 differential scanning calorimeter. Each sample
(ca. 5 mg) was measured under a nitrogen atmosphere
with a DSC-scan rate of 10 K/min. Indium was used
as a calibration standard.
1
hexanamide was about 60%. H-NMR (DMSO-d6):
d1.28 (m, ±CH2CH2CH2C(yO)±), d1.52 (m, ±CH2
CH2CH2C(CyO)±), d2.19 (t, ±CH2C(yO)±), d2.71
(m, ±CH2NH2), d4.38 (d, ±CH2±Py), d7.25 (t 1 d,
PyH-3, 5), d7.76 (t, PyH-4), d8.40, d8.50 (t 1 d, ±
NHCH2±Py, PyH-6).
3. Results and discussion
3.1. Synthesis of MPYIP and MPYC5IP
2.7. Synthesis of MPY-branched polyisoprene with C5
spacer (MPYC5IP) (6)
The synthetic route of MPYIP (2) is shown in Fig.
1. The polymer modi®ed with the MPY group has
been obtained by the reaction of 2-aminomethyl-
pyridine and carboxylic acid connected with a
Carboxylic acid-branched polyisoprene (20 g) and
1-(N-pyrid-2-ylmethyl)-6-amino-hexanamide (20 g)

208
N. Moriguchi et al. / Journal of Molecular Structure 562 (2001) 205±213
O
O
O
O
O
O
CH3OH
1
O
OH
OCH3
O
1) SOCl2 / THF / DMF
2)
N
CH2NH2
/ THF / DMF
2
O
N
H
O
OCH3
N
Fig. 1. Synthetic route of MPYIP (2).
polymer [15]. Therefore, in order to introduce the
MPY group to polyisoprene, ®rst we synthesized the
maleic anhydride-branched polyisoprene by an ene
reaction. Next the carboxylic acid-branched polyiso-
prene (1) was obtained by opening of the maleic
anhydride ring with methanol. Then MPYIP (2) was
obtained by the reaction with 2-aminomethylpyridine.
The MPY-modi®ed polyisoprenes with various
substitution degrees are quantitatively synthesized
by this procedure. The substitution degree of MPY
group to the MPYIP was 3.1 mol% per isoprene
monomer unit.
The MPY group of MPYIP is adjacent to the b-
methyl ester group. In the previous papers [15,16], we
indicated that the stoichiometric complexation of the
MPY group with ZnCl2 was necessary to the improve-
ment of the material property. The adjacent methyl
ester group possibly prevents the complex formation
and/or aggregation by the steric hindrance. In order to
clarify this effect, we also synthesized MPYC5IP (6)
with a C5 spacer between the MPY group and the
isoprene main chain.
The synthetic route of the MPY group with a C5
spacer is shown in Fig. 2. The MPY group with the
spacer was obtained from 6-aminohexanoic acid as a
starting compound. First the amino group was
protected with a tert-butoxycarbonyl group, and then
6-(tert-butoxycarbonylamino)-hexanoic acid (3) was
obtained. Second 1-(N-pyrid-2-ylmethyl)-6-(tert-
butoxycarbonylamino)-hexanamide (4) was obtained
by esteri®cation of carboxylic acid of the compound 3
and 2-aminomethylpyridine. Third 1-(N-pyrid-2-
ylmethyl)-6-amino-hexanamide (5) was obtained by
removal of the protecting group of the compound 4
with tri¯uoroacetic acid. The compound 5 is the
MPY group with the C5 spacer. Thus the
MPYC5IP (6), which is the MPY-branched polyiso-
prene with the spacer, was obtained by the reaction of

N. Moriguchi et al. / Journal of Molecular Structure 562 (2001) 205±213
209
Fig. 2. Synthetic route of MPYC5IP (6).
the carboxylic acid-branched polyisoprene (1) and the
compound 5. The substitution degree of the MPY
group in the MPYC5IP is 3.0 mol% per isoprene
monomer unit.
Table 1 shows the characteristics of the MPYIP and
MPYC5IP. Both the MPY-modi®ed polyisopurenes
without ZnCl2 were viscous liquid around room
temperature. However, as the amount of ZnCl2 in
these polymers increased, the viscosity of the polymer
increased. Finally the ZnCl2 complexes of MPYIP and
MPYC5IP were observed as solid when more than an
equivalent ZnCl2 to the MPY group was added, which
is the same behavior as MPYSIs (MPY-modi®ed
poly(dimethyl siloxane)) [15].
3.2. IR study
In the previous paper [15], we indicated that the IR
Table 1
Characteristics of MPY-modi®ed polyisoprene
Type of modi®cation
Degree of substitution (mol%)
Viscositya (P)
MPYIP
Branched
3.1
3.0
1.0 £ 104
1.6 £ 104
MPYC5IP
Branched with a C5 spacer
a
Zero-share viscosity (h0) at 508C.

210
N. Moriguchi et al. / Journal of Molecular Structure 562 (2001) 205±213
Table 2
Characteristic IR wavenumbers of MPYIP±ZnCl2 complexes with various ratios of ZnCl2 to MPY group
MPY/ZnCl2 (mol/mol)
Amide group
n(CyO) (cm21
1664
Pyridine ring
)
d(py) (cm21
)
MPYIP
1:0
401
MPYIP±ZnCl2
1:0.5
1:1
1664, 1645, 1610
1664, 1645, 1610
1664, 1645, 1610
418, 401
418
1:2
418
absorption bands of the amide group and the pyridine
ring in the MPY group were stoichiometrically shifted
when ZnCl2 was added to various types of the MPY-
modi®ed poly(dimethyl siloxane). These shifts of the
IR bands mean that the MPY group in the polymer is
formed by the complex with ZnCl2 [17]. Table 2
shows the characteristic IR wavenumbers of the
MPYIP±ZnCl2 complexes with various ratio of
ZnCl2 to the MPY group. The out-of-plane pyridine
ring deformation (d(py)) wavenumber of the MPYIP
was 401 cm21. However, that of the MPYIP±ZnCl2
was observed at the higher wavenumber (418 cm21).
As shown in the X-ray crystal analysis of the low
molecular-weight model compounds [16], this shift
indicates that a Zn atom of ZnCl2 coordinates to a N
atom of the pyridine ring. When an equivalent ZnCl2
to the MPY group was added, the lower wavenumber
(401 cm21) of d(py) disappeared. This result suggests
that the ZnCl2 stoichiometrically coordinates to a
pyridine ring so as to form the 1:1 complex.
of the Zn atom to the O atom of the amide group,
which suggests that the chelate ring consisted of the
Zn atom, the O atom of the amide group and the N
atom of the pyridine is formed. However, the absorp-
tion bands at the higher wavenumber were still present
at the addition of an excess of ZnCl2 to the MPY
group. We do not exactly assign these absorption
bands, since the weak absorption band of CyC (of
isoprene unit) stretching overlaps. Nevertheless, the
absorption band at 1645 cm21, at least, is probably
assigned the uncomplexed and/or hydrogen-bonded
amide group. As a result, the uncomplexed amide
group of the MPYIP exists even if an excess of
ZnCl2 to the MPY group is added. This indicates
that the amide group of the MPYIP forms the non-
stoichiometric complex with ZnCl2 in contrast to the
pyridine group above described.
The reason for such
a
non-stoichiometric
complexation in the MPYIP±ZnCl2 system is prob-
ably the steric hindrance of the adjacent methyl
ester group. In order to clarify this point, we also
investigated the complexation of the MPYC5IP,
which has the C5 spacer between the MPY group
and the isoprene main chain, with ZnCl2 (Table 3).
The stoichimetric coordination of ZnCl2 to the
pyridine ring was observed like a similar behavior
The CyO stretching (n(CyO)) wavenumber of the
amide group in the uncomplexed MPYIP was
1664 cm21 (Table 2). When ZnCl2 was added to the
MPYIP, the absorption bands at the lower wave-
number (1645 and 1610 cm21) were observed. The
band at 1610 cm21 obviously shows the coordination
Table 3
Characteristic IR wavenumbers of MPYC5IP±ZnCl2 complexes with various ratios of ZnCl2 to MPY group
MPY/ZnCl2 (mol/mol)
Amide group
n(CyO) (cm21
1645
Pyridine ring
)
d(py) (cm21
)
MPYC5IP
1:0
401
MPYC5IP±ZnCl2
1:0.5
1:1
1645, 1610
1645, 1610
1645, 1610
418, 401
418
1:2
418

N. Moriguchi et al. / Journal of Molecular Structure 562 (2001) 205±213
211
Table 4
Melting temperature (Tm) and enthalpy (DHm) of MPYIP±ZnC2 and MPYC5IP±ZnCl2 complexes
MPY/ZnCl2 (mol/mol)
Tm (8C)
DHma (J/mol)
MPYIP±ZnCl2
1:1
1:2
103
105
3.6 £ 103
3.5 £ 103
MPYC5IP±ZnCl2
1:1
1:2
111
143
3.4 £ 103
4.7 £ 103
a
DHm is calibrated as the value per MPY group sustituted in MPYIP and MPYC5IP.
as the MPYIP. In addition, the shift of n(CyO) wave-
number of the amide group was observed (1645±
1610 cm21). These results suggest that ZnCl2 also
coordinates to the O atom of the amide group and
the N atom of the pyridine ring in the MPYC5IP±
ZnCl2 system. Unfortunately, it was impossible to
prove that the MPY group of the MPYC5IP formed
the stoichiomeric complex with ZnCl2, since the
n(CyO) band of the amide group between the C5
spacer and the isoprene chain overlapped to that of
the MPY group.
room temperature, although the uncomplexed
MPYIP and MPYC5IP are liquid (Table 1). This
behavior is similar to that of the MPYSI±ZnCl2
complex. When an equivalent ZnCl2 to the MPY
group are added, the ZnCl2 complex of the MPYSI
in which the MPY group is branched with more than
4.0 mol% of the substitution degree has the high
melting temperature (about 1408C) and enthalpy
(about 8:0 £ 103 J=mol†: The result from the thermal
analysis of the MPYSI±ZnCl2 complex indicates that
the MPY±Zn complexes in the MPYSI strongly
aggregate each other by the thermal attractive inter-
action as a driving force.
3.3. Thermal analysis
Table 4 shows the melting temperature (Tm) and
enthalpy (DHm) of the MPYIP±ZnCl2 and
MPYC5IP±ZnCl2 complexes with various mole ratios
of ZnCl2 to the MPY group. The melting temperatures
of MPYIP±ZnCl2 (1:1) and MPYC5IP±ZnCl2 (1:1)
were lower (103 and 1118C, respectively) than
expected by the result of the MPYSI±ZnCl2 system.
In addition, even if two times as much ZnCl2 as the
stoichiometric ratio of the MPY±ZnCl2 complex was
added, Tm was still 1058C. On the other hand, the Tm of
the MPYC5IP±ZnCl2 (1:2) was 1438C as expected
(Fig. 3). DHm of the MPYC5IP±ZnCl2 (1:2) was
also higher than those of other complexes. Obviously,
the MPY±Zn complexes in the MPYC5IP±ZnCl2
(1:2) strongly aggregate each other.
The MPYIP±ZnCl2 and MPYC5IP±ZnCl2 com-
plexes with more than an equivalent mole ratio of
ZnCl2 to the MPY group is obtained as solid at
The degree of aggregation of the MPY±ZnCl2
complexes is in¯uenced by the structure of the aggre-
gates. In the aggregates with the high Tm, the MPY±Zn
complexes orderly line up [16]. However, since the
MPY±Zn complex in the MPYIP is adjacent the bulky
methyl ester group and isoprene main chain, the MPY±
Zn complexes are not able to line up by the steric
hindrance. In addition, the steric hindrance causes a
non-stoichiometric complexation of the MPY group in
the MPYIP with ZnCl2. This type of complexation has
Fig. 3. DSC pro®les of MPYC5IP±ZnCl2 complexes with the mole
ratio of MPY/ZnCl2, 1:1 and 1:2.

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N. Moriguchi et al. / Journal of Molecular Structure 562 (2001) 205±213
Table 5
Glass-transition temperature (Tg) of MPYIP, MPYC5IP and their
place in the MPYC5IP±ZnCl2 complex. However,
Tg of the MPYIP±ZnCl2 (1:2) was slightly higher
than that of the uncomplexed MPYIP. This result
suggests that the aggregation of hard-segments has
in¯uence on soft-segments in the MPYIP±ZnCl2
complex with an excess of ZnCl2 because of the
close arrangement of the MPY±Zn complex and the
isoprene unit. This result also indicates that the MPY
group of MPYC5IP, which has the C5 spacer, is
superior as the hard-segment to that of MPYIP.
ZnCl2 complexes
MPY/ZnCl2 (mol/mol)
Tg (8C)
Polyisoprene
0:0
1:0
1:1
1:2
261.2
260.4
261.2
257.0
MPYIP±ZnCl2
MPYC5IP±ZnCl2
1:0
1:1
1:2
261.2
262.3
261.9
4. Conclusions
the defective components such as a non-chelate
complex and free Zn salts, which also prevent the
complex from forming a well-ordered structure [14].
Since the MPYC5IP has the C5 spacer between the
MPY group and the maleic ester group, the MPY group
is not hindered from the formation the complex with
ZnCl2 by the bulky methyl methyl ester group. The
complexstructureformedinthiswaymustbetheunique
chelate structure, so that the strong inter-complex inter-
action is shown. As the MPY group is mobile due to the
¯exible spacer, the MPY±Zn complexes aggregate
rather effectively. Thus the MPYC5IP±ZnCl2 (1:2)
has the high Tm. From these results, we con®rm that
the spacer is so effective to accomplish the strong aggre-
gation of MPY±Zn complexes.
Inthepresentstudy,twotypesofpolyisoprenesmodi-
®ed by the MPY group, those are the MPYIP and
MPYC5IP, were synthesized. The MPY group of
MPYIP is closely connected with an isoprene chain.
On the other hand, that of MPYC5IP is connected
with an isoprene chain through the C5 spacer. Although
the uncomplexed MPYIP and MPYC5IP were obtained
as liquid state, their complexes with more than an
equivalent ZnCl2 to the MPY groups were solid state.
Consequently, theMPY±ZnCl2 complexwascon®rmed
to enhance the aggregation of the polyisoprene remark-
ably as well as poly(dimethyl siloxane). Moreover, in
the IR spectroscopic studies, we found that the MPY
amide group of MPYIP was prevented from forming
the complex with ZnCl2 by the steric hindrance. As a
result, the ZnCl2 complex of MPYC5IP showed the
higher melting temperature and enthalpy than that of
MPYIP. In addition, the better phase-separation
between hard and soft segments in the MPYC5IP±
ZnCl2 complex was also observed. From these results,
we conclude that the MPY±ZnCl2 complex functions as
a hard-segment of elastomers in various types of
polymer system, and moreover the presence of a spacer
between the MPY group and the main chain of polymers
enhances the aggregation of polymers more effectively.
The mole ratio (MPY)/(ZnCl2) of the MPYC5IP±
ZnCl2 complex with the high Tm at about 1408C is 1:2
(Table 4), which is twice the stoichiometric amount of
ZnCl2 in the MPY±ZnCl2 complex. The reason is, we
consider, that a part of ZnCl2 coordinates with the
maleic amide±ester group connected to the C5 spacer
and the isoprene main chain. It is supported from the
result that the IR absorption band (n(CyO)) of the
maleic ester group (usually 1740 cm21) was observed
at the additional lower wavenumber (1718 cm21
when an excess of ZnCl2 was added.
)
Table 5 shows the glass-transition temperature (Tg)
of MPYIP±ZnCl2 and the MPYC5IP±ZnCl2
complexes. The MPYC5IP±ZnCl2 complex showed
the same Tg as the starting polyisoprene and uncom-
plexed MPYC5IP. This result indicates that the aggre-
gation of the hard-segment (MPY±ZnCl2 complex)
has no in¯uence on the mobility of the soft-segment
(isoprene units) of MPYC5IP. Thus the complete
phase-separation of hard and soft segments take
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