Solid-state polymerizations of 7-alkoxycarbonyl-7-cyano-1,4-benzoquinone methides

Article abstract of DOI:10.1021/ma049596r

Thermal polymerizations and photopolymerizations of 7-alkoxycarbonyl-7-cyano-1,4-benzoquinone methides (methoxy (2a), ethoxy (2b), propoxy (2c), isopropoxy (2d), butoxy (2e), and sec-butoxy (2f)) were investigated in the solid state. In the thermal polyme

Full text of DOI:10.1021/ma049596r

7938
Macromolecules 2004, 37, 7938-7944
Solid-State Polymerizations of
7-Alkoxycarbonyl-7-cyano-1,4-benzoquinone Methides
Ta k a h ito Itoh ,*,† Sh in ji Nom u r a ,† Na gisa Sa itoh ,† Ta k a h ir o Un o,† Ma sa ta k a Ku bo,†
Ka zu k i Sa d a ,‡ Ka tsu n a r i In ou e,§ a n d Mik iji Miya ta §
Department of Chemistry for Materials, Faculty of Engineering, Mie University, 1515 Kamihama-cho,
Tsu-shi, Mie 514-8507, J apan; Department of Chemistry and Biochemistry,
Graduate School of Engineering, Kyushu University, 6-10-1 Hakozaki, Higashi-ku,
Fukuoka 630-8528, J apan; and Department of Material and Life Science,
Graduate School of Engineering, Osaka University and Handai FRC, 2-1 Yamadaoka,
Suita, Osaka 565-0871, J apan
Received March 1, 2004; Revised Manuscript Received J uly 28, 2004
ABSTRACT: Thermal polymerizations and photopolymerizations of 7-alkoxycarbonyl-7-cyano-1,4-ben-
zoquinone methides (methoxy (2a ), ethoxy (2b), propoxy (2c), isopropoxy (2d ), butoxy (2e), and sec-butoxy
(2f)) were investigated in the solid state. In the thermal polymerization in the solid state, 2a , 2c, 2d , and
2e polymerized to give glassy solids or a mass of crystals, but both 2b and 2f did not polymerize. In the
photopolymerization in the solid state, all monomer crystals except for 2a polymerized to give
corresponding polymers as needlelike solids. The needlelike polymer obtained by photopolymerization of
highly reactive 2c was amorphous by powder X-ray diffraction measurement. Crystal structure of 2c
was determined by single-crystal X-ray structure analysis, and the molecular packing in the crystals
was discussed.
In tr od u ction
molecules stack in a columnar structure with the angle
formed between the stacking axis and longer axis of
quinodimethane moiety of 30-33° and the distance
between equivalent atoms in the stacked monomers of
7.0-7.6 Å.6 Quinone methides are a member of quinoid
family; it was reported that they are isolable as crystal
forms at room temperature, and their polymerization
behavior in solution is similar to that of the substituted
quinodimethanes in solution.7-10 If they have molecular
stacking mode in the crystals similar to the quino-
dimethanes 1a -f, they are expected to polymerize
topochemically. To expand the scope of monomers that
undergo polymerization topochemically, we investigated
the solid-state polymerization reactivities of a series of
7-alkoxycarbonyl-7-cyano-1,4-benzoquinone methides
(methoxy (2a ), ethoxy (2b), propoxy (2c), isopropoxy
(2d ), butoxy (2e), and sec-butoxy (1f)).
Solid-state polymerization implies that polymeriza-
tion proceeds starting from bulk monomer crystals, and
it has been divided into two classes: topotactic and
topochemical polymerizations.1 The former is the po-
lymerization that provides a polymer with a specific
crystal structure formed under control of the crystal
lattice of the monomer, and the latter is the polymeri-
zation that proceeds with no movement of the center of
gravity of the monomer molecule and only slight rota-
tion of the monomer molecule around the gravity; that
is, the crystallographic position and symmetry of the
monomer crystals are retained in the resulting polymer
crystals. Therefore, topochemical polymerization is a
promising method to obtain polymers with highly
controlled structures. A limited number of monomers
such as derivatives of diacetylene,1 2,5-distyrylpyra-
zine,2 triene and triacetylene,3 and muconic acid and
sorbic acid4 have been reported to undergo topochemical
polymerizations. Recently, we reported that 7,7,8,8-
tetrakis(methoxycarbonyl)quinodimethane (1a) gave two
crystal forms, and they exhibited drastic differences in
the polymerization ability between them and also po-
lymerization proceeds topochemically.5 Moreover, we
synthesized novel 7,7,8,8-tetrakis(alkoxycarbonyl)quin-
odimethanes (1b-f) with various alkoxy groups and
discussed the relationship of the solid-state polymeri-
zation reactivity with the molecular packing in the
crystals on the basis of crystal structure analysis.6 As
the result, we found principles for the topochemical
polymerizations of quinodimethane monomers in the
solid state to predict the polymerization reactivity. In
the crystals of the polymerizable monomers, monomer
Exp er im en ta l Section
Mea su r em en ts. All melting points were obtained with a
Yanaco MP-50 melting point apparatus. The number-average
molecular weights, Mn, of the polymers were determined by
gel permeation chromatography (GPC) on a J asco PU-2080
Plus equipped with TOSOH UV-8020 ultraviolet (254 nm)
detector and TSK gel G2500H8 (bead size with 10 µm,
molecular weight range 1.0 × 102-2.0 × 104) and TSK gel
† Mie University.
‡ Kyushu University.
§ Osaka University and Handai FRC.
* Corresponding author: phone +81-59-231-9410; Fax +81-59-
231-9410; e-mail itoh@chem.mie-u.ac.jp.
10.1021/ma049596r CCC: $27.50 © 2004 American Chemical Society
Published on Web 09/15/2004

Macromolecules, Vol. 37, No. 21, 2004
7-Alkoxycarbonyl-7-cyano-1,4-benzoquinone Methides 7939
Sch em e 1
4-[Cya n o(p r op oxyca r b on yl)m et h ylen e]cycloh exa n -
on e (3c). From dipropyl malonate, 3c was obtained as white
needles (70% yield); mp 87-88 °C. IR (KBr, cm-1): νCN 2198,
νCdO 1687, νCdC 1563, νC-O 1235, 1101. 1H NMR (CDCl3): δ
4.20 (q, J ) 6.6 Hz, 2H), 3.41 (t, J ) 6.9 Hz, 2H), 3.13 (t, J )
6.9 Hz, 2H), 2.55 (m, 4H), 1.74 (m, 2H), 1.01 (t, J ) 7.6 Hz,
3H). 13C NMR (CDCl3): δ 208.2, 174.2, 161.3, 114.6, 104.7,
67.4, 33.9, 36.8, 31.8, 27.9, 21.7, 10.2. Anal. Calcd for C12H15
-
NO3: C, 65.14%; H, 6.83%; N, 6.33%. Found: C, 64.98%; H,
6.89%; N, 6.35%.
4-[Cya n o(isop r op oxyca r bon el)m eth ylen e]cycloh exa n -
on e (3d ). From diisopropyl malonate, 3d was obtained as
white needles (80% yield); mp 52-54 °C. IR (KBr cm-1): νCN
2198, νCdO 1670, νCdC 1566, νC-O 1233, 1086. 1H NMR
(CDCl3): δ 5.12 (m, J ) 6.3 Hz, 2H), 3.40 (t, J ) 6.9 Hz, 2H),
3.12 (t, J ) 6.9 Hz, 2H), 2.54 (m, 4H), 1.33 (d, J ) 6.3 Hz,
6H). 13C NMR (CDCl3): δ 208.3, 173.7, 160.8, 114.7, 105.2,
70.0, 37.0, 36.9, 31.8, 27.9, 21.5. Anal. Calcd for C12H15NO3:
C, 65.14%; H, 6.83%; N, 6.33%. Found: C, 65.14%; H, 6.91%;
N, 6.32%.
G3000H8 (bead size with 10 µm, molecular weight range 1.0
× 102-6.0 × 104) using tetrahydrofuran (THF) as an eluent
at a flow rate of 1.0 mL/min and polystyrene standards for
calibration. The NMR and IR spectra were recorded on a J EOL
J NM-EX270 FT NMR spectrometer using chloroform-d with
tetramethylsilane as an internal standard at 25 °C and a
J ASCO IR-700 spectrometer, respectively.
The powder X-ray diffraction (XRD) measurement of the
polymers was carried out using a Rigaku Rotaflex RU-200B
in the 2θ range from 10° to 90° at a scan speed of 0.5°/min
with sampling width of 0.02°. The graphite-monochromated
Cu KR line (λ ) 1.541 78 Å) was used with the power of the
X-ray generator 40 kV and 150 mA. The single-crystal X-ray
data were collected on a Rigaku RAXIS-RAPID imaging plate
diffractometer using Cu KR radiation (λ ) 1.541 78 Å) mono-
chromated with graphite. The structure was solved by the
direct methods with the program SIR88 and refined by full-
matrix least-squares procedures. The calculation was per-
formed using the TEXSAN crystallographic software package
of the Molecular Structure Corp.
4-[Cya n o(bu toxyca r bon yl)m eth ylen e]cycloh exa n on e
(3e). From dibutyl malonate, 3e was obtained as white needles
(85% yield); mp 65-66 °C. IR (KBr, cm-1): νCN 2198, νCdO 1684,
1
νCdC 1564, νC-O 1192, 1094. H NMR (CDCl3): δ 4.25 (t, J )
6.6 Hz, 2H), 3.40 (t, J ) 6.9 Hz, 2H), 3.13 (t, J ) 6.9 Hz, 2H),
2.55 (m, 4H), 1.71 (m, 2H), 1.43 (m, 2H), 0.96 (t, J ) 7.4 Hz,
3H). 13C NMR (CDCl3): δ 208.2, 174.1, 161.3, 114.6, 104.8,
65.8, 36.95, 36.86, 31.8, 30.3, 27.9, 18.9, 13.5. Anal. Calcd for
C
13H17NO3: C, 66.36%; H, 7.29%; N, 5.95%. Found: C, 66.21%;
H, 7.37%; N, 5.99%.
4-[Cya n o(sec-b u t oxyca r b on yl)m e t h yle n e ]cycloh e x-
a n on e (3f). From di(sec-butyl) malonate, 3f was obtained as
a yellow oil (85% yield). IR (neat, cm-1): νCN 2204, νCdO 1681,
1
νCdC 1572, νC-O 1234, 1084. H NMR (CDCl3): δ 4.94 (m, 1H),
Mon om er Syn th esis. 4-[(Alkoxycarbonyl)cyanomethylene]-
cyclohexanones (3a -f) and 7-alkoxycarbonyl-7-cyano-1,4-ben-
zoquinone methides (2a -f), including new compounds 2c and
3c, were synthesized by the same procedure reported previ-
ously (Scheme 1).7,8
3.41 (t, J ) 6.9 Hz, 2H), 3.13 (t, J ) 6.9 Hz, 2H), 2.58 (m, 4H),
1.67 (m, 2H)1.30 (d, J ) 6.3 Hz, 3H), 0.95 (t, J ) 7.6 Hz, 3H).
13C NMR (CDCl3): δ 208.3, 173.7, 160.9, 114.7, 105.2, 74.5,
36.95, 36.86, 31.8, 28.5, 27.9, 19.2, 9.4. Anal. Calcd for C13H17
-
NO3: C, 66.36%; H, 7.29%; N, 5.95%. Found: C, 66.39%; H,
7.35%; N, 5.92%.
4-[(Alk o x y c a r b o n y l)c y a n o m e t h y le n e ]c y c lo h e x a n -
on es (3a -f). Gen er a l P r ep a r a tion Meth od . 1,4-Cyclohex-
anedione monoethylene ketal (10 g, 64 mmol) and alkyl
cyanoacetate (70 mmol) were refluxed in the presence of 0.4 g
of ammonium acetate and 2 mL of acetic acid in 150 mL of
toluene using a Dean-Stark water separator to isolate water
formed for 48 h. The reaction mixture was washed twice with
100 mL of water and dried over anhydrous magnesium sulfate.
It was placed under reduced pressure to remove toluene to
give a pale yellow solid, to which was added 200 mL of a 2%
aqueous sulfuric acid solution, and refluxed for 1 h. After
cooling, the reaction mixture was extracted with chloroform
(400 mL × 3). The combined organic fractions were washed
twice with 100 mL of water, dried over anhydrous magnesium
sulfate, and filtered, and the solvent of the filtrate was
evaporated under reduced pressure. The crude product was
purified by column chromatography (SiO2, chloroform) followed
by recrystallization from hexane.
4-[Cya n o(m et h oxyca r b on yl)m et h ylen e]cycloh exa n -
on e (3a ). From dimethyl malonate, 3a was obtained as white
needles (69% yield); mp 67-69 °C. IR (KBr, cm-1): νCN 2200,
νCdO 1686, νCdC 1568, νC-O 1238, 1095. 1H NMR (CDCl3): δ
3.86 (s, 3H), 3.42 (t, J ) 6.9 Hz, 2H), 3.14 (t, J ) 6.9 Hz, 2H),
2.56 (m, 4H). 13C NMR (CDCl3): δ 208.3, 175.0, 161.6, 114.6,
104.2, 52.6, 36.8, 36.7, 31.8, 27.9. Anal. Calcd for C10H11NO3:
C, 62.16%; H, 5.74%; N, 7.25%. Found: C, 61.85%; H, 5.73%;
N, 7.32%.
7-Alk oxyca r bon yl-7-cya n o-1,4-ben zoqu in on e Meth id es
(2a -f). Gen er a l P r ep a r a tion Meth od . About 2 g of 3a -f
was dissolved in 800 mL of chloroform, and then into the
resulting solution were added 10 g of activated manganese
dioxide and 10 g of 3 Å molecular sieves. The mixture was
refluxed with stirring for 40 min, cooled, and then filtered.
The orange filtrate was placed under reduced pressure to
remove chloroform to give an orange solid residue, which was
dissolved in a small amount of chloroform. The resulting
solution was passed through a silica gel column by using
chloroform as an eluent. The orange elution band was collected
and placed under reduced pressure to remove solvent to obtain
an orange solid, which was recrystallized from hexane to give
orange needles.
7-Cya n o-7-(m eth oxyca r bon yl)-1,4-ben zoqu in on e Me-
th id e (2a ). Yield 26%; mp 105-108 °C. IR (KBr, cm-1): νCN
2194, νCdO 1699, νCdC 1608, νC-O 1222, 1068. 1H NMR
(CDCl3): δ 8.60 (d, J ) 10.2 Hz, 1H), 7.70 (d, J ) 10.2 Hz,
1H), 6.64 (d, J ) 10.2 Hz, 1H), 6.56 (d, J ) 10.2 Hz, 1H), 3.97
(s, 3H). 13C NMR (CDCl3): δ 186.1, 160.9, 148.8, 136.1, 133.5,
132.7, 132.5, 114.5, 111.2, 53.8. UV (CHCl3) λ 320 nm (ꢀ )
3.18 × 104). Anal. Calcd for C10H7NO3: C, 63.49%; H, 3.73%;
N, 7.40%. Found: C, 62.38%; H, 3.56%; N, 7.73%.
7-Cyan o-7-(eth oxycar bon yl)-1,4-ben zoqu in on e Meth ide
(2b). Yield 20%; mp 57-59 °C. IR (KBr, cm-1): νCN 2194, νCd
1704, νCdC 1611, νC-O 1223. 1H NMR (CDCl3): δ 8.56 (d, J )
O
4-[Cya n o(et h oxyca r b on yl)m et h ylen e]cycloh exa n on e
(3b). From diethyl malonate, 3b was obtained as white needles
(55% yield); mp 57-59 °C. IR (KBr, cm-1): νCN 2202, νCdO 1692,
10.2 Hz, 1H), 7.71 (d, J ) 10.2 Hz, 1H), 6.63 (d, J ) 10.2 Hz,
1H), 6.56 (d, J ) 10.2 Hz, 1H), 4.40 (q, J ) 7.2 Hz, 2H), 1.42
(t, J ) 7.2 Hz, 3H). 13C NMR (CDCl3): δ 186.1, 160.9, 148.4,
136.2, 133.4, 132.8, 132.3, 114.4, 111.4, 63.4, 13.89. UV (CHCl3)
λ 320 nm (ꢀ ) 3.08 × 104). Anal. Calcd for C11H9NO3: C,
65.02%; H, 4.46%; N, 6.89%. Found: C, 64.81%; H, 4.43%; N,
6.95%.
1
νCdC 1565, νC-O 1236, 1087. H NMR (CDCl3): δ 4.29 (q, J )
7.2 Hz, 2H), 3.40 (t, J ) 6.9 Hz, 2H), 3.13 (t, J ) 6.9 Hz, 2H),
2.55 (m, 4H), 1.37 (t, J ) 7.2 Hz, 3H). 13C NMR (CDCl3): δ
208.6, 174.6, 161.7, 115.1, 105.2, 62.4, 37.3, 37.2, 32.2, 28.3,
14.4. Anal. Calcd for C11H13NO3: C, 63.75%; H, 6.32%; N,
6.76%. Found: C, 63.90%; H, 6.58%; N, 6.67%.
7-Cya n o-7-(p r op oxyca r bon yl)-1,4-ben zoqu in on e Me-
th id e (2c). Yield 22%; mp 68-69.5 °C. IR (KBr, cm-1): νCN

7940 Itoh et al.
Macromolecules, Vol. 37, No. 21, 2004
Ta ble 1. Th er m a l P olym er iza tion s of 2a -f in th e Solid Sta te
run
monomer
mp, °C
temp, °C
time, h
form
conv, %
Mn/104
Mw/Mn
1
2
3
4
5
6
2a (Me)
2b (Et)
2c (Pr)
2d (iPr)
2e (Bu)
2f (sBu)
105
57
68
91
61
58
95
50
60
80
50
50
24
24
48
24
48
48
melt
51
0
10
81
41
0
0.4
1.77
needle
mass
mass
mass
needle
3.8
2.1
3.1
-
1.51
1.45
1.52
Ta ble 2. P h otop olym er iza tion s of 2a -f in th e Solid Sta te
2194, νCdO 1699, νCdC 1608, νC-O 1222, 1068. 1H NMR
(CDCl3): δ 8.59 (d, J ) 10.2 Hz, 1H), 7.71 (d, J ) 10.2 Hz,
1H), 6.63 (d, J ) 10.2 Hz, 1H), 6.56 (d, J ) 10.2 Hz, 1H), 4.31
(t, J ) 6.6 Hz, 2H), 1.79 (m, 2H), 1.04 (t, J ) 7.6 Hz, 3H). 13C
NMR (CDCl3): δ 186.1, 160.5, 148.4, 136.2, 132.8, 114.4, 111.4,
68.8, 21.7, 10.2. UV (CHCl3) λ 304 nm (ꢀ ) 3.15 × 104). Anal.
Calcd for C12H11NO3: C, 66.35%; H, 5.10%; N, 6.45%. Found:
C, 65.54%; H, 4.97%; N, 6.37%.
time,
h
conv,
%
Mn/104 Mw/Mn
run monomer
form
1
2
3
4
5
6
2a (Me)
2b (Et)
2c (Pr)
2d (iPr)
2e (Bu)
2f (sBu)
70
70
70
70
70
70
needle solid
needlelike solid
needlelike solid 100
needlelike solid 100
needlelike solid
needlelike solid
0
69
1.6
1.4
1.0
2.1
1.6
1.56
1.45
1.47
1.49
1.67
47
18
7-Cya n o-7-(isop r oxyca r bon yl)-1,4-ben zoqu in on e Me-
th id e (2d ). Yield 25%; mp 91-92 °C. IR (KBr, cm-1): νCN 2196,
νCdO 1687, νCdC 1540, νC-O 1250, 1087. 1H NMR (CDCl3): δ
8.58 (d, J ) 10.2 Hz, 1H), 7.69 (d, J ) 10.2 Hz, 1H), 6.59 (d,
J ) 10.2 Hz, 1H), 6.52 (d, J ) 10.2 Hz, 1H), 5.22 (m, J ) 6.3
Hz, 1H), 1.41 (d, J ) 6.3 Hz, 6H).13C NMR (CDCl3): δ 186.1,
160.0, 148.2, 136.3, 133.4, 132.9, 132.3, 114.5, 111.9, 71.93,
21.57. UV (CHCl3) λ 321 nm (ꢀ ) 3.18 × 104). Anal. Calcd for
°C lower than each melting point, and the results are
summarized in Table 1.
2a , 2c, 2d , and 2e polymerized to give the corre-
sponding polymers as glassy solids or a mass of crystals,
which were soluble in chloroform, THF, benzene, and
dichloromethane but insoluble in hexane, methanol, and
diisopropyl ether. With the progress of polymerization,
monomer needle crystals of 2a gradually melted to form
glassy solids, and monomer needle crystals of 2c, 2d ,
and 2e each became a mass of crystals without melting,
indicating that the collapse of the crystals takes place
during polymerization. The number-average molecular
weights (Mn) of obtained polymers were determined to
be 4000-38 000 by GPC. No polymerizations occurred
for 2b and 2f, and unreacted monomers were recovered
quantitatively. The change by appearance of these
monomer crystals in the thermal polymerizations indi-
cates that all monomers 2b-f do not polymerize with
retaining crystal lattice.
C
12H11NO3: C, 66.35%; H, 5.10%; N, 6.45%. Found: C, 66.35%;
H, 5.01%; N, 6.47%.
7-Cyan o-7-(bu toxycar bon yl)-1,4-ben zoqu in on e Meth ide
(2e). Yield 22%; mp 61-62 °C. IR (KBr): νCN 2196, νCdO 1680,
1
νCdC 1610, νC-O 1247, 1069. H NMR (CDCl3): δ 8.55 (d, J )
10.2 Hz, 1H), 7.73 (d, J ) 10.2 Hz, 1H), 6.63 (d, J ) 10.2 Hz,
1H), 6.52 (d, J ) 10.2 Hz, 1H), 4.35 (t, J ) 6.6 Hz, 2H), 1.76
(m, 2H), 1.54 (m, 2H), 0.98 (t, J ) 7.3 Hz, 3H). 13C NMR
(CDCl3): δ 186.3, 160.6, 148.5, 136.2, 133.4, 132.8, 132.4,
114.48, 111.7, 67.2, 30.3, 19.0, 13.6. UV (CHCl3) λ 320 nm (ꢀ
) 3.26 × 104). Anal. Calcd for C13H13NO3: C, 67.52%; H, 5.67%;
N, 6.06%. Found: C, 67.40%; H, 5.61%; N, 6.10%.
7-Cya n o-7-(sec-bu toxyca r bon yl)-1,4-ben zoqu in on e Me-
th id e (2f). Yield 11%; mp 57.5-58 °C. IR (KBr, cm-1): νCN
2192, νCdO 1682, νCdC 1587, νC-O 1233, 1097. 1H NMR
(CDCl3): δ 8.55 (d, J ) 10.2 Hz, 1H), 7.70 (d, J ) 10.2 Hz,
1H), 6.59 (d, J ) 10.2 Hz, 1H), 6.55 (d, J ) 10.2 Hz, 1H), 5.04
(m, 1H), 1.74 (m, 2H), 1.38 (d, J ) 6.3 Hz, 3H), 0.98 (t, J ) 7.6
Hz, 3H). 13C NMR (CDCl3): δ 186.1, 160.1, 148.2, 136.2, 133.3,
132.9, 132.3, 114.4, 112.1, 76.4, 28.5, 19.2, 9.4. UV (CHCl3) λ
320 nm (ꢀ ) 3.06 × 104). Anal. Calcd for C13H13NO3: C, 67.52%;
H, 5.67%; N, 6.06%. Found: C, 67.37%; H, 5.65%; N, 6.09%.
P olym er iza tion P r oced u r es. For solid-state polymeriza-
tions, a given amount of monomer crystal was put into a Pyrex
ampule, which was degassed under reduced pressure and then
sealed. Thermal polymerization was carried out by setting the
ampule in an oil bath at a temperature 10 °C lower than each
melting point of monomers 2a -f for a given time. Photopo-
lymerization was carried out at 30-35 °C under UV irradiation
by using a high-pressure mercury lamp (Fuji Glass Work Type
BH-400, 400 W) at a distance of 12 cm. The conversion was
determined from the ratio of the peak area due to quinoid
protons of 2a -f to that due to the phenylene protons of
Next, we tried polymerizations of these monomer
crystals 2a -f by irradiation using a 400 W high-
pressure Hg lamp at 30-35 °C, and the results are
shown in Table 2.
Shapes of the monomer needle crystals did not change
during irradiation, but their orange color changed to
pale yellow for 2b-f and was retained for 2a . The
monomers 2b-f polymerized to give corresponding
polymers with the Mn of 10 000-21 000, but 2a did not
polymerize. As the monomer crystals of 2b-f did not
polymerize in the dark at 30-35 °C, polymer formation
upon UV irradiation is due to photoinitiation. In this
photopolymerization, both 2c and 2d showed the high-
est polymerization reactivity among the monomers 2a -
f, and the 2a and 2b with less bulky substituents
(methoxy and ethoxy groups) and the 2e and 2f with
bulky substituents (butoxy and tert-butoxy groups) were
less reactive. The relationship of the polymerization
reactivity with substituents for the quinoid monomers
such as 7-alkoxycarbonyl-7-cyano-1,4-benzoquinone me-
thides,7,8 7,7-bis(alkoxycarbonyl)-1,4- benzoquinone me-
thides,9 7,8-diacyl-7,8-dicyanoquinodimethanes,11-13
7,8-bis(alkylthio)-7,8-dicyanoquinodimethanes,14,15 and
11,12-bis(alkylthio)-11,12-dicyano-2,6-naphthoquinodi-
methanes16 was investigated in their solution polymer-
izations previously, and it was pointed out that the
polymerization reactivity is exclusively determined by
the steric effect of the alkoxy, acyl, and alkylthio
substituents. Therefore, low reactivity of 2e and 2f with
bulky alkoxy groups is due to the bulkiness of substit-
uents, but the reason for low reactivity of 2a and 2e
1
polymer by H NMR spectroscopy.
Resu lts a n d Discu ssion s
Solid -Sta te P olym er iza tion . Previously, we re-
ported that 7,7,8,8-tetrakis(alkoxycarbonyl)quinodi-
methanes gave two crystal forms depending upon the
recrystallization conditions, which have different po-
lymerization reactivity in the solid state.5,6 Unfortu-
nately, all monomers 2a -f gave only one crystal form
under all attempted recrystallization conditions. Here,
orange needles obtained by the recrystallization from
hexane were used for the solid-state polymerizations.
We tried thermal polymerizations of these monomer
crystals 2a -f by heating in dark at a temperature 10

Macromolecules, Vol. 37, No. 21, 2004
7-Alkoxycarbonyl-7-cyano-1,4-benzoquinone Methides 7941
Ch a r a cter iza tion of P olym er . The needlelike solids
obtained by photopolymeriztion of 2c in the solid state
1
were characterized by H and 13C NMR and IR spec-
troscopies and powder XRD measurement. The 1H NMR
spectrum of polymer of 2c, purified by dissolution-
precipitation treatment, is shown in Figure 2, together
with monomer 2c.
The peaks at 8.59, 7.71, 6.63, and 6.56 ppm assigned
to quinoid protons of monomer 2c disappeared in the
1H NMR spectrum of the resulting polymer, and new
signals due to the phenylene protons were observed at
7.75 and 7.16 ppm. In the 13C NMR spectrum, the peaks
at 186.1 ppm due to the exocarbonyl carbon and 111.4
ppm due to the disubstituted exomethylene carbon of
monomer 2c disappeared, and new peaks at 155.8 ppm
assigned to the carbon next to oxygen in the phenoxy
group and at 64.4 ppm due to the quaternary carbon
were observed. Also, a characteristic absorption band
at 1504 cm-1 assigned to the exocyclic conjugated
carbon-carbon double bond was absent in the IR
spectrum of the resulting polymer. Those changes
observed in the 1H and 13C NMR and IR spectra support
that polymerization of 2c takes place at the disubsti-
tuted exomethylene carbon atom and exocarbonyl oxy-
gen with formation of the stable aromatic structure. The
1H and 13C NMR and IR spectra of polymer obtained
by this solid-state polymerization were in good agree-
ment with those of polymer obtained by the melt
polymerization of 2c in the presence of 2,2′-azobis-
(isobutyronitrile)(AIBN) as initiator, indicating that
both polymers obtained by melt and solid-state poly-
merizations may have completely the same structure.
Also, 1H and 13C NMR and IR spectra of polymers
obtained by the photopolymerizations of other mono-
mers 2b, 2e, 2d , and 2f were in good agreement with
those of corresponding polymers obtained by the melt
or solution polymerizations in the presence of AIBN.
F igu r e 1. Time-conversion plot for photopolymerization of
2c in the solid state.
with less bulky groups is not clear at present. It is
plausible that the packing structure mode of the mol-
ecules in the crystals affects significantly the polymer-
ization reactivity as pointed out previously for the solid-
state polymerization of substituted quinodimethanes.6
The time-conversion plot for the photopolymeriza-
tions in the solid state of 2c is shown in Figure 1, where
the conversion increases with time and greatly at the
latter stage.
Generally, time-conversion plots in solution and bulk
polymerizations show convex curves because the po-
lymerization rate becomes gradually slow at the latter
stage for diminished monomer concentration. The time-
conversion plot profile for the photopolymerization of
2c in the solid state is significantly different from the
conventional one in solution polymerization. The rise
of the polymerization rate in the solid state might be
due to the difference in the mobility of the molecules
and the relative position of the molecules between the
solid state and the solution. In the solution, collisions
between monomer and monomer and between propa-
gating polymer chain and monomer are diminished with
a decrease in monomer concentration. On the other
hand, in the solid state, the relative position of the
monomer molecules does not change significantly com-
pared with the solution because molecular movement
is restricted, and moreover mechanical strain is imposed
on the crystals upon polymerization.
Monomer crystals changed color from orange to pale
yellow with retaining the crystal shape. Thus, we
compared the monomer needle crystals with needlelike
F igu r e 2. 1H NMR spectra in chloroform-d of (a) monomer 2c and (b) polymer obtained by the photopolymeization of 2c in the
solid state.

7942 Itoh et al.
Macromolecules, Vol. 37, No. 21, 2004
peaks, which implies that it is amorphous. The powder
XRD patter at 66% conversion shows that both the
monomer crystal phase and the polymer amorphous
phase coexist. The remainder of this monomer crystal
phase until relatively high conversion indicates that the
polymerization takes place locally in the crystals; that
is, polymerization starting at a defect in the crystal
lattice or the crystal surface may proceed as heteroge-
neous reaction1 where the chain growth will occur with
a much higher probability around the preformed chain
than elsewhere in the crystals.
F igu r e 3. Powder XRD patterns of (a) monomer 2c, (b)
product at 66% conversion, and (c) product at 100% conversion
obtained by the photopolymerization of 2c in the solid state.
Cr ysta l Str u ctu r e a n d P a ck in g of Molecu les.
Previously, we discussed the relationship of the polym-
erization reactivity of the 7,7,8,8-(alkoxycarbonyl)quino-
dimethanes in the solid state with the molecular pack-
ing in the crystals on the basis of crystal structure
analysis.6 Here, we investigated the crystal structure
of 2c by X-ray crystallography to clarify the packing
mode of the monomer molecules in the crystals. The
single crystal of 2c was prepared successfully by slow
solvent evaporation from hexane/dichloromethane solu-
tion. The crystallographic data of 2c are summarized
in Table 3, and the crystal structure is shown in Figure
4 together with those of topochemically polymerizable
1a (prism) for comparison.
products in more detail by SEM measurement. The
needlelike product obtained by photopolymerization in
solid state has a smooth surface, and also the sharp edge
observed in monomer crystals disappeared. This sug-
gests strongly that the destruction of crystal lattice took
place during polymerization.
To investigate crystallinity of polymers obtained, the
powder XRD measurements at different conversions for
the monomer 2c, which showed the highest polymeri-
zation reactivity, were carried out. The powder XRD
patterns of the monomer 2c and the reaction mixtures
at 66% conversion and at 100% conversion are shown
in Figure 3.
The powder XRD pattern of the monomer 2c showed
very sharp peaks, but the powder XRD pattern at 100%
conversion was broad, and there are no significant
2c molecules stack along one axis to form columnar
structures as shown in Figure 5a. As defined previously,
we investigated the stacking manners in the column
F igu r e 4. Crystal structures of monomers 2c and 1a (prism). Open and solid circles represent carbon and oxygen atoms,
respectively. Hydrogen atoms are omitted for clarity.

Macromolecules, Vol. 37, No. 21, 2004
7-Alkoxycarbonyl-7-cyano-1,4-benzoquinone Methides 7943
F igu r e 5. Stacking models for 2c and 1a (prism) in the crystals and the definition of stacking parameters for the prediction of
the topochemical polymerization reactivity. ds is the stacking distance between the adjacent monomers in a column; dco and dcc
are the distance between the reacting exomethylene carbon and exocarbonyl oxygen or exomethylene carbon, respectively; θ1 and
θ2 are the angles between the stacking axis and longer axis of the monomer molecule and the shorter axis of the molecule,
respectively.
Ta ble 3. Cr ysta llogr a p h ic Da ta for Cr ysta l of 2c a n d 1a
solid-state photopolymerization to proceed topochemi-
cally, resulting in an amorphous polymer.
(P r ism )
monomer
formula
2c
1a (prism)
Con clu sion s
C
12H11NO3
C
16H16O8
336.29
monoclinic
P21h/n (#14)
8.6787(7)
7.5719(7)
12.761(1)
90
fw
217.22
triclinic
P1h (#2)
10.4163(5)
11.914(1)
4.7895(3)
91.125(2)
92.977(3)
80.613(1)
585.59(7)
2
Thermal polymerizations and photopolymerizations
of 7-alkoxycarbonyl-7-cyano-1,4-benzoquinone methides
(2a -f) in the solid state were investigated. In the
thermal polymerization in the solid state, 2a , 2c, 2d ,
and 2e polymerized to give glassy solids or a mass of
crystals, but both 2b and 2f did not polymerize. In the
photopolymerization in the solid state, all monomer
crystals except for 2a polymerized to give corresponding
polymers as needlelike solids, which were amorphous.
Crystal structure of 2c was determined by single-crystal
X-ray structure analysis, and it was found that molec-
ular packing of 2c in the crystals is significantly
different from that of topochemically polymerizable 1a
(prism). This difference resulted in the formation of
amorphous polymer of 2c.
crystal system
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
105.193(2)
90
809.2(1)
2
1.380
1828
1477
0.046
0.106, 0.133
1.27
55.0
Z
F
calc, g/cm3
1.232
unique reflecns
no. of obsd reflecns
R1
1999
1996
0.064
0.128, 0.154
1.91
R, Rw
GOF
2θmax, deg
temp, °C
136.4
23
25
Ack n ow led gm en t. A part of this work was sup-
ported by “Nanotechnology Support Project” of the
Ministry of Education, Culture, Science and Technology
(MEXT), J apan.
structure by using structural parameters (ds, dco, θ1, and
θ2) to discuss molecular arrangements of monomers in
the crystal structures in relation to the polymerization
reactivity in the solid state of the substituted quin-
odimethanes.6 In the case of 2c, structural parameters
of θ1, θ2, ds, and dco are to be 76°, 49°, 4.8 Å, and 6.3 Å,
respectively. As a typical example of the topochemically
polymerizable substituted quinodimethanes, the colum-
nar structure of 1a (prism) is shown in Figure 5b, where
the corresponding parameters are to be θ1 ) 30°, θ2 )
89°, ds ) 7.6 Å, and dcc ) 3.9 Å.6 The structural
parameters of 2c are greatly different from those of 1a
(prism). It is considered, therefore, that this significant
difference does not allow polymerization of 2c in the
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