Induction of smectic layering in nematic liquid crystals using immiscible components. 5. Laterally attached side-chain liquid crystalline poly(norbornene)s and their low molar mass model compounds with short fluorocarbon segments

Article abstract of DOI:10.1021/ma0113430

5-[[[2′,5′-Bis[(4″-n-((perfluoroalkyl)alkoxy)benzoyl)oxy] benzyl]oxy]carbonyl]bicyclo[2.2.1]hept-2-enes with short fluorocarbon segments were polymerized by ring-opening metathesis polymerization in THF at room temperature using Mo(CHCMe₂Ph)(N-2,6-ⁱPr₂Ph)(O^tBu) ₂ as the initiator. Although hydrocarbon and fluorocarbon segments as short as three methylenic units each induce smectic layering in the corresponding 2,5-bis{[4′-(n-(perfluoroalkyl)alkoxy)benzoyl]oxy}toluene model compounds, the polymers require at least eight and three, or five and four methylenic units in the hydcrocarbon and fluorocarbon segments, respectively, to organize into smectic layers; polymers with shorter hydrocarbon and/or fluorocarbon segments are nematic.

Full text of DOI:10.1021/ma0113430

Macromolecules 2002, 35, 2105-2115
2105
Induction of Smectic Layering in Nematic Liquid Crystals Using
Immiscible Components. 5. Laterally Attached Side-Chain Liquid
Crystalline Poly(norbornene)s and Their Low Molar Mass Model
Compounds with Short Fluorocarbon Segments
Aa r on C. Sm a ll a n d Coleen P u gh *
Department of Polymer Science, Maurice Morton Institute of Polymer Science, The University of Akron,
Akron, Ohio 44325-3909
Received J uly 27, 2001; Revised Manuscript Received November 12, 2001
ABSTRACT: 5-[[[2′,5′-Bis[(4′′-n-((perfluoroalkyl)alkoxy)benzoyl)oxy]benzyl]oxy]carbonyl]bicyclo[2.2.1]hept-
2-enes with short fluorocarbon segments were polymerized by ring-opening metathesis polymerization
in THF at room temperature using Mo(CHCMe2Ph)(N-2,6-iPr2Ph)(OtBu)2 as the initiator. Although
hydrocarbon and fluorocarbon segments as short as three methylenic units each induce smectic layering
in the corresponding 2,5-bis{[4′-(n-(perfluoroalkyl)alkoxy)benzoyl]oxy}toluene model compounds, the
polymers require at least eight and three, or five and four methylenic units in the hydrocarbon and
fluorocarbon segments, respectively, to organize into smectic layers; polymers with shorter hydrocarbon
and/or fluorocarbon segments are nematic.
Sch em e 1. Sid e-Ch a in Liqu id Cr ysta llin e
P olyn or bor n en es a n d th e Cor r esp on d in g Mod el
Com p ou n d s w ith 2,5-Bis[(4′-n -
In tr od u ction
The chemical structure of the mesogen is the primary
factor dictating which phase(s) a liquid crystal forms.
For example, liquid crystals based on phenyl benzoate
mesogens tend to form nematic (n) mesophases.1 How-
ever, few tools have been developed for converting the
type of liquid crystalline phase exhibited by a given
chemical structure, despite the discovery2 of liquid
crystals in 1888. One such concept is that lateral
substitution of the mesogen can be used to convert
smectic mesophases into nematic mesophases.3 We
recently established a second concept by demonstrating
that both nematic low molar mass liquid crystals
(LMMLCs) and laterally attached side-chain liquid
crystalline polynorbornenes with 1,4-bis[(4′-n-alkoxy-
benzoyl)oxy]benzene mesogens can be forced to order
into smectic layers by terminating their n-alkoxy sub-
stituents (n ) 4-6,8 methylenic units) with immiscible
fluorocarbon segments (m ) 6-8 perfluoromethylenic
units) (Scheme 1);4 siloxane segments are also effective
although they are both flexible and much less incompat-
ible with hydrocarbons than fluorocarbons are.5
((p er flu or oa lk yl)a lk oxy)ben zoyl)oxy]ben zen e
Mesogen s a n d Th eir Hyd r oca r bon An a logu es
To induce smectic layering, we chose hydrocarbon and
fluorocarbon segments that were long enough to micro-
phase separate according to the microphase-separated
lamellar structures formed by diblock H(CH2)n(CF2)mF
and triblock H(CF2)m(CH2)n(CF2)mF molecules with 4 e
n e 14 and m g 6.6 Microsegregation of the hydrocarbon
and fluorocarbon segments of 2,5-bis[(4′-n-((perfluoro-
heptyl)octyloxy)benzoyl)oxy]toluene is apparently so
strong that neither lateral n-alkanoyl nor bulky al-
kanoate or benzoate substituents disrupt the smectic
layering.7 This paper investigates the minimum lengths
of the hydrocarbon and fluorocarbon segments necessary
for inducing smectic mesomorphism in the same side-
chain liquid crystalline polymers (SCLCPs) and model
compounds. As exemplified in Scheme 1, we have found
that appropriate model compounds for laterally attached
SCLCPs are based on identical mesogens with the same
terminal substituents but with a lateral substituent that
mimics both the chemical structure and length of the
spacer.4,5,8 We consider the laterally attached SCLCPs
to be the most challenging system possible for inducing
smectic mesophases because both the molecular archi-
tecture9,10 and use of only a short spacer11 favor forma-
tion of a nematic mesophase. In addition, the 1,4-
bis(benzoyloxy)benzene mesogens tend to form only
nematic mesophases, especially at these n-alkoxy sub-
stituent lengths.1 Therefore, we expect that some com-
binations of hydrocarbon and fluorocarbon lengths will
* To whom correspondence should be addressed.
10.1021/ma0113430 CCC: $22.00 © 2002 American Chemical Society
Published on Web 02/09/2002

2106 Small and Pugh
Sch em e 2. Syn th esis of th e 2,5-Bis[(4′-n -
Macromolecules, Vol. 35, No. 6, 2002
Ta ble 1. Th er m a l Tr a n sition s a n d Th er m od yn a m ic
P a r a m eter s of 2,5-Bis[(4′-n -
((p er flu or oa lk yl)a lk oxy)ben zoyl)oxy]tolu en e Mod el
((p er flu or oa lk yl)a lk oxy)ben zoyl)oxy]tolu en esa
Com p ou n d s w ith m ) 3-4 (n ) 3-6,8)
phase transitions, °C (∆H, kJ /mol)
n
m
3
4
5
6
8
3
4
5
6
8
3
4
5
6
8
2
2
2
2
2
3
3
3
3
3
4
4
4
4
4
k 112 (47.1)
k 109 (50.8)
s
s
A 145 (0.357) n 155 (1.06)
A 113 (0.377) n 154 (1.54)
i
i
i
i
i
i
i
i
i
i
i
i
i
i
i
k 96 (41.1) sC 82b
k 97 (44.4) sC 117b
k 103 (70.6) sC 104b
k 122 (26.3) sC 119b
sA 151b
n 151 (4.14)
sA 151 (1.90) n 152 (2.94)
sA 149 (6.97)
sA 184 (4.41)
k 105 (38.6) sC 152 (0.078) sA 169 (5.80)
k 88 (24.7) sC 123b
k 99 (59.1) sC 147b
k 105 (60.6) sC 149b
sA 174 (7.25)
sA 169 (8.22)
sA 162 (10.1)
k 110 (26.7) sC 157 (0.083) sA 199 (5.97)
k 96 (26.7) sC 173 (0.135) sA 189 (7.58)
k 86 (22.5) sC 162 (0.086) sA 186 (7.76)
k 113 (45.3) sC 172 (0.084) sA 185 (7.18)
k 94 (57.4) sC 169 (0.150) sA 176 (9.76)
a
Observed on heating; k ) crystalline, sC ) smectic C, sA
)
smectic A, n ) nematic, and i ) isotropic; n methylenic units, m
perfluoromethylenic units. Transition detected only by polarized
b
Sch em e 3. Syn th esis of th e 2,5-Bis[(4′-n -
((p er flu or oa lk yl)a lk oxy)ben zoyl)oxy]tolu en e Mod el
Com p ou n d s w ith m ) 2 (n ) 3-6,8)
optical microscopy.
addition of a perfluoroalkyl iodide across the double
bonds of the n-alkenyloxy substituents, followed by
reduction of the resulting alkyl iodide using tributyltin
hydride under free radical conditions. The model com-
pounds with the shortest fluorocarbon length (m ) 2)
were readily synthesized by functionalizing the substit-
uents first, and then constructing the mesogen (Scheme
3). Although the order is different, all of the steps in
Scheme 3 are analogous to those in Scheme 2.
Table 1 summarizes the thermal transitions of the 15
model compounds. The data were obtained on heating
and are from thermally equilibrated samples, i.e.,
samples that were recrystallized from solution and/or
from the melt after short annealing times. In most cases,
crystallization from the melt to the most thermody-
namically stable phase is slower than the time scale of
the differential scanning calorimetry (DSC) experiment.
This results in either incomplete recrystallization or
crystallization to a less stable crystalline phase if
sufficient annealing time is not allowed.
We identified the mesophases by polarized optical
microscopy. In contrast to the model compounds with
longer hydrocarbon and fluorocarbon segments,4 these
compounds do not tend to align homeotropically, and it
therefore was not necessary to pretreat the glass slides
with a hydrocarbon solvent. Figure 1a shows a repre-
sentative schlieren nematic texture,12 with both two-
brush and four-brush singularities, that was observed
upon cooling the n, m ) 6, 2 model compound from the
isotropic melt. Further cooling into the smectic A (sA)
phase yielded a typical focal-conic fan texture12 (Figure
1b) and into the smectic C (sC) phase yielded a typical
paramorphotic broken focal-conic fan texture12 (Figure
1c).
Figures 2 and 3 plot the isotropization temperature
of the model compounds as a function of the total
number of carbons in both the hydrocarbon and fluoro-
carbon segments (n + m) and the number of carbons
(n) in the hydrocarbon segments, respectively, including
those prepared previously4 with longer hydrocarbon and
fluorocarbon segments. Both figures also plot the tem-
perature of the nematic-isotropic transitions of their
hydrocarbon analogues,10,13,14 (m ) 0). In general, all of
the transition temperatures decrease with increasing
hydrocarbon length as the molecules become more like
be effective at inducing smectic layering in the low
molar mass model compounds, but not in the corre-
sponding SCLCPs.
Resu lts a n d Discu ssion
Syn th esis a n d Th er m otr op ic Beh a vior of th e
Mod el Com p ou n d s. The 2,5-bis{[4′-(n-(perfluoroalkyl)-
alkoxy)benzoyl]oxy}toluene model compounds were pre-
pared by the routes shown in Schemes 2 and 3. Due to
the insolubility of 4-[n-(perfluoroalkyl)alkoxy]benzoic
acids with longer hydrocarbon and fluorocarbon seg-
ments, we previously synthesized the model compounds
with n ) 4-6,8 and m ) 6-8 by constructing the
mesogen first and then introducing the fluorocarbon
segments.4 As shown in Scheme 2, we also prepared the
model compounds with n ) 3-6,8 and m ) 3-4 by this
route. Ethyl 4-hydroxybenzoate was etherified with an
ω-bromo-1-alkene, followed by saponification of the ester
group under basic conditions to produce the 4-n-(al-
kenyloxy)benzoic acids. The mesogenic core was then
generated by coupling the 4-n-(alkenyloxy)benzoic acids
with methylhydroquinone in the presence of dicyclo-
hexylcarbodiimide (DCC) as a dehydrating agent. The
perfluoroalkyl groups were introduced by free radical

Macromolecules, Vol. 35, No. 6, 2002
Induction of Smectic Layering 2107
F igu r e 1. Polarized optical micrographs (200×) observed on cooling 2,5-bis[(4′-n-((perfluoroethyl)hexoxy)benzoyl)oxy]toluene (n,
m ) 6, 2) from the isotropic melt: (a) 151 °C, nematic schlieren texture; (b) 130 °C, sA focal-conic fan texture; (c) 101 °C, sC
paramorphotic broken focal-conic fan texture.
polyethylene (HDPE Tm ) 138 °C15), and increase with
increasing fluorocarbon length as they become more like
poly(tetrafluoroethylene) (PTFE Tm ) 332 °C15). As
shown in Figure 2, when the isotropization temperature

2108 Small and Pugh
Macromolecules, Vol. 35, No. 6, 2002
Ta ble 2. Ch a n ges in En th a lp y p er Meth ylen ic Un it for
th e Th er m a l Tr a n sition s of th e 2,5-Bis[(4′-n -
((p er flu or oa lk yl)a lk oxy)ben zoyl)oxy]tolu en es w ith
Lon ger Hyd r oca r bon a n d F lu or oca r bon Segm en tsa
change in enthalpy (kJ /mol)
n
m
∆Hm/n
11
4.8
8.2
6.3
∆HsC-sA/m
∆Hi/n+m
4
5
6
8
4
5
6
8
4
5
6
8
6
6
6
6
7
7
7
7
8
8
8
8
0.077
0.072
0.077
0.10
0.099
0.13
0.090
0.11
0.14
0.88
0.99
0.87
0.71
0.61
0.70
0.52
0.51
0.72
0.62
0.63
0.58
11
7.1
7.6
6.4
12
6.5
0.16
0.18
0.20
F igu r e 2. Temperature of isotropization of 2,5-bis[(4′-n-
((perfluoroalkyl)alkoxy)benzoyl)oxy]toluenes as a function of
the total number of carbons in the n-alkoxy substituents at
various fluorocarbon lengths (m perfluoromethylenic units).
9.8
6.9
mean
8.1 ( 2.2
0.12 ( 0.041
0.70 ( 0.14
a
Calculated from the data observed on heating in ref 4; n
methylenic units, m perfluoromethylenic units.
segments are presumably long enough to microphase
separate,4 the hydrocarbon and fluorocarbon segments
apparently disorder separately at different transitions.
On the basis of the relatively constant, albeit with a
slight odd-even alternation, change in enthalpy at the
k-sC transition for a given hydrocarbon length as a
function of fluorocarbon length, the linear hydrocarbon
segments apparently disorder primarily at the crystal-
line melting transition. Therefore, as summarized in
Table 2, the change in enthalpy per methylenic unit at
melting (∆Hm/n) is relatively constant at 8.1 ( 2.2 kJ /
mol. Based on the invariant change in enthalpy at the
sC-sA transition to changes in the hydrocarbon length
for a given fluorocarbon, the fluorocarbon segments
apparently disorder primarily at the sC-sA transition.
Therefore, the change in enthalpy at the sC-sA transi-
tion per perfluoromethylenic unit (∆HsC-sA/m) is rela-
tively constant at 0.12 ( 0.041 kJ /mol (Table 2). The
change in enthalpy of isotropization is independent of
both hydrocarbon and fluorocarbon length, which indi-
cates that the molecules finally lose their orientational
order at isotropization, and the change in enthalpy of
isotropization per total number of methylenic and per-
fluoromethylenic groups [∆Hi/(n + m)] is essentially
constant at 0.70 ( 0.14 kJ /mol (Table 2).
F igu r e 3. Temperature of isotropization of 2,5-bis[(4′-n-
((perfluoroalkyl)alkoxy)benzoyl)oxy]toluenes as a function of
the number of carbons (n) in the hydrocarbon substituents at
various fluorocarbon lengths (m perfluoromethylenic units).
is plotted as a function of the total number of methylenic
units in the n-(perfluoroalkyl)alkoxy substituents, the
temperatures of isotropization of the fluorinated model
compounds are generally higher than those of the
hydrocarbon analogues. The only exceptions are the m
) 2 compounds that, like the hydrocarbon analogues,
undergo isotropization from a nematic mesophase rather
than from a sA mesophase. The point at which the
clearing temperature changes from a nematic-isotropic
(i) to a sA-i transition is the point at which the Ti vs m
+ n line crosses the m ) 0 line on the graph.
As summarized in Table 1, terminating the n-alkoxy
substituents of the nematic model compounds with
fluorocarbon segments of three or four perfluorometh-
ylenic units is still effective at inducing smectic layering;
all of the fluorinated model compounds with m ) 3-4
exhibit a crystalline (k)-sC-sA- i phase sequence. In
contrast, the m ) 2 model compounds exhibit a nematic
phase in addition to the sA phase when n ) 3-4; the m
) 2 model compounds with n ) 5-6 exhibit a nematic
phase in addition to both sA and sC mesophases. Only
the m ) 2 model compound with the longest hydro-
carbon segment (n, m ) 8, 2) exhibits only smectic
mesophases. This indicates that the hydrocarbon and
fluorocarbon segments are not microphase separated
when m ) 2 and n ) 3-6 and that their smectic
mesophases are not the result of immiscibility between
the two segments.
These values may be useful for elucidating which
hydrocarbon and fluorocarbon lengths of the new model
compounds with shorter fluorocarbon segments are
microphase separated; Table 1 lists the enthalpy changes
associated with their transitions. As shown in Table 3,
the values of ∆Hm/n and ∆Hi/(n + m) deviate signifi-
cantly from the values in Table 2 only for the two
compounds with the shortest hydrocarbon and fluoro-
carbon segments (n ) 3, 4, m ) 2). This indicates that
the hydrocarbon and fluorocarbon segments of only
these two compounds are not microphase separated.
However, the two m ) 2 compounds with n ) 5,6 also
exhibit a nematic mesophase, in which the two segments
must be mixed, before undergoing isotropization. In
addition, all of the ∆Hm/m values in Table 3 are
significantly lower than those in Table 2, which might
indicate that the hydrocarbon and fluorocarbon seg-
ments are not microphase separated in any of the model
compounds with shorter fluorocarbon segments (m )
2-4).
As discussed previously for the model compounds
whose hydrocarbon (n g 4) and fluorocarbon (m g 6)
The plots in Figure 3 may help resolve this discrep-
ancy. If the hydrocarbon and fluorocarbon segments are

Macromolecules, Vol. 35, No. 6, 2002
Induction of Smectic Layering 2109
Ta ble 3. Ch a n ges in En th a lp y p er Meth ylen ic Un it for
th e Th er m a l Tr a n sition s of th e 2,5-Bis[(4′-n -
((p er flu or oa lk yl)a lk oxy)ben zoyl)oxy]tolu en es w ith Sh or t
F lu or oca r bon Segm en tsa
Sch em e 4. Syn th esis of th e 5-{[[2′,5′-Bis[(4′′-n -
((p er flu or oa lk yl)a lk oxy)ben zoyl)oxy]ben zyl]oxy]-
ca r bon yl}bicyclo[2.2.1]h ep t-2-en e Mon om er s
change in enthalpy (kJ /mol)
n
m
∆Hm/n
∆HsC-sA/m
∆Hi/n+ma
3
4
5
6
8
3
4
5
6
8
3
4
5
6
8
2
2
2
2
2
3
3
3
3
3
4
4
4
4
4
16
13
0.28
0.32
0.59
0.60
0.70
0.74
0.83
0.91
0.91
0.92
0.85
0.95
0.86
0.72
0.82
8.2
7.4
8.8
8.8
9.6
4.9
9.8
7.6
8.9
6.7
4.5
7.6
7.2
b
b
b
b
0.026
b
b
b
0.021
0.034
0.022
0.021
0.038
a
Change in enthalpy of the sA-i transition (all m ) 3; all m )
4; n,m ) 8,2) or the sum of the sA-n-i transitions (all m)2 except
Ta ble 4. Th er m a l Tr a n sition s a n d Th er m od yn a m ic
P a r a m eter s of 5-{[[2′,5′-Bis[(4′′-n -
b
n)8); n methylenic units, m perfluoromethylenic units. Transi-
tion detected only by polarized optical microscopy.
((p er flu or oa lk yl)a lk oxy)ben zoyl)oxy]-
ben zyl]oxy]ca r bon yl}bicyclo[2.2.1]h ep t-2-en esa
microphase separated, then the chemical structure of
the immiscible segment should have little influence on
the transition temperatures relative to the hydrocarbon
analogues with the same number of methylenic units
in their n-alkoxy substituents, except as a weighting
factor at the hydrocarbon-fluorocarbon interface, which
restricts the motions of the hydrocarbon segments and
thereby increases the transition temperatures. There-
fore, we suspect that the hydrocarbon and fluorocarbon
segments are not inherently microphase separated in
any of the 11 compounds in Figure 3 whose isotropiza-
tion temperatures are lower than those of the hydro-
carbon analogues. This includes all of the m ) 2
compounds, the m ) 3 compounds with the four shortest
hydrocarbon segments (n ) 3-6), and the m ) 4
compounds with the two shortest hydrocarbon segments
(n ) 3, 4). In these cases, the smectic mesophases may
arise because of the high polarity of the molecules due
to the fluorocarbon segments. The remaining four
compounds with longer hydrocarbon segments in the m
) 3 and m ) 4 series have higher isotropization
temperatures than their hydrocarbon analogues, which
indicates that their hydrocarbon and fluorocarbon seg-
ments are microphase separated.
phase transitions, °C (∆H, kJ /mol)
n
m
% endo
3
4
5
6
8
3
4
5
6
8
3
4
5
6
8
2
2
2
2
2
3
3
3
3
3
4
4
4
4
4
67
75
62
67
67
59
31
57
75
25
65
67
73
45
31
k 111 (54.6)
k 112 (38.2)
k 79 (29.6)
k 91 (60.1)
k 54 (23.1)
k 97 (25.0)
k 101 (29.0)
k 76 (22.5)
k 65 (19.9)
i
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i
i
i
i
i
i
i
i
i
i
i
i
[n 47]b
n 57 (1.73)
s
s
A 82 (3.19)
A 80 (3.19)
k 56 (23.3) [sC 31]b sA 82 (4.50)
k 53 (16.7) [sC 44]b sA 115 (3.49)
k 88 (23.8) [sC 74]b sA 107 (3.74)
k 83 (32.5)
k 68 (20.6) [sC 51]b sA 114 (5.00)
k 58 (32.5) A 108 (5.52)
sA 114 (4.41)
s
a
Observed on heating; k ) crystalline, sC ) smectic C, sA
)
smectic A, n ) nematic, and i ) isotropic; [monotropic]; n
b
methylenic units, m perfluoromethylenic units. Transition de-
tected only by polarized optical microscopy.
with shorter fluorocarbon segments. In this case, the
monomers with both short hydrocarbon (n ) 3-4 or 5)
and short fluorocarbon (m ) 2-3) segments do not
exhibit any liquid crystalline phases, and the n, m ) 6,
2 monomer exhibits only a monotropic nematic meso-
phase. In addition, the smectic mesophases of the n, m
) 8, 2 model compound have been converted to a
nematic mesophase in the corresponding monomer. As
summarized in Table 4, the enthalpy changes associated
with these transitions are also smaller than those of the
model compounds.
Syn t h esis a n d Th er m ot r op ic Beh a vior of t h e
P olym er s. The poly{5-[[[2′,5′-bis[(4”-n-((perfluoroalkyl)-
alkoxy)benzoyl)oxy]benzyl]oxy]carbonyl]bicyclo[2.2.1]-
hept-2-ene}s were prepared by ring-opening metathesis
polymerization (ROMP) of the monomers as shown in
Scheme 5. The polymerizations were carried out at 25
°C in a drybox using extensively degassed THF as the
solvent and Mo(N-2,6-iPr2Ph)(CHCMe2Ph)(O-t-Bu)2 as
the initiator, then quenched after 2 h with benzalde-
hyde. Unlike the polymers with m ) 6-8,4 the poly-
norbornenes with m ) 2-4 were completely soluble in
THF at room temperature, and the solutions remained
Syn t h esis a n d Th er m ot r op ic Beh a vior of t h e
Mon om er s. As outlined in Scheme 4, the monomers
were synthesized directly from the model compounds
by free radical bromination at the benzylic position,
followed by phase transfer catalyzed esterification with
potassium bicyclo[2.2.1]hept-2-ene-5-carboxylate.
Table 4 summarizes the thermotropic behavior of the
equilibrated monomers. The monomers prepared previ-
ously with m ) 6-8 generally exhibited an enantiotropic
sA mesophase and a monotropic sC mesophase,4 which
was observed only on cooling; the isotropization and
crystalline melting transition temperatures were also
lower than those of the model compounds. That is,
lateral substitution of the model compounds at the
benzylic position with a bulky norbornyl group sup-
presses all of the transition temperatures, especially
that of the sC-sA transition, due to the decreased
packing density. The additional bulk of the norbornyl
group has an even greater effect on the new monomers

2110 Small and Pugh
Macromolecules, Vol. 35, No. 6, 2002
Ta ble 6. Th er m a l Tr a n sition s a n d Th er m od yn a m ic
P a r a m eter s of P oly{5-[[[2′,5′-bis[(4′′-n -
Sch em e 5. Rin g-Op en in g Meta th esis P olym er iza tion
of 5-{[[2′,5′-Bis[(4′′-n -((p er flu or oa lk yl)a lk oxy)ben zoyl)-
oxy]ben zyl]oxy]ca r bon yl}bicyclo[2.2.1]h ep t-2-en es
((p er flu or oa lk yl)a lk oxy)ben zoyl)oxy]ben zyl]oxy]-
ca r bon yl]bicyclo[2.2.1]h ep t-2-en e}sa
phase transitions, °C (∆H, kJ /mru)
n
m
3
4
5
6
8
3
4
5
6
8
3
4
5
6
8
2
2
2
2
2
3
3
3
3
3
4
4
4
4
4
g 76
g 75
g 65
g 65
g 61
g 81
g 85
g 75
g 90
g 61
g 96
g 91
g 81
g 77
g 81
i
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i
n 99 (2.00)
n 94 (0.777)
n 102 (1.30)
n 104 (1.21)
n 106 (0.855)
n 108 (0.834)
n 120 (0.798)
n 124 (1.18)
s
A 139 (3.18)
n 137 (0.710)
n 144 (1.18)
s
s
s
A 164 (2.59)
A 171 (3.06)
A 169 (4.00)
a
Observed on heating; g ) glass, sC ) smectic C, sA ) smectic
A, and i ) isotropic; n methylenic units, m perfluoromethylenic
units; mru ) moles repeat unit.
Ta ble 5. P olym er iza tion of 5-{[[2′,5′-Bis[(4′′-n -
((p er flu or oa lk yl)a lk oxy)ben zoyl)oxy]ben zyl]oxy]-
ca r bon yl}bicyclo[2.2.1]h ep t-2-en es a n d Ch a r a cter iza tion
of th e Resu ltin g P olym er sa
GPCb
n
m
[M]0/[I]0
yield (%)
Mn × 10-4
DPn
pdi
3
4
5
6
8
3
4
5
6
8
3
4
5
6
8
2
2
2
2
2
3
3
3
3
3
4
4
4
4
4
50
54
50
52
45
49
52
38
49
51
52
50
50
53
50
88
39
34
82
18
84
20
86
82
92
75
78
75
65
80
3.24
7.59
3.12
2.26
3.03
9.98
1.38
4.37
4.36
2.75
4.61
6.06
7.44
4.37
5.99
40
89
36
25
31
108
15
45
43
26
45
58
69
40
52
1.43
1.47
1.34
1.40
1.49
1.36
1.16
1.28
1.32
1.25
1.34
1.45
1.57
1.45
1.39
F igu r e 4. Temperature of isotropization of poly{5-[[[2′,5′-bis-
[(4′′-n-((perfluoroalkyl)alkoxy)benzoyl)oxy]benzyl]oxy]carbonyl]-
bicyclo[2.2.1]hept-2-ene}s as a function of the total number of
carbons in the n-alkoxy substituents at various fluorocarbon
lengths (m perfluoromethylenic units).
a
Polymerized in THF at room temperature for 2 h; n methylenic
b
units, m perfluoromethylenic units. Number average molecular
weight (Mn), number average degree of polymerization (DPn), and
polydispersity (pdi)Mw/Mn) determined by gel permeation chro-
matography (GPC) relative to polystyrene.
a sA mesophase. The m ) 3 and m ) 4 polymers with
shorter hydrocarbon segments, and with the exception
of the n, m ) 3, 2 polymer, all of the m ) 2 polymers
exhibit only a nematic mesophase. The changes in the
enthalpy of isotropization reported in Table 6 are also
consistent with those of the n-i and sA-i transitions
reported previously4 for the polymers with longer hy-
drocarbon and fluorocarbon segments, and in Table 1
for the model compounds.
A polarized optical micrograph is presented in the
Supporting Information which is representative of the
texture observed for the majority of the SCLCPs pre-
sented in Table 6. The nematic schlieren texture grows
in via tiny droplets, and although highly threaded, the
2- and 4-brush singularities are visible. The polymers
with a sA mesophase first exhibit well-defined batonnets
on cooling from the isotropic melt before developing into
an ill-defined, highly threaded texture.
Figures 4 and 5 plot the isotropization temperature
of the polymers as a function of the total number of
carbons in both the hydrocarbon and fluorocarbon
segments (n + m) and the number of carbons (n) in the
hydrocarbon segments, respectively, for fluorocarbon
lengths of m ) 2-4 and m ) 6-8.4 Both figures also
plot the temperature of the nematic-isotropic transi-
tions of their hydrocarbon analogues10,13 (m ) 0). All of
homogeneous throughout the polymerization. In almost
all cases, however, the polymers were contaminated
with a low molecular weight tail, and in some cases a
double molecular weight shoulder due to oxygen.16
Hence the polymers were purified by fractional precipi-
tation prior to thermal analysis. Table 5 summarizes
the final molecular weights and molecular weight
distributions (pdi) of the polymers used for thermal
analysis. The polynorbornenes generally had a degree
of polymerization (DPn) greater than 25, which is the
minimum required for the thermotropic behavior of
mesogenic polynorbornenes to be independent of mo-
lecular weight.10,11
Table 6 summarizes the thermal transitions of the 15
polynorbornenes. The data were obtained on heating
and are from thermally equilibrated samples. In con-
trast to the model compounds, terminating the n-alkoxy
substituents of the nematic polymers with fluorocarbon
segments of three or four perfluoromethylenic units is
only effective at inducing smectic layering when the
hydrocarbon segment contains at least eight or five
methylenic units, respectively; these compounds exhibit

Macromolecules, Vol. 35, No. 6, 2002
Induction of Smectic Layering 2111
and changes in enthalpy at each transition, microseg-
regation of the two components in these amphiphilic
molecules is apparently weak at the minimum lengths
required for smectic layering.
Exp er im en ta l Section
Ma ter ia ls. Acryloyl chloride (96%), 4-bromo-1-butene (97%),
8-bromo-1-octene (98%), 5-bromo-1-pentene (97%), ethyl 4-hy-
droxybenzoate (99%), methyl hydroquinone (99%), penta-
fluoroethyl iodide (97%), perfluorobutyl iodide (98%), and
tetrabutylammonium hydrogen sulfate (TBAH, 99%) were
used as received from Aldrich. Allyl bromide (Lancaster),
6-bromo-1-hexene (Fluka, 95%), 1,3-dicyclohexylcarbodiimide
(DCC, 99%, Acros), 4-(dimethylamino)pyridine (DMAP, Lan-
caster, 99%), heptafluoropropyl iodide (Lancaster, 98%), p-
toluenesulfonic acid (Mallinckrodt), and tributyltin hydride
(Fluka, 97%) were also used as received. 2,2′-Azobisisobuty-
ronitrile (AIBN, Kodak) was recrystallized from methanol
below 40 °C. Benzaldehyde (Aldrich, 99%) was distilled under
N2 before use. N-Bromosuccinimide (NBS, Aldrich, 99%) was
recrystallized from boiling water. Cyclopentadiene was freshly
cracked from dicyclopentadiene (Aldrich, 95%). Mo(CHCMe2-
Ph)(N-2,6-iPr2Ph)(OtBu)2 was synthesized by a literature
procedure,19except that hexanes were used throughout the
synthesis instead of pentane, or purchased from Strem and
used after recrystalization from dry hexanes. Potassium
bicyclo[2.2.1]hept-2-ene-5-carboxylate (68% endo, 32% exo) was
synthesized as previously reported.4 CH2Cl2 was washed with
10% HNO3 in H2SO4, stored over CaCl2, and then distilled from
CaH2 under N2. Reagent grade dimethyl sulfoxide (DMSO) was
dried by distillation from CaH2 under N2. Hexanes used in all
drybox procedures were washed with 5% HNO3 in H2SO4,
stored over CaCl2, and then distilled from purple sodium
benzophenone ketyl under N2. Reagent grade tetrahydrofuran
(THF) and toluene were dried by distillation from purple
sodium benzophenone keytl under N2. THF used as a poly-
merization solvent was vacuum transferred from purple
sodium benzophenone ketyl on a high vacuum line and then
vigorously degassed by several freeze-pump-thaw cycles
immediately before use. All other reagents and solvents were
commercially available and used as received.
Tech n iqu es. All polymerizations were performed under a
N2 atmosphere in a Vacuum Atmospheres drybox. All other
reactions were performed outside the drybox under a N2
atmosphere. 1H NMR spectra (δ, ppm) were recorded on a
Bruker AC-200 (200 MHz), Bruker AM-300 (300 MHz),
Mercury 300 (300 MHz), Bruker AM-360 (360 MHz), or a
Varian Unity INOVA 400 (400 MHz) spectrometer. Unless
noted otherwise, all spectra were recorded in CDCl3. 1H
resonances were measured relative to residual solvent reso-
nances and referenced to Me4Si. Relative molecular weights
were determined by gel permeation chromatography (GPC) at
35 °C using THF as solvent (1.0 mL/min), a set of 50, 100,
500, 104, and linear (50-104) Å Styragel 5 µ columns, a Waters
486 tunable UV/Vis detector set at 290 nm, and a Waters 410
differential refractometer. Elemental analyses were performed
on a PE 2400 Series II CHNS/O Analyzer by CHN/AA services,
Department of Chemistry, University of Michigan. Two analy-
ses were performed on each sample submitted, and the average
values are reported.
F igu r e 5. Temperature of isotropization of poly{5-[[[2′,5′-bis-
[(4′′-n-((perfluoroalkyl)alkoxy)benzoyl)oxy]benzyl]oxy]carbonyl]-
bicyclo[2.2.1]hept-2-ene}s as a function of the number of
carbons (n) in the hydrocarbon substituents at various fluoro-
carbon lengths (m perfluoromethylenic units).
the polymers whose isotropization temperatures are at
or below the Ti vs n line in Figure 5 for the hydrocarbon
analogues (m ) 0) undergo isotropization from a ne-
matic mesophase rather than from a sA mesophase.
However, a few of the polymers with nematic meso-
phases have isotropization temperatures slightly above
the Ti vs n + m line in Figure 4 for the hydrocarbon
analogues (m ) 0). In addition, unlike the SCLCPs with
m ) 6-8 and all of the model compounds, the transition
temperatures increase with increasing hydrocarbon
length. This suggests that the hydrocarbon and fluoro-
carbon segments of the polymers are not microphase
separated when m e 4.
Con clu sion s
Nematic LMMLCs and laterally attached side-chain
liquid crystalline polynorbornenes with 1,4-bis[(4′-n-
alkoxybenzoyl)oxy]benzene mesogens can be forced to
order into smectic layers by terminating their n-alkoxy
substituents with fluorocarbon segments. Since ali-
phatic hydrocarbons and fluorocarbons are highly im-
miscible,17 we attribute this layered organization to
microphase separation of the two components of the
amphiphilic substituents; however, the immiscibility of
n-alkanes and n-perfluoroalkanes is directly propor-
tional to their lengths.18 In contrast to this concept for
inducing smectic layering in nematic liquid crystals,
smectic liquid crystals can be converted to nematic
liquid crystals by laterally substituting the mesogen
with bulky groups.3 Therefore, as the bulk of the lateral
substituent on the 1,4-bis{[4′-(n-(perfluoroalkyl)alkoxy)-
benzoyl]oxy}benzene mesogens increases from methyl,
to norbornyl, to polynorbornyl, increasingly longer
hydrocarbon and/or fluorocarbon segments are required
to induce smectic layering. The 2,5-bis{[4′-(n-(perfluoro-
alkyl)alkoxy)benzoyl]oxy}toluene model compounds ex-
hibit only smectic mesophases when the hydrocarbon
and fluorocarbon segments are both as short as three
methylenic units. The norbornene monomers exhibit
smectic mesophases when the hydrocarbon and fluoro-
carbon segments are as short as five and three, or three
and four, methylenic units, respectively. The polynor-
bornenes require at least eight and three, or five and
four, methylenic units in the hydrocarbon and fluoro-
carbon segments, respectively, to organize into smectic
layers. Nevertheless, on the basis of the isotropization
temperatures relative to their hydrocarbon analogues
The thermotropic behavior of all compounds was determined
by a combination of differential scanning calorimetry (DSC)
and polarized optical microscopy. A Perkin-Elmer DSC-7
differential scanning calorimeter was used to determine the
thermal transitions, which were read as the maximum or
minimum of the endothermic or exothermic peaks, respec-
tively. Glass transition temperatures (Tgs) were read as the
middle of the change in heat capacity. All heating and cooling
rates were 10 °C/min. Both enthalpy changes and transition
temperatures were determined using indium as a calibration
standard. All samples were initially heated three times and
cooled twice; their equilibrium transition temperatures and
enthalpies were subsequently determined through extensive
annealing and quenching studies. A Leitz Laborlux 12 Pol S

2112 Small and Pugh
Macromolecules, Vol. 35, No. 6, 2002
polarized optical microscope (magnification 200x) equipped
with a Mettler FP82 hot stage and a Mettler FP90 central
processor was used to observe the thermal transitions and to
analyze the anisotropic textures.12 Thin samples were prepared
by melting a minimum amount of compound between a clean
glass slide and a cover slip and rubbing the cover slip with a
spatula.
4-(n -Alk en yloxy)ben zoic Acid s (n ) 3)6, 8) a n d 4-(n -
(P er flu or oa lk yl)a lk oxy)ben zoic Acid s (n ) 3)6, 8; m )
2). 4-(n-Prop-2′-enyloxy)benzoic acid and the 4-(n-(perfluoro-
alkyl)alkoxy)benzoic acids were prepared in 73-94% yield as
described previously for the 4-(n-alkenyloxy)benzoic acids4 with
n ) 4-6, 8. For example, ethyl 4-(n-prop-2′-enyloxy)benzoate
(6.2 g, 30 mmol) and sodium hydroxide (2.4 g, 61 mmol) in
ethanol (50 mL) and water (50 mL) were refluxed overnight.
After cooling to room temperature, the solution was acidified
to a pH of 2 with concentrated HCl. The resulting precipitate
was collected and recrystallized from ethanol (135 mL) to yield
4.4 g (82%) of 4-(n-prop-2′-enyloxy)benzoic acid as white
Syn th esis of Mon om er s a n d P r ecu r sor s. Eth yl 4-(n -
Alk en yloxy)ben zoa tes (n ) 3)6, 8). Ethyl 4-(n-prop-2′-
enyloxy)benzoate was prepared in 81% yield as described
previously for the ethyl 4-(n-alkenyloxy)benzoates4 with n )
1
4-6, 8. H NMR: 1.37 (t, J ) 7.1 Hz, CH3CH2O2C), 4.34 (q, J
1
crystals. H NMR: 4.62 (dt, J ) 5.3, 1.5 Hz, OCH2), 5.33 (dq,
) 7.1 Hz, CH2O2C), 4.59 (dt, J ) 5.3, 1.5 Hz, OCH2), 5.31 (dq,
J ) 10.5, 1.4 Hz, E-HCHdCH), 5.42 (dq, J ) 17.3, 1.6 Hz,
Z-HCHdCH), 6.05 (ddt, J ) 17.3, 10.4, 5.3 Hz, CH)CH2), 6.92
(AA′XX′, 2 aromatic H ortho to OCH2), 7.99 (AA′XX′, 2 aromatic
H ortho to CO2).
J ) 10.5, 1.4 Hz, E-HCHdCH), 5.44 (dq, J ) 17.3, 1.6 Hz,
Z-HCHdCH), 6.06 (ddt, J ) 17.3, 10.5, 5.3 Hz, CH)CH2), 6.96
(AA′XX′, 2 aromatic H ortho to OCH2), 8.06 (AA′XX′, 2 aromatic
H ortho to CO2). Anal. Calcd for C10H10O3: C, 67.41; H, 5.66.
Found: C, 67.49; H, 5.81.
Eth yl 4-(n -(P en ta flu or oeth yl)a lk oxy)ben zoa tes (n )
3)6, 8; m ) 2). The ethyl 4-(n-(pentafluoroethyl)alkoxy)-
benzoates were synthesized in 36-68% yield as in the follow-
ing example. Ethyl 4-(n-prop-2′-enyloxy)benzoate (4.1 g, 20
mmol) and AIBN (0.32 g, 2.0 mmol) were placed in a 100 mL
heavy walled glass reactor. The reactor was placed in liquid
N2 for 20 min, a slight vacuum was pulled, and then penta-
fluoroethyl iodide (8.5 g, 35 mmol) was condensed into the
flask. The solution was degassed by several freeze-pump-
thaw cycles and then heated at 70 °C under a static vacuum.
After 16 h, the conversion was determined by 1H NMR and
the above process was repeated until over 95% of the ethyl
4-(n-prop-2′-enyloxy)benzoate was consumed. AIBN (0.50 g, 3.0
mmol) and tributyltin hydride (8.0 mL, 30 mmol) were then
added to the reactor and the reaction heated at 70 °C under
N2 for 2 h. After 1H NMR demonstrated that the reduction
was complete, the mixture was dissolved in CH2Cl2/hexanes/
petroleum ether (5:2:1, 20 mL) and purified by repeated
column chromatography using silica gel as the stationary
phase and CH2Cl2/hexanes/petroleum ether (5:2:1) as the
eluent. The solvent was removed in vacuo to yield 2.9 g (44%)
of ethyl 4-(n-(pentafluoroethyl)propoxy)benzoate as a white
solid. Recrystallization from dry hexanes (30 mL) yielded 2.3
g (36%) of a white crystalline solid, mp ) 73 °C. 1H NMR: 1.38
(t, J ) 7.1 Hz, CH3CH2O2C), 2.12 (m, CH2CH2CF2), 2.26 (m,
CH2CF2), 4.09 (t, J ) 5.9 Hz, OCH2), 4.35 (q, J ) 7.1 Hz,
CH2O2C), 6.90 (AA′XX′, 2 aromatic H ortho to OCH2), 8.00
(AA′XX′, 2 aromatic H ortho to CO2). Anal. Calcd for
4-(n -(P en ta flu or oeth yl)p r op oxy)ben zoic Acid . 1H
NMR: 2.14 (m, CH2CH2CF2), 2.28 (m, CH2CF2), 4.11 (t, J )
5.9 Hz, OCH2), 6.94 (d, J ) 8.9 Hz, 2 aromatic H ortho to
OCH2), 8.07 (d, J ) 8.9 Hz, 2 aromatic H ortho to CO2). Anal.
Calcd for C12H11F5O3: C, 48.33; H, 3.72. Found: C, 48.23; H,
3.73.
4-(n -(P en ta flu or oeth yl)bu toxy)ben zoic
Acid .
1H
NMR: 1.83 (m, CH2CH2CF2), 1.90 (m, CH2CH2O), 2.13 (m,
CH2CF2), 4.07 (t, J ) 5.9 Hz, OCH2), 6.90 (d, J ) 8.8 Hz, 2
aromatic H ortho to OCH2), 7.99 (d, J ) 8.9 Hz, 2 aromatic H
ortho to CO2). Anal. Calcd for C13H13F5O3: C, 50.01, 4.20.
Found: C, 49.80; H, 4.36.
4-(n -(P en ta flu or oeth yl)p en toxy)ben zoic
Acid . 1H
NMR: 1.61 (m, CH2CH2CH2CF2), 1.68 (m, CH2CH2CF2), 1.86
(m, CH2CH2O), 2.07 (m, CH2CF2), 4.05 (t, J ) 6.3 Hz, OCH2),
6.92 (d, J ) 8.8 Hz, 2 aromatic H ortho to OCH2), 8.05 (d,
J
C
) 8.7 Hz, 2 aromatic H ortho to CO2). Anal. Calcd for
14H15F5O3: C, 51.54; H, 4.63. Found: C, 51.38; H, 4.51.
4-(n -(P en ta flu or oeth yl)h exoxy)ben zoic
Acid .
1H
NMR: 1.50 (m, (CH2)2CH2CH2CF2), 1.64 (m, CH2CH2CF2), 1.84
(m, CH2CH2O), 2.04 (m, CH2CF2), 4.04 (t, J ) 6.2 Hz, OCH2),
6.93 (d, J ) 8.7 Hz, 2 aromatic H ortho to OCH2), 8.06 (d,
J
C
) 8.9 Hz, 2 aromatic H ortho to CO2). Anal. Calcd for
15H17F5O3: C, 52.94; H, 5.04. Found: C, 53.07; H, 5.20.
4-(n -(P en ta flu or oeth yl)octyloxy)ben zoic Acid . 1H
NMR: 1.38 (m, (CH2)3CH2CH2CF2), 1.48 (m, CH2CH2CH2O),
1.59 (m, CH2CH2CF2), 1.81 (m, CH2CH2O), 2.01 (m, CH2CF2),
4.02 (t, J ) 6.5 Hz, OCH2), 6.93 (d, J ) 8.9 Hz, 2 aromatic H
ortho to OCH2), 8.05 (d, J ) 8.9 Hz, 2 aromatic H ortho to
CO2). Anal. Calcd for C17H21F5O3: C, 55.43; H, 5.75. Found:
C, 55.42; H, 6.00.
C
14H15F5O3: C, 51.54; H, 4.63. Found: C, 51.55; H, 4.57.
Eth yl 4-(n -(P en ta flu or oeth yl)bu toxy)ben zoa te. Mp )
44 °C. 1H NMR: 1.38 (t, J ) 7.1 Hz, CH3CH2O2C), 1.81 (m,
CH2CH2CF2), 1.87 (m, CH2CH2O), 2.12 (m, CH2CF2), 4.05 (t,
J ) 5.9 Hz, OCH2), 4.35 (q, J ) 7.1 Hz, CH2O2C), 6.90 (AA′XX′,
2 aromatic H ortho to OCH2), 7.99 (AA′XX′, 2 aromatic H ortho
to CO2). Anal. Calcd for C15H17F5O3: C, 52.94; H, 5.04.
Found: C, 52.73; H, 4.83.
2,5-Bis[(4′-(n -a lk en yloxy)ben zoyl)oxy]tolu en es (n
)
3)6, 8) a n d 2,5-Bis[(4′-(n -(p er flu or oa lk yl)a lk oxy)ben -
zoyl)oxy]tolu en es (n ) 3)6, 8; m ) 2). 2,5-Bis[(4′-(n-prop-
2′′-enyloxy)benzoyl)oxy]toluene and the 2,5-bis[(4′-(n-(per-
fluoroalkyl)alkoxy)benzoyl)oxy]toluenes were prepared in
84-95% yield as described previously for the 2,5-bis[(4′-(n-
alkenyloxy)benzoyl)oxy]toluenes4 with n ) 4-6, 8.
Eth yl 4-(n -(P en ta flu or oeth yl)p en toxy)ben zoa te. Mp )
60 °C. 1H NMR: 1.38 (t, J ) 7.1 Hz, CH3CH2O2C), 1.58 (m,
CH2CH2CH2CF2), 1.68 (m, CH2CH2CF2), 1.85 (m, CH2CH2O),
2.06 (m, CH2CF2), 4.02 (t, J ) 6.2 Hz, OCH2), 4.34 (q, J ) 7.1
Hz, CH2O2C), 6.89 (AA′XX′, 2 aromatic H ortho to OCH2), 7.99
(AA′XX′, 2 aromatic H ortho to CO2). Anal. Calcd for
2,5-Bis[(4′-(n -p r op -2′′-en yloxy)ben zoyl)oxy]tolu en e. 1H
NMR: 2.25 (s, ArCH3), 4.64 (m, CH2CH), 4 H), 5.35 (m,
E-HCHdCH, 2 H), 5.45 (m, Z-HCHdCH, 2 H), 6.08 (m,
CH)CH2, 2 H), 7.00 (m, 4 aromatic H ortho to OCH2), 7.08
(dd, J ) 8.6, 2.8 Hz, 1 aromatic H para to CH3), 7.13 (d, J )
2.7 Hz, 1 aromatic H ortho to CH3), 7.17 (d, J ) 8.6 Hz, 1
aromatic H meta to CH3), 8.15 (m, 4 aromatic H ortho to CO2).
Anal. Calcd for C27H24O6: C, 72.96; H, 5.44. Found: C, 73.22;
H, 5.63.
C
16H19F5O3: C, 54.24; H, 5.40. Found: C, 53.98; H, 5.45.
Eth yl 4-(n -(P en ta flu or oeth yl)h exoxy)ben zoa te. Mp )
42 °C. 1H NMR: 1.38 (t, J ) 7.1 Hz, CH3CH2O2C), 1.50 (m,
(CH2)2CH2CH2CF2), 1.63 (m, CH2CH2CF2), 1.82 (m, CH2CH2O),
2.03 (m, CH2CF2), 4.01 (t, J ) 6.3 Hz, OCH2), 4.34 (q, J ) 7.1
Hz, CH2O2C), 6.89 (AA′XX′, 2 aromatic H ortho to OCH2), 7.98
(AA′XX′, 2 aromatic H ortho to CO2). Anal. Calcd for
2,5-Bis[(4′-(n -(p en ta flu or oeth yl)p r op oxy)ben zoyl)oxy]-
tolu en e. 1H NMR: 2.15 (m, CH2CH2CF2, 4 H), 2.25 (s, ArCH3),
2.31 (m, CH2CF2, 4 H), 4.14 (m, OCH2, 4 H), 6.99 (m, 4
aromatic H ortho to OCH2), 7.09 (dd, J ) 8.6, 2.7 Hz, 1
aromatic H para to CH3), 7.13 (d, J ) 2.9 Hz, 1 aromatic H
ortho to CH3), 7.18 (d, J ) 8.7 Hz, 1 aromatic H meta to CH3),
8.17 (m, 4 aromatic H ortho to CO2). Anal. Calcd for
C
17H21F5O3: C, 55.43; H, 5.75. Found: C, 55.52; H, 5.64.
Eth yl 4-(n -(P en ta flu or oeth yl)octyloxy)ben zoa te. Mp )
43 °C. 1H NMR: 1.38 (m, CH3CH2O2C and (CH2)3CH2CH2CF2),
1.46 (m, CH2CH2CH2O), 1.59 (m, CH2CH2CF2), 1.80 (m,
CH2CH2O), 2.01 (m, CH2CF2), 4.00 (t, J ) 6.5 Hz, OCH2), 4.34
(q, J ) 7.1 Hz, CH2O2C), 6.89 (AA′XX′, 2 aromatic H ortho to
OCH2), 7.98 (AA′XX′, 2 aromatic H ortho to CO2). Anal. Calcd
for C19H25F5O3: C, 57.57; H, 6.36. Found: C, 57.57; H, 6.50.
C
31H26F10O6: C, 54.39; H, 3.83. Found: C, 54.40; H, 3.81.
2,5-Bis[(4′-(n -(p en ta flu or oeth yl)bu toxy)ben zoyl)oxy]-
t olu en e. 1H NMR: 1.84 (m, CH2CH2CF2, 4 H), 1.92 (m,

Macromolecules, Vol. 35, No. 6, 2002
Induction of Smectic Layering 2113
CH2CH2O, 4 H), 2.14 (m, CH2CF2, 4 H), 2.25 (s, ArCH3), 4.09
(m, OCH2, 4 H), 6.98 (m, 4 aromatic H ortho to OCH2), 7.08
(dd, J ) 8.5, 2.8 Hz, 1 aromatic H para to CH3), 7.13 (d, J )
2.7 Hz, 1 aromatic H ortho to CH3), 7.18 (d, J ) 8.7 Hz, 1
aromatic H meta to CH3), 8.16 (m, 4 aromatic H ortho to CO2).
Anal. Calcd for C33H30F10O6: C, 55.62; H, 4.24. Found: C,
55.72; H, 4.28.
8.16 (m, 4 aromatic H ortho to CO2). Anal. Calcd for
C
35H30F14O6: C, 51.73; H, 3.72. Found: C, 51.84; H, 3.84. Anal.
Calcd for C37H30F18O6: C, 48.70; H, 3.31. Found: C, 48.85; H,
3.48.
The 1H NMR spectra of the 2,5-bis[(4′-(n-(perfluoroalkyl)-
pentoxy)benzoyl)oxy]toluenes with m ) 3-4 are identical: 1.62
(m, CH2CH2CH2CF2, 4 H), 1.71 (m, CH2CH2CF2, 4 H), 1.88
(m, CH2CH2O, 4 H), 2.11 (m, CH2CF2, 4 H), 2.24 (s, ArCH3),
4.07 (m, OCH2, 4 H), 6.97 (m, 4 aromatic H ortho to OCH2),
7.08 (dd, J ) 8.6, 2.8 Hz, 1 aromatic H para to CH3), 7.13 (d,
J ) 2.5 Hz, 1 aromatic H ortho to CH3), 7.18 (d, J ) 8.7 Hz, 1
aromatic H meta to CH3), 8.16 (m, 4 aromatic H ortho to CO2).
Anal. Calcd for C37H34F14O6: C, 52.86; H, 4.08. Found: C,
52.95; H, 4.11. Anal. Calcd for C39H34F18O6: C, 49.80; H, 3.64.
Found: C, 49.77; H, 3.88.
2,5-Bis[(4′-(n -(p en ta flu or oeth yl)p en toxy)ben zoyl)oxy]-
1
tolu en e. H NMR: 1.63 (m, CH2CH2CH2CF2, 4 H), 1.71 (m,
CH2CH2CF2, 4 H), 1.88 (m, CH2CH2O, 4 H), 2.08 (m, CH2CF2,
4 H), 2.24 (s, ArCH3), 4.07 (m, OCH2, 4 H), 6.98 (m, 4 aromatic
H ortho to OCH2), 7.08 (dd, J ) 8.7, 2.6 Hz, 1 aromatic H para
to CH3), 7.13 (d, J ) 2.4 Hz, 1 aromatic H ortho to CH3), 7.18
(d, J ) 8.6 Hz, 1 aromatic H meta to CH3), 8.16 (m, 4 aromatic
H ortho to CO2). Anal. Calcd for C35H34F10O6: C, 56.76; H, 4.63.
Found: C, 56.88; H, 4.89.
The 1H NMR spectra of the 2,5-bis[(4′-(n-(perfluoroalkyl)-
hexoxy)benzoyl)oxy]toluenes with m ) 3-4 are identical: 1.52
(m, (CH2)2CH2CH2CF2, 8 H), 1.66 (m, CH2CH2CF2, 4 H), 1.86
(m, CH2CH2O, 4 H), 2.07 (m, CH2CF2, 4 H), 2.24 (s, ArCH3),
4.06 (m, OCH2, 4 H), 6.98 (m, 4 aromatic H ortho to OCH2),
7.08 (dd, J ) 8.8, 2.5 Hz, 1 aromatic H para to CH3), 7.13 (d,
J ) 2.5 Hz, 1 aromatic H ortho to CH3), 7.18 (d, J ) 8.7 Hz, 1
aromatic H meta to CH3), 8.16 (m, 4 aromatic H ortho to CO2).
Anal. Calcd for C39H38F14O6: C, 53.92, 4.41. Found: C, 53.70;
H, 4.56. Anal. Calcd for C41H38F18O6: C, 50.84; H, 3.95.
Found: C, 50.86; H, 3.99.
The 1H NMR spectra of the 2,5-bis[(4′-(n-(perfluoroalkyl)-
octyloxy)benzoyl)oxy]toluenes with m ) 3-4 are identical: 1.39
(m, (CH2)3CH2CH2CF2, 12 H), 1.50 (m, CH2CH2CH2O, 4 H),
1.62 (m, CH2CH2CF2, 4 H), 1.83 (m, CH2CH2O, 4 H), 2.04 (m,
CH2CF2, 4 H), 2.24 (s, ArCH3), 4.05 (m, OCH2, 4 H), 6.97 (m,
4 aromatic H ortho to OCH2), 7.08 (dd, J ) 8.6, 2.6 Hz, 1
aromatic H para to CH3), 7.13 (d, J ) 2.7 Hz, 1 aromatic H
ortho to CH3), 7.17 (d, J ) 8.6 Hz, 1 aromatic H meta to CH3),
8.15 (m, 4 aromatic H ortho to CO2). Anal. Calcd for
2,5-Bis[(4′-(n -(p en ta flu or oeth yl)h exoxy)ben zoyl)oxy]-
1
tolu en e. H NMR: 1.63 (m, CH2CH2CH2CF2, 4 H), 1.71 (m,
CH2CH2CF2, 4 H), 1.88 (m, CH2CH2O, 4 H), 2.04 (m, CH2CF2,
4 H), 2.24 (s, ArCH3), 4.07 (m, OCH2, 4 H), 6.98 (m, 4 aromatic
H ortho to OCH2), 7.08 (dd, J ) 8.7, 2.8 Hz, 1 aromatic H para
to CH3), 7.13 (d, J ) 2.7 Hz, 1 aromatic H ortho to CH3), 7.18
(d, J ) 8.7 Hz, 1 aromatic H meta to CH3), 8.16 (m, 4 aromatic
H ortho to CO2). Anal. Calcd for C37H38F10O6: C, 57.81; H, 4.98.
Found: C, 57.85; H, 4.96.
2,5-Bis[(4′-(n -(p en ta flu or oeth yl)octyloxy)ben zoyl)oxy]-
tolu en e. 1H NMR: 1.39 (m, (CH2)3CH2CH2CF2, 12 H), 1.49
(m, CH2CH2CH2O, 4 H), 1.60 (m, CH2CH2CF2, 4 H), 1.83 (m,
CH2CH2O, 4 H), 2.02 (m, CH2CF2, 4 H), 2.24 (s, ArCH3), 4.05
(m, OCH2, 4 H), 6.97 (m, 4 aromatic H ortho to OCH2), 7.08
(dd, J ) 8.6, 2.6 Hz, 1 aromatic H para to CH3), 7.13 (d, J )
2.6 Hz, 1 aromatic H ortho to CH3), 7.17 (d, J ) 8.6 Hz, 1
aromatic H meta to CH3), 8.15 (m, 4 aromatic H ortho to CO2).
Anal. Calcd for C41H46F10O6: C, 59.71; H, 5.62. Found: C,
59.60; H, 5.88.
2,5-Bis[(4′-(n -(p e r flu or oa lk yl)a lk oxy)b e n zoyl)oxy]-
t olu en es (n ) 3)6, 8; m ) 3)4). The 2,5-bis[(4′-(n-(per-
fluoroalkyl)alkoxy)benzoyl)oxy]toluenes were prepared in 46-
80% yield as in the following example. 2,5-Bis[(4′-(n-prop-2′′-
enyloxy)benzoyl)oxy]toluene (2.1 g, 4.8 mmol), heptafluoro-
propyl iodide (2.3 mL, 16 mmol), AIBN (0.28 g, 1.7 mmol) and
dry toluene (1.4 mL) were combined in a Schlenk flask, which
was then sealed with a rubber septum. The solution was
degassed by several freeze-pump-thaw cycles and then filled
with N2 and heated at 70 °C for 16 h. This process was
C
43H46F14O6: C, 55.85; H, 5.01. Found: C, 55.74; H, 5.08. Anal.
Calcd for C45H46F18O6: C, 52.74; H, 4.52. Found: C, 52.53; H,
4.63.
2,5-Bis[(4′-n -((p e r flu or oa lk yl)a lk oxy)b e n zoyl)oxy]-
ben zyl br om id es (n ) 3)6, 8; m ) 2)4). The 2,5-bis[(4′-
n-((perfluoroalkyl)alkoxy)benzoyl)oxy]benzyl bromides were
prepared in 41-70% yield as in the following example. A
solution of 2,5-bis[(4′-(n-(pentafluoroethyl)propoxy)benzoyl)-
oxy]toluene (1.6 g, 2.3 mmol), AIBN (21 mg, 0.13 mmol) and
NBS (0.74 g, 4.2 mmol) in benzene (14 mL) was heated at
reflux for 4 h. The resulting orange mixture was then poured
immediately into 5% aq sodium bisulfite (40 mL) in a sepa-
ratory funnel. The organic layer was collected and the solvent
was removed by rotary evaporation. The residue was dissolved
in a minimal amount of CH2Cl2 (3 mL) and precipitated in
cold methanol (100 mL). The precipitate was collected and
dried in vacuo to yield 1.2 g (68%) of a white solid containing
60% 2,5-bis[(4′-(n-(pentafluoroethyl)propoxy)benzoyl)oxy]benzyl
bromide (41% overall yield), 6% unreacted 2,5-bis[(4′-(n-
(pentafluoroethyl)propoxy)benzoyl)oxy]toluene, and 34% 2,5-
bis[(4′-(n-(pentafluoroethyl)propoxy)benzoyl)oxy]benzyl dibro-
mide. This crude product was used without further purification.
The 1H NMR spectra of the 2,5-bis[(4′-(n-(perfluoroalkyl)-
1
repeated until H NMR demonstrated that greater than 90%
of the olefin had been consumed. AIBN (0.28 g, 1.7 mmol),
tributyltin hydride (4.6 mL, 17 mmol) and dry toluene (10 mL)
were then added to the flask and the reaction was heated
under N2 at 70 °C for 2 h. After 1H NMR demonstrated that
the reduction was complete, the reaction was poured into cold
hexanes (50 mL) and the precipitate was collected. The
precipitate was then purified by column chromatography using
silica gel as the stationary phase and CH2Cl2/hexanes/
petroleum ether (5:2:1) as the eluent. The solvent was removed
by rotary evaporation and the resulting solid was recrystallized
from ethanol (60 mL) and toluene (5 mL) to yield 1.7 g (46%)
of 2,5-bis[(4′-(n-(perfluoropropyl)propoxy)benzoyl)oxy]toluene
as white crystals. The 1H NMR spectra of the 2,5-bis[(4′-(n-
(perfluoroalkyl)propoxy)benzoyl)oxy]toluenes with m ) 3-4
are identical: 2.17 (m, CH2CH2CF2, 4 H), 2.25 (s, ArCH3), 2.32
(m, CH2CF2, 4 H), 4.14 (m, OCH2, 4 H), 6.99 (m, 4 aromatic H
ortho to OCH2), 7.09 (dd, J ) 8.6, 2.9 Hz, 1 aromatic H para
to CH3), 7.13 (d, J ) 2.7 Hz, 1 aromatic H ortho to CH3), 7.18
(d, J ) 8.6 Hz, 1 aromatic H meta to CH3), 8.17 (m, 4 aromatic
H ortho to CO2). Anal. Calcd for C33H26F14O6: C, 50.52; H, 3.34.
Found: C, 50.38; H, 3.53. Anal. Calcd for C35H26F18O6: C,
47.53; H, 2.96. Found: C, 47.46; H, 3.17.
propoxy)benzoyl)oxy]benzyl bromides with
m ) 2-4 are
identical: 2.17 (m, CH2CH2CF2, 4 H), 2.33 (m, CH2CF2, 4 H),
4.15 (m, OCH2, 4 H), 4.45 (s, ArCH2Br), 7.00 (m, 4 aromatic H
ortho to OCH2), 7.29 (m, 3 aromatic H of central ring), 8.19
(m, 4 aromatic H ortho to CO2).
The 1H NMR spectra of the 2,5-bis[(4′-(n-(perfluoroalkyl)-
butoxy)benzoyl)oxy]benzyl bromides with m ) 2-4 are identi-
cal: 1.86 (m, CH2CH2CF2, 4 H), 1.93 (m, CH2CH2O, 4 H), 2.18
(m, CH2CF2, 4 H), 4.10 (m, OCH2, 4 H), 4.45 (s, ArCH2Br),
6.99 (d, 4 aromatic H ortho to OCH2), 7.29 (m, 3 aromatic H of
central ring), 8.18 (d, 4 aromatic H ortho to CO2).
The 1H NMR spectra of the 2,5-bis[(4′-(n-(perfluoroalkyl)-
butoxy)benzoyl)oxy]toluenes with m ) 3-4 are identical: 1.86
(m, CH2CH2CF2, 4 H), 1.93 (m, CH2CH2O, 4 H), 2.15 (m,
CH2CF2, 4 H), 2.24 (s, ArCH3), 4.09 (m, OCH2, 4 H), 6.98 (m,
4 aromatic H ortho to OCH2), 7.08 (dd, J ) 8.4, 2.7 Hz, 1
aromatic H para to CH3), 7.13 (d, J ) 2.7 Hz, 1 aromatic H
ortho to CH3), 7.18 (d, J ) 8.7 Hz, 1 aromatic H meta to CH3),
The 1H NMR spectra of the 2,5-bis[(4′-(n-(perfluoroalkyl)-
pentoxy)benzoyl)oxy]benzyl bromides with
m ) 2-4 are
identical: 1.62 (m, CH2CH2CH2CF2, 4 H), 1.69 (m, CH2CH2-
CF2, 4 H), 1.89 (m, CH2CH2O, 4 H), 2.11 (m, CH2CF2, 4 H),
4.07 (m, OCH2, 4 H), 4.45 (s, ArCH2Br), 6.99 (m, 4 aromatic H

2114 Small and Pugh
Macromolecules, Vol. 35, No. 6, 2002
ortho to OCH2), 7.29 (m, 3 aromatic H of central ring), 8.18
(m, 4 aromatic H ortho to CO2).
H, 4.59. Anal. Calcd for n, m ) 4,3, C43H38F14O8, 31% endo:
C, 54.44; H, 4.04. Found: C, 54.75; H, 4.21. Anal. Calcd for n,
m ) 4, 4, C45H38F18O8, 67% endo: C, 51.54; H, 3.65. Found:
C, 51.08; H, 3.72.
The 1H NMR spectra of the 2,5-bis[(4′-(n-(perfluoroalkyl)-
hexoxy)benzoyl)oxy]benzyl bromides with m ) 2-4 are identi-
cal: 1.52 (m, (CH2)2CH2CH2CF2, 8 H), 1.66 (m, CH2CH2CF2, 4
H), 1.86 (m, CH2CH2O, 4 H), 2.08 (m, CH2CF2, 4 H), 4.07 (m,
OCH2, 4 H), 4.45 (s, ArCH2Br), 6.99 (m, 4 aromatic H ortho to
OCH2), 7.29 (m, 3 aromatic H of central ring), 8.17 (m, 4
aromatic H ortho to CO2).
The 1H NMR spectra of the 5-{[[2′,5′-bis[(4′′-(n-(perfluoro-
alkyl)pentoxy)benzoyl)oxy]benzyl]oxy]carbonyl}bicyclo[2.2.1]-
hept-2-enes with m ) 2-4 are identical: 1.31 (m, endo
norbornyl 6- and 7-CH2), 1.62 (m, CH2CH2CH2CF2, 4 H), 1.71
(m, CH2CH2CF2, 4 H), 1.88 (m, CH2CH2O and exo norbornyl
6-CH2), 2.10 (m, CH2CF2 and exo norbornyl 5-CH), 2.86 (m,
endo norbornyl 1-CH), 2.89 (m, exo norbornyl 4-CH), 2.92 (m,
endo norbornyl 5-CH), 2.95 (m, exo norbornyl 1-CH), 3.14 (m,
endo norbornyl 4-CH), 4.07 (t, J ) 6.2 Hz, OCH2, 4 H), 5.08
(AB, endo ArCH2O), 5.15 (s, exo ArCH2O), 5.80 (m, endo
norbornyl 2-CH), 6.04 (m, exo norbornyl 2-CH), 6.10 (m,
norbornyl 3-CH), 6.98 (m, 4 aromatic H ortho to OCH2), 7.27
(m, 3 aromatic H of central ring), 8.15 (m, 4 aromatic H ortho
to CO2). Anal. Calcd for n, m ) 5, 2, C43H42F10O8, 62% endo:
C, 58.90; H, 4.83. Found: C, 58.82; H, 4.91. Anal. Calcd for n,
m ) 5, 3, C45H42F14O8, 57% endo: C, 55.33; H, 4.33. Found:
C, 55.28; H, 4.48. Anal. Calcd for n, m ) 5, 4, C47H42F18O8,
73% endo: C, 52.42; H, 3.93. Found: C, 52.33; H, 4.09.
The 1H NMR spectra of the 5-{[[2′,5′-bis[(4′′-(n-(perfluoro-
alkyl)hexoxy)benzoyl)oxy]benzyl]oxy]carbonyl}bicyclo[2.2.1]-
hept-2-enes with m ) 2-4 are identical: 1.31 (m, endo
norbornyl 6- and 7-CH2), 1.52 (m, (CH2)2CH2CH2CF2, 8 H), 1.65
(m, CH2CH2CF2, 4 H), 1.84 (m, CH2CH2O and exo norbornyl
6-CH2), 2.08 (m, CH2CF2 and exo norbornyl 5-CH), 2.85 (m,
endo norbornyl 1-CH), 2.89 (m, exo norbornyl 4-CH), 2.91 (m,
endo norbornyl 5-CH), 2.95 (m, exo norbornyl 1-CH), 3.14 (m,
endo norbornyl 4-CH), 4.06 (t, J ) 6.3 Hz, OCH2, 4 H), 5.08
(AB, endo ArCH2O), 5.15 (s, exo ArCH2O), 5.80 (m, endo
norbornyl 2-CH), 6.04 (m, exo norbornyl 2-CH), 6.10 (m,
norbornyl 3-CH), 6.98 (m, 4 aromatic H ortho to OCH2), 7.28
(m, 3 aromatic H of central ring), 8.15 (m, 4 aromatic H ortho
to CO2). Anal. Calcd for n, m ) 6, 2, C45H46F10O8, 67% endo:
C, 59.73; H, 5.12. Found: C, 59.78; H, 5.16. Anal. Calcd for n,
m ) 6, 3, C47H46F14O8, 75% endo: C, 56.18; H, 4.61. Found:
C, 55.88; H, 4.69. Anal. Calcd for n, m ) 6, 4, C49H46F18O8,
45% endo: C, 53.27; H, 4.20. Found: C, 53.17; H, 4.41.
The 1H NMR spectra of the 5-{[[2′,5′-bis[(4′′-(n-(perfluoro-
alkyl)octyloxy)benzoyl)oxy]benzyl]oxy]carbonyl}bicyclo[2.2.1]-
hept-2-enes with m ) 2-4 are identical: 1.31 (m, endo
norbornyl 6- and 7-CH2), 1.39 (m, (CH2)3CH2CH2CF2, 12 H),
1.50 (m, CH2CH2CH2O, 4 H), 1.58 (m, CH2CH2CF2, 4 H), 1.83
(m, CH2CH2O and exo norbornyl 6-CH2), 2.02 (m, CH2CF2, 4
H), 2.17 (m, exo norbornyl 5-CH), 2.85 (m, endo norbornyl
1-CH), 2.89 (m, exo norbornyl 4-CH), 2.91 (m, endo norbornyl
5-CH), 2.95 (m, exo norbornyl 1-CH), 3.14 (m, endo norbornyl
4-CH), 4.05 (t, J ) 6.3 Hz, OCH2, 4 H), 5.08 (AB, endo
ArCH2O), 5.15 (s, exo ArCH2O), 5.80 (m, endo norbornyl 2-CH),
6.04 (m, exo norbornyl 2-CH), 6.10 (m, norbornyl 3-CH), 6.98
(d, 4 aromatic H ortho to OCH2), 7.28 (m, 3 aromatic H of
central ring), 8.14 (d, 4 aromatic H ortho to CO2). Anal. Calcd
for n, m ) 8, 2, C49H54F10O8, 67% endo: C, 61.25, 5.66. Found:
C, 61.21; H, 5.50. Anal. Calcd for n, m ) 8, 3, C51H54F14O8,
25% endo: C, 57.74; H, 5.13. Found: C, 57.48; H, 5.19. Anal.
Calcd for n, m ) 8, 4, C53H54F18O8, 31% endo: C, 54.83; H,
4.69. Found: C, 54.39; H, 4.78.
The 1H NMR spectra of the 2,5-bis[(4′-(n-(perfluoroalkyl)-
octyloxy)benzoyl)oxy]benzyl bromides with
m ) 2-4 are
identical: 1.39 (m, (CH2)3CH2CH2CF2, 12 H), 1.50 (m, CH2-
CH2CH2O, 4 H), 1.60 (m, CH2CH2CF2, 4 H), 1.83 (m, CH2CH2O,
4 H), 2.02 (m, CH2CF2, 4 H), 4.06 (m, OCH2, 4 H), 4.45 (s,
ArCH2Br), 6.99 (m, 4 aromatic H ortho to OCH2), 7.29 (m, 3
aromatic H of central ring), 8.17 (m, 4 aromatic H ortho to
CO2).
In addition to the above resonances, products from this
reaction contained singlets at 2.24 ppm (ArCH3) due to residual
starting material, and at 6.8 (ArCHBr2) and 7.7 ppm (1
aromatic H ortho to CHBr2) due to dibrominated material.
5-{[[2′,5′-Bis[(4′′-n -((p er flu or oa lk yl)a lk oxy)b en zoyl)-
oxy]ben zyl]oxy]ca r bon yl}bicyclo[2.2.1]h ep t-2-en es (n )
3)6, 8; m ) 2)4; 25)75% en d o). The monomers were
prepared in 33-85% yield as in the following example for n,
m ) 3, 2. A solution of 2,5-bis[(4′-(n-(pentafluoroethyl)propoxy)-
benzoyl)oxy]benzyl bromide (1.2 g, 0.93 mmol ArCH2Br),
TBAH (46 mg, 0.13 mmol), potassium bicyclo[2.2.1]hept-2-ene-
5-carboxylate (0.23 g, 1.3 mmol) and dry DMSO (0.70 mL) in
dry THF (7.0 mL) was heated at 60 °C for 22 h. The reaction
mixture was poured into cold water (100 mL) and extracted
twice with CH2Cl2 (100 mL total). The combined organic layers
were passed through a short column of basic activated alumina
using CH2Cl2 as the eluent. The solvent was removed by rotary
evaporation and the residue was purified by column chroma-
tography using silica gel as the stationary phase and a
gradient of CH2Cl2/hexanes as the eluent. The solvent was
removed by rotary evaporation and the residue was recrystal-
lized from ethanol (35 mL) and toluene (1 mL) to yield 0.57 g
(75%) of 5-{[[2′,5′-bis[(4′′-(n-(pentafluoroethyl)propoxy)benzoyl)-
oxy]benzyl]oxy]carbonyl}bicyclo[2.2.1]hept-2-ene as a white
solid. Before polymerization, the monomer was recrystallized
in a drybox from dry hexanes (12 mL) and toluene (9 mL);
1
yield, 0.47 g (62%). The H NMR spectra of the 5-{[[2′,5′-bis-
[(4′′-(n-(perfluoroalkyl)propoxy)benzoyl)oxy]benzyl]oxy]car-
bonyl}bicyclo[2.2.1]hept-2-enes with m ) 2-4 are identical:
1.31 (m, endo norbornyl 6- and 7-CH2), 1.83 (m, exo norbornyl
6-CH2), 2.17 (m, CH2CH2CF2 and exo norbornyl 5-CH), 2.33
(m, CH2CF2, 4 H), 2.86 (m, endo norbornyl 1-CH), 2.89 (m, exo
norbornyl 4-CH), 2.92 (m, endo norbornyl 5-CH), 2.95 (m, exo
norbornyl 1-CH), 3.14 (m, endo norbornyl 4-CH), 4.15 (t, J )
5.9 Hz, OCH2, 4 H), 5.09 (AB, endo ArCH2O), 5.15 (s, exo
ArCH2O), 5.80 (m, endo norbornyl 2-CH), 6.04 (m, exo nor-
bornyl 2-CH), 6.10 (m, norbornyl 3-CH), 6.99 (m, 4 aromatic
H ortho to OCH2), 7.29 (m, 3 aromatic H of central ring), 8.16
(m, 4 aromatic H ortho to CO2). Anal. Calcd for n, m ) 3, 2,
C
39H34F10O8, 67% endo: C, 57.08; H, 4.18. Found: C, 56.99;
H, 4.23. Anal. Calcd for n, m ) 3, 3, C41H34F14O8, 59% endo:
C, 53.49; H, 3.72. Found: C, 53.34; H, 3.85. Anal. Calcd for n,
m ) 3, 4, C43H34F18O8, 65% endo: C, 50.60; H, 3.36. Found:
C, 50.56; H, 3.52.
P o ly {5-[[[2′,5′-b is [(4′′-n -((p e r flu o r o a lk y l)a lk o x y )-
b en zoyl)oxy]b en zyl]oxy]ca r b on yl]b icyclo[2.2.1]h ep t -2-
en e}s (n ) 3)6, 8; m ) 2)4). The polynorbornenes were
prepared in 18-92% yield as in the following example. In a
drybox, a solution of 5-{[[2′,5′-bis[(4′′-(n-(pentafluoroethyl)-
propoxy)benzoyl)oxy]benzyl]oxy]carbonyl}bicyclo[2.2.1]hept-2-
ene (0.30 g, 0.36 mmol) in degassed THF (9.5 g) was added
dropwise over 3 min to a solution of Mo(CHCMe2Ph)(N-2,6-
iPr2Ph)(OtBu)2 (4 mg, 7 µmol) in THF (0.52 g) at 25 °C. After
being stirred at 25 °C for an additional 2 h, benzaldehyde (20
µL, 0.20 mmol) was added and the mixture was stirred for
another 30 min. The solution was removed from the drybox
and the polymer was precipitated in methanol (70 mL). The
precipitate was collected and reprecipitated from THF (14 mL)
into methanol (100 mL) to yield 0.26 g (88%) of poly{5-[[[2′,5′-
bis[(4′′-n-((perfluoroethyl)propoxy)benzoyl)oxy]benzyl]oxy]-
The 1H NMR spectra of the 5-{[[2′,5′-bis[(4′′-(n-(perfluoro-
alkyl)butoxy)benzoyl)oxy]benzyl]oxy]carbonyl}bicyclo[2.2.1]-
hept-2-enes with m ) 2-4 are identical: 1.31 (m, endo
norbornyl 6- and 7-CH2), 1.85 (m, CH2CH2CF2 and exo nor-
bornyl 6-CH2), 1.93 (m, CH2CH2O, 4 H), 2.18 (m, CH2CF2 and
exo norbornyl 5-CH), 2.86 (m, endo norbornyl 1-CH), 2.89 (m,
exo norbornyl 4-CH), 2.92 (m, endo norbornyl 5-CH), 2.95 (m,
exo norbornyl 1-CH), 3.14 (m, endo norbornyl 4-CH), 4.10 (t,
J ) 5.5 Hz, OCH2, 4 H), 5.08 (AB, endo ArCH2O), 5.15 (s, exo
ArCH2O), 5.80 (m, endo norbornyl 2-CH), 6.04 (m, exo nor-
bornyl 2-CH), 6.10 (m, norbornyl 3-CH), 6.98 (m, 4 aromatic
H ortho to OCH2), 7.28 (m, 3 aromatic H of central ring), 8.15
(m, 4 aromatic H ortho to CO2). Anal. Calcd for n, m ) 4, 2,
C
41H38F10O8, 75% endo: C, 58.02; H, 4.51. Found: C, 57.83;

Macromolecules, Vol. 35, No. 6, 2002
Induction of Smectic Layering 2115
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carbonyl]bicyclo[2.2.1]hept-2-ene} as a white powder; Mn
3.24 × 104, Mw/Mn ) 1.43.
)
Ack n ow led gm en t. Acknowledgment is made to the
donors of the Petroleum Research Fund, administered
by the American Chemical Society, for support of this
research. C.P. also acknowledges the National Science
Foundation for an NSF Young Investigator Award
(1994-2000), and matching funds from Goodyear Tire
& Rubber Company and A. Schulman, Inc. We also
thank Professor Vincent Pecoraro for giving A.C.S.
laboratory space during his final two years at the
University of Michigan to carry out many of the
syntheses described in this paper.
Su p p or tin g In for m a tion Ava ila ble: Figure showing a
polarized optical micrograph of the nematic schlieren texture
of the n, m ) 6, 2 polymer. This material is available free of
charge via the Internet at http://pubs.acs.org.
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