Crystal and molecular structures of poly(1,4-phenylenesulfone) and its trisulfone and tetrasulfone oligomers

Article abstract of DOI:10.1021/ma011597l

The structures of poly(1,4-phenylenesulfone), [1,4-ArSO₂]_n (Ar = 1,4-phenylene), and its tetrasulfone oligomer ArSO₂ArSO₂ArSO₂ArSO₂Ar (Ar = phenyl or 1,4-phenylene) have been determined fro

Full text of DOI:10.1021/ma011597l

Macromolecules 2002, 35, 1685-1690
1685
Crystal and Molecular Structures of Poly(1,4-phenylenesulfone) and Its
Trisulfone and Tetrasulfone Oligomers
How a r d M. Colqu h ou n *,‡ a n d P eter L. Ald r ed
Department of Chemistry, University of Reading, Whiteknights, Reading, RG6 6AD, U.K.
F r a n z H. Koh n k e† a n d P en elop e L. Her ber tson
Department of Chemistry, University of Manchester, Manchester, M13 9PL, U.K.
Ia n Ba xter a n d Da vid J . Willia m s*
Department of Chemistry, Imperial College, South Kensington, London, SW7 2AY, U.K.
Received September 10, 2001; Revised Manuscript Received November 20, 2001
ABSTRACT: The structures of poly(1,4-phenylenesulfone), [1,4-ArSO2]n (Ar ) 1,4-phenylene), and its
tetrasulfone oligomer ArSO2ArSO2ArSO2ArSO2Ar (Ar ) phenyl or 1,4-phenylene) have been determined
from X-ray powder diffraction data interfaced to molecular simulation and diffraction modeling. An initial
model for the tetrasulfone oligomer was developed using conformational and packing information obtained
from a single-crystal X-ray determination of the structure of the trisulfone ArSO2ArSO2ArSO2Ar, in which
the aromatic ring planes lie essentially orthogonal to a plane defined by the bridging C-S-C groups.
Energy-minimization and crystallographic refinement of the tetrasulfone structure by Pawley and Rietveld
methods yielded an agreement factor (Rwp) of 15.3%., and an analogous approach led to solution of the
crystal structure of poly(1,4-phenylenesulfone) (Rwp ) 5.5%). In all three structures, the diaryl sulfone
units adopt near-perfect open-book conformations and the molecules crystallize with the aromatic rings
of laterally adjacent chains essentially parallel. The polymer unit cell is C-centered orthorhombic (two
chains per cell), space group Cmcm, with a ) 10.79, b ) 5.05, and c ) 9.97 Å. The polymer chain adopts
21 helical geometry, and crystal packing is dominated by SdO‚‚‚H-C interactions (O‚‚‚H ) 2.68 Å).
In tr od u ction
from limited diffraction data is now a more feasible
proposition. Here we report a detailed study of the poly-
(1,4-phenylenesulfone) system, including a single-crystal
X-ray analysis of the model trisulfone oligomer 2,
determination of the structure of its tetrasulfone ho-
mologue 4 from X-ray powder data and diffraction
modeling, and finally solution and refinement of the
crystal and molecular structure of the polymer itself,
also from X-ray powder data. Preliminary molecular
simulation studies of polymer 1 have been described in
an earlier communication.8
Aromatic polyethersulfones are among the most im-
portant of all commercial high-performance polymers,1
but structural characterization of these materials has
been severely restricted by their essentially amorphous
character.2 As a result, little is known about the
conformational and chain-packing characteristics of
sulfone-based aromatic polymers, although efforts have
recently been made to develop computational ap-
proaches to this problem.3,4
Unlike the vast majority of polyethersulfones, the
“parent” polysulfone 1 is highly crystalline, very high
melting (Tm > 500 °C) and extremely insoluble.5 Efforts
were made some years ago to determine its structure
from X-ray fiber data,6 but the samples used in that
study were obtained by peroxide oxidation of oriented,
amorphous poly(1,4-phenylenesulfide), and doubts have
recently been expressed as to whether such procedures
actually afford poly(1,4-phenylenesulfone).7 The re-
ported unit cell parameters and calculated density (on
a basis of two chains per cell) were entirely consistent
with the oxidized material consisting of poly(1,4-phen-
ylenesulfone), but the very limited X-ray fiber data
available precluded a more conclusive structural analy-
sis at that time.
Exp er im en ta l Section
Syn th esis of P olym er 1 a n d Its Oligom er s. Poly(1,4-
phenylenesulfone) (1) and the trisulfone oligomer (2) were
synthesized as described by Robello et al.7 The previously
unreported tetrasulfone oligomer (4) was obtained as shown
in Scheme 1. A mixture of 1,4-benzenedithiol (5.90 g, 41.5
mmol), 4-chlorophenyl phenyl sulfone (23.07 g, 91.3 mmol),
and potassium carbonate (26.4 g, 191 mmol) in dimethylform-
amide (DMF, 130 mL) was heated to 150 °C and stirred under
nitrogen for 24 h before cooling to room temperature and
adding to water (2 L). The solid was filtered off, washed with
water, and dried. Recrystallization from 1,2-dichlorobenzene,
with charcoal treatment and hot filtration, gave white crystals
of the disulfide-disulfone 3, (19.80 g) which were filtered off,
washed with diethyl ether, and dried under vacuum. Mp:
237-239 °C. A solution of compound 3 (1.00 g) in chloroform
(20 mL) and trifluoroacetic acid (20 mL) was treated with 50%
hydrogen peroxide (3.20 g) and heated with stirring to 70 °C.
After 1 h, additional 50% hydrogen peroxide (2.00 g) was added
and stirring was continued at 70 °C for a further 6 h. The
suspension was then cooled to room temperature, poured into
water (500 mL), and the white solid was filtered off, dried,
extracted with hot 1,2,4-trichlorobenzene (400 mL), refiltered,
and finally washed with acetone and dried under vacuum to
However, recent developments in computational dif-
fraction-simulation and structural refinement tech-
niques mean that the detemination of polymer structure
† On leave from the Dipartimento di Chimica Organica
e
Biologica, Universita` di Messina, Salita Sperone 31, 98166 Mes-
sina, Italy.
‡ Contact information. Telephone/Fax:(+)44 118 931 6196. E-
mail: h.m.colquhoun@rdg.ac.uk.
10.1021/ma011597l CCC: $22.00 © 2002 American Chemical Society
Published on Web 01/23/2002

1686 Colquhoun et al.
Sch em e 1. Syn th esis of Oligom er 4
Macromolecules, Vol. 35, No. 5, 2002
using the program systems Cerius2, (v. 3.5) and Materials
Studio (v. 1.2), both from Accelrys Inc., San Diego, CA.
Cr ysta l Da ta for Oligom er 2 (Sin gle-Cr ysta l Diffr a c-
tion ). C24H18O6S3, M ) 498.56, monoclinic, space group C2, a
) 10.880(2) Å, b ) 5.014(1) Å, c ) 20.198(4) Å, â ) 101.65(3)°,
U ) 1079.1(4) Å3, Z ) 2, T ) 293 K, Dc ) 1.534 g cm-3, µ(Cu
KR) ) 35.03 cm-1, F(000) ) 516. R1 ) 0.0742, wR2 ) 0.1998
for 830 independent observed and absorption-corrected reflec-
tions [2θ < 126°; I > 2σ(I)]. Full crystallographic details are
available as Supporting Information.
Cr ysta l Da ta a n d Str u ctu r e Deter m in a tion for Oligo-
m er 4 (P ow d er Diffr a ction ). C30H22O8S4, M ) 638.76,
monoclinic, space group C2/c, a ) 10.841 Å, b ) 4.952 Å, c )
49.441 Å, â ) 92.39°, U ) 2652.4 Å3, Z ) 4, T ) 173 K, Dc )
1.60 g cm-3. Data collection range, 2θ ) 4.98-48°, synchrotron,
λ ) 1.400 Å. Peak profile function: Thompson-Cox-Hastings,
U ) 0.1191, V ) -0.5133, W ) 0.0116, X ) -0.0513, Y )
-0.2388, Z ) 0.00059. Peak asymmetry correction: Besar-
Baldinozzi, P1 ) 0.1333, P2 ) -0.0374, P3 ) -0.2336, P4 )
-0.0655. Crystallite dimensions: a ) 208, b ) 169, c ) 166
Å. Lattice strain: a ) 0.984, b ) 1.201, c ) 1.111%. Zero point
correction, -0.0268°. Agreement factors: Rwp ) 0.153; Rp
)
0.110. Atomic coordinates are given as Supporting Information.
Cr ysta l Da ta a n d Str u ctu r e Deter m in a tion for P oly-
m er 1 (P ow d er Diffr a ction ). [C12H8O4S2]n, M ) (280.33)n,
orthorhombic, space group Cmcm, a ) 10.790 Å, b ) 5.050 Å,
c ) 9.975 Å, U ) 543.6 Å3, Z ) 2, T ) 173 K, Dc ) 1.71 g cm-3
.
Data collection range, 2θ ) 6.04-49.48°, synchrotron, λ )
1.400 Å. Peak profile function: Thompson-Cox-Hastings, U
) 5.0707, V ) 14.388, W ) -1.9639, X ) 0.14216, Y ) 0.11384,
Z ) 0.00154. Peak asymmetry correction: Besar-Baldinozzi,
P1 ) 3.7721, P2 ) 0.04535, P3 ) -7.6357, P4 ) -0.93191.
Polymer crystallite dimensions: a ) 1584, b ) 610, c ) 106
Å. Lattice strain: a ) 0.151, b ) 2.544, c ) 0.134%. Zero point
afford the tetrasulfone 4 (1.02 g, 92% yield), mp 397-399 °C.
[M + Na]+ ) 661 Da (MALDI-TOF). Anal. Calcd. for
C
30H22O8S4: C, 56.41; H, 3.47. Found: C, 57.10; H, 3.38.
Cr ysta llogr a p h ic Meth od s. Crystals of oligomer 2 were
correction, -0.0226°. Agreement factors: Rwp ) 0.055; Rp
)
grown by very slow cooling of a dilute solution in dimethyl-
formamide. Single-crystal X-ray data for 2 were measured on
a Siemens P4/RA diffractometer with graphite-monochromated
Cu KR radiation (λ ) 1.5418 Å) using ω-scans, and the
structure was solved using the SHELXTL-PC program system.
X-ray powder data for oligomer 4 and for polymer 1 were
measured at the CLRC-Daresbury Synchrotron Radiation
Source, at a wavelength of 1.400 Å. The finely powdered
samples were held in Lindemann tubes, cooled to -100 °C.
During data collection the sample tube was continuously
rotated about its long axis, perpendicular to the X-ray beam.
Computational model-building, diffraction-simulation and crys-
tallographic refinement from powder data were carried out
0.123.
Resu lts a n d Discu ssion
Preliminary diffraction-modeling studies of poly(1,4-
phenylenesulfone) (1) using laboratory X-ray powder
data had suggested a C-face centered crystal structure
in which the aromatic rings within each polymer chain
are oriented orthogonally to the C-S-C plane of the
linking sulfone groups.8 To confirm (or otherwise) the
correctness of such a structure, we first investigated the
structure of a model trisulfone oligomer (2) by single-
F igu r e 1. Molecular structure of the trisulfone oligomer 2, projected (a) parallel and (b) perpendicular to the plane defined by
C(1)-S(1)-C(1A).

Macromolecules, Vol. 35, No. 5, 2002
Poly(1,4-phenylenesulfone) 1687
Ta ble 1. Selected Bon d Len gth s (Å), Bon d An gles (d eg),
a n d Tor sion An gles (d eg) for Oligom er 2
bond
length (Å)
bonds
angle (deg)
S(1)-C(1)
C(4)-S(2)
S(2)-C(7)
S(1)-O(1)
S(2)-O(2)
S(2)-O(3)
C(1)-C(2)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(5)-C(6)
C(7)-C(8)
C(8)-C(9)
C(9)-C(10)
C(10)-C(11)
C(11)-C(12)
1.776(9)
1.762(8)
1.758(9)
1.442(7)
1.440(6)
1.441(7)
1.390(10) C(1A)-S(1)-O(1)
1.400(20) C(1)-S(1)-O(1)
1.400(11) C(4)-S(2)-O(2)
1.391(11) C(4)-S(2)-O(3)
1.358(14) C(7)-S(2)-O(2)
1.402(12) C(7)-S(2)-O(3)
1.350(20)
C(1)-S(1)-C(1A)
C(4)-S(2)-C(7)
103.7(6)
104.7(5)
O(1)-S(1)-O(1a)
O(2)-S(2)-O(3)
119.9(6)
120.0(5)
108.1(3)
108.0(4)
107.8(3)
107.8(4)
107.7(4)
107.9(4)
1.380(20) C(1A)-S(1)-C(1)-C(2)
1.360(20) C(1A)-S(1)-C(1)-C(6)
1.370(20) C(3)-C(4)-S(2)-C(7)
C(5)-C(4)-S(2)-C(7)
89.0(6)
90.1(6)
88.7(6)
89.3(6)
89.5(6)
88.7(6)
C(4)-S(2)-C(7)-C(8)
C(4)-S(2)-C(7)-C(12)
C-H (defined) 0.976
crystal X-ray methods, thereby affording the first un-
ambiguous geometric, conformational, and packing data
for this type of polysulfone.
The molecular structure of 2 is shown in Figure 1,
projected both perpendicular and parallel to the O-O
vector of the central sulfone unit. Key bond lengths,
bond angles, and torsion angles are given in Table 1.
The distance between atoms S(2) and S(2A), which are
related by a crystallographic 2-fold axis through S(1),
is 9.92 Å. This separation represents the structural
repeat-distance for polymer 1 and, by the convention
which aligns the polymer chain with the crystallo-
graphic c axis, gives a provisional value for the c-
dimension of the polymer unit cell. The aromatic rings
are essentially orthogonal to the plane of the three
sulfur atoms, with independent C-C-S-C torsion
F igu r e 3. Rietveld difference plot (lower line) for oligomer 4,
based on the final structure containing four molecules per unit
cell. Experimental data (background-subtracted) are shown as
+ marks, calculated data as a solid line, and calculated peak
positions as tick marks.
angles of 88.7, 89.5, 88.7, 89.3, 89.0, and 90.1° leading
to a sequence of three almost perfect “open-book”
geometries at the sulfone bridges. This type of confor-
mation is generally believed to represent the torsional-
energy minimum for a diaryl sulfone unit,9,10 but
although a simple orbital overlap model involving Cpπ
-
Sdπ interactions has been proposed to account for this
preference,11 no more rigorous quantum-mechanical
explanation has yet been reported.
The two molecules of oligomer 2 within the unit cell
are related by C-face centering and are thus aligned
parallel with one another. The oligomer chains are
however not aligned precisely along the c axis of the
unit cell, but lie perpendicular to the ab plane (Figure
2) and thus make an angle of 11.65° to the c direction,
so presumably optimizing end-to-end packing interac-
tions. The only significant intermolecular contacts are
of the type C-H‚‚‚OdS, where the O‚‚‚H distances and
C-H‚‚‚O angles are 2.68 Å and 148° respectively. Given
the polarity of these contacts (Hδ+‚‚‚Oδ-) they may be
viewed as weak but cooperative hydrogen bonding
interactions. With a well-defined oligomer structure
12
available, the Dreiding II force field
within Cerius2
was reparametrized so that it reproduced the structure
of oligomer 2 to a good degree of accuracy, and this
modified force field was used in further analyses of the
poly(1,4-phenylenesulfone) system.
The previously unreported tetrasulfone oligomer 4 (an
even more realistic model for polymer 1 than the
trisulfone homologue 2) was synthesized as shown in
Scheme 1, but efforts to grow X-ray quality single
crystals were frustrated by its extreme insolublity.
However, since oligomer 4 gave a reasonably well-
resolved X-ray powder pattern, it seemed possible that
extrapolation from the crystal structure of 2 might
enable the structure of 4 to be determined by diffraction
modeling.
F igu r e 2. Unit cell of oligomer 2, containing two molecules
per cell.

1688 Colquhoun et al.
Macromolecules, Vol. 35, No. 5, 2002
F igu r e 5. Rietveld difference plot (lower line) for the final
structure of polymer 1. Experimental data (background-
subtracted) are shown as + marks, calculated data as a solid
line, and calculated peak positions as tick marks.
and Rietveld methods (Figure 3) led to the final struc-
ture shown in Figure 4, having a weighted-profile R
value (Rwp) of 15.3%. Oligomer 4 has four molecules per
unit cell with crystallographic inversion symmetry about
the center of each molecule, but otherwise the structure
is similar to that of 2, with the same conformation and
the same symmetry relationship (C-face-centering) be-
tween laterally adjacent chains. In oligomer 4 however,
the longer oligomer chains are aligned more closely to
the c direction, resulting in a much smaller â-angle for
the unit cell.
The chain conformations determined for oligomers 2
and 4 clearly suggest that an orthogonal torsional
relationship between the aromatic rings and the bridg-
ing sulfone units should also occur in the corresponding
polymer chain. Similarly, the C-centered relationship
between laterally adjacent oligomer chains in the struc-
tures of both 2 and 4 provides strong support for this
type of packing in poly(1,4-phenylenesulfone) itself.
Interestingly, the crystal structure of oligomer 2 could
be used directly to generate a preliminary model for the
unit cell of polymer 1, since the two molecules in the
oligomer unit cell are related by simple C-centering and
pack strictly in register to give a well-defined lamellar-
type structure. By connecting the sulfur atoms S(2) and
S(2A) of four translationally related oligomer molecules,
a provisional C-centered polymer unit cell with a )
10.89, b ) 5.01, and c ) 9.92 Å and with R ) 90.0, â )
90.0, and γ ) 90.0° could be generated.
F igu r e 4. Unit cell of oligomer 4, containing four molecules
per cell.
A preliminary model for the tetrasulfone 4, containing
two molecules per unit cell, was thus constructed using
geometric, conformational and symmetry data derived
from the crystal structure of 2, and this model was
energy-minimized using the modified Dreiding II force
field described above. However, although the powder
pattern predicted for this preliminary structure showed
close similarities to the experimental pattern for oligo-
mer 4 (notably in the positions and intensities of the
001, 002, 003, 004, and 200 reflections), a number of
serious discrepancies remained. It thus seemed that a
structure for oligomer 4 directly analogous to that of
oligomer 2 could not be correct.
In fact, reexamination of the end-to-end packing of
oligomer molecules in the crystal of 2 showed that the
same arrangement could not be present in a structure
for 4 which has only two molecules per unit cell, because
of the now-odd number of aromatic rings in the oligomer
chain. However, the same type of end-to-end packing
could be present in crystalline oligomer 4 if the unit cell
contained four molecules rather than two, the two
additional molecules being generated by the introduc-
tion of a 2-fold axis parallel to b. Construction and
minimization of such a model for 4, using the force-field
developed from the structure of 2, led to a structure in
space group C2/c whose simulated powder pattern gave
very good qualitative agreement with the observed
pattern. Further refinement of this structure by Pawley
The experimental X-ray powder pattern for polymer
1 (Figure 6) was indexed in terms of a just such a C-face-
centered orthorhombic unit cell. From this pattern, the
cell dimensions were determined as a ) 10.79, b ) 5.05,
and c ) 9.96 Å, in reasonably good agreement with both
the above, oligomer-derived unit cell and with the
polymer unit cell obtained by Tsvankin et al. from X-ray
fiber data (a ) 11.00, b ) 5.05, c ) 9.75 Å).6 A model

Macromolecules, Vol. 35, No. 5, 2002
Poly(1,4-phenylenesulfone) 1689
F igu r e 6. Crystal structure of polymer 1 shown projected on the three faces of the unit cell and also shown in perspective.
Ta ble 2. F r a ction a l Atom ic Coor d in a tes a n d Isotr op ic
cluded that Cmcm remains quite the most probable
space group for poly(1,4-phenylenesulfone).
A simulated powder-diffraction pattern for this struc-
ture gave excellent agreement between observed and
calculated peak positions, and refinement of the struc-
ture by Pawley and Rietveld methods eventually gave
a weighted-profile agreement factor (Rwp) of 5.5% (Fig-
ure 5).
Tem p er a tu r e F a ctor s (Å2) for th e Asym m etr ic Un it of
P olym er 1, in Sp a ce Gr ou p Cm cm
atom
x
y
z
Ui
S
O
C(1)
C(2)
H
0.00000
0.11559
0.00000
-0.11133
-0.18966
-0.38008
-0.52354
0.16711
0.08389
0.14298
0.25000
0.25000
-0.10984
-0.05485
-0.09359
0.1838
0.1417
0.0002
0.0461
0.1360
The final structure, with atom labeling, is shown in
Figure 6 projected along the a, b, and c directions,
together with a perspective view of the unit cell. Atomic
coordinates and isotropic atomic thermal parameters for
the asymmetric unit [C1.5HS0.25O0.5] in space group
Cmcm are given in Table 2. Crystal packing appears to
be dominated by [SdO‚‚‚H-C] interactions (O‚‚‚H )
2.68 Å, C-H‚‚‚O ) 150°) analogous to those observed
in the structure of oligomer 2; there are no other
intermolecular contacts at or below van der Waals
distances.
The unit cell reported here for polymer 1, although
derived from the powder pattern of material formed by
self-polycondensation of [1,4-FC6H4SO2]-, is neverthe-
less in reasonably good agreement with the cell derived
from the fiber pattern of material produced by peroxide
oxidation of amorphous poly(1,4-phenylenesulfide)
(orthorhombic, two chains per cell, a ) 11.00, b ) 5.05,
and c ) 9.75 Å, and Dc ) 1.73 g cm-3).6 A simulated
X-ray fiber pattern for polymer 1 (contour plot, based
on the unit cell reported here) is shown in Figure 7,
together with the experimental fiber pattern from ref
6. The very close agreement between these two patterns
strongly suggests that oxidation of amorphous poly(1,4-
phenylenesulfide) does in fact produce a material in
for the polymer crystal, having two chains per unit cell,
was constructed in Cerius2 using bond lengths, bond
angles, and torsion angles derived from oligomer 2,
although the symmetry relationship between the two
chains was not specified at this stage. Minimization of
this structure using the modified Dreiding II force field
described above, within the experimentally derived unit
cell, led quite unambiguously to a C-centered arrange-
ment of the chains, and analysis of the symmetry
elements in the present in the model provisionally
identified the space group as Cmcm. The final space
group assignment is however dependent on whether the
C-C-S-C torsion angle remains at exactly 90°. Any
deviation from this value would destroy the axial mirror
symmetry of the chain and would thus be inconsistent
with the orthorhombic space group. However, provided
the C2 axis through sulfur and the inversion center at
the center of the aromatic ring are retained, a nonor-
thogonal torsion angle would be permitted within the
monoclinic space group C2/c. In practice, reducing the
energy-barrier associated with the originally imposed
90° torsional preference led to no significant change of
the C-C-S-C torsion angle, and it is therefore con-

1690 Colquhoun et al.
Macromolecules, Vol. 35, No. 5, 2002
lateral dimensions (a and/or b) than their oligomeric
analogues,13 and it is thought that this effect results
from the presence of amorphous or chain-folding re-
gions, present in high molar mass polymers but absent
from low molar mass or oligomeric material. Chains
entering a thin, lamellar crystallite from an amorphous
and/or chain-folded region are laterally stressed by the
transition from a low-density to a high-density phase
and thus adopt a more expanded crystal lattice than
would occur in low molar mass material, where the
chains are contained entirely within the crystallite.14
In the present work, the observed expansion of the
a-dimension from 10.79 Å in our low molar mass
powder-sample to 11.00 Å in the fiber-sample previously
obtained by oxidation of oriented, high molar mass poly-
(1,4-phenylene sulfide),6 is clearly quite consistent with
this explanation.
Ack n ow led gm en t. We thank the Royal Society, the
Engineering and Physical Sciences Research Council of
the United Kingdom, and the University of Reading for
support of this research. We are grateful to Professor
A. J . Ryan for access to synchrotron facilities, and to
Dr. A. Ben-Haida for help in the synthesis of oligomer
4.
Su p p or tin g In for m a tion Ava ila ble: Tables of full crys-
tallographic data for the single-crystal structure of oligomer
2 and atomic coordinates for oligomer 4 and a figure showing
the structure for 2. This material is available free of charge
via the Internet at http://pubs.acs.org.
Refer en ces a n d Notes
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(7) Robello, D. R.; Ulman, A.; Urankar, E. J . Macromolecules
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F igu r e 7. Experimental X-ray fiber pattern (flat plate, Cu
(8) Colquhoun, H. M. Polymer 1997, 38, 991
KR radiation) from ref 6, together with
a fiber pattern
simulated from the crystal structure reported here for polymer
(9) Kendrick, J . J . Chem. Soc., Fraday Trans. 1990, 86, 3995
(10) Baxter, I.; Colquhoun, H. M.; Hodge, P.; Kohnke, F. H.;
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1.
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(13) See, for example: Colquhoun, H. M.; O’Mahoney, C. A.;
Williams, D. J . Polymer 1993, 34, 218.
(14) Hoffman, J . D.; Miller, R. L.; Marand, H.; Roitman, D. B.
Macromolecules 1992, 25, 2221.
which poly(1,4-phenylenesulfone) comprises at least the
crystalline phase.
The differences in unit cell dimensions between the
powder and fiber samples undoubtedly reflect the rela-
tive molecular weights of these materials. It is well
established that semicrystalline polymers of high molar
mass generally adopt unit cells with significantly greater
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