Supporting Information
Ordered stacking of regioregular head-to-tail polyalkylthiophenes:
insights from the crystal
structure of form I’ poly(3-n-butylthiophene)
Paolo Arosio, Antonino Famulari, Margherita Moreno, Guido Raos, Marinella Catellani, Stefano Valdo Meille*.
Form I’
a Form I
b c
10
20
30
2θ (°)
40
50
Figure S1. X-ray diffraction patterns of poly(3-n-butylthiophene): (a) native: form I’; (b) annealed at 180 °C and slowly cooled: form I; (c) sample melted at 290 °C and quenched into ice-water. The full amorphous pattern, specifically the FWHM of the lower angle peak, is poorly compatible with the diffraction pattern of both form I or form I’ PBT.
Table SI 1. Refined non-structural parameters Zero correction (2θ) (deg.)
-0.019
Profile function parameters[a] U
-35.08280
V
18.92003
W
0.75146
A[b]
7.3880
Preferred orientation parameter[c] G
0.0000
Isotropic thermal vibration parameter B
8.0
Background parameters Segmented line points location
Intensity
2θ°
(counts 10-3)
5.0
0.0307
7.5
0.0366
10.5
0.0489
13.3
0.0520
16.0
0.0545
19.0
0.0966
21.4
0.1243
23.0
0.1270
25.0
0.1185
28.0
0.1101
31.0
0.0809
34.5
0.0504
40.0
0.0406
49.0
0.0220
Average crystallite dimensions (Å) La
110.0
Lb
50.0
Lc
38.0
[a] Peak shapes are calculated analytically through a Cauchy function: f(z) = (C/Hk)[1 + 4z2]-1; with z = (2i - 2k)/Hk and Hk2 = Utan2θk +Vtanθk + W. [b] Peak asymmetry is accounted for by splitting a peak into two halves with different FWHM, so that Hk΄ - Hk˝ = 2(A/(2θ)2), where A is a refinable parameter. [c] Preferred orientation parameter is PO = exp(-Gαk2) where αk is the angle between the scattering vector of the kth reflection and the scattering vector of a fixed (the preferred) reflection of indices h’k’l ’ given in the input file, in this case 010.
The crystal structure of poly-3-n-butylthiophene was refined using the Rietveld technique, i.e. by the best fitting of the whole X-ray powder pattern profile. The program ‘Debvin’1SI-3SI, which allows for constrained refinements using available a priori structural information, was used throughout. In the C2221 space group the lattice parameters refined to the following values: a = 7.64(1) Å, b = 7.75 (1) Å, c = 24.97(8) Å yielding a calculated density of 1.24 g/cc. In Table 3 of the paper the final fractional atomic coordinates of all non-hydrogen atoms for poly3-n-butylthiophene are reported. The final disagreement factor is R2’ = 0.093 (R2’ = Σ|Iobs - Icalc|/Σ Inet where Inet = Iobs - Ibkg) A number of non-structural parameters were refined as well; they are listed in Table SI 1. A zero correction was applied to the whole profile pattern. The background level was obtained as a segmented line with 14 nodes separated by 1.6 to 9° on the 2θ scale and refined on the intensity scale but constrained to follow qualitatively a plausible amorphous diffraction pattern. A Cauchy function was used to fit peak shapes; peak asymmetry was assumed and described using two halfpeak functions with different half-height widths. The possibility of preferred orientation along the 010 direction was taken into account but was found to be insignificant (see value of G in Table SI2). Crystallite dimensions were also refined: half height widths of each reflection in the whole diffraction profile are considered directly related to the Miller indices hkl and to the mean crystallite dimensions along the three crystallographic axes.4SI,5SI Refinement of U, V and W parameters in the Caglioti-Cox6SI equation led to values of coherence lengths (crystallite dimensions) of about 110Å, 50 Å, and 38Å along a, b and c respectively. Initial infinite chain models were devised by molecular mechanics calculations, adopting at the preliminary stage the CVFF force field, as implemented into the Materials Studio suite of programs.7SI
Supporting Information References (1SI) Immirzi, A. Acta Cryst. 1980, B36, 2378. (2SI) Millini, R.; Perego, G. S.; Bruckner, S. Mater. Sci. Forum, 1991, 71/82, 239. (3SI) Bruckner, S.; Immirzi, A. J. Appl. Cryst. 1997, 30, 207. (4SI) Allegra, G.; Bassi, I. W; Meille, S.V. ; Acta Crystallogr, 1978, A34, 652. (5SI) Perego, G. S.; Cesari, M.; Allegra, G. J. Appl. Crystallography, 1984, 17, 403. (6SI) Caglioti, G.; Paoletti, A.; Ricci, F. P. Nucl. Instrum. Methods, 1958, 3, 223. (7SI) Materials Studio and Discover are products of Accelrys Inc. (see www.accelrys.com).
