The strong differences observed in the models of form I obtained by two very
different methodologies highlight the intrinsic difficulties of structure determination for polymers like P3HT. Although both methods present specific advantages,
additional structural information is necessary to discriminate between them. In
particular, it needs to be clarified to what extent the structure of form I observed
for extended-chain crystals (M w < 10 kDa) differs from that observed for foldedchain crystals (M w > 10 kDa). As yet, a rather continuous variation of the unit cell
parameters of form I P3HT with increasing M w was reported for spin-coated thin
films [66]. Therefore, it cannot be excluded that the packing of P3HT chains in form
I is a function of molecular weight and could therefore evolve in a more or less
continuous way between the two models shown in Fig. 9.
Fig. 8 (a–c) Projections of the P3HT crystal structure along the a-, b-, and c-axes of the unit cell.
(d) Rectangular subcell accounting for the packing of the n-hexyl side chains in the crystal
structure of P3HT. The view corresponds to the projection along the n-hexyl side chain direction
(corresponding to the direction [1 2 0] in the unit cell of P3HT). (Reproduced with permission from
[47] © 2010, American Chemical Society)
96
M. Brinkmann et al.
different methodologies highlight the intrinsic difficulties of structure determination for polymers like P3HT. Although both methods present specific advantages,
additional structural information is necessary to discriminate between them. In
particular, it needs to be clarified to what extent the structure of form I observed
for extended-chain crystals (M w < 10 kDa) differs from that observed for foldedchain crystals (M w > 10 kDa). As yet, a rather continuous variation of the unit cell
parameters of form I P3HT with increasing M w was reported for spin-coated thin
films [66]. Therefore, it cannot be excluded that the packing of P3HT chains in form
I is a function of molecular weight and could therefore evolve in a more or less
continuous way between the two models shown in Fig. 9.
Fig. 8 (a–c) Projections of the P3HT crystal structure along the a-, b-, and c-axes of the unit cell.
(d) Rectangular subcell accounting for the packing of the n-hexyl side chains in the crystal
structure of P3HT. The view corresponds to the projection along the n-hexyl side chain direction
(corresponding to the direction [1 2 0] in the unit cell of P3HT). (Reproduced with permission from
[47] © 2010, American Chemical Society)
96
M. Brinkmann et al.