Solid State Structure of Poly (9, 9-dinonylfluorene)

Article pubs.acs.org/Macromolecules

Solid State Structure of Poly(9,9-dinonylfluorene) Mika Torkkeli,† Frank Galbrecht,‡ Ullrich Scherf,‡ and Matti Knaapila*,§ †

Department of Physics, University of Helsinki, 00014 Helsinki, Finland Fachbereich Chemie, Bergische Universität Wuppertal, 42097 Wuppertal, Germany § Department of Physics, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark ‡

ABSTRACT: We report on X-ray diffraction and grazing-incidence X-ray diffraction data of poly(9,9-dinonylfluorene) (PF9) in bulk, thin films and in the 1% methylcyclohexane gel. We denote the main crystalline phase as α phase and propose that the unit cell is monoclinic (a = 29.31 Å, b = 23.65 Å, c = 33.33 Å, and γ = 84.70°) in bulk and orthorhombic (a = 28.70 Å, b = 23.48 Å, and c = 33.23 Å) in thin films. This structure corresponds to the layered structure along the a-axis (along the elongated side chains and perpendicular to the seemingly stiff polymer chains) and to the stacking of aromatic main chain units along the b-axis. The polymer chains are aligned along the c-axis. Monoclinic structure agrees with the layer spacing of 14.6 Å, the stacking period d(040) = 5.89 Å and the monomer repeat distance of 8.33 Å. The α phase experiences an order−disorder transition at 170 °C upon heating. In the 1% methylcyclohexane gel, this structural motif is maintained but with the loss of longrange order. This is interpreted as a formation of mesomorphic β phase with an orthorhombic unit cell (a = 29.1 Å, b = 28.1 Å, and c = 16.7 Å). Structural analogues to other 9,9-di-n-alkyl-substituted polyfluorenes are discussed in terms of unit cell parameters and backbone geometry.

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mesomorphic β phase18 and a (twisted glassy) g-phase.19 Also known are crystalline structures of PF620,21 and poly(9,9diheptylfluorene) (PF7)22 that manifest similar but not identical structures. However, there are no structural reports on crystalline PF9 or PF10 even though we have clarified their phase behavior in dense methylcyclohexane (MCH) solutions23 and gels.24 Central to our work has been to identify ordered network nodes and the phase transition between gel and isotropic phases where the transition temperature decreases with increasing side chain length. In this work, we provided indexing for ordered PF9 nodes in MCH. The main crystalline PF phase is generally denoted as α phase and discussed in terms of lattice parameters where the crystallographic c-axis is located along the supposedly stiff polymer backbone. The α phase of PF8 was first proposed to manifest a zigzag conformation where the fiber periodicity of 33.4 Å corresponds to four monomer units.25 After further refinement, Chen et al.26 ended up with an orthorhombic unit cell with the lattice parameters a = 25.6 Å, b = 23.4 Å, and c = 33.6 Å. Another model proposed by Brinkmann27 manifests also an orthorhombic unit cell, four monomer units plus a tetradial construction of side chains. For the α and α′ phases of PF6, Chen et al.21 proposed a monoclinic unit cell with the lattice parameters a = 21.5 Å, b = 24.7 Å, c = 33.2 Å, and α = 96° and a triclinic unit cell with the lattice parameters a = 20.5 Å, b = 25.8 Å, c = 33.0 Å, and α = β = 96°. Afterward, we found that PF7 has seemingly similar

INTRODUCTION Poly(9,9-dialkylfluorene)s (PFs) represent a core class of conjugated homopolymers.1 Most research in this materials class has been focused on poly(9,9-dioctylfluorene) (abbreviated as PFO or PF8) which was originally proposed as a blue emitter for polymer LEDs.2 This polymer forms a so-called β phase3 which shows narrow optical line widths and a low amplified spontaneous emission threshold and allows fabrication of lasing devices.4 Later on, PF8 was processed into a variety of advanced materials, e.g., electrospun fibers,5 gels,6 xerogels,7 and polymer wrapped carbon nanotubes.8 The same holds for poly(9,9-dihexylfluorene) (PF6)9 used e.g. in arrays of silica nanoparticles10 and poly(9,9-didecylfluorene) (PF10) that forms nanorings when deposited from mixtures of selective solvents.11 Less attention has been placed on poly(9,9-dinonylfluorene) (PF9). Panorazzo et al.12 detailed time-resolved emission of PF9. Elsewhere, Ouisse et al.13 blended PF9 with organic salts and demonstrated transparent light-emitting electrochemical cells (OLECs). These authors found that salt and PF9 are phase-segregated and the charge transport occurs predominantly at the interface. Degradation at this interface is the limiting factor for device performance.14 The structure of PFs should be understood in several levels reaching from single polymer conformations to the solid state crystals and beyond, including mosaic structures of crystallites and aggregates in solutions as well as gels and cross-linked systems.15 Most efforts concerning the unit cell structure has been concentrated on PF8 that exhibits crystalline α and α′ phases16 with distinctive nanoribbons17 and noncrystalline amorphous, glassy, nematic, and isotropic phases as well as a © XXXX American Chemical Society

Received: March 14, 2015 Revised: July 5, 2015

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DOI: 10.1021/acs.macromol.5b00547 Macromolecules XXXX, XXX, XXX−XXX

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Macromolecules orthorhombic α phase with a = 26.0 Å, b = 22.5 Å, and c = 33.4 Å.22 This PF7 α phase was found only in thin films while bulk was dominated by other solid state phase that was not related to its α phase. We denoted this structure as γ phase. In this paper, we report on the previously not reported solid state structure of PF9. We propose that the unit cell for PF9 is monoclinic and illustrate how the thin film environment, heating, and the incorporation of poor solvent MCH influence this structure. Similarities and differences between PF9 and other linear side chain PFs are analyzed. The objectives of this work are twofold. First, it details PF9 structure and makes it possible to separate α phase in the solid state and β phase in gels. Second, it completes the structural series of PFs that now reaches from PF6 to PF9. This series is becoming increasingly comparable to that of poly(3-alkylthiophenes) whose structures are known from poly(3-butylthiophene) to poly(3-octyldecylthiophene).28 This overall information helps us identify not only structural properties of individual polymers but also structural trends over the polymer series.

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h under inert gas. (3) For gels, PF9 was dissolved in 10 mg/mL MCH (>99%, Merck) at 80−90 °C until completely transparent solution was formed. This solution was cooled down to −21 °C for 30 min, which leads to the gelation as described in ref 24. This gel was shear-coated on silicon substrate using a doctor-blade method. The film thickness was 10−50 μm. The gel characterization was performed immediately after the sample preparation. X-ray Diffraction (XRD). XRD measurements at room temperature were carried out using 1 mm thick bulk samples in a direct transmission geometry. The diffractometer consisted of a sealed Cuanode X-ray tube, Montel/pinhole optics for obtaining a monochromatic (E = 8.04 keV) beam of ca. 0.8 mm × 0.8 mm (vertical × horizontal) cross section and MAR345 image plate detector at 454 mm distance. XRD measurements at elevated temperatures were carried out at the I711 Beamline at MAX-Lab in Lund. The beam was monochromized using an asymmetrically cut single Si(111) monochromator focused on the sample The X-ray energy was 12.5 keV. The beam size was 0.5 mm × 0.5 mm (vertical × horizontal), and the diffraction patterns were measured using a Titan CCD with 165 mm diameter (Oxford Diffraction). The temperature was controlled using a Huber HTC 9634 high temperature monitored by an external thermocouple. The heating and cooling rates were ca. 3 °C/min. Grazing-Incidence X-ray Diffraction (GIXRD). GIXRD measurements of spin-coated films were conducted at the erstwhile Beamline W1.1 at the Hamburger Synchrotronstrahlungslabor (HASYLAB) of the Deutsches Electronen Synchrotron (DESY) in Hamburg. The beam was monochromatized with a double crystal Si(111) monochromator to X-ray energy of 9.8 keV. The beam was narrowed with slits to 0.2 mm × 1 mm (vertical × horizontal), and the diffraction patterns were recorded with a flat Molecular Dynamics image plate at 285 mm distance. For the spin-coated samples, the incidence angle was ω = 0.12°. The gel samples were measured similarly but with the incoming beam parallel to the substrate. The scattering patterns were also scanned along horizontal lines with the exit angle (2θ) fixed at the vertical position of layer lines of reflections. However, in the grazing-incidence mode, the zeroth layer line was measured with 2θ = 2 ω, i.e., along the Yoneda peak. The scans were recorded with a scintillation detector using an angular step of 0.05° and detector slit width of ca. 0.12°. Additional GIXRD experiments were conducted at the Beamline BW4 at HASYLAB at DESY.29 The measurement procedures were otherwise similar as at W1.1, but the Xray energy was 9.0 keV and the images were recorded with a MAR165 detector at 196 mm distance. All GIXRD measurements were carried out at room temperature.

EXPERIMENTAL SECTION

Materials. PF9 with number- and weight-average molecular weights of Mn = 109 kg/mol and Mw = 221 kg/mol, respectively, was prepared in Yamamoto-type homocouplings of the corresponding 2,7-dibromo-9,9-dialkylfluorene with Ni(COD)2 exactly as described in ref 2. PF9 was compared to the similarly synthesized PF8 with Mn = 48 kg/mol and Mw = 132 kg/mol. Figure 1a shows the chemical structure of PF9.

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RESULTS AND DISCUSSION Generic Features of Main Crystalline Solid State Phases of PFs. Figure 1b plots a simplified idea of crystalline phases of linear side chain PFs. This structure corresponds to the layered structure along the a-axis (along the elongated side chains, perpendicular to stiff polymer main chains). Stacking of aromatic main chain units defines the b-axis and stiff polymer chains the c-axis. PFs are composed of dialkylmethylene-bridged biphenyl repeat units which manifest an interring distortion angle of about 11° between neighboring fluorene units. Light scattering studies of PF solutions indicate rodlike overall conformation with the persistence length of 6−10 nm (see e.g. Grell et al.30 and Somma et al.31). The rodlike form stems from a helical main chain geometry. Previous structural studies detail α and α′ phases of PF816,25−27 and PF6.21 The α phase is the predominant crystalline form and presumably stable. The α′ phase involves a slight variation in the unit cell dimensions and lowered symmetry. PF7 has also an α phase with significant similarity to α-PF8.22

Figure 1. (a) Chemical structure of PF9. (b) Structural idea of the crystalline phase of linear side chain PFs. This manifests layers of stiff polymers where the aromatic moieties are stacked perpendicular both to the layers and polymer backbone. Polymer backbone is marked by red and the side chains by blue. Three types of samples were characterized. (1) For bulk measurements, isotropic crystalline samples were prepared from pure polymer samples by annealing at 203 °C under inert gas, followed by a subsequent slow cooling which possesses crystallization. (2) For thin film studies, polymer was dissolved in 10 mg/mL toluene (>99%, Romil) by heating (85 °C) and stirring. This solution was spin-coated (2500 rpm, 60 s) on glass substrates, and the films were annealed for 3 B


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very close to that of PF8. The cell is slightly larger along the aaxis and almost identical along the b- and c-axes. We propose a slight deviation from orthorhombic to the monoclinic system with a unique axis c. This is revealed by the splitting of off-axis reflections (e.g., (110)) as indicated in Figure 2. Figure 3 plots GIXRD patterns of PF9 film. Corresponding data of PF8 are shown for comparison. This time the PF9 indexing corresponds to the orthorhombic structure with a = 28.70 Å, b = 23.48 Å, and c = 33.23 Å. There is a qualitative difference between the GIXRD data of PF9 and that of PF8 or PF7.22 Both PF8 and PF7 produce wellaligned patterns with tens of reflections, while similarly prepared PF9 shows only a few and much weaker reflection arcs. Furthermore, the GIXRD patterns of PF9 show more distinct amorphous component. We propose that this difference is related to the lower symmetry of PF9 crystals and stems from either (or both) longer side chains or higher molecular mass. Figure 4 shows the XRD curves of PF9 during a temperature scan. On heating, the above-mentioned reflections turn broad halos at 170 °C, which indicates a weakly ordered hightemperature structure. This is similar nematic structure as reported to PF8.18 This transition is reversible on cooling, with the hysteresis of about 20 °C. The high-temperature structure becomes macroscopically oriented, as seen in the 2-dimensional scattering patterns (not shown). The reflections are sharpened after the temperature ramp, which indicates higher degree of crystallinity. GIXRD Curves of PF9 Gel. Figure 5a plots GIXRD curves of doctor-blade coated PF9 films, when coated from 1% MCH gel. When mixed in the poor solvent MCH, the linear side chain PFs including PF9 form a network of polymer sheets.24 A part but not all of these sheets display a mesomorphic structure and optical characteristics corresponding to the ones that were originally used to define PF8 β phase.3 Analogously, we used these characteristics to define PF9 β phase.24 The crystallites in bulk and 1% gel are clearly different, and the latter structure is associated as PF9 β phase as described in ref 24. The peaks arising from the gel are broader, in agreement with a mesomorphic rather than crystalline structure. The layer motif is similar to both phases, but the peak at 1.5 Å−1 pertaining to the monomer repeat for the β phase is shifted in relation to the phase. This is a common feature of all the PFs indicating a more stretched or planar main chain conformation. While the solid state film is primarily crystalline, the β phase is a minority compound and suggestively located in the ordered gel nodes. This is consistent with the fact that even though the α crystallites become stacked on the plane, the β domains remain randomly distributed in films. The unit cell is still proposed to be orthorhombic with a = 29.1 Å, b = 28.1 Å, and c = 16.7 Å. This structure is similar to the α phase structure, but the c-direction incorporates 2 instead of 4 repeat units. The unit cell is larger along the b-axis which is attributed to the solvent molecules incorporated into the structure. The crystallite size is smaller, which is plausible assuming solvent molecules within the structure. Figure 5b shows the GIXRD curves of PF9 gel after 6 h aging under an inert gas (helium). In the nanometer level, the solution and gel aging is known to lead increased aggregation23 and nanofiber formation.33 The PF9 gel becomes much more concentrated with aging, but the same peaks can be identified as in the initial 1% gel. This implies that any structural

The length of c-axis corresponds to four repeat units for all reported crystalline PFs except for the γ phase of PF7. Thus, unlike in the simplified model of Figure 1b, the polymer chain takes a slightly staggered form where the torsion angles are not in strict trans position. As noted by Brinkmann,27 it is not certain whether the 4-fold periodicity involves main chains, side chains, or both. Since the PF7 γ phase adopts a period of two monomer units, the 4-fold period of crystalline phase is likely induced by the side-chain interaction. (Note that this consideration holds only for the crystalline phases. The solvent or solvent vapor treated PF8 shows mesomorphic “noncrystalline” β phase which shows the identity period of two monomers.) We assume that a generic crystalline model should account for three common characteristics: (1) linear dependence of layer spacing with the increasing number of side chain beads, N; (2) structural stability of the structure in the bc-plane, also apparent for gels; (3) relation between the mesomorphic β phase and the (200) reflection. Besides its bulk state, PFs should be characterized in thin films. The alignment of rigid polymers against the substrate improves crystalline order. Furthermore, as demonstrated with PF7, it can induce a structural order different from those in the bulk state.22 In the wider context of conjugated polymers, possible are also distinct orientation types of crystallites depending on the processing conditions.32 XRD and GIXRD Curves of Crystalline PF9. Figure 2 plots a XRD curve of PF9 after melting (at 230 °C) and

Figure 2. A powder XRD curve of bulk PF9 (upper curve, red). Indexing corresponds to the proposed monoclinic structure. The layer spacing, stacking period, and monomer repeat are determined from the reflections (200), (040), and (008) as indicated by green arrows. A powder curve of similarly prepared PF8 is shown for comparison (lower curve, blue). The correspondence of reflections between the orthorhombic PF8 structure and the monoclinic PF9 structure are indicated with dotted connecting lines. Almost all reflections of PF8 occur in PF9 in a comparable relative intensity.

subsequent cooling back. The unit cell is found by invoking structural similarity to the orthorhombic PF8.26 The indexing corresponds to the monoclinic structure with a = 29.31 Å, b = 23.65 Å, c = 33.33 Å, and γ = 84.70°. In this case the layer spacing is d(200) = 14.59 Å, the stacking period d(040) = 5.89 Å, and the monomer unit 2 × d(008) = 8.33 Å. This structure corresponds the mass density 0.962 g/cm3. The structure is C


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Figure 3. Quadrants of GIXRD patterns of PF9 (a) and PF8 films (b). Here qv is the scattering vector along the surface normal and qh on the surface of film substrate. Indexing corresponds to the proposed orthorhombic structure. Polymer layers are stacked out-of-plane and aromatic stacks inplane.

side chain length varies from 6 to 9 carbon units (these are not all data reported to date). Figure 6 plots the unit cell parameters for the main crystalline phases illustrating possible trends as a function of side chain length (or the number of side chain beads, N). When the XRD patterns of PF9 are considered, there are clear similarities to its analogies, PF6-PF8. First, the strongest reflection (200) shifts toward smaller angles with increased side chain length. Second, a strong reflection (008) is always seen at constant position, around q = 1.5 Å. Physically, these two reflections correspond to main chain layers separated by side chains and periodicity of the polymer chain. This view is justified by the fact that solvent cast and annealed samples tend to orient in thin films with the former reflection pointing out of the sample surface and the latter staying along the sample surface. The (200) reflection matches the first maximum of β phase. The distances calculated from the peak positions indicate that the layer spacing increases from 10.74 to 14.59 Å when the side chain length is increased from 6 to 9 but is out of trend for α-PF7 (14.43 Å). The average increase is 1.28 Å per CH2 unit, which matches the change in the side chain length. The (Bragg) periodicity along the c-axis chain is 4.17 Å for α-PF7, PF8, and PF9 and marginally less for PF6 (4.13 Å). This agrees with the nonstretchable polymer main chain. The b-axis is not as apparent but typically a relatively strong reflection is present at slightly above q = 1.0 Å−1. This is

Figure 4. XRD curves of bulk PF9 as a function of temperature. The arrow shows the sequence of curves. The heating and cooling rates were ca. 3 °C/min.

reorganization in the aggregate level may not influence the polymer level structure. The period along the b-axis has decreased plausibly due to loss of solvent, but it is still larger than in the crystalline α-form. Comparison between PF9 and Other PFs: Crystalline Structure. Table 1 compiles selected lattice parameters for selected crystalline phases of linear side chain PFs, when the D


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Figure 5. GIXRD curves of PF9 film spread from 1% MCH gel initially (a) and after 6 h on aging (b). The initial data and the MCH background are shown by solid and dashed red lines. The curves after data reduction measured out-of-plane and in-plane are shown by green and dark yellow curves. The main reflections are indexed according to orthorhombic unit cells a = 29.1 Å, b = 28.1 Å, and c = 16.7 Å for the 1% gel and a = 28.2 Å, b = 26.0 Å, and c = 33.5 Å for the aged sample.

Incidentally, the strong reflection at q = 1.50 Å−1 corresponds to half of the monomer repeat and requires a shift of half a monomer of one chain with respect to the neighboring chain. Therefore, it seems plausible that the side chains organize in layers where the interlayer distance corresponds to the Bragg distance of this peak. Interestingly, this peak also coincides with the packing scheme of long aliphatic hydrocarbons. A single peak at q = 1.50 Å−1 would be linked in hexagonal (αH) arrangement of the aliphatic chains while two maxima at q = 1.50 Å−1 and q = 1.62 Å−1 would point to the orthorhombic βO structure.34 Comblike polymers exhibit side chain crystallization, when the side chain length exceeds 8 carbon units for flexible polymers or 12 carbon atoms for rigid polymers.35 The side chains are understood to be cocrystallized within the subsequent main chain and side chain layers. Since PF9 side chains are shorter than 12 units, we assume that the side chains are not able to crystallize in the α or β forms within the overall PF crystal. If this was the case, the PF9 crystallinity could be driven by the side chain crystallinity being commensurate with the polymer repeat. Comparison between PF9 and Other PFs: Backbone Geometry Analysis. The c-axis periodicity of crystalline (α) PFs corresponds to four repeat units. This does not necessarily mean periodicity of the main chain. It can also mean that main chain has the identity period of two monomers and the side chain conformation has identity period of four. Next, we seek for chain geometries that meet this periodicity. The PF backbone is bridged by the sp3-bonded carbon which forces a bond angle 11° between successive monomers. The main chain needs to adopt a helical geometry, where the torsion angle τ takes constant values throughout the main chain. The simplest helix would be obtained by letting τ = 180°, i.e., by setting all torsions to planar “trans” positions. This conformation corresponds to two repeat units. This helix is however, unfavorable due to repulsion between the hydrogens in ortho positions. Numerous studies indicate that optimal PF torsion angle deviates from planar by 25°−50°.36,37 For example, τ of the

Table 1. Lattice Parameters for the Selected Crystalline Phases of Linear Side Chain PFs α-PF6 α′-PF6 α-PF7 γ-PF7 α-PF8 α-PF9 α-PF9

a (Å)

b (Å)

c (Å)

21.5 20.5 26.0 28.8 25.6 29.31 28.70

24.7 25.8 22.5 9.6 23.4 23.65 23.48

33.2 33.0 33.4 16.8 33.6 33.33 33.23

α = 96.5° α, β = 96°

γ = 84.7°

Z

ref

8 8 8 4 8 8 8

21 21 22 22 26 this work this work

Figure 6. Lattice parameters a (red squares), b (blue circles), and c (green diamonds) of the main crystalline phases of linear side-chain polyfluorenes against the side-chain length. Open symbols for PF9 represent proposed monoclinic and crosses orthorhombic structure. Taken from Table 1.

indexed as (040) for PF621 and as (140) for PF826. As this is the strongest reflect along (or near) the b-axis, we associate the corresponding Bragg spacings d040 and d140 with the interchain distance within the layers (aka stacks). E


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Macromolecules branched side chain poly[9,9-bis(2-ethylhexyl)fluorene] PF2/6 is approximately 69°,38 which is very close to the observed torsion potential minimum at ϕ = 68°.39 The branched side chains of PF2/6 are in the amorphous state, perhaps allowing “a more optimal” conformation of the main chain, whereas the linear side chains compete energetically and force the main chain toward a more extended state. Figure 7 shows possible main chain conformations following the ideas introduced in ref 40. Figure 8 plots the measured

Figure 8. Observed (arrows) and calculated (curves) monomer repeats for the considered PF conformations. The molecular geometry of monomeric dioctylfluorene is used for the calculated curves according to McFarlane et al.41 (a) or Rathnayake et al.42 (b).

Figure 7. Various possibilities for the main chain conformation with a four monomer periodicity. The first four produce a periodic structure by rotation of the torsion angles alone while the last two require some adjustment of bond angles.

monomers plus 180° rotation (c2/1). Finally, (TS)2 and S2S2 have translation symmetry by two repeat units followed by mirror operation (c2/m). The first symmetry c2 is unlikely for the α-crystals because it does not fit with the unit cell of four repeat units.

repeat unit periodicities compared to those calculated from the known molecular geometry of monomeric 9,9-di-n-octyl-9Hfluorene according to McFarlane et al.41 or Rathnayake et al.42 Besides the aforementioned 21 helix, the four monomer identity period is satisfied by 41. Apart from these simple helices, two alternating τ’s are required. Using notations of sp3chain to denote chain torsions T for trans (τ = 180°), S (skew) for 90 < τ < 180, and G (gauche) for 0 < τ < 90, two sets of strictly periodic conformations can be found: TSTS ((TS)2 for short) and (GS)2. In both cases the torsion can take arbitrary values between 0 and 180° so S and G symbols are interchangeable. The two helical conformations are their special cases. Moreover, we can consider simple back and forth twisted geometries SSSS and SSSS. Because of the bond angle between repeat units, these geometries do not produce periodicity so far the intermonomer bond is linear. The deviation from linearity increases the more τ differs from the trans position. These geometries have three kinds of molecular symmetries about the c-axis: (TT)2 and (SS)2 have translational symmetry of two repeat units (c2). 41 and (GS)2 are two helical forms (right- and left-handed forms) and translation symmetry of two

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CONCLUSIONS In this work, we study solid state PF9 and propose structures for crystalline α phase in bulk (monoclinic) and in thin films (orthorhombic). The crystalline PF9 turns into a weakly ordered LC phase above 170 °C. PF9 maintains similar but not identical structural motif in MCH gel, and we denote this as the β phase. The periodicity along the polymer chain (c-axis) corresponds to four repeat units for the α phase and two units for the β phase. The β crystallites are smaller and the structure is larger along the stacking direction (b-axis). This is attributed to the solvent molecules within the β structure. This work provides a detailed description of the solid state structure of PF9. It distinguishes PF9 structures in the solid state and gel. Furthermore, it completes the knowledge of the solid state structures of 9,9-di-n-alkyl-substituted PF’s, which now includes all the members from PF6 to PF9. F


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(23) Knaapila, M.; Almásy, L.; Garamus, V. M.; Ramos, M. L.; Justino, L. L. G.; Galbrecht, F.; Preis, E.; Scherf, U.; Burrows, H. D.; Monkman, A. P. Polymer 2008, 49, 2033−2038. Bright, D. W.; Dias, F. B.; Galbrecht, F.; Scherf, U.; Monkman, A. P. Adv. Funct. Mater. 2009, 19, 67−73. (24) Knaapila, M.; Dias, F. B.; Garamus, V. M.; Almásy, L.; Torkkeli, M.; Leppänen, K.; Galbrecht, F.; Preis, E.; Burrows, H. D.; Scherf, U.; Monkman, A. P. Macromolecules 2007, 40, 9398−9405. Knaapila, M.; Bright, D. W.; Stepanyan, R.; Torkkeli, M.; Almásy, L.; Schweins, R.; Vainio, U.; Preis, E.; Galbrecht, F.; Scherf, U.; Monkman, A. P. Phys. Rev. E 2011, 83, 051803. (25) Grell, M.; Bradley, D. D. C.; Ungar, G.; Hill, J.; Whitehead, K. S. Macromolecules 1999, 32, 5810−5817. (26) Chen, S. H.; Chou, H. L.; Su, A. C.; Chen, S. A. Macromolecules 2004, 37, 6833−6838. Chen, S. H.; Su, C. H.; Su, A. C.; Sun, Y. S.; Jeng, U.; Chen, S. A. J. Appl. Crystallogr. 2007, 40, s573−s576. (27) Brinkmann, M. Macromolecules 2007, 40, 7532−7541. (28) Winokur, M. J. Structural Studies of Conducting Polymers. In Handbook of Conducting Polymers; Skotheim, T. A., Elsenbaumer, R. L., Reynolds, J. R., Eds.; Marcel Dekker: New York, 1998; pp 707−726. Kline, R. J.; McGehee, M. D. J. Macromol. Sci., Polym. Rev. 2006, 46, 27−45. Brinkmann, M. J. Polym. Sci., Part B: Polym. Phys. 2011, 49, 1218−1233. (29) Roth, S. V.; Döhrmann, R.; Dommach, M.; Kuhlmann, M.; Kröger, I.; Gehrke, R.; Walter, H.; Schroer, C.; Lengeler, B.; MüllerBuschbaum, P. Rev. Sci. Instrum. 2006, 77, 085106. (30) Grell, M.; Bradley, D. D. C.; Long, X.; Chamberlain, T.; Inbasekaran, M.; Woo, E. P.; Soliman, M. Acta Polym. 1998, 49, 439− 444. (31) Somma, E.; Loppinet, B.; Chi, C.; Fytas, G.; Wegner, G. Phys. Chem. Chem. Phys. 2006, 8, 2773−2778. (32) Kline, R. J.; McGehee, M. D.; Toney, M. F. Nat. Mater. 2006, 5, 222−228. Donley, C. L.; Zaumseil, J.; Andreasen, J. W.; Nielsen, M. M.; Sirringhaus, H.; Friend, R. H.; Kim, J.-S. J. Am. Chem. Soc. 2005, 127, 12890−12899. DeLongchamp, D. M.; Kline, R. J.; Jung, Y.; Lin, E. K.; Fischer, D. A.; Gundlach, D. J.; Cotts, S. K.; Moad, A. J.; Richter, L. J.; Toney, M. F.; Heeney, M.; McCulloch, I. Macromolecules 2008, 41, 5709−5715. (33) Xu, L.; Zhang, J.; Peng, J.; Qiu, F. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 633−639. (34) Luyten, M. C.; van Ekenstein, G. O. R. A.; ten Brinke, G.; Ruokolainen, J.; Ikkala, O.; Torkkeli, M.; Serimaa, R. Macromolecules 1999, 32, 4404−4410. (35) Lee, J. L.; Pearce, E. M.; Kwei, T. K. Macromolecules 1997, 30, 6877−6883. (36) Chunwaschirasiri, W.; Tanto, B.; Huber, D. L.; Winokur, M. J. Phys. Rev. Lett. 2005, 94, 107402. (37) Chan, K. L.; Sims, M.; Pascu, S. I.; Ariu, M.; Holmes, A. B.; Bradley, D. D. C. Adv. Funct. Mater. 2009, 19, 2147−2154. (38) Knaapila, M.; Torkkeli, M.; Monkman, A. P. Macromolecules 2007, 40, 3610−3614. (39) Hong, S. Y.; Kim, D. Y.; Kim, C. Y.; Hoffmann, R. Macromolecules 2001, 34, 6474−6481. (40) Knaapila, M.; Konôpková, Z.; Torkkeli, M.; Haase, D.; Liermann, H.-P.; Guha, S.; Scherf, U. Phys. Rev. E 2013, 87, 022602. (41) McFarlane, S.; McDonald, R.; Veinot, J. G. C. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 2005, 61, o671−o673. (42) Rathnayake, H. P.; Cirpan, A.; Delen, Z.; Lahti, P. M.; Karasz, F. E. Adv. Funct. Mater. 2007, 17, 115−122.

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected] (M.K.). Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The research leading to these results has received funding from the European Community’s Seventh Framework Program (FP7/2007-2013) under grant agreement no. 312284. We thank Wolfgang Caliebe and Jan Perlich of HASYLAB and Dörthe Haase of MAX IV Laboratory for help in the beamline work.

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Solid State Structure of Poly (9, 9-dinonylfluorene)

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