Supplemental Information for Hole-transporting side-chain polystyrenes based on TCTA with tuned glass transition and optimized electronic properties

The development of crosslinkable materials for the fabrication of solution processable OLEDs presents challenges, especially regarding the adjustment of the glass transition (Tg), which has a significant influence on crosslinking kinetics and device life-time. Crosslinkable hole transport materials based on poly(N,N-bis(4-(9H-carbazol-9-yl)phenyl)-4-vinylaniline) (poly-TCTA) with covalently attached plasticizers for Tg control and azide functionalities for azide-alkyne crosslinking are presented. These polymers have an optimal Tg of around 150 °C and show superior crosslinking performances and solution resistibilities. Incorporation of electron-pushing alkoxides to the pendant groups combines the Tg adjustment approach with a systematic tuning of the HOMO level from −5.7 to −5.3 eV. All presented polymers have good charge transport and injection properties and are ideal for applications in phosphorescent OLEDs due to their high triplet energies (>2.8 eV). The new crosslinkable poly-TCTA-based materials are applied as hole-transport layers (HTLs) in fully solution-processed OLEDs. An improvement of the device performance is demonstrated for OLEDs with additional crosslinked HTL.

Fig. S7 UV/Vis scans of 3a 43 AZ 15 (with XL) polymer films on quartz-substrates.Spectra were recorded before and after crosslinking at 170 °C for 40 Minutes and after a rinsing-step with toluene.

Materials and Methods
All materials were obtained from Sigma-Aldrich Chemical Company (Munich, Germany), Acros Organics (Geel, Belgium), Lumtec (Taiwan) or Synthon Acmari Chemie (Wolfen, Germany) and used without any further purification unless otherwise stated.Silica gel 60 (Merck) (Darmstadt, Germany) was used in the separation and purification of compounds by column chromatography.Separations with gradient column chromatography were obtained using a TELEDYNE ISCO CombiFlash Rf system.Solvents for column chromatography, recrystallization, and purification were received from Th. Geyer GmbH (Berlin, Germany) and J. T. Baker (Deventer, Netherlands).Dry solvents were received from Sigma-Aldrich Chemical Company, stored over molecular sieve and sealed under an inert atmosphere.All reactions were done in inert atmosphere in argon or nitrogen by using common Schlenk techniques.
Thin layer chromatography was done with POLYGRAM SIL G/UV 254 TLC-plates.
High-resolution (500 MHz) 1 H-NMR and 13 C-NMR (125 MHz) spectra were recorded on a UNITY INOVA 500 spectrometer from Varian at room temperature.
Size exclusion chromathography (SEC) has been performed at 25 °C in THF to determine the molecular weights using a combination of Separation module 2695e (Waters), Dual  Absorbance Detector 2487, and Refractive Index Detector 2414.A SEC-column set with 5 µm high crosslinked porous polystyrene-divinylbenzene matrix from Waters (7.8 mm x 300 mm; Styragel Guard column, HR3, HR4, HR5) for separation and narrowly distributed, linear polystyrene standards from Agilent Polymer Laboratories (Varian) for weight determination were used.Polymer solutions (2 mg l -1 in THF) were stirred for 24 h at 22 °C and filtered (1 µm PTFE) before 2 x 100 µl of the solution was injected.Molecular weights were calculated with the Empower software from Waters.
Isothermal ATR-FTIR Spectroscopy was done with a Digilab Scimitar FTS2000 FTIR Spectrometer, connected to a Golden Gate Mk II ATR-system (Specac) coupled with a heating stage (max.200 °C).Dissolved samples were drop-casted onto the preheated sample stage, the first measurement was started after complete solvent evaporation (around 3 seconds) and additional spectra were recorded in certain timeintervals until completed reaction.
Thermal analysis of 3-5 mg per polymer sample was performed with differential scanning calorimetry (DSC) using a Netzsch DSC 204 Phoenix with a scanning rate of 10 K min -1 .The glass transition was obtained from the second heating cycle.
UV/Vis and photoluminescence spectra: About 30 nm thick films were spun from toluene solutions (concentrations 5 g l -1 , 1000 rpm) onto silica glass substrates.Absorption was measured using a Cary 5000 UV/Vis spectrometer.
Photoelectron spectroscopy was performed using a Riken Keiki AC-2 at a power of 50 nW.Investigated polymer layers were prepared by drop-casting onto glass substrates.All measurements were carried out at least three times.
CV measurements: Voltammograms were obtained with an EG&G Parc model 273 potentiostat.A three electrode configuration was used in an undivided cell, which consisted of a glassy carbon electrode (area 0.5 cm 2 ) onto which the polymer film was deposited, a platinum mesh as the counter electrode, and an Ag/AgCl (3 M NaCl and sat.AgCl) reference electrode.0.1 M Bu 4 NBF 4 in acetonitrile was used as electrolyte and prior to each measurement the electrochemical cell has been deoxygenated with nitrogen.The electrochemical cell was calibrated by the use of a ferrocene standard (-4.8 eV against standard hydrogen electrode) [1][2][3] and the ferrocene half-wave potential has been determined to be 512 mV for this assembly.1 wt% polymer solutions in CHCl 3 were prepared and 5 µl were deposited on the glassy carbon electrodes.The prepared electrodes were kept under vacuum and dried at 60 °C for 2 h.The oxidation potential was determined by the peak potential of measured polymer films as marked in Fig. S7.The corresponding HOMO levels were calculated using equation S1 and S2.Multilayer OLED fabrication: Patterned ITO glass substrates were cleaned and coated with a PEDOT:PSS layer as described in the above section.Further preparation and measurements were conducted in inert N 2 atmosphere.For the devices with additional hole-transport layer (HTL), the HTL material was spin-coated from a 4 g/l toluene solution at 2000 rpm.The resulting layer thickness was ca.15-20 nm.Crosslinking of the HTL was performed by heating at 170°C for 40 min.Then, the ternary emission layer blend (Ir-based emitter:co-Host-001:polymer 9a 0.5:2:1 per wt. 4 was spin-coated from a 20 g/l solution in toluene at 2000 rpm, followed by heating at 180°C for 30 min.The cathode materials were evaporated under high vacuum conditions: 5 nm Ba at ca. 0.5 Å/sec, followed by 100 nm Ag at ca. 5 Å/sec. PL transients where recorded exciting films at 355 nm with 150 ps length YAG laser (EKSPLA) pulses and collecting light using Jobin Yvon spectrograph and gated iCCD camera (Stanford Computer Optics) by exponentially increasing delayed and integration times as described in ref. 5 This allows to record up to 10 orders of magnitude in time and intensity of the PL decay.

Synthesis of 2-methoxy-9H-carbazole
This reaction was performed according to modified literature procedures.

Synthesis of 3,6-diethoxy-9H-carbazole
This reaction was performed according to modified literature procedures.
The resulting filtrate was adsorbed on silica and purification by flash chromatography on silica with a gradient of n-hexane and ethyl acetate afforded the product (12.3g, 39.5 mmol, 86 % yield) as a white solid.
The resulting filtrate was adsorbed on silica and purified by flash chromatography on silica using DCM as eluent afforded the product (11.0g, 35.2 mmol, 77 % yield) as a white solid.

Activation of copper bronze
This reaction was performed according to a modified literature procedure.The copper bronze needs to be freshly activated prior Ullmann coupling.Long storage-periods led to reduction of product yields.A suspension of dendritic copper (2.00 g, 31.5 mmol, 1.0 equiv) and iodine (0.40 g, 3.15 mmol, 0.1 equiv) were stirred for ten min.at RT.The solvent was filtered off and the residual solid was washed with acetone and subsequently stirred for 20 min. in conc.HCl (20 mL) and acetone (20 mL).After filtration the solid was dried in vacuo with additional heating.The resulting copper bronze was kept under inert conditions until it was used as a catalyst.
The organic phase was separated, dried over anhydrous Na2SO4, filtrated and concentrated in vacuo.Purification by flash chromatography on silica using toluene as eluent afforded the product (12.6 g, 20.9 mmol, 78 % yield) as a white solid.
Purification by flash chromatography on silica using toluene as eluent afforded the product (9.40 g, 10.6 mmol, 94 % yield) as a white solid.

Polymer Synthesis 3a-f
All polymerizations were performed according to a literature procedure 13 in a glovebox under argon atmosphere.Anhydrous THF was distilled prior use to remove stabilizers.N,N-azobisisobutyronitrile was recrystallized in MeOH by dissolution at RT and crystallization at -20 °C.

General technique I
The monomer(s) (1 equiv) and AIBN (0.02 equiv) were stirred in THF (toluene for 3f) with a concentration of 0.1 g•L -1 for 72 hours at 50 °C.The resulting solution was allowed to cool down to RT and was demonomerized by precipitation in nheptane/EAc 4:1 (for 3c, 3f in MeOH/Et 2 O 2:1).The precipitate was filtered using Teflon-filters (20 µm).The solid was dissolved in THF (toluene for 3f) and the precipitation process was repeated until all residual monomer was removed (as judged by TLC with precipitation solvent as eluent).

Fig. S1
Fig. S1 Differential-scanning calorimetry scans of polymer 3aAZ 15 with and without

Fig. S4
Fig. S4 ATR-FTIR scans of polymer 3a 43 AZ 15 with XL at 170 °C.The first spectrum is

Fig. S7
Fig. S7 Exemplary cyclic voltammogram of polymer 3a.The arrow marks the read