Hybrid mechanism of nucleation and cooperative propagation in a single-crystal-to-singlecrystal transition of a molecular crystal

Transcription

1 Hybrid mechanism of nucleation and cooperative propagation in a single-crystal-to-singlecrystal transition of a molecular crystal Hyunjoong Chung 1, Christian Ruzié 2, Yves Geerts 2, Ying Diao 1 * 1 Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States. Supporting Information Contents Methods Section. Figure S1. Measured angle between the phase boundary line and crystal edge. Figure S2. Initiation location of martensitic transition in 1 st heating cycle Figure S3. POM images of various crystals during the first and last cycle. Figure S4. 1 st cycle hysteresis for all pristine crystal samples. Figure S5. Histogram of first and final cycle hysteresis. Figure S6. Two crystal samples transition temperatures over multiple cycles. Figure S7. Direct observation of the three-step mechanism in a defected crystal. Figure S8. 1 st cycle hysteresis for all pristine and needle-pricked crystal samples. Figure S9. Initiation location in each heating cycle of a defected crystal. Figure S10. Histogram of P-1 and P-2 speeds represented in Figure 3a. Figure S11. Measured propagation distance of the phase boundary line as a function of time. Figure S12. Histogram of Initial and final cycle P-2 speeds represented in Figure 3b. Table S1. Interaction energy results for the LT (298K) and HT form (370K). Table S2. Initial and final propagation 2 speeds. Each sample is defined as P-2 step propagation speeds along the same direction.

2 Methods Synthesis. ditbu-btbt was synthesized by Friedel Crafts alkylation using the conditions of diacylation of BTBT with AlCl 3 as Lewis acid. To a solution of BTBT (2.00 g, 8.32 mmol) in dry CH 2 Cl 2 (150 ml) was added AlCl 3 (3.99 g, mmol) in one portion, at 20 C and under an argon atmosphere. Then, the reaction mixture was cooled down to 78 C. Next, tert-butyl chloride (3.64 ml, mmol) was then added dropwise in about 30 min. The reaction mixture was stirred at 78 C for 2 h. The reaction was quenched by the addition of ice/water (100 ml). Volatiles were removed under reduced pressure. The formed precipitate was isolated by filtration, washed with water and methanol and dried. Further recrystallization in heptane afforded a white crystalline powder 1. DitBu-BTBT single crystal fabrication. Using a blend of 10 wt % polystyrene (MW 290k, Sigma Aldrich) and anhydrous tetralin (Sigma Aldrich), 10 mg ml -1 of ditbu-btbt was used as the stock solution. To fabricate single crystals for in situ microscopy study, the solution was stirred and heated at 100 C for 5 minutes, and 2µL~8µL of the solution was dropcasted onto a clean silicon substrate (1cm x 1cm) at room temperature. The substrates were cleaned with toluene, acetone, and isopropanol, respectively. The drop was left in a hood under room temperature and moderate humidity to evaporate for at least 18 hours. This procedure yielded single crystals with size ranging from 50 µm to 400 µm. Polarized optical microscopy. Single crystal samples were placed in a heating chamber under a Nikon H550S with a high-speed camera (Infinity 1) and heating stage (linksys32 temperature control). The heating chamber was capped with a sealable lid during heating and cooling cycles, and the rate was kept constant at 2 C min -1 for all experiments. Time-lapse images were taken for all in situ experiments with various frame rates ranging from 5 to 40 fps. The average speed was measured by dividing the propagating distance by the time it takes for complete transition of the phase boundary line. Depending on the initiation location, an average propagation speed was measured for each direction. Often times the initiation started from the middle of the crystal, so the propagation speed in both ends of the crystal were measured. In this way we were able to obtain more than 1 set of data per crystal, resulting in 45 sets of propagation speed from 30 crystals. When comparing P-2 propagation speeds for multiple cycles, only the speeds along the

3 same direction were directly compared. Image analysis was performed with Nikon NIS Elements, Linksys32 data capture, and ImageJ. Calculations. Interaction energy calculations were performed on CrystalExplorer17 2. Single crystal X-ray cif files of ditbu-btbt from 298K and 370K were used for the calculations. From a reference molecule, six nearest neighboring molecules along the herringbone plane and two out-of-plane (along the a axis) were selected for calculation. Energy model CE-B3LYP model was used with 6-31G(d,p) basis set, along with Grimme s D2 dispersion corrections. All total energy calculations have an uncertainty 3 of 1.0 kj mol -1.

4 Figure S1. Measured angle between the phase boundary line and crystal edge. All samples from in situ microscopy showed very similar angles, and some were selected and shown here.

5 Figure S2. Initiation location of martensitic transition in 1 st heating cycle. 5 crystals were chosen out of the 15 that showed initiation from a corner is shown on top, and the case in which initiation did not start from a corner is shown below. The red arrows point to the location of initiation. As mentioned in the manuscript, in the case where corner initiation did not occur, a neighboring crystal is visibly pushing down on the crystal, causing initiation.

6 Figure S3. POM images of various crystals during the first and last cycle. Multiple transition cycles naturally introduce defects to the crystal, as observed from POM. Although the crystals become much more defected, they keep structural integrity. All crystals heated and cooled at 2 K min -1. All scale bars are 50 µm.

7 Figure S4. 1 st cycle hysteresis for all pristine crystal samples. A wide range of hysteresis exists in the pristine crystal samples. POM images of crystal samples with maximum (22.5K) and minimum (7.3K) hysteresis are shown.

8 Frequency (%) first cycle hysteresis final cycle hysteresis Hysteresis ( C) Figure S5. Histogram of the first and final cycle hysteresis. The histogram of the measured first and final cycle hysteresis from 30 independent crystal samples, both fit with Gaussian distributions with means at and degrees, respectively. The shift of the Gaussian curves indicates the clear decrease in hysteresis from the first to the final cycle.

9 Figure S6. Two crystal samples transition temperatures over multiple cycles. (a) A large change in hysteresis is observed between the first and fifth thermal cycle, and comparison of the before and after transition POM images show a significant increase in defect density. (b) A small change in hysteresis is observed between the first and eighth cycle. The POM images show almost no change to the crystal surface in this case.

10 Figure S7. Direct observation of the three-step mechanism in a defected crystal. The initiation clearly originates from the defect in the middle, and also in the propagation 1 (P-1) step, the propagations originate from the defect and propagate upward and downward. Only when the propagation from the P-1 step extend all the way across the crystal, the propagation 2 step begins. With these defects, the P-1 and P-2 propagation speeds were relatively slower, and was thus clearly observable from in situ microscopy (refer to SI video S2 for the full process).

11 Figure S8. 1 st cycle hysteresis for all pristine and needle-pricked crystal samples. The first cycle hysteresis of four needle-pricked crystals are clearly much lower than the pristine crystals. We can infer from the POM image (Fig.S3) and the low hysteresis of 7.3K of the pristine crystal that it is closer to the needle-pricked than pristine crystals.

12 Figure S9. Initiation location in each heating cycle of a defected crystal. The initiation locations for a defected crystal in all eight cycles are near the introduced defects. This is in contrast to pristine crystals, where the locations were stochastic. The crystal during heating cycles are shown here, but a similar trend was observed upon cooling.

13 Figure S10. Histograms of P-1 and P-2 speeds using the same data set shown in Figure 3a. A total of 29 samples were measured at a particular cycle where P-1 speed was detectable. P-1 speeds are orders of magnitude faster than P-2 speeds in all cases.

14 Figure S11. Measured propagation distance of the phase boundary line as a function of time. The local propagation speed is faster in the beginning, and slows down near the end. The average propagation speed for all crystals were calculated as the total distance divided by the total transition time.

15 Figure S12. Histogram of initial and final cycle P-2 speeds using the same data set shown in Figure 3b. Note the significant decrease in P-2 speed at the final cycle, due to the increase of defect density that formed through multiple thermal cycles. The insets show distribution of the majority of the P-2 speed in initial and final cycle.

16 Supplementary Tables ditbu-btbt LT form ditbu-btbt HT form Interaction Pair Interaction Energy (kj/mol) Elec/ pol. Disp. Rep. Total Interaction Pair Interaction Energy (kj/mol) Elec/ pol. Disp. Rep. Total I II III I II III Table S1. Interaction energy results for the LT (298K) and HT form (370K). Each component of interaction energy corresponds to electrostatic/polarization, dispersion, and repulsion, respectively. The results were calculated from Crystal Explorer, using the cif files obtained for ditbu-btbt.

17 Table S2. Initial and final propagation 2 speeds. Each sample is defined as P-2 step propagation speeds along the same direction. The last column is the ratio of initial to final propagation speed, showing that most samples have orders of magnitude difference between them.

18 References 1. Schweicher, G.; Lemaur, V.; Niebel, C.; Ruzie, C.; Diao, Y.; Goto, O.; Lee, W. Y.; Kim, Y.; Arlin, J. B.; Karpinska, J.; Kennedy, A. R.; Parkin, S. R.; Olivier, Y.; Mannsfeld, S. C. B.; Cornil, J.; Geerts, Y. H.; Bao, Z. N., Bulky End-Capped [1]Benzothieno[3,2-b]benzothiophenes: Reaching High-Mobility Organic Semiconductors by Fine Tuning of the Crystalline Solid-State Order. Adv. Mater. 2015, 27 (19), M. J. Turner, J. J. M., S. K. Wolff, D. J. Grimwood, P. R. Spackman, D. Jayatilaka, M. A. Spackman CrystalExplorer Mackenzie, C. F.; Spackman, P. R.; Jayatilaka, D.; Spackman, M. A., CrystalExplorer model energies and energy frame-works: extension to metal coordination compounds, organic salts, solvates and open-shell systems. Iucrj 2017, 4,