Nanomechanical Function from Self-Organizable Dendronized Helical Polyphenylacetylenes

Transcription

1 Supporting Information to Nanomechanical Function from Self-Organizable Dendronized Helical Polyphenylacetylenes Virgil Percec,,* Jonathan G. Rudick, Mihai Peterca, and Paul A. Heiney Roy & Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania and Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania, Table of Contents 1. Temperature Dependence Analysis via Transmission Optical Microscopy...S2 Figure SF1...S2 Figure SF2...S2 Figure SF3...S3 Figure SF4...S3 Figure SF5...S3 Figure SF6...S4 2. Nanomechanical Weight Lifting Experiment.... S4 Figure SF7...S4 3. Experimental...S4 Materials...S4 Techniques...S5 Preparation of Oriented Fibers...S5 Temperature Dependence of the Column Diameter of the Dendronized PPA via X-ray Diffraction Experiments...S6 Temperature Dependence Analysis via Transmission Optical Microscopy...S6 Nanomechanical Weight Lifting Experiments...S6 4. Supporting References....S7 S1

2 1. Temperature Dependence Analysis via Transmission Optical Microscopy Supporting Figure SF1. Transmission optical microscopy images of the poly[(3,4,5)12g1-4ebn] Supporting Figure SF2. Transmission optical microscopy images of the poly[(3,4-3,5)8g2-4ebn] S2

3 Supporting Figure SF3. Transmission optical microscopy images of the poly[(3,4-3,5)10g2-4ebn] Supporting Figure SF4. Transmission optical microscopy images of the poly[(3,4-3,5)12g2-4ebn] Supporting Figure SF5. Transmission optical microscopy images of the poly[(3,4-3,5)14g2-4ebn] S3

4 Supporting Figure SF6. Transmission optical microscopy images of the poly[(3,4-3,5)16g2-4ebn] 2. Nanomechanical Weight Lifting Experiment static friction (not included in the weight) Supporting Figure SF7. Experimental set-up used in the nanomechanical weight lifting. (a) detailed image of the oriented fiber set-up; (b) side view of the experimental set-up; (c) detailed of the coin weight decomposition on an incline plane. Remark: reported weight lift does not include the static friction, if static friction is considered the actual mechanical lift is even larger than reported. 3. Experimental Materials. Procedures for the preparation of materials used in the experiments and their characterization have been reported previously. 1,2 S4

5 Techniques. X-ray diffraction (XRD) measurements were performed using Cu-K 1 radiation ( = Å) from a Bruker-Nonius FR-591 rotating anode X-ray source with a 0.2 x 0.2 mm 2 filament operated at 3.4 kw. The Cu radiation beam was collimated and focused by a single bent mirror and sagitally focused through a Si (111) monochromator, generating in a 0.3 x 0.4 mm 2 spot on a Bruker AXS Hi-Star multiwire area detector. To minimize attenuation and background scattering, an integral vacuum was maintained along the length of the flight tube and within the sample chamber. Samples were held in quartz capillaries ( mm in diameter), mounted in a temperature-controlled oven (temperature precision: ± 0.1 C, temperature range from -120 C to 270 C). The distance between the sample and the detector was 12.0 cm for wide angles diffraction experiments and 54.0 cm for intermediate angles diffraction experiments, respectively. All XRD measurements were done with the aligned sample axis perpendicular to the beam direction. XRD peaks position and intensity analysis was performed using Datasqueeze Software (version 2.01) that allows background elimination and Gaussian, Lorentzian, Lorentzian squared, or Voigt peak-shape fitting. Molecular modeling and simulation experiments were performed using the Materials Studio Modelling (version 3.1) software from Accelrys. Package s Discover module was used to perform the energy minimizations on the supramolecular structures with the following settings: PCFF or COMPASS force fields, and Flechter-Reeves algorithm for the conjugate gradient method. Reported molecular models are in agreement with the small and wide angle XRD results on powder or oriented fibers and with the experimental densities results. 1,2 Preparation of Oriented Fibers. In all cases a fine-grinded powder of the dendronized PPA was loaded in a custom-made extrusion device. After heating the device to the desired temperature, in general above the glass transition temperature and the io h phase, the fiber was fabricated via extrusion from the h liquid crystal phase. The presence of h liquid crystal phase at high temperature was essential in the extrusion process, being the major factor that facilitates a higher degree of orientational S5

6 order of the fabricated fibers. Typical extruded fiber dimensions are diameter ~0.5 mm and length ~5 to 20 mm. Temperature Dependence of the Column Diameter of the Dendronized PPA via X-ray Diffraction Experiments. The sample, powder or oriented fiber, was loaded in a thin wall glass capillary that was mounted in a custom made oven. Using a cooling or heating rate of 5 to 10 / min the sample temperature was set with a precision of ±0.2 C, the typical XRD collection time was between 5 to 10 min. The error in temperature for the X-ray temperature scans was estimated to be in the order of 3 C due to the presence of a thermal gradient between the sample and heating/cooling stage. The experimental set-up has two thermal contacts, one between sample-and-glass capillary wall and a second one between glass capillary and heating/cooling stage. Temperature Dependence Analysis via Transmission Optical Microscopy. The fabricated oriented fibers were cut for the transmission optical microscopy to a length of ~ mm due to the microscope view-field limitation. The fiber was placed directly on a thin microscope glass slide and loaded in a Mettler FP82HT hot stage. Microscopy images were collected on a computer using the microscope Olympus BX51 equipped with a digital camera. A typical thermal scan experiment consisted in setting the desired temperature of the stage with a heating or cooling rate of 5 to 10 /min and recording the microscopy image. The fiber length percentage change was estimated from the image. As in the case of the X-ray thermal scans, the fiber length thermal change recorded in the optical microscopy experiment is subject to a temperature error. In this case it was ±5 C due to the thermal contact between the sample glass slide and hot stage. Representative microscopy data are shown in Figure 2 and in Supporting Figures SF1 to SF6. Nanomechanical Weight Lifting Experiments. An oriented fiber fabricated from the poly[(3,4-3,5)16g2-4ebn] was cut to the length of 6.5 mm and loaded in a thin wall glass capillary that was sealed only at one end such that at the other end a small part of the fiber was outside free to slide. This was done to reduce the slight bending of the oriented fibers at high temperatures and at the same S6

7 time to avoid the need to tape directly the fiber using a tape that would prohibit any further expansion or contraction of the oriented fiber. The capillary with the loaded fiber was stuck to a glass microscope slide using commercially available transparent tape. After this, the slide was mounted in the Mettler FP82HT hot-stage and using a small box the hot stage was inclined with about 8±1 from the horizontal. Between the glass microscopy slide and the hot stage a small piece of millimeter-grid paper was inserted to be able to record the approximate fiber length. At room temperature a dime was placed at the tip of the fiber and using a digital camera a picture was taken. The hot stage was subsequently heated such that the estimated temperature of the oriented fiber was about 80 C and a second picture was taken to record the change in the fiber length. The 250-times weight lifted was calculated based on the vector division of the dime weight into two components: a component parallel to the surface that equals m coin sin(8 ) and a perpendicular to the surface contact that equals m coin cos(8 ) (Figure 5 and Supporting Figure SF7). The actual fiber expansion force must be greater than the estimated 250-times its weight since it has to compensate for the static friction between the dime and the glass surface. More experiments are needed in order to quantify the static friction. At higher temperature the poly[(3,4-3,5)16g2-4ebn] oriented fiber loses the rigidity to hold the dime and bends. This reduced rigidity at very high temperatures was expected since at high temperature the columns have more and more flexibility in the peripheral region, and the sample became soft and somewhat sticky. The above experiment was repeated three times for poly[(3,4-3,5)12g2-4ebn] and poly[(3,4-3,5)16g2-4ebn]. In both cases the weight lifting experiment was repeated at least once on the same fiber. This was done to demonstrate the reversibility of the oriented fiber thermal expansion-contraction process and to demonstrate the reusability of the same dendronized PPA material. 3. Supporting References (1) a) Percec, V.; Rudick, J. G.; Peterca, M.; Wagner, M.; Obata, M.; Mitchell, C. M.; Cho, W.-D.; Balagurusamy, V. S. K.; Heiney, P. A. J. Am. Chem. Soc. 2005, 127, ; b) Percec, S7

8 V.; Rudick, J. G.; Peterca, M.; Staley, S. R.; Wagner, M.; Obata, M.; Mitchell, C. M.; Cho, W.-D.; Balagurusamy, V. S. K.; Lowe, J. N.; Glodde, M.; Weichold, O.; Chung, K. J.; Ghionni, N.; Magonov, S. N.; Heiney, P. A. Chem. Eur. J. 2006, 12, ; c) Percec, V.; Peterca, M.; Rudick, J. G.; Aqad, E.; Imam, M. R.; Heiney, P. A. Chem. Eur. J. 2007, 13, (2) a) Percec, V.; Obata, M.; Rudick, J. G.; De, B. B.; Glodde, M.; Bera, T. K.; Magonov, S. N.; Balagurusamy, V. S. K.; Heiney, P. A. J. Polym. Sci., Part A: Polym. Chem. 2002, 40, ; b) Percec, V.; Aqad, E.; Peterca, M.; Rudick, J. G.; Lemon, L.; Ronda, J. C.; De, B. B.; Heiney, P. A.; Meijer, E. W. J. Am. Chem. Soc. 2006, 128, ; c) Percec, V.; Rudick, J. G.; Peterca, M.; Aqad, E.; Imam, M. R.; Heiney, P. A. J. Polym. Sci., Part A: Polym. Chem. 2007, 45, S8