SUPPORTING INFORMATION

Transcription

1 SUPPORTING INFORMATION Rapid, puncture-initiated healing via oxygen-mediated polymerization Scott R. Zavada, Nicholas R. McHardy, Keith L. Gordon, and Timothy F. Scott* Experimental Section Materials: Ethylene glycol dimercaptopropionate (EGDMP) was donated by Evans Chemetics. Trimethylolpropane diallyl ether (TMPDAE) and tributylborane (TBB) were purchased from Sigma-Aldrich; TMPDAE and EGDMP were vacuum distilled prior to use and TBB was used as received. N-Nitrosophenylhydroxylamine aluminum salt, a radical inhibitor, was purchased from Wako Chemicals and used as received. The 1 mm poly(butadiene)-graft-poly(methyl acrylate-co-acrylonitrile) (PBG Barex 210 IG from Ineos) and partially neutralized poly(ethyleneco-methacrylic acid) (EMAA Surlyn 8940 from DuPont) panels were provided by the NASA Langley Research Center. Synthesis: Trimethylolpropane triallyl ether (TMPTAE) was formed, using a method from the literature, 1 by reacting TMPDAE in toluene solution overnight at 70 C with excess sodium hydride and allyl bromide. Monomer degassing: Prior to all experiments (both real-time FTIR and ballistics), all liquid monomers were degassed by at least 12 freeze-pump-thaw cycles: ml of monomer, in a glass vacuum flask, was frozen in liquid nitrogen; the headspace above the frozen monomer was evacuated by applying a vacuum of less than 0.5 torr; and, after sealing the flask, the frozen 1

2 monomer was allowed to melt at room temperature. These steps were repeated until no gas bubbles evolved during the thaw step. Dynamic Mechanical Analysis (DMA): Performed using a DMA Q 800 from TA instruments. Temperature was ramped from -60 C to 40 C while under tension with a 0.1% strain and frequency of 1 Hz. 2

3 Figure S1. Photographs of sealed sample cell utilized in IR kinetics experiments. Top photograph: closed sample cell, sitting within an anaerobic chamber, showing the chalcogenide fiber optic cable and reflective light collimators that carry the infrared beam to and from the sample cell, as well as the gas lines that deliver the oxygen/nitrogen gas mixtures. Bottom photograph: open cell showing the glass slide upon which the thiol ene monomer formulation is placed. 3

4 Figure S2. Model thiol ene-tbb resin reaction kinetics under anaerobic conditions. A model thiol ene resin, formulated with 2 wt% TBB, was monitored with FTIR spectroscopy in the absence of oxygen. 4

5 Figure S3. FTIR spectra of thiol ene formulations prior to and after polymerization kinetics experiments. a-d) Spectra, with varying TBB concentrations, prior to oxygen exposure and after 10 minutes exposure are shown with blue and red lines, respectively. e) Two spectra of a formulation containing 2% TBB measured 10 minutes apart while kept under anaerobic conditions. Reactions were monitored by observing the disappearance of the allyl ether (3100 cm -1 ) and thiol 5

6 (2570 cm -1 ) absorbance peaks, using the methyl absorbance peak at 4370 cm -1 as an internal standard. 6

7 Figure S4. Reaction kinetics of oxygen-mediated thiol ene polymerization. Conversion versus time for thiol (left) and allyl ether (right) functional groups in EGDMP/TMPDAE resins formulated with 2% TBB when exposed exposed to 1%, 10%, and 21% oxygen-in-nitrogen gas mixtures. 7

8 Figure S5. Photographs of a healed panel. a) Entrance- and b) exit-side photographs of a healed puncture site with the rear EMAA layer removed. c) Vacuum applied to entrance-side puncture site of this test panel with the EMAA layer removed. Note the vacuum gauge shows a vacuum of 2.3 x 10-1 Torr, corresponding to a P across the polymerized thiol ene plug of ~0.999 atm. 8

9 Figure S6. Storage modulus and tan δ of EGDMP/TMPTAE monomer formulations polymerized either by an oxygen-mediated process (i.e., exposing a TBB-containing formulation to the atmosphere) or photopolymerization (i.e., irradiating a photoinitiator (Irgacure 184)-containing formulation with 365 nm light at 10 mw/cm 2 for one hour). 9

10 Figure S7. Estimating maximum temperature of hot spot by using Gaussian fitting of thermal IR data. a) As the thermal IR camera exclusively measures over a pre-determined temperature range ( C, scale = 1 cm), Gaussian data fitting is used to estimate the actual maximum temperature across a slice, shown as a green line, centered on the hot spot. b) The measured temperatures are shown as circles and the fitted Gaussian as a line. 10

11 Figure S8. Measuring monomer formulation thickness. A standard curve was created by measuring the area underneath the thiol peak (2572 cm -1 ) of the EGDMP-TMPDAE monomer formulation at various thicknesses. The thickness was controlled by infusing the monomer formulation between two glass slides separated by shims of known dimensions. A plot of area versus thickness gives a regression line of Area = Thickness (μm) Using the spectra taken from the IR kinetics experiments, the average area was 2.71±0.24, corresponding to a thickness of 18.7±1.6 μm. 11

12 Table S1. Summary of all the reactive liquid monomer formulations subjected to ballistics testing. Abbreviations: ethylene glycol dimercaptopropionate (EGDMP) and trimethylolpropane triallyl ether (TMPTAE). Experiment number Thiol monomer Allyl ether monomer Tributylborane (wt%) 1 EGDMP TMPTAE 0% 2 EGDMP TMPTAE 0.5% 3 EGDMP TMPTAE 1.0% 4 EGDMP TMPTAE 2.0% 5 Air gap 12

13 Table S2. Time for temperature decay to 75 C and 125 C after ballistics puncture, determined using the data reported in Figure 2d. Experiment number Tributylborane (wt%) t 125 C (s) t 75 C (s) 1 0% % % % Air gap

14 Description of videos: High-speed, thermal IR, and post-ballistics videos in.avi format are included. The files are named per the following convention: type of video experiment number (from Table S1) thiol monomer (i.e., EGDMP) allyl ether monomer (i.e., TMPTAE) weight percent of tributylborane (0 or 2 wt%). (1) Scott, T. F.; Kloxin, C. J.; Draughon, R. B.; Bowman, C. N. Macromolecules 2008, 41 (9),