www.sciencemag.org/cgi/content/full/334/6058/965/dc1 Supporting Online Material for Silica-Like Malleable Materials from Permanent Organic Networks Damien Montarnal, Mathieu Capelot, François Tournilhac, Ludwik Leibler * *To whom correspondence should be addressed. E-mail: ludwik.leibler@espci.fr This PDF file includes: Materials and Methods Figs. S1 to S13 Table S1 Movie S1 caption. Published 18 November 2011, Science 334, 965 (2011) DOI: 10.1126/science.1212648 Other Supporting Online Material for this manuscript includes the following: (available at www.sciencemag.org/cgi/content/full/334/6058/965/dc1) Movie S1
Silica-like malleable materials from permanent organic networks Damien Montarnal, Mathieu Capelot, François Tournilhac, and Ludwik Leibler * Matière Molle et Chimie, UMR 7167 CNRS-ESPCI, Ecole Supérieure de Physique et Chimie Industrielles, 10 rue Vauquelin, 75005 Paris, France Supporting online material 1. Methods All the chemical products are commercially available and were used as received without further purification. Pripol 1040 was kindly provided by Uniqema. It is a mixture of C 18 fatty acids derivatives, containing about 23 wt% dimers and 77 wt% trimers. DGEBA (DER 332) was purchased from Sigma Aldrich. Zinc acetate dihydrate, zinc acetylacetonate and glutaric anhydride were purchased from Acros Organics. Soft networks were synthesized from a mixture of dimers and trimers of fatty acids and DGEBA. In a first step, about 20g of the fatty acids (Pripol 1040, 296 g/mol COOH ) and the catalyst (Zn(Ac) 2, 2 H 2 O) at different concentrations: 1, 5 and 10 mol% to the COOH groups were introduced in a 100mL round-bottom flask. Temperature was gradually increased from 100 C to 180 C while maintaining the mixture under vacuum. Evolution of acetic acid indicated that the fatty acids replace the acetates as ligands of Zn. The mixture was left at 180 C under vacuum until no gas evolution was observed and catalyst particles were fully solubilized (2-3 h). In a PTFE beaker were added the previous fatty acid mixture containing solubilized catalyst and DGEBA (174 g/mol epoxy ). The stoichiometry between COOH and epoxy is 1:1. 1
Typically, we used 15.75g of the mixture of fatty acids and catalyst and 9.25g of DGEBA. The mixture was heated to 130 C until phase miscibility occurred, manually stirred, and then quickly poured into a 10cm 10cm 0.15cm brass mold sandwiched with antiadhesive silicone paper. The mold was placed in an heating press and left for at least 6 h at 130 C. Hard networks were synthesized from DGEBA (1 eq. epoxy groups), zinc acetylacetonate dihydrate (0.1%, 5% and 10% epoxy equivalents) and glutaric anhydride (0.5 epoxy equivalents). The catalyst was first dissolved in DGEBA by heating, anhydride was added, and the homogenized mixture was poured into a 10cm x 10cm 0.15cm brass mould and cured at 140 C for 12h. Stress relaxation experiments were conducted in an Anton Paar MCR 501 rheometer using a 25mm plate-plate geometry on soft epoxy-acid samples with thickness of 1.4mm. After a 20 min temperature equilibration (from 100 to 200 C), a 5 % strain step was applied and the stress was monitored over time. A constant normal force of 10 N was applied throughout the measurement to ensure a good contact of the material with the geometries. Prior to these measurements, we checked that 5 % deformations were within the linear range using strain sweep experiments. Swelling experiments were performed in trichlorobenzene on a 13mm x 11mm x 1.4mm epoxy-acid sample. The temperature was increased from 100 C to 180 C by 20 C steps. For each step, the temperature was kept constant for 1 hour; at 180 C, the sample was kept immersed for another 16h in order to be sure that the equilibrium was attained. The helical shapes of Figure 2 and 3 were manufactured from ribbons (made respectively from epoxy-acid and epoxy-anhydride samples) with dimensions 100mm x 8mm x 1.4mm in a transparent oven by application of succession of twist and relaxation steps at about 180 C. Birefringence was observed between cross-polarizers. 2
The injection molding tests were performed at 250 C with a DSM injector on epoxy-acid samples containing 5 mol% of Zn(ac) 2 catalyst. About 5g of soft networks was cut into 2 mm pieces and loaded into the barrel heated at 250 C. The content of the barrel was injected using a 16 bar pressure for 30s into a mold with a dogbone shape (ISO 527-3) heated at 200 C. After waiting for 10 minutes, the mold was water-cooled down to 25 C in 5 min and the sample was removed. Tensile tests were performed on epoxy-anhydride dogbone samples (10mm x 3mm x 1.4mm) with a strain rate of 2mm/min using an Instron 5564 tensile machine. The material was ground with a Fritsch Pulverisette 14 and reprocessed under an heating press in a 10cm 3cm 0.15cm brass mold at 240 C for 2 minutes. Dilatometry was performed on rectangular hard network samples (10mm x 4mm x 1.4mm) by using a TA-Q800 DMA apparatus in the tension film geometry. The length was measured while applying heating rates of 0.2 C/min, 1 C/min and 5 C/min from 25 to 300 C. A weak elongational stress of 10 kpa was applied throughout the measurement to avoid buckling. 3
2. Monitoring of the epoxy-acid reaction by infrared spectroscopy Curing was monitored by Fourier transform infrared spectroscopy (FTIR) using a Bruker Tensor 37 spectrometer fitted with an ATR cell. A thin layer of epoxy-fatty acids mixture, with 5 mol% Zn(ac) 2,2H 2 0 and stoichiometry of one epoxy for one acid, was deposited on an ATR cell, heated at 130 C. Spectra were taken every 3 minutes. As the reaction occurred, the epoxy and acid characteristic peaks (δ COC at 914cm -1 and υ C=O acid at 1710cm -1 ) disappeared and the ester peak (υ C=O ester at 1735cm -1 ) appeared. The traces showed that the reaction was complete after only 30 minutes (Figure S1). Nonetheless, all the samples were cured at least 6 hours to ensure the completion of the reaction. Figure S1 - Carbonyl (1690-1760 cm -1 ) and epoxy (900-930 cm -1 ) regions of FTIR spectra during the curing of epoxy-acid networks at 130 C. Spectra were taken every 3 mins. 4
3. Model Compounds Since trans-esterification reactions consist of an exchange between an ester and a hydroxyl group (Figure S2), no peaks are expected to shift in the FTIR spectra. In the same way, the glycolic protons are expected to overlap in the 1 H NMR spectra, thus rendering the detection of the exchange reaction difficult via spectroscopic techniques. O R O O OH R' O R' R O O OH O R' R O O O O + + HO OH O R' R Figure S2 - Trans-esterification occuring between two β-hydroxylesters. Exchange reactions could however be detected by employing characterization techniques which are sensitive to the size of the molecules. To this purpose, two small β-hydroxyl-esters (E18 and E19) that contain alkyl tails with different lengths were separately synthesized (Figure S3). If inter-species transesterification occurs, alkyl tails should exchange between the molecules, yielding new molecules (E17 and E20). All four molecules have different sizes and should therefore be distinguishable on GC-MS chromatograms. Model compounds E18 and E19 were respectively synthesized from the reaction of 1 eq. of octanoic acid (resp. decanoic acid) and 1 eq. of benzylglycidyl ether (resp. phenylglycidyl ether). Syntheses were conducted at 120 C in bulk at the 5g scale. 2-MI (0.06 eq.) was added as a catalyst to favor the epoxy-acid esterification reaction. E18 and E19 were used as synthesized without further purifications. 5
Figure S3 - Molecules of reactants E-18 and E-19, and exchange products E-17 and E-20. In a test tube were added model compounds E18 (1 eq.) and E19 (1 eq.) and one catalyst (0.05 eq.). The mixture was homogenized and heated at 150 C under a gentle nitrogen flow. Aliquots were taken from the mixture at different times, dissolved in methanol, and analyzed with Shimazu GC-2010 gas chromatograph coupled to mass spectrometry (electron ionization at 70 ev). Attribution of the peaks was realized thanks to MS data and is reported in Table S1. Diesters and diols are also products of ester exchange (data not shown here). The gas chromatography traces are shown on Figure S4. Figure S4 Gas chromatography traces of a mixture of E-18 and E-19 at 150 C, after 0, 4 and 24h. At t=0, the material is the 1:1 mixture of E18 and E19. After 4 hours at 150 C, satellite GC signals corresponding to E17 and E20 molecules appear at slightly shorter and longer retention times, respectively. After 24 hours at 150 C, E17, E18, E19 and E20 are equally abundant. 6
To monitor the progress of reaction, the ratio r was defined as the ratio between the hydroxylesters produced during the reaction (E-17 and E-20) and the starting hydroxylesters (E-18 and E-19). Additional characterization showed that the GC detector response was indeed identical for the four esters. Zinc acetate and zinc acetylacetonate were selected as the best catalysts after a screening of known trans-esterification catalysts (data not shown here). The concentration of the catalyst plays an important role in the kinetics (Fig. S5). Figure S5 Kinetics of ester exchange with 1 or 5% Zn(ac) 2 at 125 C and 150 C followed with the ratio r=([e17] +[ E20])/([E18] + [E19]). 7
Name Formula Elution time (min) Characteristic MS peaks (M/z, g/mol) H-9 4.4 61, 77, 94, 107, 137, 168 H-10 4.7 61, 77, 91, 105, 107, 121, 182 E-17 7.6 57, 77, 94, 107, 127, 201, 294 E-18 7.9 57, 91, 107, 127, 181, 201, 308 E-19 8.4 57, 71, 77, 85, 94, 107, 155, 229, 322 E-20 8.6 57, 71, 77, 85, 91, 107, 155, 229, 336 DE-25 9.9 57, 94, 127, 201, 327 DE-26 10.3 57, 91, 127, 201, 327 DE-27 11 57, 71, 85, 94, 127, 155, 201, 229, 355 DE-28 11.6 57, 71, 85, 91, 127, 155, 201, 229, 355 DE-29 12.7 57, 71, 85, 94, 155, 229, 383 DE-30 13.6 57, 71, 85, 91, 155, 229, 383 Table S1 - Attribution of GC chromatogram peaks. Molecules are named after their types (hydroxyls, esters and diesters) and their total number of carbons. 8
4. Soft networks DSC was performed on a TA Q1000 apparatus. Two heating cycles, from -100 to 150 C, were recorded at 10 C/min. Figure S6 - DSC thermograms (second heating on top and first cooling at the bottom) of soft networks catalyzed with 1 mol% and 5 mol% Zn(Ac) 2. DMA experiments were conducted on a TA Q800 apparatus in the film tension geometry. Heating ramps were applied at 3 C/min from -50 to 150 C. Rectangular samples of 5mm 1.5mm cross-section and about 8mm length were tested at 1 Hz and 15μm amplitude. Figure S7 - DMA traces (1 Hz, 3 C/min) of a soft network catalyzed with 5 mol% Zn(Ac) 2. 9
Tensile tests at room temperature were performed on dogbone samples (25mm x 4 mm x 1.4 mm) using an Instron 5564 tensile machine with a strain rate of 10 mm/min. A video extensometer was used to determine the real deformation. Figure S8 Tensile test of a soft network catalyzed with 5% Zn(Ac) 2 at 10mm/min at room temperature. Cyclic deformation tests were performed on dogbone samples (25mm x 4 mm x 1.4 mm) using an Instron 5564 tensile machine. The sample was first elongated to 150% and relaxed until 0%. After a recovery of 1 hour, the sample was extended until break. The strain rate was 10 mm/min. A video extensometer was used to measure the real deformation. The experiments were performed at room temperature. Figure S9 Strain-stress plot for a soft network catalyzed at 5% Zn(Ac) 2 with one cycle at room temperature. 10
The ester vibration was monitored by Fourier transform infrared spectroscopy (FTIR) using a Bruker Tensor 37 spectrometer fitted with an ATR cell. A thin layer of epoxy-fatty acids mixture, with 5%mol Zn(ac) 2,2H 2 0, was deposited on an ATR cell, heated at 130 C and cured overnight to ensure a complete reaction. Temperature was then increased from 130 C to 200 C by 5 C steps, and a spectrum was taken after a 5 minutes equilibration at each step. Two more spectra were taken after respectively 15 and 30 minutes at 200 C. The spectra show no changes in the ester signals at 1735 cm -1 (Fig. S10), confirming that no ester bonds were broken during the heating. Figure S10 - Ester signals of a cured soft sample show no changes with temperature from 130 C to 200 C, even after 30 minutes. 11
5. Hard networks The ester vibration was monitored by Fourier transform infrared spectroscopy (FTIR) using a Specac transmission Variable Temperature Cell (VTC). A thin layer of epoxy-glutaric anhydride mixture, with 10 mol% Zn(acac) 2, was sandwiched between KBr pellets and maintained with a solid holder in the VTC. After a sufficient time to ensure that curing is complete (18 h), temperature was raised by 5 C steps every hour from 140 C to 240 C. No changes were observed in the intensities of ester signals (1735 cm -1 ) in this temperature range (Fig. S11). Figure S11 Ester signals of a cured hard sample show no changes with temperature. 12
DSC was performed on a TA Q1000 apparatus. Two heating cycles, from -20 C to 200 C, were recorded at 10 C/min. Figure S12 - DSC thermograms of hard networks catalyzed with 0.1 mol%, 5 mol% and 10 mol% of Zn(acac) 2. DMA experiments were conducted on a TA Q800 apparatus in the film tension geometry. Heating ramps of 3 C/min were applied from 25 C to 200 C. Rectangular samples of 5mm 1.5mm cross-section and about 8mm length were tested at 1 Hz and 15μm amplitude. Figure S13 - DMA traces (1 Hz, 3 C/min) of hard networks catalyzed with 5 mol% and 10 mol% of Zn(acac) 2. 13
Movie S1. The epoxy polymer is flexible enough for us to twist it multiple times. The resulting helical fusilli-like ribbon is clamped into place to impose the twisted structure. Viewing the object in cross polarized light shows the accumulated stresses caused by the twisting. The ribbon was heated for 2 minutes using a hot air gun, which causes the internal structure of the polymer to change through bond exchange reactions, but without an overall flowing of material. A second viewing in polarized light shows that the stresses have mostly disappeared. Once released from the lower clamp, the twisted ribbon structure is retained.