Marine bio-inspired underwater contact adhesion Sean K. Clancy, Antonio Sodano, Dylan J. Cunningham, Sharon S. Huang, Piotr J. Zalicki, Seunghan Shin, * and B. Kollbe Ahn * Marine Science Institute, University of California Santa Barbara, Santa Barbara, CA 0, Green Materials and Process Group, Korea Institute of Industrial Technology, Cheonan, Chungnam 0, South Korea Supporting Information Scheme S. A visualization of our approach to prepare marine bio-inspired acrylate films. S
0 Gel Permeation Chromatography (GPC) The molecular weight averages and polydispersity were obtained with Gel Permeation Chromatography (GPC) using chloroform as a solvent with 0. % TEA at C. The system was made up of two polystyrene gel columns (Agilent PLgel µm MIXED-D, 00 x. mm; flow rate.0 ml/min) which were connected to a Waters Alliance System pump and a Waters 0 Differential RI detector. The columns were calibrated against ten standard polystyrene samples (M w =,000). The injected volume was 0 µl and the run time was minutes. GPC curves for Sample after incubation and polymerization are presented in Figure S. GPC shows that the polymer peak at ~. min retention time significantly increased after prolonged exposure to UV radiation, whereas the peak of the unreacted monomers at retention time ~ min decreased. Figure S. GPC curves of Sample after incubation (a) and polymerization (b). Numbers near the peaks represent the peak molecular weight (M p ). S
Probe Tack Test The peak value in the force vs time curve represents probe tack strength and is defined as the maximum force required to overcome the energy of adhesion. The final probe tack strength value was reported in N/cm and found by dividing the maximum force by the area of the probe tack tip (~0.0 cm ). Figure S shows a typical probe tack test graph. Figure S. Example of a typical probe tack test curve. The blue line represents the average force value. 0 0 Attenuated Total Reflection Infrared Spectroscopy (ATR-IR) The mid-infrared spectra were recorded in the range between 0 cm - and 000 cm - on a PerkinElmer Spectrum Two spectrometer (USA) using a diamond crystal. Spectral data were accumulated after scans with a spectral resolution of cm -. The incubated sample was placed on the surface of the ATR crystal as a drop, while the polymerized sample was put in direct contact with the crystal. In order to improve contact, pressure was applied to the sample with the machine arm. The spectra presented here belong to benzyl-functionalized Samples and with a ratio : AA:DMAEMA (Figures S-S) and Sample (Figure S), prepared with no ionic components. We believe that the signal coming from AA and DMAEMA is hidden by the more conspicuous presence of BA (0% 0%) and EHA (0%) which have a greater influence on the spectra. This might explain the absence of a broad peak at around 00 cm - belonging to the hydroxyl group present in AA. In all the three spectra, it is possible to distinguish the sharp carbonyl C=O peak at cm - and the C O absorption band at 00 cm - which remain unaffected after polymerization. Benzene C=C C peaks attributed to aromatic ring stretch can be found at cm - and cm -. The peaks at 0 cm - and 0 cm -, attributed to the acrylate double bond, were used to monitor the polymerization of acrylates. In the following spectra, the apparent reduction in peak size at 0 cm - and at 0 cm - suggests successful polymerization in the samples after prolonged exposure to UV radiation.,, S
Figure S. ATR-IR spectrum of Sample. Figure S. ATR-IR spectrum of Sample. S
Figure S. ATR-IR spectrum of Sample. Figure S. The peak at 0 cm -, attributed to CH=CH twisting, seen prior to UV exposure (a), after incubation (b), and after polymerization (c), diminishes upon exposure to UV radiation. S
Gas Chromatography (GC) Gas Chromatography (GC) analysis was performed on a SHIMADZU GC-00 PLUS (Kyoto, Japan) equipped with Rxi -ms Columns (fused silica) (0 m, id: 0. mm, dr: 0. µm) equipped with a mass spectrometry detector. The temperature of the injection port was 0 C with helium as the carrier gas and a flow rate of. ml/min. The GC analysis was run using chloroform as a solvent ( ml). The pure monomers were passed through the machine first in order to evaluate retention times. Chromatograms of Samples,, and, prepared with benzyl acrylate (BA), are shown in Figures S-S. 0 Figure S. Gas chromatogram of Sample. Figure S. Gas chromatogram of Sample. Figure S. Gas chromatogram of Sample. Gas Chromatography reveals minimal amounts of unreacted monomers and other residues in the samples after UV polymerization. Some unreacted DMAEMA and side products of EHA and BA S
0 residues are observed in Samples and (. min) and attributed to incomplete polymerization. EHA residue (. min) is consistently present in higher concentration than BA residue (. min) in all samples. No trace of AA, already present in low concentration, appears in any scan. No residual toluene appears present. Because polymerization involves multiple UV scans and subsequent airstream drying, we presume that low solvent concentration and increased temperature due to UV exposure are responsible for toluene evaporation during polymerization. This also suggests that the immiscible toluene solvent is not present to interfere in the cleavage of silyl protecting groups during immersion of catechol acrylate samples in acidic solution. Differential Scanning Calorimetry (DSC) The glass transition temperature (T g ) of UV polymerized samples was obtained by heating mg of the sample on aluminum hermetic pans from -0 C to 00 C on a Discovery DSC (TA Instruments, USA). The experiment was carried out in a nitrogen atmosphere and the temperature was increased at a rate of 0 C/min. Figure S0. DSC scan of sample. S
Figure S. DSC scan of sample. Figure S. DSC scan of sample. ABBREVIATIONS AA, acrylic acid; ATR-IR, Attenuated Total Reflection Infrared Spectroscopy; BA, benzyl acrylate; CA, catechol acrylate; DI, deionized water; DMAEMA, -(dimethylamino)ethyl methacrylate; DSC, differential scanning calorimetry; EHA, -ethylhexyl acrylate; GC, Gas Chromatography; GPC, Gel S
Permeation Chromatography; PET, polyester film; PT, Probe Tack; T g, glass transition temperature; UV, ultraviolet. 0 REFERENCES. Moharram, M. A.; Rabie S. M., El-Gendy H. M., Infrared Spectra of γ-irradiated Poly(acrylic acid) Polyacrylamide Complex. Journal of Applied Polymer Science 00,, Issue.. Cameron, G.G.; Kane, D. R.; The Thermal Degradation of Poly(benzyl acrylate). Polymer,, -0. Oprea, S.; Vlad S.; Stanciu, A.; Macoveanu, M.; Epoxy urethane acrylate. European Polymer Journal 000,, -. Studer, K.; Decker, C.; Beck, E.; Schwalm R.; Overcoming oxygen inhibition in UV-curing of acrylate coatings by carbon dioxide inerting, Part I. Progress in Organic Coatings 00,, -00. Park, Y. J.; Lim, D. H.; Kim, H. J.; Park, D. S.; Sung, I. K.; UV- and thermal-curing behaviors of dual curable adhesives based on epoxy acrylate oligomers. International Journal of Adhesion and Adhesives 00,, 0- S