Supporting Information UV INITIATED BUBBLE FREE FRONTAL POLYMERIZATION IN AQUEOUS CONDITIONS Paul Michael Potzmann, Francisco Javier Lopez Villanueva, Robert Liska, Institute of Applied Synthetic Chemistry, Vienna University of Technology, Vienna, Austria BASF we create chemistry, Ludwigshafen, Germany VIDEO Video of a bubble free frontal polymerization: http://www.ias.tuwien.ac.at/researchdivisions/macromolecular-chemistry/macromolecular-chemistry/photopolymers/applications/ The Video shows an example of a bubble frontal polymerization in a water based formulation, given in table 1 of the main manuscript. X-RAY STRUCTURAL ANALYSIS Data was collected on a Bruker AXS SMART APEX II four-circle diffractometer with κ-geometry. Data was collected with φ and ω-scans and 1 frame widths. The data were corrected for polarization and Lorentz effects, and an empirical absorption correction (SADABS) was employed. The cell dimensions were refined with all unique reflections. SAINT PLUS software (Bruker Analytical X-ray Instruments, 2007) was used to integrate the frames. Details of the X-ray investigations are given in Table 1. The structures were solved by the Patterson method (SHELXS97). Refinement was performed by the full-matrix least-squares method based on F 2 (SHELXL97) with anisotropic thermal parameters for all non-hydrogen atoms. Hydrogen atoms of the phenyl ring were inserted in calculated positions and
refined riding with the corresponding atom, hydrogen atoms of the coordinated water were found in the electron density map. CCDC 1430411 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Center via www.ccdc.cam.ac.uk/data_request/cif. Table 1: Crystallographic data for Empirical formula C 6 H 7 KO 8 S 2 M r 310.34 crystal system monoclinic space group P2 1 /n a (pm) 739.17(4) b (pm) 580.80(3) c (pm) 2661.82(14) α ( ) 90 β ( ) 94.1545(18) γ ( ) 90 V (pm 3 ) 10 6 1139.74(10) Z 4 D x (Mg m -3 ) 1.809 μ (mm -1 ) 0.859 crystal size (mm) 0.3 0.2 0.1 no. measured, independent, observed refl. [I > 2σ(I)] 14635, 2330, 2158 R int 0.0497 θ max ( ) 26.42 R[F2 > 2σ(F)],ωR(F 2 ),S 0.0238, 0.0612, 1.048 no. reflections / parameters 2330/ 162 weighting scheme [a] ω = 1/[σ 2 (F 0 2 ) + (0.0281P) 2 + 0.8128P] δρ max, δρ min (e Å -3 ) 0.420, -0.450 [a] P = (F 0 2 +2F c 2 )/3
Figure 1: Crystal structure of FRONTAL POLYMERIZAION EXPERIMENTS 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 Velocity [cm/min] 100 95 90 85 80 Maximum Temperature [ C] 500 450 400 350 300 250 200 150 Front starting time [s] 0.2 0.1 75 100 50 0 70 0 Figure 2: comparison of the front reaction parameters of highly diluted systems containing and Figure 2 shows the comparison of and regarding the front properties. The experiments were performed with the basis formulation given in table 2. The reactivity of can be considered comparable to, regarding the magnitude of the properties. The measured velocity of was only slightly faster to, while the maximum temperature was the same within the
significance of the detection method. Only for the front starting time the application of led to significantly better results, both in absolute value of the faster initiation and also in the better reproducibility of the measurement. As azo initiators should show additional photosensitivity, this improvement can be only explained by the bubble free initiation volume. Table 2: basis formulation [wt %] Component 27.00% Monomer mixture AAc:BAM 98:2 wt % 0.60% / corresponding to 0.0045 mol per double bond 0.15% w-bapo 72.25% Water Due to their lower reactivity persulfates cannot be investigated with similar formulations. They show similar front velocities in formulations containing 34 % monomer content resulting in temperatures above 110 C. Increasing the monomer content in Azo 44 as well as based formulations from 27 to 34 % increases the front velocity above 1.5 cm/min which is about three times the velocity of persulfate based experiments. DOUBLE BOND CONVERSION (HPLC) The conversion of the polymerization reaction was determined by evaluation of the residual monomer content via HPLC. Other analytical methods were not possible due to the high water content of the samples and the fact that the final samples were cross linked. Individual measurements were made on acrylic acid and acrylamide to create calibration curves of concentration versus the integral in relation to the internal standard naphthalene. Both linear regression functions showed good coefficients of determination for the applied concentrations. (> 0.99) Ring shaped polymer samples were extracted with acetonitrile and the extraction solutions directly measured. From the determined concentrations and the dry weight of the samples the conversion was calculated by the use of the following formula. The applied concentrations refer to the used extraction volume inclusive the water contained in the wet sample.
C c res.mono. c dry poly. c AA c AAm A Conversion of the monomer [wt.%] concentration of the residual monomer [mg/ml] Concentration of the dry insolubel polymer sample [mg/ml] measured concentration of acrylic acid [mg/ml] measured concentration of acrylamide [mg/ml] Content of the monomer in the sample without water For simplification it was assumed that the crosslinker is completely converted and no short oligomers were extracted. NMR experiments, after evaporation of extraction solvent, confirmed that the content of extracted oligomers was low and the error does not exceed 0.04 %. To ensure the reproducibility of the method conversion measurements were performed at least three times. According to the described procedure the conversion of all performed reactions was above 98 %.