Thermal imidization kinetics of ultrathin films of hybrid poly(poss-imide)s

Transcription

1 SUPPTING INFMATIN belonging to the article Thermal imidization kinetics of ultrathin films of hybrid poly(pss-imide)s Michiel J.T. aaijmakers,, Emiel J. Kappert,, Arian Nijmeijer and Nieck E. Benes *, Inorganic Membranes, University of Twente, Department of Science and Technology, MESA + Institute for Nanotechnology, P.. Box 217, 7500 AE Enschede, The Netherlands PolyPSS-imide synthesis Poly[PSS-(amic acid)]s were synthesized by interfacial polymerization of octa-ammonium functionalized PSS in water and a dianhydride solution in toluene. Five different dianhydrides were used as precursor for the poly[pss-(amic acid)]s; 4,4-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyl tetracarboxylic dianhydride (BPDA), 4,4'-oxydiphthalic anhydride (DPA), 4,4 -(4,4 - isopropylidene diphenoxy) bis(phthalic anhydride) (BPADA). Scheme S1 shows an overview of the synthesis of the poly[pss-(amic acid)]s from the octa-ammonium PSS and dianhydride precursors, and the subsequent imidization of the poly[pss-(amic acid)] to a polyimide. The octa-ammonium PSS is first dissolved in water. The ammonium groups are partially deprotonated using NaH, to form the more reactive amine groups. The solution is subsequently contacted with the dianhydride solution in toluene. A heat treatment is applied to convert the amic acid groups to cyclic imides.

2 3FC CF3 Scheme S1. Schematic representation of the synthesis of polypss-imides via interfacial polymerization. (a) = (CH2)3 NH 3 + Cl - NaH -HCl ' ' ' = ' ' ' (CH2)3 NH 2 ' (b) Pyromellitic dianhydride (PMDA) 3,3,4,4 -biphenyl tetracarboxylic dianhydride (BPDA) 4,4 oxydiphthalic anhydride (DPA) 4,4 -(4,4 -isopropylidinediphenoxy) bis(phthalic anhydride) (BPADA) 4,4-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) PSS PSS 1 HN 1 ' (H2C)3 ' (H2C)3 HN (CH2)3 NH 1 ' (CH2)3 H N H PSS Amic acid PSS H H N 1 HN ' ' (H2C)3 (c) (H2C)3 PSS PSS (CH2)3 1 HN 1 ' (CH2)3 NH 1 ' (H2C)3 ' (H2C)3 HN 1=amic acid 2=imide PSS (CH2)3 NH 1 ' (CH2)3 N Imide PSS PSS N 1 HN ' (H2C)3 ' (H2C)3 (CH2)3 ' (CH2)3 NH 1 PSS Conversion processes during thermal imidization During the heat treatment of the poly[pss-(amic acid)]s, reaction steps associated with drying and imidization (1+2), silanol condensation (3) and decomposition (4) are observed. Scheme S2 shows the reaction mechanism of step 2 and 3 that occur. During step 2 of the heat treatment process, mainly conversion of amic acid to imide groups occurs (blue). During step 3, additional water loss is observed that originates from recombination of silanol groups to form siloxane groups (red).

3 Scheme S2. verview of the water loss originating from imidization and silanol condensation reactions. Imidization 1. amic acid H -H 2 F 3 C CF 3 2. imide H recombination to -- H N N (H 2 C) 3 H H H 3. lanol H 4. loxane -H 2 The silanol condensation reaction is observed from attenuated total reflection Fourier transform infrared spectroscopy (AT-FTI) measurements of poly[pss-(amic acid)] samples that were heat treated at different temperatures. Figure S1 shows the relative intensity of infrared peaks that are characteristic for - bonds in a cage or ladder (i.e., a broken PSS cage) structure, and peaks that are characteristic for silanol groups. The peak at 3230 cm -1 could include vibrations from water present in the material. Although the scatter in the data makes a quantitative analysis difficult, the data shows a trend of increasing ladder and cage formation with increasing treatment temperatures, at the expense of silanol groups.

4 elative peak intensity (au.) ladder at 1040 cm cm cm cm elative peak intensity (au.) Figure S1. (left panel) elative intensity of the infrared peaks at 1040 and 1090 cm -1, corresponding to a -- bond in ladder and cage configuration, respectively; (right panel) elative intensity of the infrared peaks at 910 and 3230 cm -1, both corresponding to silanol groups. All infrared spectra were normalized with respect to the CF 3 band at 1254 cm 1. All peak intensities are normalized with respect to their initial peak intensity. Thickness and refractive indices The thickness and refractive index have been measured using spectroscopic ellipsometry. Figure S2 shows the evolution of the thickness (top panels) and refractive index (bottom panels) of polypss-(amic acid)s prepared using PMDA, BPDA, DPA, BPADA and 6FDA precursors, as function of temperature (left panel) and as function of time during the subsequent dwell at 345 C (right panel). The data in Figure S2 correspond to the relative thickness data in Figure 3 and relative refractive index data in Figure 4.

5 PMDA 140 Thickness (nm) BPDA DPA Thickness (nm) 80 BPADA FDA Time (min) 1.52 DPA 1.52 efractive index (-) FDA BPADA PMDA BPDA Time (min) efractive index (-) Figure S2. (top panels) Thickness and (bottom panels) refractive index of the polypss-(amic acid)s layer as function of temperature (left), and dwell time at 345 C after heating from 50 to 345 C at a heating rate of 5 C min -1. The polypss-(amic acid) layers were prepared atop a γ- alumina coated α-alumina disc using PMDA, BPDA, DPA, BPADA and 6FDA precursors.

6 Duplicate measurements were performed to validate the optical model of the spectroscopic ellipsometry measurements. Figure S3 shows the refractive index and thickness data of two polypss-(amic acid) prepared using DPA (left panel). The data shows a similar evolution in thickness and refractive index. The absolute values of the thickness are slightly different, which can be related to the reproducibility of the interfacial polymerization reaction Thickness (nm) n (-) Figure S3. efractive index and thickness data of two polypss-(amic acid)s prepared using DPA (left panel). The linear thermal expansion coefficient of the polypss-imides has been determined by measuring the thickness at 50 C and 345 C. Table S1 shows the linear thermal expansion coefficients of the polypss-imides

7 Table S1. Linear thermal expansion coefficient of polypss-imides prepared using PMDA, BPDA, DPA, BPADA and 6FDA Thickness at 50 C Thickness at 345 C Linear thermal expansion coefficient Dianhydride (nm) (nm) (10-6 C -1 ) linker PMDA BPDA DPA BPADA FDA Kinetic analysis Figure S4 (left panel) shows the conversion of the mass loss of 6FDA-PSS as a function of temperature for heating rates β=5,10,15 and 20 C min -1. The shift in the curves introduced by the different heating rates is an indication of kinetically limited processes. A plateau in the conversion curves is related to the absence of mass loss processes. The curves before and after the plateau can therefore be appointed to distinct, serial reaction steps. The conversion profile demonstrates 3 distinct mass loss steps: step 1 from α = , step 2 from α = , and step 3 from α = The effective activation energy for mass loss as a function of the conversion can be calculated by performing an isoconversional analysis. 1 This activation energy is referred to as an effective activation energy, as it is in fact an average over the activation energies of the different reactions taking place at a specific value of the conversion. The occurrence of multiple reactions within the distinct steps is apparent from the release of different fragments that is observed in the TGA-MS data. Step 1 is dominated by the loss of water from the

8 material, accompanied by the release of small amounts of C 2 and aromatic fragments. Step 2 is only coupled to the loss of water. In step 3, aromatics, C 2 and water are released. Figure S4 Conversion (-) C min C min C min C min Apparent activation energy (kj mol -1 ) Step kj mol -1 Step kj mol -1 Step kj mol Conversion (-) (right panel) shows the effective activation energy for the thermal imidization steps of poly(pss-amic acid) prepared with 6FDA. The three distinct steps result in three plateaus in the effective activation energy: For step 1, E a ~225 kj mol -1 ; for step 2, E a ~150 kj mol -1 ; for step 3, E a increased from ~225 to ~400 kj mol -1.

9 Conversion (-) C min C min C min C min Apparent activation energy (kj mol -1 ) Step kj mol -1 Step kj mol Conversion (-) Step kj mol -1 Figure S4. (left panel) Conversion of the mass loss of 6FDA-based poly[pss-(amic acid)] as function of temperature, for heating rates β=5,10,15 and 20 C min -1 under N 2 atmosphere. (right panel) Apparent activation energy as function of conversion, determined by the isoconversional analysis of TGA-data for the thermal treatment of 6FDA based poly[pss-(amic acid)]. nly an activation energy is insufficient for performing kinetic calculations, as the reaction rate is typically expressed as a function of A, the pre-exponential constant, and f(α). An overview of possible reaction models is given in Table S2. Table S2. verview of possible reaction models, taken from 2 eaction model (name + abbreviation) f(α) Power law P4 4α 3/4 Power law P3 3α 2/3 Power law P2 2α 1/2 Power law P2/3 2/3α 1/2 Mampel (first order) F1 1-α Avrami-Erofeev A4 4(1-α)[-ln(1-α)] 3/4

10 Avrami-Erofeev A3 3(1-α)[-ln(1-α)] 2/3 Avrami-Erofeev A2 2(1-α)[-ln(1-α)] 1/2 Contracting sphere 3 3(1-α) 2/3 Contracting cylinder 2 2(1-α) 1/2 ne-dimensional diffusion D1 1/2α -1 Two-dimensional diffusion D2 [-ln(1-α)] -1 Three-dimensional diffusion (Jander) D3 3/2(1-α) 2/3 [1-(1-α) 1/3 ] -1 Three-dimensional diffusion (Ginstling- 3/2[(1-α) -1/3-1] -1 Brounshtein) D4 In order to get insight into the reaction model, a temperature program containing isothermal dwells was ran. The temperatures of the isothermals were chosen such that in every isothermal step, one of the reactions was taking place. In line with previous observations, the profile of the conversion versus the time revealed a decelerating reaction profile that is commonly associated to the reaction order (F) or diffusion (D) models from Table S To determine which reaction model captures the data most adequately, and to obtain the value for the pre-exponential constant, the data given in Figure S4 (left panel) was fit by a multivariate kinetic model. To perform this analysis, the 3 steps in the activation energy were first fitted individually, using the activation energies obtained from Figure S4 right panel) as starting values. The data was fit 14 times, one time for each reaction models given in Table S2. These individual fits were followed by a combined fit of the full conversion range. For the fitting of the first step, it was found that the data could not be captured using a single kinetic triplet (A, E a, and f(α)). This is of no surprise, as the MS-data gave clear evidence for multiple reactions occurring in this step. Surprisingly, however, fitting of the data with a combination of two individual reactions did not result in a good fit either. Therefore, it was tried to fit the data with a distributed activation energy. Here, a Weibull-distribution was chosen to model the distributed activation energy. For certain values of the parameters, this distribution can

11 be mathematically equivalent to a Gamma-distributed activation energy or a nth order reaction (cite: Burnham&Braun 1999 Energy & Fuels ). Using the Weibull-distribution, the data could be accurately fit, as long as the fitting was started from a conversion value of α = Below this value, the individual curves do not demonstrate a shift with heating rate, implying a thermodynamic equilibrium. Step 2 could be captured accurately using a single kinetic triplet. Tests for the different reaction models revealed that a first order reaction (F1) model captured the data most accurately. For step 3, again a distribution in the activation energy was required for the fitting. Again this is with no surprise, since the degradation of the organic fragments typically consist of many different reactions, smeared out over a broad temperature range. These reaction distributions are commonly fit with distributed kinetic parameters. 8 Figures S5-9 show the overview of all m/z-signals of the mass spectroscopy measurements as a function of the temperature for poly[pss-(amic acid)]s prepared using the different dianhydrides E-8 1E

12 Figure S5. m/z-signals of the mass spectroscopy measurements as a function of the temperature for poly[pss-(amic acid)]s prepared using 6FDA. 3.5E-11 3E E-11 2E E E E-12 3E E-12 2E E E E-12 6E E E E E E E E E-13 8E-13 7E-13 1E E E E E Figure S6. m/z-signals of the mass spectroscopy measurements as a function of the temperature for poly[pss-(amic acid)]s prepared using BPADA.

13 E E E E E-11 8E-12 6E E-13 8E-13 7E E-8 1E E Figure S7. m/z-signals of the mass spectroscopy measurements as a function of the temperature for poly[pss-(amic acid)]s prepared using BPDA E E-11 2E E E-11 8E E E E E E E E-8 1E Figure S8. m/z-signals of the mass spectroscopy measurements as a function of the temperature for poly[pss-(amic acid)]s prepared using DPA.

14 E E E E E-11 2E E E E E-11 8E-12 6E E E E E E E-13 8E-13 7E E-13 9E E E E-8 1E E Figure S9. m/z-signals of the mass spectroscopy measurements as a function of the temperature for poly[pss-(amic acid)]s prepared using PMDA.

15 eferences 1. Vyazovkin, S.; Burnham, A. K.; Criado, J. M.; Pérez-Maqueda, L. A.; Popescu, C.; Sbirrazzuoli, N. Thermochimica Acta 2011, 520, (1-2), Vyazovkin, S.; Chrissafis, K.; Di Lorenzo, M. L.; Koga, N.; Pijolat, M.; oduit, B.; Sbirrazzuoli, N.; Suñol, J. J. Thermochimica Acta 2014, 590, Seo, Y.; Lee, S. M.; Kim, D. Y.; Kim, K. U. Macromolecules 1997, 30, (13), Yilmaz, T.; Güçlü, H.; Özarslan, Ö.; Yildiz, E.; Kuyulu, A.; Ekinci, E.; Güngör, A. Journal of Polymer Science, Part A: Polymer Chemistry 1997, 35, (14), Seo, Y. Polymer Engineering and Science 1997, 37, (5), Kim, Y. J.; Glass, T. E.; Lyle, G. D.; McGrath, J. E. Macromolecules 1993, 26, (6), Lu, H.; Zhou, J.; He, T. Journal of Applied Polymer Science 2001, 79, (11), Burnham, A. K.; Braun,. L. Energy & Fuels 1999, 13, (1), 1-22.