3 glycidyloxypropyl trimethoxysilane

Aluminum hydroxide (reagent grade, ATH), zinc acetate dehydrate [ACS reagent, ≥98%, Zn(CH₃COO)₂·2H₂O], 2-methylimidazole (99%, 2-MIM), aluminum nitrate nonahydrate [≥98%, Al(NO₃)₃·9H₂O], iron(iii) nitrate nonahydrate [ACS reagent, ≥98%, Fe(NO₃)₃·9H₂O], magnesium nitrate hexahydrate [ACS reagent, 99%, Mg(NO₃)₂·6H₂O], methanol (anhydrous, 99.8%), ethanol (absolute alcohol, without additive, ≥98%), sodium bicarbonate (ACS reagent, ≥99.7%, NaHCO₃), sodium hydroxide (ACS reagent, ≥97%, pellets, NaOH), ammonia solution (2 M in ethanol), (3-glycidyloxypropyl) trimethoxysilane (≥98%, KH560) and triphenylphosphine (≥95%) were all provided by Sigma-Aldrich Chemical Co. Epoxy resin (Epoxydhedraz C) was provided by R&G Faserverbundwerkstoffe GmbH-Germany. Diamino diphenyl sulfone (DDS) and DOPO were supplied by TCI Chemicals Company.

Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS, Clevios PH1000) was purchased from Heraeus Holding. Naphthalenetetracarboxylic dianhydride (NDA), 1,2,4,5-tetraaminobenzene tetrahydrochloride (TABH), poly(phosphoric acid) (PPA), methanesulfonic acid (MSA), chloroform, 1,2-dichlorobenzene, ethylene glycol, (3-glycidyloxypropyl)trimethoxysilane and 4-dodecylbenzenesulfonic acid were purchased from Sigma-Aldrich. BBL (η = 6.3 dl g⁻¹ in MSA at 30 °C, M_w = 35 kDa) was made by polycondensation of NDA and TABH in PPA at elevated temperatures^{17 (link),31 (link)}.

3-Glycidyloxypropyl)trimethoxysilane (GLYMO, ≥98%) and iminodiacetic acid (IDA, 98%) were obtained from Sigma-Aldrich (Buchs, Switzerland). Ethylenediaminetetraacetic acid disodium salt dihydrate (EDTA-Na₂, ≥99%) was purchased from Fluka (Buchs, Switzerland). Nickel(II) sulfate hexahydrate (NiSO₄·6H₂O, ACS), sodium hydroxide pellets (NaOH, >99%) and sodium chloride (NaCl, ACS) were purchased from Merck (Darmstadt, Germany). Hydrochloric acid (HCl, Supra 35%) was ordered from Carl Roth (Karlsruhe, Germany). Deionized water was purified by Milli-Q^® Reference water purification system (Merck Millipore, Darmstadt, Germany) and was specified by an electrical resistivity of 18.2 MΩcm.
Gas supply for AAS: Acetylene 2.6 (>99.6 vol%, Messer Austria, Gumpoldskirchen, Austria); compressed air.
The following 12 silica gels differing in pore and particle size were gained: Carl Roth (Karlsruhe, Germany), 35 Å (40–63 µm), 60 Å (20–45 µm), 60 Å (30–200 µm), 60 Å (35–70 µm), 60 Å (40–63 µm), 60 Å (200–500 µm), 150 Å (35–70 µm), 150 Å (70–200 µm), 1000 Å (35–70 µm), and 250 Å (40–63 µm); Fluka (Buchs, Switzerland), 60 Å (63–200 µm); and Sigma-Aldrich (Buchs, Switzerland), 100 Å (63–200 µm).

The materials used in this work were BaTiO₃ (Sigma-Aldrich, Saint louis, MO, USA, <100 nm particle size, ≥99%) in the cubic crystalline phase, Epofix Cold-Setting embedding resin (Bisphenol-A-Diglycidylether, Electron Microscopy Sciences, Hatfield, PA, USA) [53 ], Triethylenetetramine (epoxy hardener) and 3-Glycidyloxypropyltrimethoxysilane (Sigma-Aldrich, Saint louis, MO, USA, ≥98%, KH-560). The dielectric and physical properties of the constituent materials: BaTiO₃, DGEBA epoxy and KH-560 are presented in Table 1 and Table 2, respectively.

The biohybrid synapses were fabricated on glass-ITO patterned substrates purchased from Xin Yan Technology Ltd. The size of the glass square substrates is 25 mm with patterned squares of ITO (20 ohm sq⁻¹) of 10 mm covering each corner. Substrates were cleaned through sonication in IPA (Sigma-Aldrich, USA) for 20 min. Employing Kapton tape and using a PMMA master mask, 2 stripes connecting opposed ITO squares (with fixed width 5 mm) were traced for the deposition of the polymer mixture. PEDOT:PSS (Hereaus, Clevios PH 1000) aqueous solution was prepared by adding 6 vol.% ethylene glycol (Sigma-Aldrich, USA) to increase the PEDOT:PSS conductivity, 0.1 vol.% dodecylbenzene sulfonic acid (Sigma-Aldrich, USA) as a surfactant, and 1 vol.% (3-glycidyloxypropyl)trimethoxysilane (Sigma-Aldrich, USA) as a crosslinking agent to improve mechanical stability. PEDOT:PSS solution was spun on the selected areas of the substrate at 1000 rpm for 2 min and baked at 120 °C for 20 min. Before operation the devices were conditioned at least 20 min in PBS solution, in order to avoid swelling effects during electrical measurements.

Two biopolyesters were used in order to evaluate the influence of fly ash: a polybutyl succinate (PBE003 from NaturePlast, Mondeville, France) and a polybutyl adipate terephthalate ecoflex™ Ecoblend C1200 from BASF (Ludwigshafen, Germany).
Fly ash (SuperPozz supplied by Holcim) noted SP with a specific surface area of 1.55 m²/g, a median diameter of 6 µm, and a cut-off diameter of 100 µm were produced by Holcim. A detailed composition was obtained by X-ray fluorescence and X-ray diffraction Rietveld analysis refinement of powder XRD data (Figure S1 and Table S1).
Three coupling agents were employed according to the type of polymer used. Two silanes, 3-Aminopropyl)triethoxysilane (noted A), 3-Glycidyloxypropyl)trimethoxysilane (noted G) from Sigma (St. Louis, MO, USA) and a titanate, isopropyl tri[di(octyl)phosphato] titanate (KR12) (noted T) from Kenrich Chemicals (Bayonne, NJ, USA), were used. Ethanol (96% v/v-PanReac, Darmstadt, Germany) was also used.
Two flame retardants, ammonium polyphosphate (Exolit AP422, from Clariant, Hürth-Knapsack, Germany, noted AP) and melamine polyphosphate (MP200, from BTC, Monheim, Germany, noted MP), were used. SuperPozz fly ash was supplied by Holcim.