Dmaema

DMAHDM was synthesized through a Menschutkin reaction where a tertiary amine group was reacted with an organohalide to be converted into a quaternary ammonium salt. The reaction was conducted by combining 10 mmol of 2-(dimethylamino) ethyl methacrylate (DMAEMA, Sigma-Aldrich, St. Louis, MO, USA) and 10 mmol of 1-bromohexadecane (BHD, TCI America, Portland, OR, USA) with 3 g of ethanol in a 20 mL scintillation vial. The vial was then stirred for 24 h at 70 °C. The solvent was left to evaporate, yielding DMAHDM as a clear, colorless and viscous liquid [20 (link)]. MPC was purchased from Sigma-Aldrich (Sigma-Aldrich, St. Louis, MO, USA).
Four groups were formulated and investigated as shown in Table 1.

The monomers 2-(dimethylamino)ethyl methacrylate (DMAEMA, Sigma Aldrich, Taufkirchen, Germany) and 2-hydroxyethyl methacrylate (HEMA, Sigma Aldrich) were stored for 24 h at 5 °C with inhibitor remover for hydroquinone (Sigma Aldrich) before use. Azobisisobutyronitrile (AIBN, Sigma Aldrich), methacryloyl chloride (MAC, Sigma Aldrich), methyl iodide (Sigma Aldrich), ammonium persulfate (APS, Sigma Aldrich), tetramethylethylenediamine (TEMED, Sigma Aldrich), tetrahydrofuran (THF, Fisher Scientific, Schwerte, Germany), n-hexane (Fisher Scientific), ethanol (Fisher Scientific), triethylamine (TEA, TCI Chemicals Deutschland, Eschborn, Germany), sodium hydroxide (NaOH, Sigma Aldrich), potassium chloride (KCl, Sigma Aldrich), sodium sulfate (Na₂SO₄, Sigma Aldrich), myoglobin (Myo, Sigma Aldrich), and bovine serum albinum (BSA, Sigma Aldrich) were all used as received. Proteins were dissolved in 0.01 M phosphate-buffered saline (1 g/L) and pH was adjusted to the isoelectric point (IEP) of BSA (pH 4.8) or Myo (pH 7) with 1 M HCl. 1,3-Propane sultone (PS, Sigma Aldrich) was heated with hot water above its melting point (31 °C) before used in liquid form. Commercially available PA TFC flat-sheet membranes NF270 (DuPont, Neu Isenburg, Germany) were cut in circular shape (diameter 48 mm) before used in dead-end mode filtration cells.

The acrylic resin Nature Cryl™ MC (GC America Inc., Alsip, IL, USA) was obtained commercially. According to the manufacturer’s instructions, the acrylic resin powder and liquid were mixed at a ratio of 1:0.5. Samples were prepared following ISO 24026–2:2020 [32 ] (Plastics — Poly (methyl methacrylate) (PMMA) moulding and extrusion materials — Part 2: Preparation of test specimens and determination of properties) standards. The antibacterial monomer DMAHDM, with an alkyl chain length of 16, was synthesized using a modified Menschutkin reaction method [32 , 33 (link)]. The advantage of this method is that the reaction product is produced quantitatively and does not require further purification [27 (link)]. Briefly, 10 mmol of 2-(dimethylamino) docecane (DMAEMA, Sigma-Aldrich, St. Louis, MO, USA), 10 mmol of 1-bromohexadecane (BHD, TCI America, Portland, OR, USA), and 3 g of ethanol were added to a 20 mL scintillation vial. The vial was capped and stirred at 70 °C for 24 h. When the reaction was complete, the ethanol solvent was evaporated, yielding DMAHDM as a clear, colorless, and viscous liquid [33 (link), 34 (link)]. DMAHDM was mixed with the acrylic resin liquid at DMAHDM/(MMA power + MMA liquid + DMAHDM) mass fractions of 1.5%. Higher DMAHDM mass fractions were not used because previous experiments showed a significant decrease in mechanical strength [30 (link)].

The monomers 2-(dimethylamino)ethyl methacrylate (DMAEMA, 98%) and (oligo ethylene glycol)methacrylate (OEGMA) (average Mn = 950 g∙mol⁻¹, 19 ethylene oxide units) were purchased from Sigma Aldrich, Greece. Both DMAEMA and OEGMA were purified using a column filled with inhibitor removers before polymerization. 2,2′-Azobis (isobutyronitrile) (AIBN), the radical initiator utilized, was purified by recrystallization from methanol. 4-Cyano-4-(dodecylsulfanylthiocarbonyl)pentanoic acid (CDP) as the CTA, methyl iodide (CH₃I) 1-iodohexane (C₆H₁₃I, ≥98%), 1-iodododecane (C₁₂H₂₅I, 98%), 1,4-dioxane (≥99.8% pure), and tetrahydrofuran (THF, ≥99.9% pure) were obtained from Sigma Aldrich, Greece and used as received, except 1-4-dioxane, which was first dried over molecular sieves. Deuterated chloroform (CDCl₃) was used as the solvent for the ¹H-NMR experiments and was also obtained from Sigma Aldrich, Greece. Dialysis tubing membranes (MEMBRA-CEL^®) from regenerated cellulose of MWCO 3500 and a diameter of 22 mm were purchased from SERVA, Heidelberg, Germany.

The synthesis and validation protocols for the AM_sils are described in detail by Okeke et al. (2019) [40 (link)]. In brief, AM_sil1 and AM_sil2 were synthesized at 50–55 °C by reacting equimolar amounts of tertiary amine, DMAEMA, with IPTMS and BrUDTMS, respectively, in the presence of chloroform and butylated hydroxytoluene. DMAEMA, IPTMS, and butylated hydroxytoluene were purchased from Sigma, St. Louis, MO, USA. BrUDTMS was purchased from Gelest Inc., Morrisville, PA, USA. Reactants and solvents (chloroform, diethyl ether, hexane; Sigma, St. Louis, MO, USA) used during synthesis and the subsequent purification were used as received, without further purification. The reaction yields were 94.8% and 36.0% for AM_sil1 and AM_sil2, respectively. Due to the generally hygroscopic nature of QA monomers, the AM_sils were stored under vacuum (25 mm Hg) before being used for resin formulation and/or copolymer disk specimen preparation.

DMAHDM was synthesized using a modified Menschutkin reaction^{33 (link)}. Briefly, 10 mmol of 2-(dimethylamino) ethyl methacrylate (DMAEMA, Sigma-Aldrich, MO, USA) and 10 mmol of 1-bromohexadecane (BHD, TCI America, Portland, OR, USA) were combined with 3 g of ethanol in a 20 mL scintillation vial. The vial was stirred at 70 °C for 24 h for the reaction to occur. The solvent was then evaporated, yielding DMAHDM as a clear, colorless, and viscous liquid^{33 (link)}. Similarly, 10 mmol 2-bromoethyl methacrylate (BEMA, Sigma-Aldrich) and 10 mmol 1-(dimethylamino) dodecane (DMAD, Sigma-Aldrich) were added in a 20 mL vial which was capped and stirred at 70 °C for 24 h. After the reaction was completed, the solvent was evaporated to yield DMADDM as a clear and viscous liquid^{34 (link)}.