2.3.1. Thickness

A hand-held digital micrometer (Mitutoyo Corporation, Tokyo, Japan) with an accuracy of 0.001 mm was used to measure the thickness of the membranes. All measurements were randomly performed at di fferent sites of the membranes.

#### 2.3.2. Ultraviolet-visible spectroscopy (UV–vis)

The transmittance spectra of the samples were acquired with a Shimadzu UV-1800 UV-Vis spectrophotometer (Shimadzu Corp., Kyoto, Japan) equipped with a quartz window plate with 10 mm diameter, bearing the holder in the vertical position. Spectra were recorded at room temperature (RT) in steps of 1 nm in the range 250–700 nm.

#### 2.3.3. Attenuated total reflection-Fourier transform Infrared (ATR-FTIR)

ATR-FTIR spectra were recorded with a Perkin-Elmer FT-IR System Spectrum BX spectrophotometer (Perkin-Elmer Inc., Massachusetts, USA) equipped with a single horizontal Golden Gate ATR cell, over the range of 600–4000 cm<sup>−</sup><sup>1</sup> at a resolution of 4 cm<sup>−</sup><sup>1</sup> over 32 scans.

#### 2.3.4. Solid-state carbon cross-polarization/magic-angle-spinning nuclear magnetic resonance (13C CP/MAS NMR)

13C CP/MAS NMR spectra were collected on a Bruker Avance III 400 spectrometer (Bruker Corporation, Massachusetts, USA) operating at a B0 field of 9.4 T using 9 kHz MAS with proton 90◦ pulse of 3 μs, time between scans of 3 s, and a contact time of 2000 μs. 13C chemical shifts were referenced to glycine (C=O at δ 176 ppm).

#### 2.3.5. X-ray diffraction (XRD)

XRD was performed on a Phillips X'pert MPD diffractometer (PANalytical, Eindhoven, Netherlands) using Cu Kα radiation (λ = 1.541 Å) with a scan rate of 0.05◦ s<sup>−</sup>1. The XRD patterns were collected in reflection mode with the membranes placed on a Si wafer (negligible background signal) for mechanical support and thus avoid sample bending.

2.3.6. Scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS)

SEM images of the cross-section of the membranes were obtained with a HR-SEM-SE SU-70 Hitachi microscope (Hitachi High-Technologies Corporation, Tokyo, Japan) operating at 4 kV. The microscope was equipped with an EDS Bruker QUANTAX 400 detector for elemental analysis. The samples were fractured in liquid nitrogen, placed on a steel plate and coated with a carbon film prior to analysis.

#### 2.3.7. Thermogravimetric analysis (TGA)

TGA was carried out with a SETSYS Setaram TGA analyzer (SETARAM Instrumentation, Lyon France) equipped with a platinum cell. The samples were heated from RT to 800 ◦C at a constant rate of 10 ◦C min−<sup>1</sup> under a nitrogen atmosphere (200 mL min−1).

## 2.3.8. Tensile tests

Tensile tests were performed on a uniaxial Instron 5564 testing machine (Instron Corporation, Maryland, USA) in the traction mode at a cross-head velocity of 10 mm min−<sup>1</sup> using a 500 N static load cell. The specimens were rectangular strips (50 × 10 mm2) previously dried at 40 ◦C and equilibrated at RT in a 50% relative humidity (RH) atmosphere prior to testing. All measurements were performed on five replicates and the results were expressed as the average value.

## 2.3.9. Water-uptake capacity

The water-uptake of the nanocomposites under different pH conditions was determined via immersion of dry specimens with 10 × 10 mm<sup>2</sup> in aqueous solutions of 0.01 M HCl (pH 2.1), phosphate buffer saline (pH 7.4) and 0.01 M NaOH (pH 12) at RT for 48 h. After removing the specimens out of the respective medium, the wet surfaces were dried in filter paper, and the wet weight (*W*w) was measured. The water-uptake is calculated by the equation: *Wuptake*(%) = (*Ww* − *<sup>W</sup>*0) × *W*−<sup>1</sup> 0 × 100, where *W*0 is the initial weight of the dry membrane.

#### *2.4. In vitro antibacterial activity*

The antibacterial activity of the nanocomposite membranes was tested against *S. aureus* and *E. coli*. The bacterial pre-inoculum cultures were grown for 24 h in tryptic soy broth (TSB) growth medium at 37 ◦C under shaking at 120 rpm. Before the assay, the density of the bacterial culture was adjusted to 0.5 McFarland in phosphate bu ffered saline (PBS) solution (pH 7.4) to obtain a bacterial concentration of 10<sup>8</sup> to 10<sup>9</sup> colony forming units *per* mL (CFU mL−1). Each membrane sample (50 × 50 mm2) was placed in contact with 5 mL of bacterial suspension. A bacteria cell suspension was tested as the control and BNC was tested as a blank reference. All samples were incubated at 37 ◦C under horizontal shaking at 120 rpm. At 24 h contact time, aliquots (100 μL) of each sample and controls were collected and the bacteria cell concentration (CFU mL−1) was determined by plating serial dilutions on tryptic soy agar (TSA) medium. The plates were incubated at 37 ◦C for 24 h. The CFU were determined on the most appropriate dilution on the agar plates. Three independent experiments were carried out and, for each, two replicates were plated. The bacteria reduction of the samples was calculated as follows: *log reduction* = *log* CFUcontrol – *log* CFUmembrane.

#### *2.5. Dye removal capacity*

The dye removal capacity of the PMPC/BNC nanocomposite membranes was evaluated by immersing dry samples (20 × 20 mm2) in 25 mL of methyl blue (MB) and methyl orange (MO) aqueous solutions (25 mg <sup>L</sup>−1, pH 5.7), and stirred (200 rpm) for 12 h at RT. Then, the membranes were removed from the solution and the residual concentration of dye determined by UV–vis spectroscopy (Shimadzu UV-1800 UV-Vis spectrophotometer, Kyoto, Japan) at 655 nm for MB and 463 nm for MO. Linear calibration curves for each dye in the range 0.4–3.1 μg mL−<sup>1</sup> were obtained: *y* = 0.1919*x* + 0.0014 (*R*<sup>2</sup> = 0.9991) for MB and *y* = 0.0881*x* − 0.0046 ( *R*<sup>2</sup> = 0.9992) for MO. The dye removal amount (mg g<sup>−</sup>1) was calculated by: *q* = (*Ci* − *Ct*) × *W*−<sup>1</sup> × *V*, where *C*i is the initial dye concentration (mg <sup>L</sup>−1), *C*t is the dye concentration at time *t* (h), *W* is the weight (g) of the membrane and *V* is the volume (L) of the dye solution.

Additionally, a dry sample of PMPC/BNC\_2 nanocomposite (20 × 20 mm2) was immersed in 25 mL of para ffin oil containing 1 mL of MB and MO aqueous solutions (25 mg <sup>L</sup>−1).
