*2.3. Gamma Radiation Grafting*

PET fabrics were exposed to 60Co γ-source (Gammabeam 651 PT, MDS Nordion, Kanata, ON, Canada) at dose rates of around 10 to 12 kGy h−<sup>1</sup> and doses between 50 and 70 kGy.

A mixture of 10 mL of HEMA:water or HEMA:PEGMA:water at di fferent volume ratios (Table 2) were placed into a Schlenk flask, argon was then bubbled for 5 min; after that, PET fabrics were soaked with the mixtures and the mixtures were degassed by three freezing cycles with argon flow; afterwards, the flask was sealed and stored inside a refrigerator for 12 h. After that, the fabrics were quickly removed and placed between two glass plates of 2.5 cm × 7.5 cm, sealed with a silicone spacer (0.5 mm thickness), and finally, the samples were irradiated at doses of 50, 60, or 70 kGy. In order to extract the residual monomer and homopolymer formed during the grafting reaction, the samples were soaked four times for 2 h in ethanol-water 25:75 ( *V*/*V*, %), followed by ethanol-water 50:50 ( *V*/*V*, %) ethanol-water 75:25 ( *V*/*V*, %), and ethanol for 12 h each. Afterwards, the samples were dried until constant weight.

**Table 2.** Surface modification of PET fabric with hydrogel using the direct gamma irradiation method; water was used as solvent.


1Calculated using the Equation (1); 2 calculated using the Equation (2).

The grafting yield (GY) in both methods was calculated using Equation (1):

$$\text{GY} = 100\% \,\text{(W}\_{\text{\$\%}} - \text{W}\_{\text{0}}\text{)}\% \text{W}\_{\text{0}} \tag{1}$$

where W0 and Wg represent the weights of the initial and the grafted fabric, respectively.

### *2.4. Characterization of Grafted Hydrogels on PET Fabrics*

FTIR-ATR spectra were recorded using a Perkin-Elmer Spectrum 400, FTIR-/FT-NIR spectrometer (Perkin Elmer Cetus Instruments, Norwalk, CT, USA) with 8 or 16 scans between 650 and 4000 cm<sup>−</sup>1. Thermal decomposition of samples was evaluated undo nitrogen flow of 50 mL min−<sup>1</sup> between 20 and 600 ◦C at a heating rate of 20 ◦C min−<sup>1</sup> using a TGA SDT 2960 Simultaneous DSC-TGA equipment (TA Instruments, New Castle, DE, USA). Glass transition temperature (*Tg*) and melting point (*Tm*) were determined by di fferential scanning calorimetry (DSC) using a TA-Instrument modulated DSC equipment (DSC 2929) (TA Instruments, New Castle, DE, USA); two heating cycles were recorded in modulation mode under a nitrogen flow of 60 mL min−<sup>1</sup> at a heating rate of 5 ◦C min−<sup>1</sup> with an amplitude of ±0.5 ◦C over a modulation period of 60 s; in both cycles, the temperature was equilibrated at –10 ◦C during 5 min before heating to 200 ◦C for the first cycle, to erase the thermal history, and up to 280 ◦C for the second one, for measurement. The thickness of the hydrogel thin-film on fabric surface was measured using SEM images of cross-sections. For the cross-section analysis, samples were fractured in liquid nitrogen and fixed on sample holder with a double-sided graphite tape. Analyses

were carried-out with a TESCAN VEGA 3 SEM-microscope (Brno, Czech Republic), at an acceleration voltage of 25 kV with a secondary electron detector. Previous to SEM analysis, all samples were sputter-coated with gold for 180 s at 18 mA using a SPI-MODULE sputter coater. The theoretical thickness of coating was 200 Å, according to the manufacturers technical information.

Water absorption equilibrium was monitored by immersion of pristine and modified PET fabrics of 2.5 cm × 2.5 cm into distilled water for 96 h. The excess of water on the materials was removed with filter paper and the swollen samples were weighed. The mass-swelling degree in water (Qwater) of the hydrogel coating was determined using Equation (2).

$$\mathbf{Q\_{water}} = 1 + ((\mathbf{W\_S} \times \varrho\_{\mathbf{h}})(\mathbf{W\_h} \ast \varrho\_{\mathbf{\tilde{s}}})) \tag{2}$$

Ws and Wh represent the weights of the adsorbed water and the mass of the dry hydrogel, respectively, where the weight of the fabric without hydrogel was subtracted; and is the density in g/mL. For this work the value of the polymer density PHEMA ( = 1.15 g/mL) was taken considering a linear polymer with molecular weight of 20,000 g/mol and = 1.15 g/mL at T = 25 ◦C, for the polymer PEGMA ( = 1.105 g/mL) was taken from a polymer with molecular weight of 300 g/mol at T = 25 ◦C. For the density of the hydrogel (h) the feed composition before crosslinking was taken as a first approximation. The density of water (s = 1.0 g/mL) was used for all calculations. Measurements were performed in triplicate and the average value is reported.

### *2.5. In Situ Synthesis of Silver Nanoparticles*

Silver nanoparticles (AgNPs) were synthesized by chemical reduction in situ of AgNO3 using NaBH4 as reducing agent. Equation (2) shows the chemical reaction:

$$2\text{AgNO}\_3 + 2\text{NaBH}\_4 \rightarrow 2\text{Ag}^\circ + \text{H}\_2 + \text{B}\_2\text{H}\_6 + 2\text{NaNO}\_3.\tag{3}$$

Pristine and hydrogel grafted PET fabrics of 1.5 cm × 1.5 cm were swollen in distilled water for five days; after that, samples were soaked in 5 mL of a AgNO3 solution (0.005 M); one day later, the pieces of fabrics were transferred into 5 mL of NaBH4 solution (0.01 M) at 0 ◦C. The fabrics were stirred gently for 2 h while cooling with an ice bath; finally, the solution was decanted, and the fabrics were washed with deionized water.

The presence of AgNPs on modified PET fabrics was determined semi-quantitatively by energy dispersive X-ray spectroscopy (EDS), by mapping measurements on surface and cross-sections using a Bruker XFlash Detector 4010 (Berlin, Germany). For surface analysis, samples of 5 mm × 5 mm were cut and fixed on sample holder with a double-sided graphite tape and for cross-section analysis, samples were prepared as described previously for SEM analysis. EDS information was processed using Quantax 200 ESPRIT 1.9 software (Bruker Nano GmbH, Berlin, Germany).
