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Figure 4. Contact angle by dropping water onto BP-g-4VP with different graft degrees.

(Figure 5). There were no significant variations in swelling A
for grafted films with grafting percentages exceeding 30
g%, with maximum swelling reaching around 17 wt%. This
water uptake capability modulated the Ag loading capacity,
as observed in the subsequent step. Higher swelling allowed
the absorption of more Ag particles on the surface and
within the grafted poly(4VP) chains.
Given that these grafted films will come into contact with
water, the dimensions of the samples were measured to check
for any potential increase in length, thickness, or volume.
We found that the changes were negligible, approaching
Δ0 mm. Therefore, despite their improved water absorption
capacity, the grafted films retained their dimensions without B
any apparent changes, reaffirming that the grafting primarily
occurred on the surface (Huang et al., 2022).
Swelling tests were conducted at different pH levels to
determine the critical pH, and the results are presented
in Table 2. While the pristine BP (0.0 g%) exhibited
consistent swelling behavior across all pH values, most of
the grafted samples showed a transition from hydrophilic
to hydrophobic behavior within the pH range of 6 – 8, with
a calculated critical pH of 7.2 ± 0.7 (Figure 6). Significantly
higher degrees of swelling were observed under acidic
conditions. In general, it was observed that higher grafting
percentages led to increased swelling, possibly due to the
strong adhesion of salts (from the buffer solution) to the Figure 5. Swelling curves in water at room temperature testing samples of
different grafting degrees (A) from 0 to 25 h and (B) at 24 h. It is observed
grafted surfaces. This phenomenon explains the observed that higher graft% produces higher limit s% until 17%, where the value is
difference in swelling behavior compared to pure water. constant for samples BP-g-4VP (30 – 65 g%).
3.4. Silver loading a neutral pH medium. These specific reaction conditions

Functionalization with Ag was the second step in the were selected. While the grafted samples exhibited higher
modification process of BP. Both BP-g-4VP and pristine swelling percentages at acidic conditions, Ag nucleation
BP were loaded with Ag from AgNO in a reaction is favored only under alkaline conditions (Pacioni et al.,
3
conducted at room temperature, under sunlight, and in 2015). However, the samples (as verified in the swelling

Volume 1 Issue 2 (2023) 6 https://doi.org/10.36922/ghes.1251