*2.2. Film Preparation*

The solution-casting technique was adopted to fabricate the films. Pure PLA (2.18 g) was dissolved in 30 mL of chloroform in a 150 mL flask. Then, the reaction mixture was magnetically stirred at a rate of 150 rpm. PLA was dissolved entirely in 2 h and starch (0.93 g) was added to the reaction mixture at ambient temperature. After dissolving the starch, a colorless solution was formed. The solution was degassed using ultrasonic irradiation for 2 h. Next, the solution was poured onto a glass plate and allowed to evaporate slowly at ambient temperature to form a film. The film was dried under vacuum to a constant weight and kept at room temperature for over a week to reach an equilibrium crystallinity [39].

Other samples were prepared with PEG as an emulsifier. These samples contained from 3 to 15 wt.% PEG (with respect to the sample weight) [46,47]. In brief and referring to the mentioned experimental procedure, the desired weight of PLA was dissolved in chloroform followed by pouring the dissolved starch into it. After obtaining a homogenous mixture, the reaction temperature was raised to 70 ◦C and then PEG in a 1:1 ratio mixture of acetone: chloroform (10 mL) was added to the reaction flask. Finally, the films were prepared the same as the procedure mentioned in the former paragraph. The thickness of films was 20–50 µm. The all-prepared composite samples are listed in Table 1.

The PSE22, PSE32, PSE<sup>42</sup> and PSE<sup>52</sup> films were prepared similarly to the PSE2, PSE3, PSE4, and PSE<sup>5</sup> and their compositions were identical, but ethanol just replaced acetone. The resulting samples were compared with the reference sample of PE and starch with the combination of 30% starch and 70% PE (PES) [48]. All the stages were performed on the reference samples as well.
