## 3 Results  
Figure 1 shows the typical dependence of the degree of grafting of PS on time with a change in the concentration of DVB in the polymerization solution from 0 to 2.5 vol. %. It can be seen that at low concentrations (up to 0.5 vol. %), the addition of DVB leads to an increase in the initial rate of grafting polymerization. Upon reaching the degree of grafting \(\sim\)70%, the gel effect (Trommsdorff effect) is observed. It should be noted that a similar increase in the degree of grafting of PS on PE in the presence of DVB was observed in [12] with direct grafting. In [14], it was also shown that the addition of DVB to St leads to an increase in the overall polymerization rate and the appearance of the gel effect. In our opinion, such an effect of DVB on the kinetics of St polymerization is due to the fact that the addition of DVB leads to the cross-linking of growing PS chains, a decrease in their translational mobility and, consequently, a decrease in the termination constant. In addition, an increase in the degree of grafting in the presence of DVB is possible due to the interaction of unvaccinated growing PS chains formed as a result of the chain transfer to the monomer and thermal polymerization of styrene with the unreacted double bond of DVB in the chain of the graft polymer. The same figure shows that at the concentration of DVB above 0.5 vol. %, the initial rate of grafting polymerization is reduced. A possible reason for this effect is a decrease in the diffusion rate of the monomer and Fe\({}^{2+}\) ions in the cross-linked network structure of the macromolecules of the grafted PS. The dependence of the degree of grafting on the concentration of DVB acquires a pronounced extreme character (Figure 2). Since the formation of the network limits monomer diffusion in the presence of DVB, the distribution of the grafted PS over the thickness of the PE film should depend on the concentration of DVB. This distribution was investigated by comparing the ratio of the optical densities of the bands at 1492 (stretching vibrations of the C-C bond in the phenyl ring of PS) and 1475 cm\({}^{-1}\) (asymmetric bending vibrations of the C-H bond in PE) (D\({}_{1492}\)/D\({}_{1475}\)) [18] measured in the transmission and multiple attenuated total internal reflection spectra [18; 19]. Indeed, as can be seen in Figure 3, an increase in the concentration of DVB in the polymerization solution leads to an increase in the D\({}_{1492}\)/D\({}_{1475}\) ratio, which was measured using the multiple attenuated total internal reflection method; over this ratio, which was measured using the transmission method, the enrichment of the film surface in PS occurs. Interestingly, when the degree of grafting reaches \(\sim\)100%, the concentrations of the grafted polymer on the surface and in the volume of the film are leveled, which indicates the course of the grafting process throughout the entire volume of the film in spite of the formation of network structures. Figure 4 shows a typical microphotograph of the cross-section film obtained in the second electrons (marked by dotted vertical lines) when grafted polymerization was carried out in the presence of DVB. It can be seen that the graft layer differs slightly in contrast to the central part. The distribution of the characteristic X-ray emission of the K\(\alpha\) sulfur and carbon lines shows a change in the PS concentration from the film surface layers to the center. The arrows indicate the defective areas in the grafted layers. Figure 1: Effect of DVB on the kinetics of grafting polymerization of St. [DVB], vol. %: 1—0, 2—0.25, 3—0.5, 4—1.5, and 5—2.5. Figure 2: Dependence of the degree of grafting of PS on the PE film on the concentration of DVB in the grafting solution at a polymerization time of 2 (1) and 4 h (2). Figure 4: Microphotograph of the cross-section of the grafted film with \(\Delta p\) = 93% ([DVB = 1 vol.