6°

and 8.45°, indicating d spacings of 1.01 nm and 1.04 nm, respectively (based on Bragg’s equation). The slightly increased d spacing of DGO-Br over DGO-OH can be also attributed to the esterification of DGO-OH with α-bromoisobutyryl bromide. Thermal properties of the graphene-PMMA nanocomposites #Selleck Pexidartinib randurls[1|1|,|CHEM1|]# were compared with pristine PMMA by differential scanning calorimetry (DSC) and TGA. Figure 3 shows the DSC and TGA results for pristine PMMA and graphene-PMMA nanocomposite (GP-5) samples. For DSC (Figure 3a), the midpoints between the onset and offset points of the transition temperature were chosen as the T g values. The graphene-PMMA nanocomposite showed a higher T g than that of the pristine PMMA, which can be attributed to the interactions between GO and PMMA. The decomposition patterns for PMMA and GP-5 are shown in Figure 3b. About 15% of GP-5 nanocomposites decomposed between 130°C and 340°C, whereas pure PMMA decomposition started at 250°C. The initial decomposition of GP-5 may be due to the presence of additional labile functional groups after surface modification using quaternization followed by esterification onto the surface of GO [23]. On the other hand, the main decomposition of PMMA ends at 400°C, whereas that of the graphene-PMMA nanocomposite ends at 430°C. The difference in the thermal stability between pristine PMMA and GP-5 indicates

that the presence of graphene layers improves the thermal properties CH5183284 in vivo of graphene-PMMA nanocomposites after in situ polymerization on the functionalized GO surface. The increased thermal stability of graphene-PMMA nanocomposites can be attributed to the attractive nature of graphene toward free radicals generated during decomposition as well as the tortuous path formation during the decomposition process

[21, 23]. Figure 3 DSC results (a) of (i) PMMA and (ii) DGO-PMMA and TGA curves (b) of (i) PMMA and (ii) DGO-PMMA. Controlled study of radical polymerization Polymerization of MMA was carried out through ATRP using multifunctional DGO-Br, and controlled radical polymerization (CRP) 5-Fluoracil was studied using GPC. The detailed GPC results ( , , and MWD) are summarized in Table 1. As shown in Figure 4, as time increased, the GPC curves shifted from the lower molecular weight region to the higher molecular weight region due to the CRP mechanism. It is also interesting to note that the PDI values for PMMA become narrower with time, which also supports the CRP mechanism. Figure 5 shows the time vs. conversion and time vs. ln[M]0/[M] plots for MMA polymerization, where [M]0 and [M] represent the initial monomer concentration and the monomer concentration at time t, respectively. The linear relation between time vs. ln([M]0/[M]) shows that the concentration of propagating radicals is almost constant throughout the polymerization process.