Synthesis and characterization of hyperbranched copolymers with free radical photopolymerization

In recent years, hyperbranched polymers have been attractive because of their architectural structures, various physical and chemical properties. Novel synthesis methods have been developed in recent years due to the usage of hyperbranched polymers both for academic studies and industrial applications. In this study, it is aimed to synthesize and characterize hyperbranched copolymers using free radical photopolymerization. For this purpose, in the first step, methacrylation reaction was carried out with 4-hydroxy-benzophenone (BPOH) and methacryloyl chloride, then type II photoinitiator, monomer and coupling agent containing methacrylated benzophenone (BPMac) was obtained. Purity of resulted product was investigated by proton nuclear magnetic resonance (1H NMR), fourier transform infrared spectroscopy (FT-IR) and gas chromatography with mass spectrometer (GC-MS). In addition, photodecomposition experiments of benzophenone and BPMac with N-methyldietylethanolamine (MDEA) were investigated. In order to obtain hyperbranched copolymers, photoinduced free radical polymerization of methyl methacrylate (MMA) and BPMac was performed in the presence of MDEA as a co-initiator in different concentrations. In these studies, photoinitiator solutions were prepared in various concentrations. In the first set, identical amount of BPMac and MDEA were used and 0.5%, 1%, 3%, 5% and 7% moles of solutions were prepared. In the second set, the same BPMac concentrations with constant co-initiator (MDEA) concentrations were prepared, photopolymerization of entire solutions was carried out. Conversion percentages were calculated gravimetrically and molecular weight values were determined by gel-permentation chromatography (GPC). Moreover, photopolymerization experiment was also carried out in the absence of MDEA in order to investigate the type II mechanism of BPMac (0.5 % mole) in MMA. In addition, thermal gravimetric analysis experiments (TGA) were also examined. Besides, BPMac and MMA were thermally polymerized by azobisisobutyronitrile (AIBN) and resulted linear copolymer was characterized by GPC and TGA.