Heterogeneous controlled radical polymerization

Heterogeneous controlled radical polymerization Reversible addition fragmentation transfer (RAFT) process... 

Cp2TiCl2 has been assessed as additive that controls polymer chain growth in the polymerization of methyl methacrylate.1224 Methyl methacrylate is easily polymerized in the photopolymerization with Cp2TiCl2 in a water-methanol mixture under irradiation of a 15 W fluorescent room lamp. The polymerization proceeded heterogeneously.1225 This process in the presence of 2,2 -bipyridyl, 1,10-phenanthroline, or sparteine as the chelating reagent has been studied.1226 Similar studies on the polymerization of methacrylate monomers such as methyl methacrylate, ethyl methacrylate, phenyl methacrylate, and benzyl methacrylate at 40 °C have also been performed.1227 The results of co-polymerization of methyl methacrylate and acrylonitrile indicate that this process proceeds through a radical mechanism.1228 The mechanism of the controlled radical polymerization of styrene and methyl methacrylate in the... 

Cellulose is a highly interesting material as a result of its materials properties, abundance, renewability and low cost. The heterogeneous grafting of cellulose fibers through controlled radical polymerization methods allows preparation of fibers with tailorable properties and built-in functionalities that can act as promising materials for advanced applications [118-121],... 

Synthesis of Nanocapsules and Polymer/ Inorganic Nanoparticles Through Controlled Radical Polymerization At and Near Interfaces in Heterogeneous Media... 

Free-radical initiation of emulsion copolymers produces a random polymerization m which the trans/ds ratio cannot be controlled. The nature of ESBR free-radical polymerization results in the polymer being heterogeneous, with a broad molecular weight distribution and random copolymer composition. The microstructurc is not amenable to manipulation, although the temperature of the polymerization affects the ratio of trans to cis somewhat... 

Homopolymerization. The free-radical polymerization of VDC has been carried out by solution, slurry, suspension, and emulsion methods. Slurry polymerizations are usually used only in the laboratory. The heterogeneity of the reaction makes stirring and heat transfer difficult consequently, these reactions cannot be easily controlled on a large scale. Aqueous emulsion or suspension reactions are preferred for large-scale operations. The spontaneous polymerization of VDC, so often observed when the monomer is stored at room temperature, is caused by peroxides formed from the reaction of VDC with oxygen, fery pure monomer does not polymerize under these conditions. Heterogeneous polymerization is characteristic of a number of monomers, including vinyl chloride and acrylonitrile. 

Various metal complexes of Ru, Fe, Cu, Ni, and Pd are active in the radical polymerizations of hydro-phobic methacrylates, acrylates, and styrenes under aqueous heterogeneous conditions to yield polymers with controlled molecular weights and relatively narrow MWDs. Importantly, a variety of these orga-nometallic catalysts are tolerant to water, despite the fact that many similar complexes often lose their catalytic activity in the presence of water or even moisture. 

The grafting from procedure requires the generation of active sites on the main polymer chain which are capable of initiating the polymerization of a second monomer. Free radicals can be created by several methods such as irradiation of a polymer in the presence of oxygen [31,32], chain transfer to the backbone [33,34] or redox reaction [35]. Several commercial products have been produced by these methods because they are simple and rather easy to perform. Nevertheless, significant amounts of homopolymers are produced, and, in combination with the poor control of radical polymerization, the final products are characterized by chemical heterogeneity. 

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