Iniferters polymeric

In this study, molecular weight of the produced polymers will not be tracked over the course of the reaction. Thus, in order to simplify the model, chain transfer mechanisms will not be considered, along with side reactions, such as the production of carbon disulfide. Each of these reactions, as well as the molecular weight, plays a significant role in the iniferter polymerizations however, to simplify the system, it is essential to examine only the core reactions which contribute significantly to the mechanism. 

Iniferter polymerizations were also combined with anionic polymerization. The representative example involves the synthesis of PCL-l7-(PMMA-co-PSt)-l7-PCL. ° A polymeric thermal iniferter, PCL-substituted tetraphenylethane, was prepared by anionic polymerization of CL in the presence of aluminum triisopropoxide and benzopinacol. The benzopinacolate groups incorporated into the polymer chain initiated the polymerization of St and MMA via a controlled radical mechanism at 95 °C to yield the desired block copolymers (Scheme 47)... 

Acar, M. H., et al. (2000). Synthesis of block copol5mer by combination of living cationic and iniferter polymerization systems. Polymer, 4/(18) 6709-6713. 

Scheme 3.1 The general mechanism steps of the iniferter polymerization.

The isolated polymers could further initiate the polymerization in the presence of second monomer to give block copolymers. Iniferter polymerization has three main characteristics over classical radical polymerization ... 

Despite all these deficiencies, iniferter polymerization allows the facile control of the polymerization reaction by means of irradiation time and UV intensity, has a comparatively fast polymerization rate compared to other C/LRP methods, as well as the fact that the polymerization can be easily performed at room temperature or below to avoid thermal polymerization of heat-sensitive monomers. Moreover, the photoiniferter technique is indispensable for surface modification in both organic and aqueous media and it is suitable for micro-patterning. Additionally, the polymerization is only initiated at reactive carbon radicals on the surface and not by cleaved dithiocarbamyl radicals, thus preventing homopolymer contamination in the bulk solution, and eliminating the need for extensive eleaning steps after brush formation. 

Compared with other modes of polymerization, redox initiation has the advantage of being applicable in aqueous media and at low temperature. Therefore, the probability of side reactions can be minimized. To conduct iniferter polymerization at room temperature, Otsu and Tazaki proposed a redox iniferter system. The system is based on the reaction of nickel (Ni - ) with an organic halide (R X) such as benzyl chloride to form the benzyl radical. 

There are a number of factors that affect the progress of the iniferter polymerization, the extent of its livingness, and thereby the control over the end product. These factors are related to iniferter structures,types of monomer and solvent,and temperature. Since the iniferter itself is incorporated into the growing/propagating polymer chain during polymerization, a desirable end group functionality can be designed by careful choice of iniferter. ... 

Scheme 3.8 Synthesis of block copolymers by combination of ring-opening polymerization and iniferter polymerization.

Table 3.5 Synthesis of block and graft copolymers via iniferter polymerization.

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