ATRP from silsesquioxane initiators

ATRP from Silsesquioxane Initiators. In addition to silsesquioxanes with vinyl based monomeric units attached to corner silicon atoms, other species can be bonded to the cubes. One such example is the silsesquioxane shown in Scheme 7. Termed benzyl chloride functionalized polyhedral oligomeric silsesquioxane (benzyl chloride-POSS), the molecule contains seven cyclopentyl groups, which provide increased solubility in organic solvents, and one benzyl chloride moiety which can serve as an initiator for ATRP. Studies of such initiators may be of interest due to the bulky nature of the initiating species. Furthermore, the high temperature stability of the inorganic cubes may lend some interesting thermal properties to polymers initiated from it. 

The first step for the core-first stars is the synthesis of multifunctional initiators. Since it is difficult to prepare initiators that tolerate the conditions of ionic polymerization, mostly the initiators are designed for controlled radical polymerization. Calixarenes [39, 58-61], sugars (glucose, saccharose, or cyclodextrins) [62-68], and silsesquioxane NPs [28, 69] have been employed as cores for various star polymers. For the growth of the arms, mostly controlled radical polymerizations were used. There are only very rare cases of stars made from nitroxide-mediated radical polymerization (NMRP) [70] or reversible addition-fragmentation chain transfer (RAFT) techniques [71,72], In the RAFT technique one has to differentiate between approaches where the chain transfer agent is attached by its R- or Z-function. ATRP is the most frequently used technique to build various star polymers [27, 28],... 

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