PS-Based Intermediates

An obvious approach to PS-based intermediates via the FRRPP process is through live PS radicals that can be used for chain extension with another set of monomers. Formation of live PS radicals at room temperature has been quite tricky, because chains terminate through conventional free-radical polymerization at relatively low polymer concentration as the temperature was being lowered slowly. Either high polymer concentration was achieved or polymer radicals had to be rapidly cooled to drastically reduce their reactivity. Both approaches were employed successfully and introduced in Chapter 3. 

Another approach to PS intermediates was made through the use of functional initiators, which provide the polymer certain functional end groups. For example, the use of V-501 initiator from Wako Chemical Co. provides carboxylic acid end groups to the polystyrene chains, which can be reacted with a basic functionality from another polymer. In order for this reaction to occur cleanly, initiator fragments as well as undecomposed initiator molecules have to be extracted 

Block copolymer based on PS and either PMAA or PAA (S-block- S-stat-MAA) or S-block-(S-stat-AA) copolymers) that were presented in Section 3.2 have been found to be good reactive intermediates. The acid groups can react with base-functional polymers in order to produce PS blocks with grafted chains on the other block. 

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