Straightforward Addition of Another Monomer s

In order for block multipolymer formation to occur uniformly from the first-stage polymer radicals with this method, the second-stage monomer should be able to diffuse fast enough in order to minimize core-shell polymer formation. Also, the second monomer set should form a second block that would have properties that are distinct from the first block. This is not easy if there is substantial first block monomer left in the reactor. However, for certain cases, this is quite feasible. 

For first-stage PS radicals formed in reactive S/ether system, the addition of methacrylic acid will result in the formation of S-block-(S-stat-MAA) copolymer, which could still possess amphiphilic properties. Also, such a block copolymer can be a good intermediate material for the formation of block-graft copolymers (see Section 4.6). 

Another experiment was done in the 300-ml Parr reactor system shown in Fig. 2.3.4. The mixture of 15 ml S, 135 ml ether, and 0.2 g V-501 was pumped into 

Since cyclohexane is a solvent for PS at the operating temperature of 80 C, the conversion is more moderate than the system that only had MAA as second-stage monomer charge. The final product from the 300-ml Parr reactor system was dried out and a dry sample was dissolved in THF. Water was added in as precipitant for the purified block copolymer. The unprecipitated block copolymer was called the raw product. In Fig. 3.2.2, size exclusion chromatography data are shown for the intermediate PS, raw block copolymer product, and purified copolymer product. 

These curves show definite formation of the S-block- S-stat-AA) material. The intermediate PS product has a peak MW of 10,000 Da, while the block copolymer has a peak MW of 300,000-400,000 Da. 

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