Poly Sty-block-DVB

The copolymers of styrene and DVB discussed so far were made via free radical polymerization, which is known to produce crosslinked polymer with a very broad distribution of X in the polystyrene segments between cross-link junctions. On the other hand anionic polymerization of styrene monomer [140] to give the corresponding living dicarbanion n-mer1 followed by addition of DVB monomer gives a crosslinked network with a very narrow range of X (i.e. twice the number of monomer units) between nodules of (DVB)y. 

Swelling of these polymers will depend not only on X, but also on the ratio x/y, such that the parameters C and X /3 (eq. 14) observed for these polymers in a given liquid should be characteristically different from those exhibited by polymers made via free-radical polymerization. 

Swelling data for Sty-co-DVB polymers that have very-narrow-range molecular weight distributions for the poly(styrene) segments between poly(DVB) nodules have been reported by Rempp [141-143] and his coworkers. The size of these nodules and the number of polystyrene segments covalently bonded to a given 

1 n-mer refers to a short range degree of polymerisation to produce a polymer with two functional endgroups. 

Why the constant Xl13 for Rempp s data [141] published in 1978 is twice that for the corresponding constant observed for his data published in 1970 is not understood. The X 3 for the 1978 data, however, is unusually high relative to that observed for sty-co-DVB polymers made via free-radical polymerization (Figs. 9-11 Xl013 = 1.77 0.13). 

---