Synthesis and self-assembly of [60]fullerene containing sulfobetaine polymer in aqueous solution

A well-defined poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA-b-C-60) was synthesized using the atom transfer radical polymerization (ATRP) technique and betainized with 1,3-sulfobetaine to yield a BetPDMAEMA-b-C-60. The solution properties were then studied by light transmittance, viscometric, H-1 NMR laser light scattering, and transmission electron macroscopic techniques. It was found that Bet-PDMAEMA-b-C-60 exhibits an upper critical solution temperature (USCT) similar to that observed for Bet-PDMAEMA in aqueous solution. However, the modification of Bet-PDMAEMA with a C-60 molecule increases the UCST of Bet-PDMAEMA in solution, which is a function of the solution ionic strength. Addition of a small amount of salt increases the UCST, similar to polyelectrolyte systems, while the presence of an excess amount of salt leads to a decrease in the UCST, attributed to the antipolyelectrolyte effect of polyampholytes. In aqueous salt solution, Bet-PDMAEMA-b-C-60 chains self-assemble into micelles that coexist with unimeric BetPDMAEMA-b-C-60 chains. TEM studies revealed that the system agglomerates when the temperature exceeds the UCST.