Solution Behavior of Topological Isomers of Poly[11-(4‘-cyanophenyl-4‘ ‘-phenoxy)undecyl acrylate]s Prepared by Atom Transfer and Conventional Radical Polymerizations

Abstract

The solution behavior of linear, three-arm star, and comb poly[11-(4‘-cyanophenyl-4‘ ‘-phenoxy)undecyl acrylate]s previously synthesized by atom transfer radical polymerization was investigated by gel permeation chromatography (GPCPSt) and light scattering measurements in CH2Cl2, THF, and CHCl3 in order to correlate their size and shape with their molecular architecture and in order to investigate the extent of branching in the corresponding polymer prepared by conventional radical polymerization. The inaccuracy of the GPCPSt molecular weights increases as the polymers become more branched: linear < three-arm star < comb; the discrepancy between the GPCPSt and absolute molecular weights of polymers fractionated from the conventional radical polymerization is between those of the three-arm star and comb polymers in all three solvents. Light scattering studies demonstrate that CH2Cl2 is the best solvent for all of the polymers, resulting in either no aggregation or an insignificant amount of aggregation, whereas all of the topologies except the comb polymers tend to aggregate in THF and CHCl3; nevertheless, the extent of aggregation is not great enough to be detected by variations in the average GPCLS-determined molecular weights measured in any of these solvents. The tendency to aggregate in all of the solvents and the radius of gyration in CH2Cl2 decrease as the branching increases: linear > three-arm star > comb, with the polymer prepared by conventional radical polymerization being similar to the branched polymers. The scaling coefficients (Rg = KMν) of all of the polymers are similar in CH2Cl2, with ν = 0.37 for the three-arm star polymers, ν = 0.39 for the comb polymers, and ν = 0.32 for the polymer prepared by conventional radical polymerization. The relative values of the contraction factors, g = 〈Rg2〉br/〈Rg2〉lin, decrease in the order gstar > gcomb > gradical for the three-arm star polymers, the comb polymers, and the polymer prepared by conventional radical polymerization, respectively, in CH2Cl2.