Side chain dendritic polymers: Synthesis and physical properties

A series of side chain dendritic polymers (SCDP) was produced by copolymerization of dendritic diols of the second, third, and fourth generation with four different semirigid and flexible diisocyanates. The polymerization reactions were conducted both in solution and in bulk. The degree of polymerization and molecular weight distribution of SCDPs were greatly influenced by the flexibility of the diisocyanates and the nature of the reaction medium. The conformation of SCDPs in solution and its dependence on the molecular weight were examined with the aid of intrinsic viscosity ([eta]) measurements. According to the results obtained, SCDPs based on the third and fourth generation monodendrons changed in conformation from spherically to cylindrically shaped structures at a certain molecular weight. The supramolecular assembly of dendritic mono- and polymers in bulk was investigated by X-ray diffraction measurements. It was demonstrated that these macromolecules were, in principle, able to form body-centered cubic lattices. Some results suggested that the ability to form such a type of higher order structures increased as a result of polymerization of dendritic monomers. These findings were supported by molecular dynamics simulations conducted on dendritic mono- and polymers. By means of such calculations, we also studied the effect of the degree of polymerization on the molecular conformation up to a degree of polymerization of seven. We derived the double logarithmic plots of the calculated values of the radius of gyration (R-g) versus molecular weight (R-g proportional to M-upsilon). In a medium consisting of a poor solvent, the data scaled according to upsilon = 0.36, which agreed well with some of the theoretical predictions made for the conventional dendrimers (theory: upsilon = 0.33). In a good solvent, however, the conformation of SCDPs approached the Gaussian distribution statistics.