SIDE-CHAIN DENDRITIC POLYMERS - SYNTHESIS AND PHYSICAL-PROPERTIES

A series of side chain dendritic polymers (SCDP) was produced by copol ymerization of dendritic diols of the second, third, and fourth genera tion with four different semirigid and flexible diisocyanates. The pol ymerization reactions were conducted both in solution and in bulk. The degree of polymerization and molecular weight distribution of SCDPs w ere 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 struc tures at a certain molecular weight. The supramolecular assembly of de ndritic mono- and polymers in bulk was investigated by X-ray diffracti on measurements. It was demonstrated that these macromolecules were, i n principle, able to form body-centered cubic lattices. Some results s uggested that the ability to form such a type of higher order structur es increased as a result of polymerization of dendritic monomers. Thes e findings were supported by molecular dynamics simulations conducted on dendritic mono- and polymers. By means of such calculations, we als o 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 gy ration (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 predic tions made for the conventional dendrimers (theory: upsilon = 0.33). I n a good solvent, however, the conformation of SCDPs approached the Ga ussian distribution statistics.