Properties of aliphatic hyperbranched polyesters in dilute solutions

The results of an investigation of the influence of the synthesis procedure, number of pseudo generations and degree of branching of hydroxy-functional ali- phatic hyperbranched polyesters (AHBP) on the values of limiting viscosity num- ber, (η), hydrodynamic radius, Rη, molar mass and polydispersity index, Q, are pre- sented in this paper. Two series of AHBP, synthesized from 2,2-bis(hydroxyme- thyl)propionic acid and di-trimethylolpropane using a pseudo-one-step and a one-step procedure were investigated. The obtained results show that the values of (η) and Rη for all examined samples are the highest in a 0.7 mass % solution of LiCl in N,N-di- methylacetamide (LiCl/DMAc), which indicates that this solvent is the best from the investigated ones. The values of (η) in N-methyl-2-pyrrolidinone (NMP) increa- sed up to the sixth pseudo generation, after which a slight decrease occurred as the consequence of the presence of side-reaction products, formed during the synthesis. The appearance of these side-reaction products was also confirmed from the charac- teristic GPC chromatograms. For the samples of AHBP synthesized using the pseu- do-one-step procedure, a good linear dependence between log (η) and log Mw was obtained up to the fifth pseudo generation, when LiCl/DMAc, NMP and DMAc were used as solvents. The values of the "shrinking" factor, g', were calculated for all investigated AHBPs.