Properties of aliphatic hyperbranched polyesters in dilute solutions

Abstract

The results of an investigation of the influence of the synthesis procedure, number of pseudo generations and degree of branching of hydroxy-functional aliphatic hyperbranched polyesters (AHBP) on the values of limiting viscosity number, [η], hydrodynamic radius, Rη, molar mass and polydispersity index, Q, are presented in this paper. Two series of AHBP, synthesized from 2,2-bis(hydroxymethyl)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 R η for all examined samples are the highest in a 0.7 mass % solution of LiCl in N,N-dimethylacetamide (LiCl/DMAc), which indicates that this solvent is the best from the investigated ones. The values of [η] in N-methyl-2-pyrrolidinone (NMP) increased 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 characteristic GPC chromatograms. For the samples of AHBP synthesized using the pseudo-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.