A one‐pot solution polymerization under mild conditions was adapted for the synthesis of well‐defined aliphatic‐aromatic polyesters with different degrees of branching. The esterification was performed at room temperature using 4,4‐bis(4′‐hydroxyphenyl)valeric acid (AB2) and 3‐(4‐hydroxyphenyl)propionic acid (AB) as monomers. DPTS was used as a catalyst and DCC as a coupling agent. Polyesters with statistical, dendritic topology, controlled degree of branching and $\overline M _{\rm w}$ > 35 000 g · mol−1 were obtained. The polymers were characterized by 1H and 13C NMR, SEC, DSC, and TGA. A strong dependence of the degree of branching and the thermal properties of the polymers depending on the AB/AB2 monomer ratio was observed.magnified image

The synthesis and characterization of aromatic−aliphatic polyesters with tailored degree of branching (DB), i.e. hyperbranched (hb), gradually branched, and linear polymers, are described. The dilute solution properties of polymers resulting from two different synthetic approaches are compared. The ABB*/AB2 approach leads to homopolymers with different DB based on the same AB2 monomer, 4,4-bis(4′-hydroxyphenyl)pentanoic acid, employing the protection of one phenolic group (B*) in the AB2 monomer followed by copolymerization with AB2 monomer at different molar ratios. Because of their identical chemical origin, well-tunable DB, comparable molar masses, an absence of aggregation in common solvents, and high refractive index increments, they are suitable as model systems in branching characterization. Their solution properties are compared to those of polymers obtained by the AB/AB2 approach. In order to study the influence of the end-groups on thermal and solution polymer properties, all terminal OH groups were modified with tert-butyldimethylsilyl chloride (SY-Cl). A different dependence of the thermal properties on branching was found for OH- and SY-terminated samples produced by the ABB*/AB2 approach. While the difference in the T g values between linear and hb structures was found to be 16 °C for SY-terminated samples, nearly identical values were obtained for OH-terminated linear and hb polyesters due to strong effect of hydrogen bond formation.

Elution fractionations of broadly molar mass-distributed, hyperbranched poly(urea-urethane)s with OH- and Ph- end groups were carried out to obtain a number of macromolecular samples possessing different molar masses at the same chemical structure. The characterization of the polymers was performed by SEC, MALLS, 1H-NMR, MALDI-TOF-MS and viscosity measurements. Modifications of the OH-end groups of the polymers were carried out. We observed a strong influence of the end groups on the solution behaviour of the hyperbranched samples. The molecular shape of the hyperbranched polymers in solution was compared to their linear analogue using the Kuhn-Mark-Houwink- Sakurada relationship. The calculated contraction factors between 0,15 and 0,7 depending on the molar masses correspond to a very compact structure of the modified branched polymers at high molar masses.

A series of samples of linear aromatic polyester of 3-phenylglutaric acid and bisphenol A was prepared with molecular weights ranging from 14 700 to 92 700. The polymers were characterized by size exclusion chromatography with triple lightscattering, viscosity, and concentration detection. Hydrodynamic parameters of the chain were determined using the theory of Yoshizaki, Yamakawa, and Nitta modified by Bohdanecký and Netopilík. The chain parameters are a useful reference in the study of aromatic hyperbranched polyesters.