Molecular weight and contraction factors of hyperbranched poly(urea-urethane)s

Abstract

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.

Synthesis of a New Hyperbranched Polyaminoester and Its Use as a Reactive Modifier in Anionic Curing of DGEBA Thermosets

“…This can be explained if we take two facts in consideration: a) the introduction of a HBP in the formulation with a molecular weight higher than the epoxy resin reduces the amount of covalent linkages to be formed; b) the reaction of hydroxyl groups with epoxides reduce the intramolecular hydrogen bonding in the HBP, which leads to an expansion of the HBP structure. The expansion of hydroxyl ended HBP on reacting was reported previously by Lederer et al [42] The reduction in the shrinkage by adding PAE to the formulation accounts for a chemical incorporation of PAE in the network structure. The bond formation is caused by an acid-base proton interchange, which leads to chain transfer processes.…”

Analytical methodology for sulfonated lignins

“…This product is sometimes referred to as the hydrodynamic volume. The general validity of the principle of universal calibration has been amply proven for all types of polymers, with the exception of hyperbranched structures [15]. However, the horizontal axis still displays the retention time or, equivalently, the retention volume.…”

Dendritic Polymers Based on Urethane Chemistry – Syntheses and Applications

“…[38] Fractionation by preparative SEC and analysis of the fractions via MALLS, MALDI-TOF-MS and NMR spectroscopy revealed a strong influence of the end groups on solubility and proved to be very compact structures in solution compared to linear polyurea urethane model systems. [39] An oligomeric A 2 þ B 3 -approach towards hyperbranched segmented poly(urethane-urea) elastomers was reported by Long, Yilgor and coworkers. [40][41][42][43] In the first step long chain linear isocyanate-terminated urethane prepolymers were synthesized by reacting difunctional poly(tetramethylene oxide) or a,v-amino-terminated poly(propylene oxide) oligomers with bis(4-isocyanatohexyl)methane (H 12 MDI).…”