Structure and rheology of hyperbranched and dendritic polymers. II. Effects of blending acetylated and hydroxy-terminated poly(propyleneimine) dendrimers with aqueous poly(ethylene oxide) solutions

Abstract

The effect of adding acetylated poly(propyleneimine) dendrimers to the structure and rheology of aqueous solutions of high molecular weight poly(ethylene oxide) (PEO) was investigated by rheology and small‐angle neutron scattering in a temperature range of 10–40 °C. In the semidilute regime, the steady shear rheology of PEO solutions was unmodified by the addition of dendrimers at a comparable weight concentration. At the highest concentrations studied, the addition of acetylated dendrimers suppressed the onset of a low‐frequency elastic modulus at the lowest temperature investigated. For comparison, the addition of PEO of a comparable molecular weight at the same weight fraction resulted in a milder suppression but, unlike the dendrimers, greatly increased the solution viscosity. The addition of acetylated dendrimers to a semidilute PEO solution at 10 °C substantially reduced the solution turbidity. These effects on the rheology and optical properties were confirmed by small‐angle neutron scattering measurements of the molecular structure of the mixture. Additional SANS measurements in the dilute regime (0.1 wt % PEO) showed quantitatively that the dendrimers decorated the PEO chains in a necklace structure, such as that observed previously for micelles. The results suggested a mechanism of rheology modification whereby the dendrimers disrupted the association network structure in the PEO solution at lower temperatures by preferentially associating with the PEO chains in solution. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 874–882, 2000

Structure and rheology of hyperbranched and dendritic polymers. I. Modification and characterization of poly(propyleneimine) dendrimers with acetyl groups

“…The novel rheological and structural properties of these dendrimer solutions points toward their application as rheology modifiers. In the next contribution,33 we explore the effects of solution‐blending these dendrimers with linear, flexible, water‐soluble polymers on the rheology and molecular structure.…”

Rheology of hyperbranched polymer melts undergoing planar Couette flow

“…It has been demonstrated that dendritic polyether and poly͑amidoamine͒ melts exhibit a Newtonian behavior over the available measurement range in experiments and the lack of entanglements in the systems observed suggests that as the dendritic topology leads to globular conformations, molecules do not interpenetrate significantly in the melt and do not combine to form aggregated structures. 4 In the case of dendritic polymers in solution, a peak is observed in the plot of intrinsic viscosity versus molecular mass. 5 This is in contrast with linear chains which obey the Mark-Houwink equation 6 and show a steady increase in the intrinsic viscosity as a function of molecular weight.…”

Influence of End Groups on Dendrimer Rheology and Conformation

“…In contrast to these earlier studies, our work focuses on determining the influence of the chemical nature of the molecular end groups on the conformation and rheology of dendrimers. Previous work with acetylated PPI dendrimers focuses on solution structure, rheology, and interactions with linear polymers in water. , In this work, we have examined both the solution architecture and melt rheology of fourth- and fifth-generation poly(propyleneimine) (PPI) dendrimers derivatized with two different acrylate monomers. The results of density measurements along with steady and dynamic rheology are analyzed to draw connections between copolymer composition, molecular structure, and bulk mechanical behavior.…”