On the molecular mechanism of clouding in aqueous solution of poly(oxyethylene)‐poly(oxypropylene)‐poly(oxyethylene) triblock copolymers

Abstract

The physical aspects of the clouding phenomenon in the aqueous solution of a poly(oxyethylene)(POE) – poly(oxypropylene)(POP) – poly(oxyethylene)(POE) triblock copolymer were investigated by applying various experimental methods: viscometry, ultrasonic technique, light scattering, infrared and Raman spectroscopy. The ultrasonic absorption studies hint at a critical behaviour. In order to understand the spectroscopic findings, conformational energies of model POE molecules as well as interaction energies between oxyethylene (OE) units and water molecules were calculated by the use of the quantum chemical PCILO method. It is suggested that the clouding is connected with conformational changes of POE segments.

Surface activity and aggregation of pristine and hydrophobically modified inulin

“…For instance, a soluble, fully hydrated polyethylene oxide molecule is hydrated by two water molecules while an ''insoluble'' polyethylene oxide unit is hydrated by a single water molecule. 34 This level of hydration of the inulin does not seem to be the origin of the final precipitation of inulin solutions.…”

Investigations of Naphthalene Solubilization in Aqueous Solutions of Ethylene Oxide-b-Propylene Oxide-b-Ethylene Oxide Copolymers

“…Karlström, on the other hand, has suggested that the origin of the increasing hydrophobicity of PEO is the result of changing conformations of ethylene oxide (EO) segments. For the segment O−C−C−O the preferred orientation about the bonds is t−g−t. , This polar conformation interacts favorably with water, there being some two water molecules per EO unit . It is of low energy but also of low statistical weight, there being only two of these conformations .…”

Effect of Sodium Chloride upon Micellization and Phase Separation Transitions in Aqueous Solutions of Triblock Copolymers: A High-Sensitivity Differential Scanning Calorimetry Study

“…Karlström on the other hand has suggested that the origin of the increasing hydrophobicity of PEO is the result of changing conformations of ethylene oxide (EO) segments. For the segment O−C−C−O the preferred orientation about the bonds is tgt. , This polar conformation interacts favorably with water, there being some two water molecules per EO unit . It is of low energy but also of low statistical weight, there being only two of these conformations …”