Neutron Scattering from a Poly(oxyethylene)−Poly(oxypropylene)−Poly(oxyethylene) Copolymer in Dilute Aqueous Solution under Shear Flow

Abstract

A small-angle neutron scattering study of the temperature dependence of the micellar structure has been performed on a 1% w/w aqueous solution of the poly(oxyethylene)−poly(oxypropylene)−poly(oxyethylene) (POE−POP−POE) block copolymer Synperonic P-85 using a Poiseuille-geometry shear flow apparatus. The system is characterized by two transition temperatures. The first is the critical micellization temperature at 24 °C. This marks the lower boundary of a spherical, later more ellipsoidal, micellar phase. The next transition is at 62 °C, above which the micelles may be adequately modeled as rigid rods. By 73 °C, rods with diameters of 10−12 nm and lengths of almost 400 nm have been attained. This micellar growth takes place without any appreciable increase in the radius of the micelles. The response of the rodlike micelles to the presence of the shear flow field is also reported.

Effects of block architecture and composition on the association properties of poly(oxyalkylene) copolymers in aqueous solution

“…This is not possible in SANS, and the three factors are always in play. The assumption S (q) = 1 restricts measurements to low concentrations 168,169) and some information is lost.…”

“…As for static light scattering (see Section 4.1.2), scattering theory for hard spheres gives a satisfactory representation of S (q). Three general models have been used to represent P (q) for spherical micelles of block copoly(oxyalkylene)s, i. e. uniform sphere 7,62,[169][170][171] , uniform-core plus a uniform-shell to represent the corona [172][173][174] , or uniform core plus a corona of Gaussian chains 138,175,176) . Several authors allow for water in the core 138,168,[174][175][176] , and some for poly(oxyethylene) blocks to penetrate the core 138,175,176) .…”

Going Ultra: How We Can Increase the Length Scales Studied in Small‐Angle Neutron Scattering

“…[ [28][29][30] However, since the changes in the scattering curves only affect the part of the scattering curve dominated by the intermicellar interactions, another reasonable explanation is that there is a change in the interaction potential between the micelles. In order to determine which of these explanations seems the most reasonable, USANS measurements were carried out.…”

Two Gel States of a PEO-PPO-PEO Triblock Copolymer Formed by Different Mechanisms

“…It was reported that Pluronic P85 with a nominal composition of (EO) 27 (PO) 39 (EO) 27 forms an ordered structure at higher concentrations due to the close packing of micelles, and a change from spherical to rodlike micelles is observed upon heating, as verified by combined small-angle neutron scattering (SANS) and smallangle X-ray scattering (SAXS). [11] Moreover, Pluronic P94 with a nominal composition of (EO) 21 (PO) 47 (EO) 21 containing a longer PO block but shorter EO blocks than Pluronic P85 has been shown to have two gel-like structures (i. e., a hard gel state at lower temperature and a soft Communication: Two gel states of a PEO-PPO-PEO (Pluronic P103) triblock copolymer in water are investigated using small-angle X-ray scattering, rheology and differential scanning calorimetry. The first gel state turns out to be the hexagonal microphase while the second gel state, showing turbidity change with four distinct regions, is somewhat disrupted.…”