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Shear‐sensitive chain extension of dissolved poly(ethylene oxide) by aluminate ions
Author(s) -
Srivastava Satyam,
Fink Zachary,
Burns Elizabeth G.,
Russell Thomas P.,
Hoagland David A.
Publication year - 2021
Publication title -
journal of polymer science
Language(s) - English
Resource type - Journals
eISSN - 2642-4169
pISSN - 2642-4150
DOI - 10.1002/pol.20200643
Subject(s) - hydrodynamic radius , aqueous solution , ethylene oxide , chemistry , dynamic light scattering , aluminate , polyelectrolyte , intrinsic viscosity , propylene oxide , ion , polymer chemistry , polymer , inorganic chemistry , chemical engineering , materials science , cement , organic chemistry , micelle , composite material , copolymer , nanoparticle , engineering
The phase behavior of poly(ethylene oxide) (PEO) in aqueous salt solutions has been studied many times but rarely for solution conditions relevant to the hydration process of cement, where PEO's interactions with surrounding ions modulate its application as both plasticizer and strength‐building additive. Here, the conformation, that is, coil size, of PEO was examined in aqueous solutions in the presence of sodium‐, calcium‐ and aluminum‐containing salts. Ion‐induced conformational changes for a model linear PEO were mostly unremarkable and consistent with past reports. However, trends for aluminum‐containing ions, which predominantly occur in water at neutral and basic pH as the monovalent hydroxo‐aluminate anion Al(OH) 4 − , were different: either present as the sodium or calcium salt, PEO's hydrodynamic radius determined by dynamic light scattering was approximately 30% larger than determined by intrinsic viscosity. The intrinsic viscosity was similar to that measured in the presence of simpler monovalent anions. We hypothesize that aluminum containing ions weakly couple the model polymer's hydroxyl end groups (present at just one chain end), creating polymeric aggregates sensitive to disruption by shearing. Supporting our argument, the hydrodynamic radius determined by dynamic light scattering dropped to the intrinsic viscosity value after hydroxyl groups were converted to methoxy groups.