Potentiometric Properties of lon-Selective Electrode Membranes Based on Segmented Polyether Urethane Matrices

摘要

Potentiometric responses of polyurethane (PU)-based membranes containing valinomycin and varying amounts of plasticizer (DOA) and/or lipophilic additive (KT↓(p)CIPB) were examined as a function of soft segment [poly(tetramethylene ether glyeol)] contents in aromatic diisocyanate-based PU matrices. Upon increasing the weight percentages (w↓(soft)) of soft segments, which in part behave like a built-in plasticizer, prodding the matrices with rubbery structure (glass transition temperature below -58 ℃), the amounts of DOA and/or KT↓(p)CIPB necessary to result in near-Nerntian response (e.g., slope > 50 mV/ decade) to potassium were substantially lowered. The apparent effect of adding plasticizer to PU-based membranes was comparable to that resulting from an increase of free carrier concentration in normal PVC-based membranes. Owing to the chemical interaction between mobile anionic sites and urethane chains, plasticizer-free PU membranes could be prepared with the PU matrices with high soft segment Contents (w↓(soft) ≥ 60 wt %). PUs composed of 60 < W↓(soft) < 80 wt % were recommended as the matrix for fabricating ISE membranes with no or low plasticizer content.