Schizophrenic micellization in aqueous solutions of the pH- and temperature responsive pentablock terpolymer PDEAEMA(x)-b-PNIPAAM(y)-b-PEG(z)-b-PNIPAAM(y)-b-PDEAEMA(x)

摘要

The micellization behavior of a temperature and pH responsive pentablock terpolymer, poly(2-(N,N-diethylamino)ethylmethacrylate)-block-poly(N-isopropylacrylamide)-block-poly(ethyleneglycol)-block-poly(N-isopropylacrylamide)-block-poly(2-(N,N-diethylamino) ethylmethacrylate, abbreviated as PDEAEMA(x)-b-PNIPAAM(y)-b-PEG(z)-b-PNIPAAM(y)-b-PDEAEMA(x), was studied. Two variants of the polymer, with difference in block lengths, were examined using light scattering and small angle neutron scattering (SANS) as the main tools, with the aim of following nanostructural changes in the system with varying temperature and pH. With a sufficiently long PDEAEMA block, micelles of overall sizes around 50 nm and with a PDEAEMA-rich corona are formed at room temperature and at low pH. A change to a system with a PDEAEMA-rich core can be obtained via a jump in pH from 3 to 9. An increase in temperature will, at low pH, lead to formation of micelles also for the polymer with a short PDEAEMA block, with a transition around 42 degrees C. If the temperature increase is instead performed at pH 9, the transition to compact PDEAEMA-core micelles occurs at a slightly lower temperature (39 degrees C). This difference is attributed to the increased hydrophobic character for a system with deprotonated PDEAEMA-blocks. (C) 2015 Elsevier Ltd. All rights reserved.