• Fuller, Gerald G.
• Tenhu, Heikki
• Hietala, Sami
• Ostrowski, Maggie
• Wu, Cynthia
• Niskanen, Jukka

Abstract

<p>Isotactic triads are introduced into poly(dimethylaminoethyl methacrylate) (PDMAEMA) when a Lewis acid yttrium(III)trifluoromethanesulfonate, Y(OTf) ₃, is present during the ATRP polymerization. The changes in the tacticities of the polymers are modest. However, the tacticity affects the phase separation process but in a different way in two studied cases, at pH 8 and 9. The pH, and thus the charge of the polymer, affects the balance between electrostatic and stereochemical effects. Upon the chain collapse, the zeta potential of the polymer decreases discontinuously at pH 9, whereas at pH 8 the potential keeps almost constant. However, even in the latter case the influence of the isotactic segments on the thermal transition may be observed. Increasing isotacticity is suggested to decrease the flexibility of the polymer chain. It also causes the polymers to adsorb in a more organized manner to the air/water interface than the atactic ones do. The change in the thermoresponsive behavior due to the changing tacticity of the polymer has been studied at the interface by observing the surface tension and by surface rheology and in the solution by conventional rheology. Differences in the elastic and viscous moduli owing to the different tacticities of the polymers are compared to those attributed to different molar masses and to varying pH.</p>

Topics

• impedance spectroscopy
• surface
• polymer
• phase
• Yttrium
• tacticity