Berlin 2015 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 40: Charged Soft Matter II

CPP 40.4: Vortrag

Mittwoch, 18. März 2015, 10:15–10:30, PC 203

Stimuli-responsive polyampholyte hydrogels - influence of charge asymmetry and ionic strength — •Margarita Dyakonova¹, Maria T. Popescu², Konstantinos Kyriakos¹, Sebastian Jaksch³, Constantinos Tsitsilianis², and Christine M. Papadakis¹ — ¹TU München, Physik-Department, Physik weicher Materie, Garching — ²University of Patras, Greece — ³JCNS at FRM II, Garching

We investigate the rheological and structural properties of physical hydrogels, formed via charge driven self-association of triblock polyampholytes PAA-P2VP-PAA and PAA-QP2VP-PAA (PAA, P2VP and QP2VP are poly(acrylic acid), poly(2-vinylpyridine) and quaternized poly(2-vinylpyridine)), which have attracted a considerable interest for use as injectable hydrogels and drug carriers. Both, the PAA and P2VP blocks are ionizable. PAA is deprotonated at high pH, whereas P2VP is positively charged at low pH. QP2VP is highly charged, independently of pH. In water, the gelation threshold is at 1.0 wt% [1]. Small-angle neutron scattering (SANS) experiments revealed the morphological changes depending on the charge asymmetry. The structure develops from uncorrelated globular aggregates to a network. These findings corroborate the ones from rheological studies, implying the formation of stiff hydrogels at low pH. Ionic strength is an alternative way of controlling the strength of electrostatic interactions. Combined SANS and rheological studies have revealed a different structure revolution inside the polyampholyte networks depending on ionic strength. [1] N. Stavrouli et al., Polymer 49, 1249 (2008).