Structure and dynamics of homogeneously and heterogeneously crosslinked PNIPAM microgels*

Thermoresponsive poly(N-isopropylacrylamide) microgel particles have been largely studied in the past due to their interesting fundamental properties as well as their potential for application in drug delivery, sensor technology or biotechnology. In this contribution, microgel particles with homogeneous and heterogeneous crosslink distribution and different crosslinker concentrations will be studied with small angle neutron scattering (SANS) and neutron spin echo spectroscopy (NSE).
The segmental dynamics of polymer chains in solution, as described by the Zimm model, is modified in microgels due to the presence of crosslinks and the crowded environment inside the particle, both inducing heterogeneities, for example “frozen” inhomogeneities or density fluctuations. Such structural heterogeneities have an impact on the segmental chain dynamics, which makes NSE, the highest resolution neutron spectroscopy technique, the experiment of choice for accessing variations and changes induced by changes in crosslink distribution and crosslink density.
An outlook on interface effects on the internal structure and inhomogeneities of microgel particles will be given.