We investigate structural and dynamic properties of colloidal particles with a soft repulsive interaction potential, and study self-assembly without and with externally applied fields. The project follows the well-established tradition of using colloids as model systems in condensed matter research to unravel basic phenomena such as phase transitions, crystallization and glass formation. Here we extend this approach to responsive soft particles such as Poly(N-isopropylacrylamide) microgels with tunable and directional interactions. We address the following key points:

(1) We use responsive neutral microgels to re-investigate recently developed approaches to disentangle glass and jamming transitions in soft particle systems.

(2) We use binary mixtures of microgels with different sizes, charge state and transition temperature to explore the rich phase diagram in binary systems of soft particles, investigate various ordered and amorphous phases and study solid-solid phase transitions.

(3) We extend the previous work to ionic microgels and develop a quantitative description of the interaction potential of ionic microgel particles with and without an applied electric field.

(4) We use them as a convenient model system for an investigation of crystallization, melting and domain growth processes and develop analogies to classical materials such as alloys.