Non NIPAM Based Smart Microgels: Systematic Variation of the Volume Phase Transition Temperature by Copolymerization

Thermoresponsive copolymer microgels based on N-n-propylacrylamide (NNPAM) and N-iso-propylmethacrylamide (NIPMAM) with varying compositions were synthesized via precipitation polymerization. Photon correlation spectroscopy (PCS) and turbidity measurements were used to investigate their volume phase transition. A linear correlation between the nominal composition and the volume phase transition temperature (VPTT) was observed. Furthermore, the hydrodynamic radii of the particles exhibit a linear dependency on the nominal composition. The presented system is suitable for the synthesis of thermoresponsive microgels with a well defined VPTT or size and gives access to tune these two crucial parameters in a systematic and controlled way by simply choosing the right composition of the monomer feed. Additionally, the first derivatives of the swelling curves obtained from turbidity measurements were analyzed in detail, allowing a quantitative comparison of the phase transition of different microgels.