Properties and internal structure of thermoresponsive acrylamide based core-shell microgels
Résumé
A gel is a dispersed system which consists of at least two different components: a solid or flexible mesh and a fluid (water in the present case). Microgels are gels in the size range of 10 nm to 1 μm and can be used in a wide range of applications like drug delivery and smart surface coatings. If the microgel consists of acrylamides like N-isopropylmethacrylamide (NIPMAM) or N-n-propylacrylamid (NNPAM) as network component, they show a volume phase transition (VPT) at a certain temperature, the volume phase transition temperature (VPTT). An increase in temperature above the VPTT leads to an abrupt decrease in size and a decrease in temperature leads to an abrupt increase in size. The VPTT is specific for each monomer. To use microgels in sensors or for nanoactuators the thermoresponse has to be precise. That is why we investigated microgels with a core-shell architecture containing NIPMAM and NNPAM. These particles show a tunable linear change in size between 22 °C and 43 °C. Furthermore, we deposited these microgels on surfaces and investigated the properties of the coating. The properties of these particles and coatings can be adjusted by selecting specific synthesis conditions. We then did small angle neutron scattering (SANS) to determine the internal structure of the core-shell microgel.