Closing the 1-5 mu m size gap:Temperature-programmed, fed-batch synthesis of mu m-sized microgels

Microgels below 1 mu m and above 20 mu m are readily accessible; however, obtaining them in size 1-10 mu m still remains a challenge. We present a surfactant-free precipitation polymerization approach, combining temperature-ramp (T-ramp) and fed-batch, generating 1-5 mu m in diameter poly(N-Vinylcaprolactam) (pVCL) microgels. Confocal microscopy and dynamic light scattering (DLS) confirm that the size of temperature-responsive pVCL microgels can be adjusted by the feeding ratio. The experimentally determined microgel sizes match the model-based predictions well. The developed synthesis method achieves high monomer conversions and provides high microgel yields as determined by Raman spectroscopy.