Nano- and Microgels of Poly(Vinyl Methyl Ether) Obtained by Radiation Techniques
Janusz M. Rosiak
Institute of Applied Radiation Chemistry,
Wroblewskiego St. 15, 93-590 Lodz, Poland
Hydroxyl radicals were generated radiolytically
in N2O-saturated aqueous solutions in the presence of poly(vinyl methyl ether) (PVME, 6×104 Da, 10-3-10-2
At low temperatures and low polymer concentrations the intramolecular crosslinking reaction is favored. A large number of radicals are formed in a short period of time during each pulse of accelerated electrons. The combination of the formed polymeric radicals is in the intramolecular way and nanogels formation occurs. Without changes in the molecular weight the dimension (radius of gyration and hydrodynamic radius), as well as the intrinsic viscosity of the nanogels decreases with increasing radiation dose. At temperatures above the LCST PVME molecules collapse to globular particles. Electron beam irradiation of these stable phase-separated structures leads to the formation of temperature-sensitive microgel particles. The additive-free method of crosslinking of polymers in aqueous solutions by high-energy radiation offers the application of these microgels in the field of medicine because of no remaining toxic substances (monomers, initiators, crosslinkers, etc.). The variation of the crosslinking density and the particle diameter can be performed by varying the polymer concentration and the radiation dose. Applying the closed-loop system reduces the amount of un-crosslinked molecules (sol content).