Experimental study of swelling and shrinking kinetics of spherical poly(N,N-diethylacrylamide) gel with continuous phase transition

The kinetics of swelling and shrinking of spherical particles of poly(N,N-diethylacrylamide) (DEAA) gel, prepared with static mixing technology, was investigated experimentally. The shrinking process was separated into late shrinking and initial shrinking by the skin layer effect. When the final temperature of temperature swing experiments was above the lower critical solution temperature (LCST) of polyDEAA, the apparent increase in the response rate constant (kv) and the polymer diffusion constant (D) were due to reduction of the friction coefficient between polymer chains and water, arising from decrease in the water viscosity. When the final temperature was below the LCST, the main factor determining kv and D was the change in the network structure of DEAA particles caused by the final temperature. The initial temperature affected the values of kv and apparent diffusion constant Dapp only in initial shrinking, in which the decrease in D with increase in the initial temperature came mainly from the spatial limitation.