What are the difficulties of crosslinking in polyacrylamide?

Difficulties POLYMER, 1990, Vol 31, August 1547 Crosslinking kinetics in polyacrylamide: H. Tobita and A. E. Hamielec mainly arise from the complicated behaviour of the pendant double bonds, namely they may react inter- molecularly and intramolecularly.

What is the kinetics of network formation in free-radical copolymerization?

Kinetics of network formation in free-radical copolymerization of acrylamide and N, N ′-methylenebis-acrylamide in aqueous solution (56.6 g comonomer per litre) at 25°C have been studied. It was found that as high as 80% of pendant double bonds are consumed immediately on polymerization and are wasted in primary cyclization.

What is the effect of primary cyclization on crosslinking reaction?

At high monomer concen- trations, the effect of primary cyclization may be small4, since the probability of finding vinyl groups other than those on its own chain is large. The effects of secondary cyclization and steric hindrance on the crosslinking reaction become significant as f2o increases.

What is the crosslinking density of a primary polymer?

As is shown in Figure 2, the crosslinking density is the same for all primary polymer molecules regardless of their birth time whenrl=r2=dd 1.0, and, as the reactivity ratios rd and r~ deviate from unity, the crosslinking density can differ appreciably with birth time.

Why do crosslinked Pam reactions occur spontaneously at 353 K?

The atomistic model of the crosslinked PAM network was constructed by molecular mechanics and molecular dynamics, and the density of crosslinked PAM and the amount of active crosslinking sites were obtained. The results show that these reactions occurred spontaneously at 353 K because of thermodynamics.

Does X-ray photoelectron spectroscopy provide a crosslinking reaction mechanism?

With the aid of X-ray photoelectron spectroscopy (XPS), a crosslinking reaction mechanism is proposed. PAM was synthesized by free-radical polymerization of acrylamide in a water solution at 303 K using potassium persulfate and sodium bisulfite as initiators.