CROSSLINKING OF POLYMERS IN SOLUTION UNDER THE INFLUENCE OF $gamma$- RADIATION
Polyvinylpyrrolidone, polyvinyl acetate, and polystyrene simultaneously undergo intermolecular crosslinking and degradation of their main chains when irradiated in solution. Below a critical concentration which depends on the Bolvent no continuous network is built up since degradation is the predominant reaction in dilute solutions. Only a few solvents or mixtures of solvents in which this critical concentration is smaller than 10 g/100 cc have been found for each of these polymers. No relation exists between the radiation sensitivity of the solvent and the rate of crosslinking of dissolved polymers. However, crosslinking seems to be slightly favored in poor solvents. Observations on the gel dose show that this often increases with increasing polymer concentration in concentrated solutions. Radical scavengers inhibit crosslinking of these polymers and often are incorporated into the polymers. A mechanism is proposed in which the formation of macroradicals and low molecular weight radicals froin the solvent by direct action of radiation are the primary steps. Crosslinks are formed by combination of macroradicals. The solvent radicals sensitize or retard crosslinking by attacking the polymer to form additional macroradicals or by deactivating macroradicals, respectively. The increase in gel dose in concentrated solutions is attributed to the decrease in the rate constant for the combination of the free macroradicals in viscous soluiions as is well known from the autoacceleration observed in the bulk polymerization of a number of vinyl monomers. (auth)
- Research Organization:
- Mellon Inst., Pittsburgh
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-14-003543
- OSTI ID:
- 4200466
- Journal Information:
- Journal of Physical Chemistry (U.S.), Journal Name: Journal of Physical Chemistry (U.S.) Vol. Vol: 63; ISSN JPCHA
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
Similar Records
RADIATION-INDUCED EFFECTS ON WATER-SOLUBLE POLYMERS IN THEIR AQUEOUS SOLUTIONS. II. CO-CROSSLINKING BETWEEN TWO DIFFERENT POLYMERS
EFFECTS OF GAMMA RADIATION ON POLYMER IN SOLUTION. I. POLY(VINYL ACETATE)