POLYMERIZATION INDUCED BY IONIZING RADIATION AT LOW TEMPERATURES. I. EVIDENCE FOR THE SIMULTANEOUS EXISTENCE OF IONIC AND FREE-RADICAL MECHANISMS IN THE POLYMERIZATION OF STYRENE AND 2,4-DIMETHYLSTYRENE

Journal Article · Sun Apr 01 04:00:00 EST 1962 · J. Polymer Sci.

DOI:https://doi.org/10.1002/pol.1962.1205816621· OSTI ID:4819164

Chen, C S.H.; Stamm, R F

By means of initiation with ionizing radiation, styrene and 2,4- dimethylstyrene were polymerized in the crystalline solid state, in the pure liquid state, and in solution at different temperatures (-80 to 25 deg C). In solution polymerization, it was found that for the same type of initiation, other conditions being constant, the mechanism by which these monomers polymerize is temperature-dependent. At lower temperatures a cationic mechanism predominates; at higher temperatures a free-radical mechanism is in the ascendancy. At intermediate temperatures, both cationic and free-radical polymerizations take place. Furthermore, these intermediate temperatures are different for different monomers, being higher in a monomer whose electronic structure is more favorable for cationic polymerization. The difference in mechanism at different temperatures has been proved by: (1) the dose rate dependencies, both of the polymerization rates and of the molecular weights of the resulting polymers; (2) the activation energies for the polymerization; and (3) the relative reactivities in the polymerizations of styrene and substituted styrenes. (auth)

• Research Organization: American Cyanamid Co., Stamford, Conn.
• NSA Number: NSA-16-023740
• OSTI ID: 4819164
• Journal Information: J. Polymer Sci., Journal Name: J. Polymer Sci. Vol. Vol: 58
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ATOMIC MODELS
CATIONS
CHEMISTRY
CRYSTALS
ENERGY
EXCITATION
FREE RADICALS
GAMMA RADIATION
IONIZATION
IONIZING RADIATIONS
IONS
IRRADIATION
LIQUIDS
METHYL RADICALS
MOLECULAR WEIGHT
MOLECULES
MONOMERS
POLYMERIZATION
RADIATION CHEMISTRY
RADIATION DOSES
RADIATIONS
REACTION KINETICS
SOLIDS
SOLUTIONS
STYRENE
TEMPERATURE
TESTING
WEIGHT
X RADIATION