Radical heterogeneous polymerization behavior ofN-methyl-?-fluoroacrylamide in benzene

The polymerization of N-methyl-alpha -fluoroacrylamide (NMFAm) initiated with dimethyl 2,2 ' -azobisisobutyrate (MAIB) in benzene was studied kinetically and with electron spin resonance. The polymerization proceeded heterogeneously with the highly efficient formation of long-lived poly(NMFAm) radicals. The overall activation energy of the polymerization was 111 kJ/mol. The polymerization rate (R-p) at 50 degreesC is given by R-p = k[MAIB](0.75 +/-0.05) [NMFAm](0.44 +/-0.0.5). The concentration of the long-lived polymer radical increased linearly with time. The formation rate (R,.) of the long-lived polymer radical at 50 degreesC is expressed by R-p . = k[MAIB](1.0 +/-0.1) [NMFAm](0 +/-0.1). The overall activation energy of the long-lived radical formation was 128 kJ/mol, which agreed with the energy of initiation (129 kJ/mol), which was separately estimated. A comparison of R-p . with the initiation rate led to the conclusion that 1-methoxycarbonyl-1-methylethyl radicals (primary radicals from MAIB), escaping from the solvent cage, were quantitatively converted into the long-lived poly(NMFAm) radicals. Thus, this polymerization involves completely unimolecular termination due to polymer radical occlusion. H-1 NMR-determined tacticities of resulting poly(NMFAm) were estimated to be rr = 0.34, mr = 0.48, and mm = 0.18. The copolymerization of NMFAm(M,) and St(M,) with MAIB at 50 degreesC in benzene gave monomer reactivity ratios of r(1) = 0.61 and r(2) = 1.79. (C) 2001 John Wiley & Sons, Inc.