SynopsisThe kinetics of chain transfer to the bifunctional initiating and transfer agents (binifem) 1,4di(2chloro-2-propyl)benzene (p-DCC), 1,3di(2chloro-2-propyl)-5-tert-butylbenzene (rn-tBuDCC), and 1,3di(2chloro-2-propyl)-4,6-dimethylbenzene (rn-DMeDCC) in the polymerization of isobutylene has been investigated. Chain transfer to monomer was shown to be absent up to -20°C in CH,Cl/n-hexane and CH,Cl,/n-hexane mixtures using the rn-tBuDCC/BCl, binifer system. Chain transfer constants (C,) to rn-tBuDCC and k J k , ratios determined in the range from -30°C to -80°C in CH,Cl/n-hexane mixtures and pure CH,Cl solvent are reported, and the activation energy differences E l , , -E , and E, -E , were calculated. Chain transfer constants to p-DCC and rn-DMeDCC were determined by the use of pure CH3C1 diluent at -50°C. The chain transfer reactivity of five different inifers is discussed and compared based on C, values obtained under identical conditions, with special regard to the new, sterically hindered binifer m-DMeDCC of extraordinary reactivity.Polymerizations were carried out in the range from -80°C to -20°C under a dry nitrogen atmosphere in a dry box using a three-necked flask (250 mL) equipped with a stirrer. Details of the procedures have been de~cribed.3*~,~ 'H-NMR spectra were taken by a Varian T-60 NMR spectrometer using carbon tetrachloride solutions (-20% by weight) and TMS standard.
RESULTS AND DISCUSSIONChain transfer studies, where applicable, are based on m, equations derived earlier.'S2 Thus
