The gamma-initiated reversible addition-fragmentation chain transfer mediated free-radical graft copolymerization of styrene and m-isopropenyl-alpha,alpha'-dimethylbenzyl isocyanate (TMI) from a polypropylene (PP) solid phase was performed with cumyl phenyldithioacetate (CPDA) as the chain-transfer agent. The initial CPDA concentration was 8 x 10(-3) mol L-1. Polymerizations were performed with a dose rate of 0.18 kGy h(-1) at the ambient temperature. Initial comonomer mixtures with 15, 30, and 50 mol % TMI were used. Depending on the amount of TMI in the initial comonomer mixture, the plot of the grafting ratio versus the time showed two grafting regimes (for 15 and 50 mol % TMI) or one (for 30 mol % TMI). Scavenger lanterns with 15 and 50 mol % TMI featured two isocyanate loading regimes, the second with higher loading capacities. The scavenger lanterns with 30 mol % TMI showed a linear loading capacity over the full grafting ratio. A maximum loading capacity of 110 mu mol per scavenger lantern was achieved with 50 mol % TMI at a grafting ratio of approximately 60 wt %. (c) 2005 Wiley Periodicals, Inc.