Pulsed-Addition ROMP: Catalytic Syntheses of Heterotelechelic Polymers via Regioselective Chain Transfer Agents

Regioselective chain transfer agents are used to synthesize narrowly dispersed heterotelechelic polymers with 15-fold decrease in catalyst consumption, using the pulsed addition ROMP (PA-ROMP) technique. Commercially available Grubbs' 3rd generation catalyst (G3) is easily prefunctionalized with the chain transfer agents in a short reaction time (30 min). After addition and consumption of a monomer, the excess chain transfer agent in the reaction medium end functionalizes the polymer chain and regenerates the initiator very quickly (within 10 minutes) via a ring-opening-ring-closing sequence. This regenerated catalyst then initiates the polymerization of a subsequent batch of mono- mer and the process is iterated for 15 times. Excellent control over molecular weight and dispersity from SEC analyses (over 15 pulses) confirmed the high efficacy of the chain transfer agents under this PA-ROMP method. The chain transfer agents are also extremely compatible with the synthesis of highmolecularweightpolymers(M/C=150)withminimalcatalystdecomposition. 1HNMRaswellasMALDI-ToFmassspectrometryfurther confirmed the high degree of chain end functionalization of the synthesized polymers.