Microstructure Characterization of Functionalized Ethylene/Propylene Polyolefins

A combination of matrix-assisted laser desorption/ionization-mass spectrometry, collision-induced dissociation (CID), nuclear magnetic resonance, and size-exclusion chromatography was used to examine the composition of a model but-3-en-1-yl(phenyl)phosphine (BPP)-functionalized poly(ethylene-co-propylene) (EP, ethylene/propylene polyolefin), which had been synthesized using a dual-headed chain shuttling agent (DHCSA). Results indicate that only a small portion of the Mn = 10 kDa EP polymer (primarily in the mass region under 5 kDa) was functionalized with BPP under the applied synthesis conditions. It was hypothesized that long-chain coiling effects hindered the post-reactor chain end functionalizing process of these high-molecular-mass species while preferentially functionalizing the more available low-mass Zn-EP-Zn species. A detailed microstructure characterization was performed using ultra-high-resolution Fourier transform mass spectrometry and CID fragmentation to gain precious insight into their chemical connectivity, end-groups, and incorporation of the linking group of the DHCSA, as well as its most probable location within the polymer chains.