Copolymerization of Ethylene with 1-Butene and Norbornene to Higher Molecular Weight Copolymers in Aqueous Emulsion

Abstract

Ethylene/norbornene and ethylene/1-butene copolymerization with nickel(II) salicylaldiminato complexes [{k2-N,O-6-C(H)=N(2,6-R2C6H3)-2,4 R'2C6H2O}NiMe(pyridine)] (1a, R = 3,5-Me2C6H3, R = I; 1b, R,R=3,5-(F3C)2C6H3; 1c, R' = 3,5-(F3C)2C6H3, R' = I; 2, R = iPr, R' = I) were studied in toluene as a reaction medium and in emulsion, the latter affording polymer dispersions. High molecular weight copolymers (Mn > 10000 g mol-1) are formed. Incorporation of ethylene is much preferred over butene incorporation, XBu/xBu ~0.05 under typical reaction conditions, by comparison incorporation of the strained olefin norbornene is higher, XNB/xNB ~0.25 (X = comonomer mole fraction in polymer; x = comonomer mole fraction in reaction mixture). Dispersions contained copolymers with up to 6 mol % comonomer (12 wt % for 1-butene; 20 wt % for norbornene). Incorporation of a few mol % of norbornene strongly decreases polymer crystallinity, which enhances the film forming properties of dispersions. Microstructure analysis by 13C NMR shows that butene is incorporated in a 1,2-, 1,3- and 1,4-fashion. Whether 1,2- or 1,3-incorporation is predominant depends on the catalyst (nature of R).