These studies provide the first evidence for styrenephosphaalkene connectivities in a phosphaalkene copolymer. The synthesis and structural characterization of new phosphaalkeneoxazolines, ArP=C(Ph)(3-C(6)H(4)Ox) [1a,b, Ar = Mes (1a), Mes* (1b), Ox = CNOCH(Pr-i)CH2], are reported. The radical-initiated homo- and copolymerization of 1a with styrene affords P-functional poly(methylenephosphine) (4a: Mn = 5300 g mol(1), PDI = 1.2) and poly(methylenephosphine-co-styrene) (5a: Mn = 4000 g mol(1), PDI = 1.1). Multinuclear NMR spectroscopic analyses of 4a and 5a provided evidence for the predominance of an addition-isomerization mechanism for the radical polymerization of 1a. In addition, signals could be assigned to CHPhP(CHPhAr) (i.e., S1a) and ArCH2CH2 (i.e., 1aS) linkages in copolymer 5a. With a monomer feed ratio of 1a:S (1:2, 33 mol % 1a) the inverse gated C-13{1H} NMR spectrum suggested an incorporation of 19 mol % 1a in copolymer 5a. Polymers 4a and 5a were further functionalized to Au(I)-containing macromolecules [4a.AuCl: M-n = 13000, PDI = 1.2; 5a.AuCl: M-n = 7500, PDI = 1.1].