The incorporationphosphorusinto the main chain or side chain of a macromoleculeis a rapidly growing interdisciplinary area of research.The unique oxidation states and coordination numbers of phosphorus in the main chain impart chemical functionality, semi-conducting, optoelectronic and physical properties that are often quite different from their organic counterparts. Of particular interest is their prospect to change properties in response to an external stimuli, either chemical or physical. This presentation will focus on our development of a polymerization chemistry for the P=C bonds of phosphaalkenes which is at the same time both analogous and very different to olefin polymerization. The resultant phosphine polymers, poly(methylenephosphine)s or PMP’s, are highly chemically functional. Also discussed will be our development of conjugated polymers featuring phosphine-alkyne moieties in the main chain, poly(p-phenyleneethynylene)s (PPYP’s). PPYP’s have emissive properties that are highly sensitive to the chemical environment at phosphorus and are therefor attractive as sensors. A case will be made that some of these new materials should be considered as “smart” polymers.