The present study investigates the challenging approach of post-polymerization modification on polymers with a sterically demanding reaction center. Therefore, the general possibility to functionalize polymethylene moieties was investigated. Poly(benzyl 2-ylidene-acetate) was synthesized by polymerization of benzyl 2-diazoacetate utilizing [(L-prolinate)Rh-I(1,5-dimethyl-1,5-cyclooctadiene)] as a catalyst. Subsequently, the modification of C1 polymerized poly(benzyl 2-ylidene-acetate) with amines was analyzed and the obtained data set was compared with experimental data derived for the C2 analog poly(benzyl acrylate). This is the first study on post-polymerization modification utilizing densely functionalized polymethylenes as starting materials. (c) 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 686-691