Relaxations in a poly(alkyl methacrylate) series are systematically influenced by chemical modifications like the variation of side-chain length, random copolymerization, or molecular weight. Recent results concerning the influence of chemical modification on special parts of the relaxation chart are reviewed. The discussion is focused on two points: (i) The influence of chemical modifications on the crossover region of dynamic glass transition, where the relaxation time of alpha relaxation and Johari Goldstein mode beta approach each other, is discussed. A general crossover scenario with a separate onset of cooperative alpha relaxation is observed for all lower members of this series. High temperature process a above and cooperative alpha relaxation below the crossover are shown to be distinct processes. Chemical modifications related to an increase in free volume shift this scenario mainly to lower frequency and temperature. Further details depend on the specific modification. (ii) The nanophase separation of incompatible main- and side-chain parts in all higher members of the poly(alkylmethacrylate) series is discussed. This effect is concluded from the coexistence of two dynamic glass transitions in these homopolyers, the conventional a (or alpha) process and an additional low temperature glass transition alpha (PE). It is shown that the low T-g process is related to cooperative motions in the polyethlene-like side-chain parts. The existence of static nanodomains in the range of 0.5 to 1.5 nm is confirmed by means of wide and small angle X-ray scattering data. The estimated nanodomain size is compared with the size of dynamic heterogeneities estimated independently from calorimetric data for the polyethylene-like glass transition using the fluctuation approach.