We investigate the behavior of polymer chains embedded in a lamellar matrix by considering both a regular periodic environment and the effect of disturbances. By using the Green’s function formalism and an attractive Kronig-Penney model, we obtain analytically exact results. For the case of a regular lamellar matrix of period xi a long polymer chain is characterized by an effective segment length l(eff), in analogy to the effective mass of electrons in solids, For potential wells deep enough there appears a gap of forbidden states which separates the low-lying, adsorption band from the higher lying, desorption band. Due to the ground-state dominance, for polymers only the lowest lying states are of physical relevance. Isolated defects of the periodic structure may localize the polymer, in the sense that infinitely long chains are confined inside a region of finite extent L around the defect. For a single defect we find L=1/(epsilon Delta xi), where epsilon is the strength of the periodic potential and Delta xi is the deviation from the periodicity. This is also valid for finite chains when their number of segments exceeds the cross-over value N-L=2L(2)/l(eff)(2).