The elongation finite-field (elongation-FF) method is applied to calculate static (hyper)polarizabilities of pi-conjugated chains, with donor and/or acceptor substituents, as well as a heterol block copolymer. Substituent effects on the linear polarizability (alpha) and second hyperpolarizability (gamma) are modest, but a large first hyperpolarizability (beta) can be induced. The dependence of beta on chain length is rationalized on the basis of quasi-symmetry and donor/acceptor strength. Our copolymer consists of alternating blocks containing pyrrole rings and silole rings, which generates a quantum well. Copolymerization induces a fairly small beta that oscillates in sign from block to block. The effect on alpha and gamma is to enhance the contribution of the pyrrole blocks and diminish, by a larger amount, the contribution of the silole blocks.