Thin films exhibiting second-order nonlinear optical (NLO) properties, as well as materials and methods for producing such films, are provided. The films are formed by depositing, on a substrate, alternate layers of a polyelectrolyte and a low molecular weight chromophore. The chromophore contains an electrophilic group that reacts with a previously deposited polyelectrolyte, and ionizable groups which present absorption sites for the next polyelectrolyte layer. The films find application in, for example, electro-optic modulators and frequency doubling devices.