Three methyl end-capped oligo(ethylene glycol) (MOEG) ethers (1b-d) and a methoxyderivative (1a) of benzofulvene monomer BF3k were synthesized and induced to polymerize spontaneously by solvent removal to obtain soluble pi-stacked polymers bearing densely grafted MOEG side chains (poly-1b-d) and model polymer poly-1a. The physicochemical features (e.g., solubility, NMR, MALDI-TOF, and absorption/emission spectra, as well as MWD, conformation plot, and thermal properties) of the synthesized polymers were compared in a structure-property relationship study. This approach afforded the following evidence. The structure of poly-1a-d is very similar to that of BF3k, suggesting that the polymerization mechanism is not affected by the presence of the electron-rich methoxy group or bulkier MOEG side chains. However, the latter appear to be capable of affecting the conformational behavior of the polymer backbone. The solubility of poly-1a-d depends on the number of the oligo (ethylene glycol) monomeric units. In particular, poly-1d, featuring a long MOEG side chain (n = 9), shows an amphiphilic character and is soluble in a number of organic solvents, whereas it interacts with water to give isolated macromolecules in equilibrium with nanosized water-soluble aggregates. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2446-2461, 2010