The pursuit of methods for design and preparation of robust nanoarchitectonic systems with integrated functionality through bottom-up methodologies remains a driving force in molecular nanotechnology. Through the use of π-conjugated covalent bonds, we demonstrate a general substrate-mediated, soft solution methodology for the preparation of extended π-conjugated polymeric nanoarchitectures in low-dimensions. Based on thermodynamic control over equilibrium polymerization at the solid-liquid interface whereby aromatic building blocks spontaneously and selectively link, close-packed arrays composed of one-dimensional (1-D) aromatic polymers and two-dimensional (2-D) macromolecular frameworks have been prepared and characterized by in situ scanning tunneling microscopy. This methodology eliminates the necessity for severe conditions and sophisticated equipment common to most current fabrication techniques and imparts almost infinite possibilities for the preparation of robust materials with designer molecular architectures.