  Exercising direct control over the unusual electronic structures arising from
quantum confinement effects in graphene nanoribbons (GNRs) - atomically defined
quasi one-dimensional (1D) strips of graphene - is intimately linked to
geometric boundary conditions imposed by the bonding within the ribbon. Besides
composition and position of substitutional dopant atoms, the symmetry of the
unit cell, the width, length, and termination of a GNR are integral factors
that collectively can give rise to highly tuneable semiconductors, innate
metallicity arising from topological zero-mode engineering, or magnetic
ordering in spin-polarized lattices. Here we present a rational design that
integrates each of these interdependent variables within a modular bottom-up
synthesis. Our hybrid chemical approach relies on a catalyst transfer
polymerization (CTP) that establishes uniform control over length, width, and
end-groups. Complemented by a surface-assisted cyclodehydrogenation step,
uniquely enabled by matrix-assisted direct (MAD) transfer protocols, geometry
and functional handles encoded in a polymer template are faithfully mapped onto
the structure of the corresponding GNR. Bond-resolved scanning tunnelling
microscopy (BRSTM) and spectroscopy (STS) validate the robust correlation
between polymer template design and GNR electronic structure and provide a
universal and modular platform for the systematic exploration and seamless
integration of functional GNRs with integrated circuit architectures.
