Borane-end-functionalized polymers have been prepared through (i) atom transfer radical polymerization (ATRP) of styrene using a silylated initiator, 1-bromo-1-(4-trimethylsilylphenyl)ethane (PEB-SiMe3), (ii) exchange of the SiMe3 end groups with BBr3, and (iii) modification of the Lewis acidic boron centers with nucleophiles. Ditelechelic alpha,omega-borane-functionalized polymers were obtained through atom transfer radical coupling (ATRC) of the silane-end-functionalized polymers followed by exchange with BBr3 and subsequent reaction with nucleophiles. Self-assembly of the borane-functionalized mono- and ditelechelic polymers into supramolecular structures by means of reversible noncovalent and covalent interactions including Lewis acid-base complexation and boroxine formation has been explored.