Synthesis and Visualization of Densely Grafted Molecular Brushes with Crystallizable Poly(octadecyl methacrylate) Block Segments

Densely grafted molecular brushes with AB and ABA “block−graft” architectures, i.e., pODMA-b-p(BPEM-g-nBuA) and pODMA-b-p(BPEM-g-nBuA)-b-pODMA, were synthesized by the “grafting from” approach using atom transfer radical polymerization (ATRP). The backbone macroinitiators were prepared in three steps. First, ATRP of ODMA or HEMA-TMS was carried out from mono- or difunctional initiators to form macroinitiators, followed by ATRP of HEMA-TMS or ODMA initiated from these macroinitiators to obtain pODMA-b-pHEMA-TMS or pODMA-b-pHEMA-TMS-b-pODMA macromolecular backbone precursors. Finally, these precursors were esterified to pODMA-b-pBPEM and pODMA-b-pBPEM-b-pODMA backbone macroinitiators. The pnBuA side chains were grafted from the pBPEM segments of these backbone macroinitiators by ATRP. AFM measurement of the final molecular brushes demonstrated that the backbone of the brushes, the pBPEM segment, was almost completely stretched on the mica surface. pODMA segments tended to associate, due to crystallization of the relatively long C18 chains, and form “dimers” for AB block brushes and “multimers” or “circles” for ABA block brushes.