Core-shell brush copolymers were prepared on the basis of a tandem synthetic strategy and used as single molecular templates for the preparation of polymeric nanomaterials. An alkoxyamine-functionalized norbornene monomer was prepared and then polymerized by ring-opening metathesis polymerization. The well-defined polymer (Mn = 122 kDa, Mw/Mn = 1.13) contained one alkoxyamine functionality per repeat unit and was then used as a polyfunctional macroinitiator for sequential nitroxide-mediated radical polymerizations of isoprene and tert-butyl acrylate. The resulting well-defined brush copolymer (Mn = 1410 kDa, Mw/Mn = 1.23) was transformed to an amphiphilic core-shell brush copolymer comprising poly(isoprene)-b-poly(acrylic acid) grafts by hydrolysis. Subsequent cross-linking of the poly(acrylic acid) block segments afforded peripherally cross-linked brush copolymer nanostructures, which served, finally, as templates for hollowed nanoscale frameworks by ozonolysis of the poly(isoprene)-based cores. Each transformation led to dramatic changes in the nanoscale composition and structure which were detected by combinations of spectroscopic measurements, atomic force microscopy imaging in the solid state, and/or dynamic light-scattering characterization in aqueous solution.

Using Grubbs' catalyst Cl2(PCy3)2Ru=CHPh for tandem catalysis, poly(methyl methacrylate)-based brush polymers were prepared by one-pot sequential ring-opening metathesis polymerization (ROMP) and atom transfer radical polymerization (ATRP) via an inimer having both an alpha-bromoisobutyrate ATRP initiator functionality and an exo-norbornenyl ROMP monomer functionality. The surface morphologies and aggregation behaviors of these nanoscopic single molecules were studied by tapping-mode atomic force microscopy measurements on mica.

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Atom transfer radical polymerization (ATRP) using a norbornenyl-functionalized initiator was established as a new synthetic method for the preparation of macromolecules that are both R-norbornenyl macromonomers and ω-haloalkyl macroinitiators. When styrene, methyl methacrylate, and tert-butyl methacrylate were used as monomer or constituted comonomer pairs, the (co)polymerization was well-controlled and the norbornenyl functionality was intact. The resulting homopolymer or statistical copolymer-based macromonomers had linear structures, quantitative R-norbornenyl functionality, controlled number-average molecular weights (M n ) 3600-24300 Da), and narrow monomodal molecular weight distributions (Mw/Mn ) 1.07-1.35). Their ω-halide terminals further allowed them to serve as macroinitiators for the syntheses of block copolymer-based R-norbornenyl macromonomers by ATRP. In contrast, the norbornenyl functionality exhibited considerable competitive reactivity in the polymerizations of methyl acrylate and tert-butyl acrylate, resulting in mixed linear and branched macromonomers/ macroinitiators. TGA analysis of R-norbornenyl macromonomers showed that the presence of norbornenyl functionality appreciably enhanced their thermal stability.

Polydimethylsiloxane (PDMS) block copolymers were synthesized by using PDMS macroinitiators with copper‐mediated living radical polymerization. Diamino PDMS led to initiators that gave ABA block copolymers, but there was low initiator efficiency and molecular weights are somewhat uncontrolled. The use of mono‐ and difunctional carbinol–hydroxyl functional initiators led to AB and ABA block copolymers with narrow polydispersity indices (PDIs) and controlled number‐average molecular weights (Mn's). Polymerization with methyl methacrylate (MMA) and 2‐dimethylaminoethyl methacrylate (DMAEMA) was discovered with a range of molecular weights produced. Polymerizations proceeded with excellent first‐order kinetics indicative of living polymerization. ABA block copolymers with MMA were prepared with between 28 and 84 wt % poly(methyl methacrylate) with Mn's between 7.6 and 35 K (PDI <1.30), which show thermal transitions characteristic of block copolymers. ABA block copolymers with DMAEMA led to amphiphilic block copolymers with Mn's between 9.5 and 45.7 K (PDIs of 1.25–1.70), which formed aggregates in solution with a critical micelle concentration of 0.1 g dm−3 as determined by pyrene fluorimetry experiments. Monocarbinol functional PDMS gave AB block copolymers with both MMA and DMAEMA. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1833–1842, 2001