The development of selective chemistries that are orthogonal to the diverse array of functional groups present in many polymeric systems is becoming an important tool for the synthesis and use of macromolecules in fields ranging from biomedical devices to nanotechnology. By combining copper-catalyzed cycloaddition chemistry with other synthetic transformations such as esterification, amidation, etc., highly efficient and modular simultaneous and cascade functionalization strategies have been developed. These single-step strategies for preparing multifunctional macromolecules represent a significant advance as compared to traditional multistep approaches, and the utility of these concepts is demonstrated by selective preparation of a diverse range of orthogonally functionalized vinyl polymers.

Bis-thymine units were used to noncovalently cross-link a complementary diamidopyridine-functionalized copolymer. Upon combination in noncompetitive solvents, discrete micron-scale spherical aggregates were formed arising from specific three-point polymer-cross-linker hydrogen bonding interactions. The diameter of these microspheres could be controlled through spacer structure. The cross-linking process was fully thermally reversible, with complete dissolution observed at 50 degrees C and reformation of the aggregates upon return to ambient temperature. This process could be repeated multiply, with lower particle dispersity observed arising from the annealing process.

The field of polymer science has undergone a renaissance in recent years as the ability to design, construct, and functionalize macromolecules to fit targeted applications develops. 1 While these applications are diverse, the majority of the polymer structures are based on polymerization or functionalization of vinyl monomers derived from a limited range of families. 2 Classic examples include the extensively studied and widely used styrenic, acrylate, or R-olefin-based monomer systems. The development of a new vinyl monomer family that combines the attractive features of thermal and chemical stability, yet having functional handles for compositional versatility, would represent a significant advance in the area of functionalized materials.Key considerations in the design of a novel type of vinyl monomer include the synthetic accessibility of the basic monomer unit and its ease of functionalization. Recently, the advantages of using the "click" chemistry concept and, specifically, the Cu(I)-catalyzed cycloaddition of azides and alkynes as a powerful tool in the design and synthesis of materials have been demonstrated. 3 The benign reaction conditions, functional group tolerance, quantitative yields, and broad applicability of this chemistry make it ideal for the development of unique vinylic monomers based on a triazole nucleus. In this report, we describe the first examples of an expanding library of triazole-based monomers, which are certain to have importance as polar and chemically versatile components for materials development.As shown in Figure 1, 4-vinyl-1,2,3-triazole monomers are expected to possess many of the outstanding features of traditional monomers, such as styrenics, vinyl pyridines, and acrylates. These features include an aromatic nucleus, stability to both acid and base treatment, a large dipole moment, and access to structural diversity through substitution at N-1. We now report the synthesis of a family of functionalized 4-vinyl-1,2,3-triazole monomers 4 that combine into a single structure many of the desirable features found in established monomers.Two distinct synthetic methods were examined for the preparation of 4-vinyl-1,2,3-triazoles. An initial one-pot approach was driven by the orthogonality of "click" chemistry which allows multiple chemical transformations to occur in solution without interference. 5 Coupling of a mixture of 1-trimethylsilyl-2-vinyl acetylene, 1, and an alkyl/aryl halide leads in one pot to the desired 4-vinyl-1,2,3-triazole derivatives. This is illustrated in Scheme 1 for iodobenzene, 2, which undergoes an in situ azidation by reaction with sodium azide and L-proline in the presence of Cu(I) to give azidobenzene, 3. Concurrently, 1 undergoes reaction with tetra-nbutylammonium fluoride to give the active terminal acetylene, 4.In situ coupling of 3 and 4, again by Cu(I) catalysis, then leads to 1-phenyl-4-vinyl-1,2,3-triazole, 5, in 73% overall yield (Scheme 1).The modular nature of "click" chemistry can also be exploited in an alternative two-step approach fo...