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Thiol-yne click chemistry is demonstrated as a modular platform for rapid and practical fabrication of highly functional, multicomponent surfaces under ambient conditions. The principle is illustrated using a postmodification strategy in which poly(propargyl methacrylate) brushes were generated via surface-initiated photopolymerization and sequentially functionalized using the radical-mediated thiol-yne reaction. Brush surfaces expressing a three-dimensional configuration of "yne" functionalities were modified with high efficiency and short reaction times using a library of commercially available thiols, including functional thiols that demonstrate applicability for pH responsive surfaces and for bioconjugation. Sequential thiol-yne reactions in conjunction with simple UV photolithography were also applied to afford micropatterned, multicomponent surfaces. The practicality of the platform was further demonstrated by carrying out thiol-yne surface reactions in sunlight, suggesting the possibility of large scale modifications using renewable energy resources. Considering the mild reaction conditions, rapid throughput, and compatibility with orthogonal chemistries, we expect this platform to find widespread use among the materials science community.

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Precursor carbazole terminated dendrons and dendrimers up to generation four (G4-D) were synthesized using a convergent approach. Sonication as a means of facilitating organic reactions in dendrimer chemistry was explored resulting in very facile and very fast (up to 50x) reaction times compared to those using traditional reflux conditions. The limits of peripheral group functionality were explored as a function of generation. The electrochemical cross-linking of the dendrimers as thin films revealed unusual cyclic voltammetry (CV) behavior depending upon the generations, which were significantly different from their linear counterpart, Poly(N-vinylcarbazole) (PVK). G1-D showed a higher extent of intermolecular cross-linking while G4-D showed a higher extent of intramolecular cross-linking. The formed films were optically clear and possess superior energy band gap properties making them an alternative candidate over PVK for future hole-transport layer materials in electro-optical devices.

We describe a facile route to prepare functional macromonomers using reversible additionfragmentation chain transfer (RAFT) polymerization. This was demonstrated in the synthesis of R-functionalized norbornenyl, vinyl, and cinnamyl macromonomers using functional chain transfer agents bearing these end groups. Various homopolymer macromonomers of well-controlled molecular weights were synthesized with nearquantitative incorporation of the end group functionality. The use of norbornenyl and vinyl CTA's resulted in a highly quantitative polymerization of styrene and methyl methacrylate (MMA) monomers yielding well-defined linear macromonomers. On the other hand, monomers with a lower reactivity such as methyl acrylate (MA) exhibited a broader polydispersity. The cinnamyl-functionalized telechelics proved the most challenging due to a competitive chain transfer between the cinnamyl group and the RAFT CTA at higher conversions. To demonstrate utilization of the macromonomer functionality, we synthesized the poly(norbornene-g-PMMA) copolymer based on the ring-opening metathesis polymerization (ROMP) of the norbornenyl-functionalized PMMA macromonomer. The main advantage of this new approach should be in the ability to prepare a variety of macromonomer structures utilizing the mild and tolerant conditions of RAFT polymerization.

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In this study, we demonstrate the synthesis of branched oligothiophene dendrons that act as electroactive surfactants for the capping of CdSe nanocrystals through a ligand exchange process. The number of dendrons per nanocrystal and the nature of surface coordination interactions were studied in detail using UV−vis, FT-IR, AFM, and photoluminescence spectroscopies. These dendron/nanocrystal complexes are very soluble in nonpolar solvents and exhibit photoinduced charge-transfer interactions between the two species. One-layer photovoltaic cells were fabricated that showed initial power conversion efficiencies of 0.29%.

A comparative analysis of the copolymerization behavior between an electro-active terthiophene and a carbazole moiety of a conjugated polymer precursor was investigated using electrochemical and hyphenated electrochemical methods. Five different precursor polymers were first synthesized and characterized using NMR, IR, and GPC. The polymers include homopolymers of individual electro-active groups (P3T, P-CBZ) and different compositions of 25, 50, and 75% (P3TC-25, P3TC50, and P3TC-75) with respect to the two electro-active groups. Since the oxidation potentials of terthiophene and carbazole lie very close to each other, highly cross-linked copolymer films of varying extent were produced depending on the composition. The copolymerization extent was found to be dependent primarily on the amount of the terthiophene, which in this case provided for a more efficient carbazole polymerization and copolymerization than with just carbazole alone (homopolymer). The extent of copolymerization, electrochromic properties, and viscoelastic changes was quantitatively investigated using a number of hyphenated electrochemistry techniques: spectro-electrochemistry, electrochemical quartz crystal microbalance studies (EC-QCM), and electrochemical surface plasmon resonance spectroscopy (EC-SPR). Each technique revealed a unique aspect of the electrocopolymerization behavior that was used to define structure-property relationships and the deposition/copolymerization mechanism.