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The coupling of hyperbranched polychloromethylstyrene (PCMS) radicals with nitrone is studied in this work. Hyperbranched PCMS radicals are generated by a redox reaction of terminal chloride groups with Cu(I)Cl. The molecular weight data show that nitrone mediated radical coupling of PCMS is a kind of step polymerization. The molecular weights of the coupled products in a fixed coupling reaction time increase as the contents of nitrone increase in a wide concentration range, whereas are less affected by the content of CuCl. FTIR and NMR spectra prove the formation of alkoxyamine in the mid-chains arising from nitrone-mediated coupling. The nitrone-coupled hyperbranched polymers show the birefringent property if being watched in a crossed polarizing microscope. The intrinsic viscosity data imply that the nitrone-coupled hyperbranched polymers in solution behave like rod-like structures. These nitrone-coupled hyperbranched polymers are thermodegradable. This kind of cylindrical polymers with highly branched substructures may find important application as anisotropic monomolecular gels or molecular reinforcement, catalyst hosts, etc. [ABSTRACT FROM AUTHOR]

The formation of ABA-type triblock copolymers is studied as a function of chain end structure of the second block (benzylic alkyl bromides compared to α-bromo esters) and the inclusion of the radical trap 2-methyl-2-nitrosopropane (MNP) in the coupling reaction. In the case of coupling poly(methyl methacrylate)- block-polystyrene (PMMA- b-PSBr), both traditional atom transfer radical coupling (ATRC) reactions and analogous radical trap-assisted ATRC (RTA-ATRC) reactions lead to ABA-type triblock copolymers. Contrastively, coupling of polystyrene- block-poly(methyl acrylate) precursors is unsuccessful in ATRC reactions lacking the nitroso radical trap, yet forming high amounts of triblock in analogous RTA-ATRC reactions, consistent with lower KATRP values of the chain end α-bromo ester. Synthesis of the triblocks is also attempted using coupling reactions of dibrominated PS and monobrominated poly(methyl acrylate), relying on selective coupling to be successful. In the presence of the radical trap MNP, substantial coupling is observed with gel permeation chromatography data indicating the formation of the triblock. Traditional ATRC reactions performed in an analogous manner do not produce the triblock to an appreciable extent, with lowered extents of coupling overall. [ABSTRACT FROM AUTHOR]

The current study describes the synthesis of iodine-end-capped polystyrene (PS) and poly(methyl methacrylate) (PMMA) precursors using reverse iodine-transfer polymerization, which, in a second step, are used in nitrone-mediated radical coupling (NMRC) reactions. Initially, the reverse iodine polymerization of both monomers is studied and optimized in order to obtain iodine-end-capped materials with controlled molecular weights and low dispersities. Subsequently, NMRC of both PS and PMMA precursors is carried out in the presence of CuCl as a halide-exchange agent. Coupling efficiencies of xc = 0.754 for PS-I and 0.84 for PMMA-I are observed; however, the addition of 10 equivalents of styrene is required to promote the coupling in the case of methacrylate. The presence of the desired alkoxyamine functionality in mid-chain position of the products is evidenced via quenching experiments. [ABSTRACT FROM AUTHOR]

A simple and efficient method to prepare telechelics by visible-light-induced radical coupling is presented. Irradiation of the toluene solutions of bromo-terminated polystyrenes prepared by atom transfer radical polymerization (ATRP) in the presence of an ester functional ATRP initiator and dimanganese decacarbonyl (Mn2(CO)10) at λ = 400-500 nm leads to the formation telechelic polymers through radical-radical coupling. Adaptability of the process for the preparation of mono- and bifunctional telechelics is demonstrated under variety of conditions of ATRP and coupling steps. [ABSTRACT FROM AUTHOR]

A new type of polyrotaxane based on the threading of γ‐cyclodextrins (γ‐CDs) along a highly hydrophobic polymer, polyisobutylene (PIB), is successfully prepared and finely characterized. The used radical coupling associated with tuned reaction time and temperature leads to a fast and controlled necklace synthesis with low reagent consumption. Synthesis exhibits appealing conversion and threading rates with almost 100% and 62–73%, respectively. A combination of well‐established SEC and NMR techniques, with a more forefront MALDI‐TOF MS approach, provides details on the original PIB and the resulting polyrotaxanes (Mw, Mn, PDI, and average number of γ‐CD threaded). Interestingly, tetramethylguanidinium‐2‐(4‐hydroxyphenylazo)benzoate in DMF for MALDI analysis is revealed as a suitable matrix to overcome solubility troubles widely observed with PIB. Moreover, rotaxanation appears as an alternative to the grafting of polar groups to modify/handle hydrophobic polymers. Such an approach offers new opportunities to achieve the synthesis, with unambiguous evidence, of new supramolecular necklaces based on highly hydrophobic polymers. Polyrotaxane based on γ‐cyclodextrins threaded along a polyisobutylene backbone is successfully synthesized and finely characterized. An optimized radical coupling leads to fast and controlled necklace synthesis with conversion and threading rates close to 100% and 62–73%, respectively. All starting materials as well as resulting necklaces are analyzed by SEC, NMR, and MALDI‐TOF MS, giving unambiguous evidences of the successful synthesis. [ABSTRACT FROM AUTHOR]