Bogdan Barboiu

Designing functional aromatic multisulfonyl chloride initiators for complex organic synthesis by living radical polymerization

The similarities and differences between sulfonyl chloride and alkyl halide initiators for metal-catalyzed living radical polymerizations are discussed. The differences in the rates of formation, reactivities, and reactions of primary radicals derived from sulfonyl halides and alkyl halides demonstrated the design principles for monosulfonyl and multisulfonyl chlorides that provided quantitative initiation and higher rates of initiation than of propagation. Multifunctional initiators with two, three, four, six, and eight sulfonyl chloride groups that produced perfect star polymers in 95% conversions were designed and synthesized on the basis of these principles.

CuI and CuII salts of group VIA elements as catalysts for living radical polymerization initiated with sulfonyl chlorides

ABSTRACT: The living radical polymerization of methyl methacrylate initiated fromsulfonyl chlorides and catalyzed by the new catalytic systems Cu 2 Y/Bpy and CuY/Bpy,where Y is O, S, Se, or Te and Bpy is 2,29-bipyridine, is described. An induction time wasobserved in all polymerization experiments. The values of the experimental rate con-stants of polymerization ( k p exp ) increased whereas the corresponding induction timesdecreased in the order Y 5 O , S , Se , Te. For the entire series of catalysts, k p exp forCuY was less than k p exp for Cu 2 Y. A mechanistic interpretation that involves the in situ generation of the CuCl/CuCl 2 pair, starting from Cu 2 Y or CuY, is provided.

Fluorocarbon‐ended polymers: Metal catalyzed radical and living radical polymerizations initiated by perfluoroalkylsulfonyl halides

Perfluoroalkylsulfonyl chlorides and bromides initiate metal catalyzed free radical polymerization of both hydrocarbon and fluorocarbon monomers affording polymers with perfluoroalkyl end groups. In the case of styrene (S) and methyl methacrylate (MMA) with Cu-based catalysts the process affords polymers with a relatively narrow molecular weight distribution and linear dependence of molecular weight on conversion, suggesting that a living radical polymerization mechanism occurs. The orders of reaction in monomer, initiator and catalyst for these polymerizations were determined. In the case of PMMA, the detailed structure of a perfluorobutane chain-end was determined by NMR analysis. Perfluoroalkylsulfonyl chlorides are stable in neutral aqueous media. This permits their use as initators for fluoroolefin polymerizations in H 2 O. Poly(tetrafluoroethylene-co-hexafluoropropylene) was obtained in good yield with few ionic end groups. The aqueous fluoroolefin polymerization appears to be catalyzed by metal zero species from the reactor walls.

Metal-catalyzed living radical graft copolymerization of butyl methacrylate and styrene initiated from the structural Defects of narrow molecular weight distribution poly(vinyl chloride)†

Poly(vinyl chloride) (PVC) prepared by the radical polymerization of vinyl chloride (VC) contains allyl chloride and tertiary chloride structural defects. The graft copolymerization initiated from the structural defects of PVC should eliminate the structural defects of PVC and, therefore, should provide novel graft copolymers that will exhibit both new physical properties and higher thermal stability than the parent PVC. The preliminary graft copolymerization experiments reported previously from our laboratory were performed with PVC with broad molecular weight distribution and did not allow kinetic experiments to be performed. Model compounds for the allyl chloride defects in PVC were used as initiators and gave almost quantitative initiation in the case of styrene (0.99), while for methacrylates the maximum initiator efficiency was only 0.40. Based on these data, the successful grafting of PVC with butyl methacrylate (BMA) and the less successful grafting of PVC with styrene were difficult to be explained. This publication reports the metal catalyzed living radical graft copolymerization experiments initiated from the structural defects of PVC with narrow molecular weight distribution. These experiments demonstrate that, contrary to the results obtained using model compounds as initiators, the structural defects of PVC provide an excellent initiation efficiency for the graft copolymerization of BMA and a less efficient initiation for the case of styrene. Under suitable reaction conditions, the initiation efficiency from the structural defects of PVC for the graft copolymer- ization of BMA can be considered to be quantitative.

Organocopper-catalyzed living radical polymerization initiated with aromatic sulfonyl chlorides

The living radical polymerization of methyl methacrylate initiated from aromatic sulfonyl chlorides and catalyzed by the new catalytic systems CuSBu/bpy CuSPh/bpy and CuCCPh/bpy (bpy = 2,2′-bipyridine) is described. For a target degree of polymerization of 200, lowering the ratio of catalyst to sulfonyl chloride group from 1/1 to 0.25/1 mol/mol decreases the values of the experimental rate constant of polymerization from 5.12 × 10−2, 2.4 × 10−2, and 1.87 × 10−2 min−1 to 1.8 × 10−3, 4.9 × 10−3, and 4.2 × 10−3 min−1 for CuSBu, CuSPh, and CuCCPh, respectively, whereas the corresponding initiator efficiency increases from 62 to 99%. The external orders of reaction in the catalyst are 0.79 for CuSPh, 0.88 for CuCCPh, and 1.64 for CuSBu. A mechanistic interpretation that involves the in situ generation of, most likely, the real catalyst CuCl, starting from combinations of CuSBu, CuSPh, and CuCCPh and sulfonyl chloride or alkyl halide growing species, is suggested.