Tomislav Pintauer

Functional polymers by atom transfer radical polymerization

Abstract Atom transfer radical polymerization (ATRP) is one of the most successful methods to polymerize styrenes, (meth)acrylates and a variety of other monomers in a controlled fashion, yielding polymers with molecular weights predetermined by the ratio of the concentrations of consumed monomer to introduced initiator and with low polydispersities. Because of its radical nature, ATRP is tolerant to many functionalities in monomers leading to polymers with functionalities along the chains. Moreover, the initiator used determines the end groups of the polymers. By using a functional initiator, functionalities such as vinyl, hydroxyl, epoxide, cyano and other groups have been incorporated at one chain end, while the other chain end remains an alkyl halide. The polymer can be dehalogenated in a one-pot process or the halogen end groups can be transformed to other functionalities using nucleophilic substitution reactions or electrophilic addition reactions. Moreover, utilizing the ability of the halogen chain end to be reactivated, radical addition reactions can be used to incorporate allyl end groups, insert one less reactive monomer unit at the chain end, or to end-cap the polymer chain. With ATRP, functionality and architecture can be combined resulting in multifunctional polymers of different compositions and shapes such as block copolymers, multiarmed stars or hyperbranched polymers.

Structural comparison of CuII complexes in atom transfer radical polymerization

The molecular structures of [CuII(dNbpy)2Br]+[CuIBr2]−, CuII(pmdeta)Br2, CuII(tNtpy)Br2, [CuII(hmteta)Br]+[Br]− and [CuII(cyclam)Br]+[Br]− n[dNbpy=4,4′-di(5-nonyl)-2,2′-bipyridine, pmdeta=N,N,N′,N″,N″-pentamethyldiethylenetriamine, tNtpy=4,4′,4″-tris(5-nonyl)-2,2′:6′,2″-terpyridine, hmteta=1,1,4,7,10,10-hexamethyltriethylenetetramine, Me4cyclam=1,4,8,11-tetraaza-1,4,8,11-tetramethylcyclotetradecane] isolated from atom transfer radical polymerizations (ATRP) were determined. The CuII complexes showed either a trigonal bipyramidal structure as in the case of the dNbpy ligand, or a distorted square pyramidal coordination in the case of triamines and tetramines. Depending on the type of amine ligand, the complexes were either neutral (triamines) or ionic (bpy and tetramines). The counterions in the case of the ionic complexes were either bromide (Me4cyclam and hmteta) or the linear [CuIBr2]− anion (dNbpy). No direct correlation was found between the CuII–Br bond length and the deactivation rate constant in ATRP, which suggests that other parameters such as the entropy for the structural reorganization between the CuI and CuII complexes might play an important role in determining the overall activity of the catalyst in ATRP.

Electrospray ionization mass spectrometric study of CuI and CuII bipyridine complexes employed in atom transfer radical polymerization

We report an electrospray ionization mass spectrometric study of Cu(I) and Cu(II) bipyridine complexes employed in atom transfer radical polymerization. Mass spectra of Cu(I)Br complexed with 2 equiv. of 4,4-di(5-nonyl)-2,2-bipyridine (dNbpy) in toluene, methyl acrylate or styrene showed the presence of [Cu(I)(dNbpy)(2)](+) cation and [Cu(I)Br(2)](-) anion. For the Cu(II)Br(2)/2dNbpy system, [Cu(II)(dNbpy)(2)Br](+), [Cu(II)(dNbpy)Br](+), [Cu(I)Br(2)](-), [Cu(II)Br(3)](-) and [Cu(II)(dNbpy)Br(3)](-) species were observed. In addition, for mixed Cu(I)Br/2dNbpy and Cu(II)Br(2)/2dNbpy systems, the negative ion mode showed only the presence of [Cu(I)Br(2)](-) anions, which are potentially formed through halogen exchange between [Cu(II)Br(3)](-) and [Cu(I)(dNbpy)(2)](+). Copyright 2000 John Wiley & Sons, Ltd.