Alkoxyamine functionality

The same heterobifunctional initiator, 2-phenyl-2-[(2,2,6,6-tetramethy-piperidino)oxy] ethyl 2-bromo-2-methyl propanoate, was employed for the synthesis of PMMA-fo-PfBuA-fo-PS triblock terpolymers via the combination of ATRP and NMP [136]. Styrene was initially polymerized through the alkoxyamine function in bulk at 125 °C, leading to PS chains with bromine end groups. Subsequent addition of fBuA in the presence of CuBr/PMDETA provided the PS-fr-PfBuA diblock. Further addition of CuCl, to achieve halogen exchange and MMA yielded the desired triblock copolymer with... 

The success of this chemistry versus a control was demonstrated by conducting a parallel experiment where PMMA was prepared under the same conditions as the preparation of XIII, except using azobisobutyronitrile (AIBN) as the initiator instead of the alkoxyamine functional azo initiator. The AIBN-and alkoxyamine functional azo-initiated PMMA were dissolved in styrene and heated at 130 °C. A film of the resulting block copolymer made using alkox-yamine-functionalized XIII was translucent and flexible whereas a film of the polymer formed by polymerizing styrene in the presence of unfunctionalized PMMA control was opaque and very brittle. 

In another example, Yildirim et al. photochemically generated anthracene radical cations in the presence of TEMPO [29]. TEMPO immediately trapped the radical to form the TEMPO-anthracene cation, which was subsequently used to initiate cationic polymerization of cyclohexene oxide (CHOX). The resulting alkoxyamine-functional polycyclohexene oxide was used to macroinitiate styrene polymerization, resulting in the formation of S-6/-CHOX (Scheme 8.9). 

The reverse strategy, polymerization of the acrylate block followed by styrene, has been successful and has allowed the preparation of well-defined block copolymers with levels of control comparable to ATRP procedures. In this strategy, an alkoxyamine functionalized poly(n-butyl acrylate) block, 70, is initially grown and then used to polymerize styrene at 123 °C under argon for 8 h. This results in 92% conver-... 

SFRP Nitroxides/alkoxyamines, functional nitroxides, imidazoline, piperizinones, morpholones, and related mediators... 

NMP and RAFT polymerization can be used to prepare segmented or multiblock copolymers directly. Polymer with in-chain alkoxyamine functionality such as 316 or 317 can be heated in S to form segmented block copolymers containing PS blocks by NMP. FIcating a mixture of the polyester (316) and polyurethane (317) provides a polymer containing novel polyester-urethane units (318) by a chain reorganization involvin exchange process can be followed by NMR. 

NMP of S with 346 as initiator gave PS with pendant oxazoline groups. Cationic polymerization of this macromonomcr gave a polyoxazolinc with PS grafts that retained the alkoxyamine functionality. ATRP with 156 as catalyst and ethyl 2-bromoisobutyrate (125a) as initiator has been used to prepare... 

Dynamic covalent chemistry has in recent years complemented tmly noncovalent and metal-bgand chemistries. Jackson and Fulton expanded this concept to block copolymer synthesis. Aldehyde and alkoxyamine functional polymeis prepared by RAFT polymerization react to form oxime bonds, a dynamic link that can be reversed tbrougb equUibriinn perturbations. The block copolymers formed were capable of furtber self-assembly into micellar sttuctures. 

As recently demonstrated by Grubbs et al. [30] and by Yin et al. [31], amphiphilic block copolymers could be prepared by NMP from alkoxyamine functional macroinitiators such as ... 

In the second method, the alkoxyamine-ftmctionalized backbone is prepared by a chemical modification of a preformed polymer. Abbasian and Entezami prepared alkoxyamine-functionalized poly(vinyl chloride) (PVC) in a three-step procedure. PVC was first arylated with toluene by Friedel-Crafts acylation followed by a bromination step using N-bromosuccinimide. The bromine atom was finally reacted via nucleophilic substitution by the TEMPO hydro-xylamine anion. PVC-g-PS was finally obtained after TEMPO-mediated polymerization of styrene. A TEMPO-functionalized isotactic poly(l-butene) macroinitiator was synthesized by Jo et al. who used a rhodium-catalyzed activation of the alkane C-H bonds and subsequent transformations of the boronate ester group into an hydroxyl pendant group. This reactive moiety was then used to attach a TEMPO-based alkoxyamine bearing another hydroxy function by an ether linkage. A method to prepare PE-g-PS from a poly(ethylene-co-m,p--methylstyrene) obtained by metallocene-catalyzed polymerization was also reported. The macroalkoxya-mine was synthesized after bromination with N-bromosuccinimide followed by a nucleophilic reaction with the TEMPO hydroxylamine anion. 

A colored polymer/aluminum hybrid pigment was synthesized by NMP initiated from the surface of aluminum flakes [60]. The latter were coated with a thin silica layer. In this case, the chemical grafting of the initiator was performed through silylation reactions. The initiator used was an SGl-based alkoxyamine functionalized with an alkoxysilane moiety. This compound was previously prepared from the intermolecular radical 1,2-addition of Blocbuilder MA in the presence of 3-(trimethoxysilyl)propyl acrylate. Styrene or n-butyl acrylate were then copolymerized with vinyl dye monomer in a controlled manner. 

---