Second step ATRP

As one-pot reactions by the simultaneous initiation of both polymerizations always affect one another, control of the overall process is often very difficult to achieve. Another fairly new strategy, the AROP of lactones [210-213], lactides [214] or benzyl-L-glutamate [215] and the controlled radical polymerization of vinyl monomer, which take place in one-pot but in consecutive fashion, has been introduced by several groups. In this strategy, the AROP of lactones, lactides, or benzyl-L-glutamate can st be initiated by either an enzymatic or a metal catalyst at low temperature. In a second step, ATRP of MMA [210-213], tBMA [212], or 2-hydroxyethyl MA [214] and NMRP of styrene [211, 215] can be activated by increasing the reaction temperature and injecting the ATRP catalyst, respectively (Scheme 11.48). The reaction was conducted in one-pot, without any intermediate work-up and purification. 

Brushes with diblock side chains have been prepared by the same concept as illustrated in Figure 13. In this case either a polystyrene block or a poly-(n-butylacrylate) block was grafted first by atom transfer polymerization, ATRP, on a poly(2-bro-mopropanoyl ethyl methacrylate), pBPEM, on which in a second step the other monomer was polymerized as the second block.189 Table 4 summarizes the molecular structure of the corresponding polymers, i.e., (i) the macroinitiator or mere backbone molecule (pPBEM) from which (ii) a brush with pnBuA homopolymer side chains (pBPEM-g—pnBuA), (iii) a... 

The possibility of grafting block copolymer chains via a two-step SI-ATRP was studied. The concomitant increase in molar mass and thickness of the hydrophilic layer proved both the living character of the polymer grafted in the first step and the efficient reinitiation in the second step [152]. An example of block copolymer used was polyDMAAm-h-polyNIPAAm, which exhibited a change in the chain conformation leading to a reduction of the hydrodynamic diameter of the particles upon an increase in temperature above the LCST, in a similar way as the polyNIPAAm homopolymer. 

In the method reported by Durmaz et al. (2006), DA reaction is rst carried out between PEG-MI precursor (prepared as in Problem 12.11) and the compound (XXI) by re uxing in THE for 48 h (95% conversion). This results in the formation of a maleimide-anthracene adduct having appropriate function groups for SFRP/NMP and ATRP. In the second step, the previously obtained adduct is used as a macroinitiator for SFRP of St at 125°C for 15h (85% conversion). In the third step, this PEG-PSt precursor with a bromine functionality in the core is employed as a macroinitiator for ATRP of tBA in the presence of Cu(I)Br and PMDETA (Fig. 11.17) at 80°C to give ABC type miktoarm star terpolymer core-(PEG)(PSt)(PtBA) (see Scheme P12.12.1). 

Recently, we report an approach for the preparation of polymer brushes on different kinds of PET surfaces (films, fibers and fabrics). The PET surfaces were first reacted with 1,2-diaminoethane by aminolysis reaction to incorporate functional groups on the surface. Then, in a second step, atom transfer radical polymerization (ATRP) initiators were grafted by reaction with bromoisobutyryl bromide. Surface-initiated ATRP was performed in bulk using styrene monomer and the adequate catalytic system in the presence of sacrificial initiator. Polymer brushes were obtained with a good controlled of polymerization (46). 

Block copolymars containing PMeVE and poly(tert-Bu acrylate), poly(acrylic acid), poly(Me acrylate), or polystyrene have been prepared by Bemaerts and Du Prez by the use of a novel dual initiator 2-bromo-(3,3-diethoxy-propyl)-2-methylpropanoate. In the first step, the living cationic homo-polymerization of MeVE is performed with the acetal end group of the dual initiator as initiating site or by the ATRP homopolymerization of tert-butyl acrylate from the bromoi-sobutyrate group of the dual initiator. In the second step in the preparation of block copolymers, well-defined PMeVE-Br and pol) -tBA-acetal homopolymers were employed as macroinitiators, respectively, in the ATRP of several monomers and cationic polymerization of MeVE. 

The first steps of a second process for divergent synthesis of dendritic polymers by ATRP are shown in Scheme 9.73.12S In this case, a caiixarcnc core... 

ATRP allows the synthesis of di-block copolymers by sequential (one-pot) or separated steps (two-pot) methods (26). To synthesize di-block, tri-block, 3-and 4-arm star-block copolymers by the two-pot method, a typical ATRP procedure was performed. First, a homopolymer was synthesized as mentioned above and then this was used as a macroinitiator. In addition to the two-pot procedure, one of the tri-block copolymers (P2 in Table 1) was also synthesized by the one-pot ATRP procedure. Once first monomer polymerized to complete conversion, the second monomer was added to the flask under nitrogen to obtain the block copolymers. In both cases, the samples were taken periodically via a syringe to follow the molecular weight of the polymer by GPC and the conversion of polymerization by GC measurements. 

The synthesis of an interesting DHBC, namely poly (4-vinylbenzoic acid-block-2-(diethylamino)ethyl methacrylate) (PVBA-PDEAEMA), has been presented by Armes and Liu [13], The synthesis was performed by ATRP using protecting group chemistry in three steps. Initially the polymerization of a tert-butyl protected PVBA macro-initiator was performed followed by the polymerization of the second monomer, DEAEMA. Finally the hydrolysis of the tert-butyl protected block was realized giving rather monodisperse block copolymers. 

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