Benzyl methacrylate block copolymers

Chart 2.6 Structure of block copolymer based on PEO and poly(benzyl methacrylate) (PBMA) containing /3-D-galactose unit. 

Dendrons attached as side chains on linear polymer chains behave different from free dendrimers and dendrons. Block copolymers, poly(3,5-bis(3,5-bis (benzyloxy)benzyloxy)-benzyl methacrylate-random-methacrylic acid)-block-poly(2-perfluorooctylethyl acrylate), possess poly(benzylether) dendrons and perfluorinated alkyl chains in their side chains (Fig. 4) [85], While an LB film of a copolymer with a medium substitution fraction of poly(benzylether) dendron side chain in poly(methacrylic acid) displays flat surface, a copolymer with high fraction of poly(benzylether) dendron side chains produces the zone texture. Dendron rich blocks are hydrophobic and oleophilic but perfluorinated blocks are solvophobic. Therefore, in this case, the solvophobicity-to-solvophilicity balance must be considered. As a result, copolymers with medium fraction of dendron are laid on solid substrate, but dendron blocks of copolymers with high fraction prefer to arrange at air side of air/ water interface and the fluorocarbon blocks are enforced to exist close to water subphase, resulting in the zone texture [86]. These situations of molecular arrangements at air/water interface are kept even after transfer on solid substrate. By contrast, when perfluorooctadecanoic acids are mixed with block copolymers with high dendron fraction, the flat monolayers are visualized as terrace [87], The monolayers are hierarchized into carboxyl, per-fluoroalkyl, and dendron layers, that is, hydrophilic, solvophobic, and oleophilic layers. In this case, perfluorooctadecanoic acids play a role for ordering of block copolymers. 

Various methacrylic-styrene copolymers were prepared in which the reactivity of methacrylate monomers used in the first step decreases in the order MM A > BuMA > benzyl methacrylate. For instance, the bulk polymerization of MMA with such an aromatic azo compound proceeds via a living radical mechanism and the sterically crowded C-C(C6H5)3 terminal bond of polymethacrylate 37 can be cleaved thermally to produce a,co-diaromatic PMMA-h-PS block copolymers in 48-72% yield. 

The Inifer technique enables us to fulfil some requirements of polymer architecture even in some radical processes. An amplified form may be applied, the Iniferter variant, where the radical initiator simultaneously acts as a transfer and terminating agent. Otsu et al. used sulphides and disulphides (tetraethylthiuram disulphide, PhSSPh, Ph2S, PhCH2SSCH2Ph) [96] and carbamates (benzyl-A,A-diethyldithiocarbamate, p-xylylene-A,7V-diethyl-dithiocarbamate) [97] in the photopolymerization of methyl methacrylate and styrene, and phenylazotriphenylmethane in the polymerization of methyl methacrylate [98]. Living radical polymerizations yield polymers with defined end groups or the required block copolymers. 

Di-block copolymers may also be formed by using dithiocarbamate free radicals. Indeed, copoljoners containing poly(styrene) and poly(hydroxyethyl methacrylate) blocks have been obtained by a two-step procedure [145]. Firstly, styrene is photopolymerized in the presence of benzyl A,A-diethyldithiocarbamate (BDC) by a living radical mechanism [146]. In fact, as the benzyl and thiyl radicals, formed by the photoliagmentation of BDC, participate mainly in the initiation and termination reactions respectively, polystyrene with a dithiocarbamate end group is thus obtained. The successive UV irradiation of this polymer, in the presence of hydroxyethyl methacrylate (HEMA), gives rise to the di-block copolymer, according to Scheme 42. 

Moad et al. functionalized a monomethylated PEG with a dithioester to prepare a RAFT macroinitiator (Mn=750, Mw/Mn=1.04). The formation of a block copolymer with either St (Mn=7800, Mw/Mn=1.07) or with benzyl methacrylate (Mn= 10,800, Mw/Mn=1.10) resulted in well-defined copolymers with no remaining PEG macroinitiator [53]. 

The RAFT process has been used to prepare a variety of block copolymers, as shown in Table 5.3 for example, DMAMEA and ethylene oxide can form diblocks with benzyl methacrylate, but more important, acrylic add and methacrylic acid can be used, which has so far been impossible employing ATRP. 

The groups of Kramer and Hawker provided an example where the target polymer could be made using sequential CFR polymerizations, but CuAAC simplified the process and made it possible to obtain the polymer with a precise molecular weight and a low polydispersity index (PDl). Attempts to make poly(benzyl methacrylate)-b-poly(butyl acrylate) with equal volume fractions of each block to be used for the determination of order-disorder transition (ODT) led to materials with imprecise volume fractions and PDls higher than 1.3. Instead, by using preformed homopolymers that were then coupled by CuAAC, the authors were able to make a small library of covalent diblock copolymers with low PDIs, while also performing fewer total reactions. 

Mori, A., Ito, Y., Sisido, M., and Imanishi, Y. (1986) Interaction of polystyrene/poly(gamma-benzyl L-glutamate) and poly(methyl methacrylate)/poly(gamma-benzy 1 L-glutamate) block copolymers with plasma proteins and platelets. 

Some specific recent applications of the GC-MS technique to various types of polymers include the following PE [49,50], poly(l-octene) [51], poly(l-decene) [51], poly(l-dodecene) [51], 1-octene-l-decene-l-dodecene terpolymer [51], chlorinated polyethylene [52], polyolefins [53, 54], acrylic acid methacrylic acid copolymers [55], polyacrylates [56], styrene-butadiene and other rubbers [57-59], nitrile rubber [60], natural rubbers [61, 62], chlorinated natural rubber [63, 64], polychloroprene [65], PVC [66-68], silicones [69, 70], polycarbonates [71], styrene-isoprene copolymers [72], substituted PS [73], polypropylene carbonate [74], ethylene-vinyl acetate copolymers [75], Nylon [76], polyisopropenyl cyclohexane a-methyl styrene copolymers [77], m-cresol-novolac epoxy resins [78], polymeric flame retardants [79], poly(4-N-alkyl styrenes) [80], polyvinyl pyrrolidone [81], vinyl pyrrolidone-methyl acryloxysilicone copolymers [82], polybutylcyanoacrylate [83], polysulfide copolymers [84], poly(diethyl-2-methacryloxy)ethyl phosphate [85], ethane-carbon monoxide copolymers [86], polyetherimide [87], bisphenol A [88], ethyl styrene [89], styrene-isoprene block copolymer [89], polyvinyl alcohol-co-vinyl acetate [90], epoxide thiol [91], maleic acid-propylene copolymer [92], P-hydroxy butyrate-P-hydroxy valerate copolymer [93], polycaprolactams [39,94], PS [95,96], polypyrrole [95,96], polyhydroxy alkanoates [97], poly(p-chloromethyl) styrene [81], polybenzooxazines and siloxy substituted polyoxadisila-pentanylenes [98,99] poly benzyl methacrylates [100], polyolefin blends after ageing in soil [101] and polystyrene peroxide [43]. 

Several s -copolymers of MMA and alkyl methacrylates with narrow MWD were also prepared with -C4HgLi-(n-C4Hg)3Al. Glass transition temperatures for the sL-copolymers of MMA and butyl methacrylate (n-BuMA) are shown in Figure 6. Recently, block and random s -copolymers of MMA and benzyl methacrylate as well as s -poly(benzyl methacrylate) prepared with -C4HgLi-R3Al were found to form stereocomplex with i -PMMA in solid and in solution [16]. 

DMAEMA (entry 20), and the mixture of MMA and MAA (entry 21) as the second block monomers, the PMMA chain successfully extended, yielding low-polydispersity block copolymers (PDI = 1.2-1.3). Instead of using an isolated macroinitiator, successive addition of two monomers was also successful.To a polymerization of MMA (first monomer) with CP-I (low-mass alkyl iodide) at an about 60% conversion, the addition of BzMA (second monomer) yielded PMMA-ft/ock-(PMMA-r(2 dom-PBzMA)s with relatively small PDIs ( 1.4) (entries 22 and 23), where PBzMA is poly(benzyl methacrylate). 

Chaikov and Dong et al. [39,40] described symmetric triblock copolymers with a glyco methacrylate middle-block and two outer poly(L-alanine) (or poly(y-benzyl L-glutamate)) blocks. The aggregates formed in dilute aqueous solution were spherical in shape and were 200-700 nm in diameter (TEM). TEM further revealed a compact structure of the aggregates like for multi-lamellar vesicles. The dimension of the particles, however, was found to decrease with increasing concentration of the copolymer. 

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