Poly methacrylates, dendronized

Other efforts based on the macromonomer approach to homopolymers having dendritic side chains, include the work of Draheim and Ritter on acrylate and methacrylate derived structures having dendritic chiral side chains based on L-aspartic esters [17a], and of Xi and coworkers with poly(methacrylate) structures containing very small benzyl ether dendritic side-chains [17b]. Unfortunately, both of these approaches met with limited success due to a significant drop in degree of polymerization (DP) when the size of the dendron used as pendant group in the macromonomers increased from G-l to G-2. 

Several work are concerned with the synthesis, characterization, dielectric behavior and conformational analysis of dendronized Polymers. Poly(methacrylates) containing phtalimidoalkyl moieties in the side chain have been recently studied i.e. poly(3,5-diphtalimido alkylphenyl methacrylate)s with ethyl (P-EthylGi), propyl (P-PropylGi) and butyl (P-ButylGi) chains as spacer groups. Where Gi indicates first generation [112],... 

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. 

The PBE dendron has a glass transition at about 40 °C and is soluble in various organic solvents (e.g., THF, acetone, toluene). It is therefore a moldable, thermoplastic, film-forming material. This practical feature is maintained for the lanthanide-cored dendrimer complexes. The complexes are partially miscible with poly(methyl methacrylate), affording transparent luminescence compositions by mixing in solvent. 

Frechet and coworkers explored the synthesis of polyester dendrons on solid support. These dendrons, based on 2,2-bis(hydroxymethyl)propanoic acid monomers, were assembled up to the fourth generation on poly(2-hydroxyethyl methacrylate-co-ethylene dimethacrylate) resin and decorated with chiral proline derivatives (Scheme 15.15). T vo methods for preparation of these materials were reported. The solid-phase divergent approach yielded polymer with higher loading but a less precise architecture than the second approach. The second approach, the divergent synthesis of the dendrons in solution, followed by the focal point deprotection and then attachment to the solid support, led to well-defined structures on the polymer, but relatively low loading. 

Azobenzene linear-dendritic BCs are composed of a non-absorbing linear block linked to a dendron functionalized with photoresponsive moieties. These materials combine the good properties of BCs, segregation ability and chromophore dilution, with control over the number of chro-mophore moieties in each macromolecular chain. Through this approach, several photoresponsive linear-dendritic BCs with azobenzene units have been prepared using dendrons derived from 2,2-bis(hydroxymethyl)propi-onic acid (bis-MPA) and PEG, PMMA, poly(ethyl methacrylate) or PS as linear segments (see examples in Fig. 16.18) (Blasco et al., 2012 del Barrio et /., 2009,2010). 

Some polymers are linear, a long chain of connected monomers. PE, PVC, Nylon 66, and poly(methyl methacrylate) are some linear commercial examples found in this book. Branched polymers can be visualized as a linear polymer with side chains of the same polymer attached to the main chain. While the branches may in turn be branched, they do not connect to another polymer chain. The ends of the branches are not connected to anything. Special types of branched polymers include star polymers, comb polymers, brush polymers, dendronized polymers [1], ladders, and dendrimers. A cross-linked polymer, sometimes called network polymer, is one in which different chains are connected. Essentially the branches are connected to different polymer chains on the ends. These three polymer structures are shown in Fig. 3.3. 

---