Functional polymers containing cyclic

Functional Polymers Containing Cyclic Imino Ethers... 

Some particularities of the extraction of ions from an aqueous organic phase, and of the phase catalyzed polyetherification will be summarized. These will represent the fundamentals of our work on the synthesis of some novel classes of functional polymers and sequential copolymers. Examples will be provided for the synthesis of functional polymers containing only cyclic imino ethers or both cyclic imino ethers as well as their own cationic initiator attached to the same polymer backbone ABA triblock copolymers and (AB)n alternating block copolymers and a novel class of main chain thermotropic liquid crystalline polymers containing functional chain ends, i.e., polyethers. 

Three major topics of research which are based on phase transfer catalyzed reactions will be presented with examples. These refer to the synthesis of functional polymers containing functional groups (i.e., cyclic imino ethers) sensitive both to electrophilic and nucleophilic reagents a novel method for the preparation of regular, segmented, ABA triblock and (A-B)n alternating block copolymers, and the development of a novel class of main chain thermotropic liquid-crystalline polymers, i.e., polyethers. 

VEC copolymerizes well with vinyl ester monomers over a range of compositions. To a more limited extent, VEC can also be incorporated into acrylic copolymers, however, we have not achieved quantitative incorporation. In the presence of styrene, essentially no VEC is incorporated into the copolymer. VEC can also be easily incorporated into a vinyl acetate/butyl acrylate latex, yielding a latex polymer containing cyclic carbonate functionality. The Tg of the copolymers can be modeled using extrapolated values for the Tg of a VEC homopolymer. 

The final class of polymers containing carboranyl units to be mentioned here is the polyphosphazenes. These polymers comprise a backbone of alternating phosphorous and nitrogen atoms with a high degree of torsional mobility that accounts for their low glass-transition temperatures (-60°C to -80°C). The introduction of phenyl-carboranyl units into a polyphosphazene polymer results in a substantial improvement in their overall thermal stability. This is believed to be due to the steric hindrance offered by the phenyl-carborane functionality that inhibits coil formation, thereby retarding the preferred thermodynamic pathway of cyclic compound formation (see scheme 12). 

Our interest in such compounds stems mainly from the possibility that they might be useful precursors to new classes of phosphorus-containing polymers or cyclic oligomers. Functional linkages such as E = NSiMe3 or CR SiMe3 could serve as sites for condensation-polymerization reactions, leading to novel cyclic or polymeric sys terns, ... 

COCs that contain cyclic poly(ene)s can be functionalized with maleic anhydride. These polymers do not have any gel particles and are completely soluble in decalin at 135°C., indicating that they are of substantially linear form and thus not crosslinked (4). 

Dendrimers (Newkome et al., 1996) and hyperbranched polymers, HBP, look like functional microgels in their compactness but they differ in two aspects they do not contain cyclic structures and, more importantly, they are much smaller, in the range of a few nanometers in size. They are prepared stepwise in successive generations (dendrimers) or they are obtained by the polyaddition/polycondensation of ABf monomers, where only the A + B reaction is possible (HBP Voit, 2000). Both molecules have tree-like structures, but a large distribution of molar masses exists in the case of HBP. 

Block copolymers of vinyl acetate with methyl methacrylate, acrylic acid, acrylonitrile, and vinyl pyrrolidinone have been prepared by copolymerization in viscous conditions, with solvents that are poor solvents for the vinyl acetate macroradical (123). Similady, the copolymerization of vinyl acetate with methyl methacrylate is enhanced by the solvents acetonitrile and acetone and is decreased by propanol (124). Copolymers of vinyl acetate containing cyclic functional groups in the polymer chain have been prepared by copolymerization of vinyl acetate with IV,IV- diallylcyan amide and N,N-diallylamine (125,126). 

If, however, the polymerization process is aimed at the preparation of functional polymers (telechelics, macromonomers), then the problem of cyclization becomes much more important, because cyclic oligomers do not contain functional end groups. 

In the context of ROMP chemistry, living polymerization reaction conditions have only been observed when well-defined carbene complexes are used as the catalysts. The first catalyst to behave in this fashion was the titanocene complex (4), while more recently, complexes containing Ta, W, and Mo have been shown to be catalysts for the living ROMP of a variety of cyclic alkenes. The Mo complex (5b) is an especially promising catalyst since it is compatible with a number of functional groups and thus can be used to synthesize a variety of functionalized polymers. 

The synthesis and the study of intrinsic properties of well-defined cyclic synthetic polymers are still a challenge in polymer science. Approaches for their preparation were first concentrated on polymers exhibiting linear ring-chain equilibria. This corresponds to polymers containing functional groups in their backbone chain such as poly(dimethylsilox-anes) (PDMSs), polyethers, polyesters, and so forth. The synthesis of cyclic polymers from carbon-carbon chains free... 

We have found that metathesis of olefmic sulfides can be successfully achieved by using, as homogeneous catalyst, the aryloxy(chloro)neopentylidene-tungsten complex 1. Thus, the self-metathesis of allyl methyl sulfide (4) and of 5-dkylthiocycloooctenes (5) (or their cometathesis with various acyclic or cyclic olefins without functional groups) can lead to a family of new olefins, dienes, or unsaturated polymers containing one or more thioether groups. 

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