Optical activity polymethacrylates

An optically active polymethacrylate (2) having a binaphthol moiety in the side chain was synthesized by radical polymerization. This polymer coated on silica gel resolved several racemates.50 However, no data on the influence of the stereoregularity of the main chain on resolution have been reported. The chiral recognition by this polymer may simply arise from the binaphthyl group. 

Anionic Catalysis Several bulky methacrylates afford highly isotactic, optically active polymers having a single-handed helical structure by asymmetric polymerization. The effective polymerization mechanism is mainly anionic but free-radical catalysis can also lead to helix-sense-selective polymerization. The anionic initiator systems can also be applied for the polymerization of bulky acrylates and acrylamides. The one-handed helical polymethacrylates show an excellent chiral recognition ability when used as a chiral stationary phase for high-performance liquid chromatography (HPLC) [97,98]. 

A large number of azobenzene-based amorphous and liquid crystalline polymers, particularly polyacrylates and polymethacrylates with chiral azobenzene pendants, have been prepared for the development of data storage and photonic devices [1-3,11-14]. For instance, the introduction of optically active mesogenic azobenzene residues into the side groups of the polymers produces chiral nematic and cholesteric phases, which are regulated by photoisomerization of the azobenzene units [10,14]. In most cases, however, the optical activity and chiroptical... 

As discussed so far in this section, the helical polymethacrylates are synthesized predominantly using anionic polymerization techniques. However, recently, more versatile, inexpensive, and experimentally simple free-radical polymerization has been proved to be an alternative, effective way to prepare helical polymethacrylates from some monomers. Although the stereochemical control of radical polymerization is generally more difficult compared with that in other types of polymerization,69 an efficient method would make it possible to synthesize helical, optically active polymers having functional side chains by direct radical polymerization without using protective groups. In the radical polymerization of bulky methacrylates, helix-sense selection is governed by the chirality of a monomer itself or an additive. 

Abrikosov-like phases are also believed to be exhibited by some optically active side-chain liquid crystal polymethacrylates where the mesogenic side-group is derived from cholesterol [41]. The polymer, of structure 7, was reported by Freidzon et al. to exhibit a twisted layered structure in its smectic... 

As anticipated, upon reaction of this polymeric ester under hydrogen with phosphonium iodide, the poly(methacrylic acid) which had formed in an 84% yield showed no optical activity. When the same ester was copolymerized with three molar equivalents of maleic anhydride, the resulting ester-anhydride copolymer had an optical rotation of [hydrogen with phosphonium iodide, the resulting polymethacrylic acid had an optical rotation of = +23° (Note the reversal of the optical rotation in this case.) This appears to have been the first demonstration of a case of asymmetric induction during vinyl polymerization. 

By certain physical factors like thermal, ultraviolet irradiation, high pressure and other chemical parameters like organic solvents the helical pol5mers are easily denaturalized. A variety of helical polymers are synthesized, which include polyisocyanates, polyisocyanides, polychloral, polymethacrylates, polysilanes, polythiophenes, poly (p-phenylene)s, poly(l-methylpropargyl-ester)s, poly(phenylacetylene)s and poly (-unsaturated ketone) [18-24] (Fig. 1). Other polymers are whose optical activity is main chain or side chain chirality dependent e.g. amino-acid-based polymers are nontoxic, biocompatible and biodegradable. 

Synthetic polymers with conformational chirality have become a research field of widespread interest in recent years, and a wide range of polymers with conformational chirality have been synthesized from various types of monomers including vinyl monomers [9, 61-63, 128-136]. The existing examples of optically active vinyl polymers with conformational chirality include isotactic, helical polyolefins bearing asymmetric side chains [133-135] and isotactic, hehcal polymethacrylates bearing bulky, achiral side chains [61-63,136]. These polymers have stereocenters in the main and/or side chains. Optically active poly(PDBS) is the first vinyl polymer with conformational chirality bearing no stereocenters in the main and side chains whose chiroptical properties arise only from a chiral conformation. 

There have also been many studies of the polymerization kinetics of organoiron monomers these have shown that such polymerizations often do not follow the same rate laws as organic monomers. Ferrocene-substituted polymethacrylates possessing nonlinear optical (NLO) properties were reported by Wright and coworkers." The copolymerization of the ferrocenyl-fimctionalized monomer (5mol%) 14 with methyl methacrylate 15 yielded the organometaUic polymer 16, as shown in scheme 4." This polymer displayed second-harmonic-generation activity and possessed... 

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