Vinyl polymers, pendant

It is clear from the preceding discussion that organometallic photoinitiators (metal carbonyl or chelate derivatives) can provide a convenient route for synthesizing vinyl polymers with a variety of different reactive end group or photoreactive pendant groups or side chains through the polymer chain. 

As shown in Figure 2.5, there are three possible stereoregular forms for monosubstituted vinyl polymers. These are isotactic, all of the pendant groups are on one side of the chiral carbon syndiotactic, the pendant groups appear on alternate sides of the chiral carbon and atactic, some mixture of geometries about the chiral carbon. 

Because of its irregular structure, ar-PP is an amorphous polymer with a softening point lower than that of it-PP. In contrast, because of its regular structure, commercial it-PP is a higher-melting crystalline solid. It is important to note that similar stereochemical concepts apply to other vinyl polymers with pendant groups, such as polyvinyl chloride (PVC) and polystyrene (PS). 

The third group ofpolychromophoric compounds to be discussed are homopolymers in which the pendant rings are separated from the backbone by one or more atoms. The polymers of allyl arenes, which lack only the n = 3 ring spacing of aryl vinyl polymers, have been studied very little. The fluorescence spectrum of poly(l-allyl-naphthalene) in dilute dichloromethane solution has been reported 28). Like 1-ethyl-naphthalene, the maximum intensity was seen at 337 nm, but a weak, broad shoulder was also recorded for the polymer at 410 nm. The fluorescence ratio Iu/IM for poly(l-allylnaphthalene) was only 1/100 th the value for P1VN 28). The excimeric nature of the 410 nm emission in the allyl-based polymer has not been confirmed, since neither the lifetime nor the excitation spectrum of this fluorescence band are known. 

Okamoto et al.113 observed that the absorption spectra of vinyl polymers with large pendant 7r-electron systems including PVK show hypochromism a frequency shift in comparison with the spectra of the small molecule model compounds. He suggested that these polymers have a certain degree of order in the structure and proposed a direct relationship between the hypochromism and photoconductivity. 

The critical micelle concentration (CMC) of Pluronics [121] has been found to be rather sensitive to temperature, which is ascribed to the changes in hydrophilicity of the ethylene oxide moiety with temperature. As shown already, monolayer viscoelasticity is correlated with the hydrophilicity of polymer backbones such as in polyethers, and that of the pendant group in vinyl polymers. It has been shown that PPO acts differently as a polyether... 

Figure 13 shows several optically active vinyl polymers and copolymers with azobenzene or stilbene residues in the side groups. All these polymers were prepared by the conventional radical polymerization, so that the main chains should be atactic or syndiotactic and may not be able to take a helical conformation even in the presence of chiral pendants. The homopolymers (28-31) [83-85]... 

Vinyl polymers, bearing pendant carbodiimide groups 200, are obtained from N-(p- or m-vinylphenyl)-N -alkylcarbodiimides. ... 

Polymerizations. A variety of polymerization conditions were examined for both the monovinyl and divinyl compounds. It was hoped that cationic polymerization of monomer 3 would give a vinyl polymer possessing tetraethylene glycol pendant groups. 

Several types of the polymer with sugar pendant and having various synthetic polymer backbones such as vinyl polymer, peptide, etc are already reported (7, 8, 9). In this study, we discussed the polymerizable sugar derivatives including vinyl group and recent advances of PVA with sugar pendant. 

Another application involves binding of agricultural chemicals in polymer formulations for slow release at a rate effective for their intended purpose avoiding the risk of the reagents being washed away by rain or irrigation. For example, the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) has been incorporated into polymers either as a chelate with iron (XVIII) or as a hydrolysable pendant ester group on a vinyl polymer (XIX). 

S. Shirai and J. Kido. Syntheses of vinyl polymers containing phenylan-thracene pendants and their application for organic EL device. Chem. Lett., 31(3) 386-387, March 2002. 

Anthracene Groups. A homopolymer from 9-(4-vinylphenyl)anthracene emits green light originating from the excimer of the anthracene units. Ruores-cent vinyl polymers containing 9-phenylanthracene pendants were synthesized and examined as an emitter layer in organic electroluminescent devices. The single-layer polymer EL device uses the homopolymer. 

Imae, L, K. Moriwaki, K. Nawa, N. Noma, and Y. Shirota. 1995. Synthesis and electrical properties of novel electrochemically-doped vinyl polymers containing end-capped quaterthiophene and quinquethiophene as pendant groups. Synth Met 69 285-286. 

Both polymers were formed from their vinyl monomers. Pendant benzoin groups can be introduced into the polymers by other techniques. One can start, for instance, with a copolymer of styrene and maleic anhydride and form ester groups ... 

Low molecular weight Schiff base complexes of many metals are well known and in the case of aromatic ligands these tend to have high thermal stability. Polymeric Schiff bases likewise have been well reported, and although many of these have the Schiff base appended as a substituent on a vinyl polymer backbone, others have the Schiff base residue as part of the mainchain. The latter continue to complex metals very well [140, 141] and one early paper reports the use of a Mn(II) polymeric complex in the aerobic oxidation of cumene at 30-100°C [142]. Indeed there is an implication in the paper that the polymer complex is stable to 200°C when complexed O2 tends to be liberated. Wohrle s group have also studied polymeric Schiff bases extensively, again mostly with pendant groups. However, they have reported a mainchain poly Schiff base [143], its complexation with Co(II), Ni(II) and Cu(II), and use of the supported complexes as catalysts in quadricyclane isomerisation to norbornadiene. 

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