Aliphatic linkings

Incorporation of flexible aliphatic links, for example by copolymerising with ethylene glycol. 

Flexibility in the aliphatic linking region of the WIN compounds has been explicitly studied and the results suggest that such a property is important for... 

Aliphatically Linked Cyclic Ammo nium Groups are obtained by reaction of TV-ethyl- AT-chloroethylaniline, TV,/V-bis(chloroc thy l)ani line, or TV-ethyl-TV-chloro-ethyl- m -toluidine with pyridine. The red cationic azo dye 17 [36986-04-6], obtained with 2-chloro-4-nitroaniline [48], is represented in numerous cationic dye product lines. Introduction of a second pyridiniumalkyl residue (18) [24447-84-5] leads to a brightening of the hue to orange. 

The glass temperatures of all products fall within the range 130°-160 °C. The partially aromatic polycarbonate has a glass temperature of 150 °C. the partially aromatic PETP has a glass temperature of 75 °C. To determine the ratio of the aromatic to the aliphatic content, we assume four chain links for the benzene rings. Then the polycarbonate has the ratio aromatic/aliphatic links = 4 6, the polyester has a ratio 4 2, and the polyamides (Table I) have a ratio 4 10. Despite the lower aromatic content the glass temperatures of some of the amorphous polyamide are... 

Multi-ferrocenyl phthalocyanines having up to 16 ferrocene units per molecule have been built with oxyethylene linkers to create aliphatically linked ferrocene units, and ethynyl bridges have been used to create ferrocenyl-linked tetrapyrroles of both phthalocyanine and porphyrin types with unsaturated links the porphyrins have two ferrocene units, which are placed on opposite meso positions. Both the aliphatically linked and the ethynyl-linked compounds were shown to exhibit no electrochemical communication between ferrocene units. ... 

The type of spacer chain can be varied without change to the mesogenic units. For example, the second structure in Fig. 2 has a short dimethylsilox-ane spacer included in the aliphatic linking chain. The inclusion of such groups can affect the overall packing of the molecules leading to reductions in melting points and the stabilization of lamellar smectic phases over nematic phases. 

It is well known that saturated five-membered chelates adopt a puckered chiral conformation. In the absence of a substituent and when the donor atoms are synunetrically substituted, the ring rapidly interconverts from one chiral conformation to the other (Fig. 10). If the aliphatic link is substituted, however, asymmetry is created and the chelate may be fixed into a single, static chiral conformation by the requirement that the substituent be equatorially disposed (Fig. 

Substantial development work has been done on other tetraaryl diphosphates and higher oligomers thereof, such as with aliphatic linking groups (109). Reactive Organic Phosphorus Compounds. 

A very strong band occurs at 1050-970 cm" in all compounds having the P—0—C (aliphatic) link. This band is probably due to an asymmetric P—O—C stretching vibration. In most ethoxy phosphorus compounds this band is a doublet. In methoxy and ethoxy phosphorus compounds a second strong band appears at 830-740 cm" probably due to symmetric P—0—C stretching. This band is usually absent in other alkoxy phosphorus compounds. 

However, the incorporation of chiral bidentate phosphine and phosphite ligands should prevent this equilibrium. For example, if the aliphatic link... 

All investigations on the mechanism of the thermo-oxidative degradation of PETP presuppose [3] that this process has a radical-chain character that proceeds by the formation and decomposition of peroxides and hydroperoxides. Simultaneously with the oxidation of aliphatic links, resulting in the formation of H O, CO, CO, and aldehydes, and in the appearance of new carboxyl and phenyl groups, there are also changes in the aromatic links of the chain associated with the formation of biphenyl structures and crosslinking of the polymer. 

The reactivity of alkylthiazoles possessing a functional group linked to the side-chain is discussed here neither in detail nor exhaustively since it is analogous to that of classical aliphatic and aromatic compounds. These reactions are essentially of a synthetic nature. In fact, the cyclization methods discussed in Chapter II lead to thiazoles possessing functional groups on the alkyl chain if the aliphatic compounds to be cyclized, carrying the substituent on what will become the alkyl side chain, are available. If this is not the case, another functional substituent can be introduced on the side-chain by cyclization and can then be converted to the desired substituent by a classical reaction. 

As a class the aliphatic polyalkenamers have low values due to a combination of low chain stiffness and low interchain attraction. The presence of double bonds has the effect of increasing the flexibility of adjacent single bonds (see Chapter 4) and overall this leads to a reduction in. Thus in the sequence from polydecenamer down to polypentenamer an increase in the double bond concentration leads to a lowering of Tg. On the other hand the Tg of polybutenamer, i.e. poly butadiene, is somewhat higher than that of polypentenamer, presumably because the proportion of stiff links, i.e. double bonds, becomes sufficiently high to override the flexibilising effect on adjacent chains. Consequently the polypentenamers have the lowest Tg values known for hydrocarbon polymers (cis- -114°C, trans- -97°C). 

Such materials are soluble in the lower aliphatic alcohols, e.g.ethanol, and in phenols. They also absorb up to 21 % of moisture when immersed in water. If this material is heated with 2% citric acid at elevated temperatures, typically for 20 minutes at 120°C, cross-linking will take place Figure 18.20). 

Clearly a wide range of phenols and amines are possible. Where appropriate multi-ringed phenols are used such as 4,4-dihydroxybenzophenone or bisphenol A then three-dimensional cross-linked polymers will be obtained. Amines may be aliphatic such as methylamine or aromatic such as aniline. 

There is, quite clearly, scope or a very wide range of epoxy resins. The nonepoxy part of the molecule may be aliphatic, cycloaliphatic or highly aromatic hydrocarbon or it may be non-hydrocarbon and possibly polar. It may contain unsaturation. Similar remarks also apply to the chain extension/cross-linking agents, so that cross-linked products of great diversity may be obtained. In practice, however, the commercial scene is dominated by the reaction products of bis-phenol A and epichlorohydrin, which have some 80-90% of the market shtu"e. 

A number of aromatic amines also function as cross-linking agents. By incorporating the rigid benzene ring structure into the cross-linked network, products are obtained with significantly higher heat distortion temperatures than are obtainable with the aliphatic amines. 

The amide group of polyacrylamide offers a reactive site to change the ionic character or to cross-link the polymer. A polyacrylamide solution undergoes general reactions of the aliphatic amide group [1,2,11]. The impor-... 

---