Phenylene groups

Rigid structures, e.g. phenylene groups, incorporated in the backbone of tbe molecule. 

The irregular structure of the polymer indicates that it will be amorphous and glass-like. The presence of the /7-phenylene group in the main chain and the lone methyl group leads to a high of about 150°C. There is, somewhat surprisingly,... 

The successful development of polyfethylene terephthalate) fibres such as Dacron and Terylene stimulated extensive research into other polymers containing p-phenylene groups in the main chain. This led to not only the now well-established polycarbonates (see Chapter 20) but also to a wide range of other materials. These include the aromatic polyamides (already considered in Chapter 18), the polyphenylene ethers, the polyphenylene sulphides, the polysulphones and a range of linear aromatic polyesters. 

The common feature of the p-phenylene group stiffens the polymer backbone so that the polymers have higher TgS than similar polymers which lack the aromatic group. As a consequence the aromatic polymers tend to have high heat deformation temperatures, are rigid at room temperature and frequently require high processing temperatures. 

Table 21.1 Comparison of properties of unfilled grades of thermoplastics containing p-phenylene groups...

It will be seen that by varying the degree of spacing between the /7-phenylene groups a series of polymers may be obtained with a spectrum of TgS, which... 

Polymers containing p-phenylene groups and other ring structures. 

Linear Polymers with p-Phenylene Groups and Other Ring Structures... 

Conducting polymers with p-phenylene groups in the backbone can be generated by the metathetical reaction shown in Eq. 14.1. Doping of these polymers with acceptors such as h. Bra, or AsFs increases the conductivity to ca. lO " cm. ... 

The phenylene group is removed oxidatively with Pb(OAc)4 in dioxane. 4-Triphenylmethylaminophenyl 4-[(C6H5)3CNH]C6H4-Formation... 

Now let us consider some reference skeletal group Go. For convenience, we shall choose as the reference skeletal group the p-phenylene group. We define... 

Rate constant for protonation/s Rate constant for deprotonation/l mol s One central ethylene group is substituted by a 1,2-phenylene group. 

Fig. 14 Crystal structure of 2 OEt-2 OPr. Two molecules making a pair (B and C) and two neighbouring molecules in the other pairs (A and D) viewed along the phenylene groups in molecules B and C. All the ester alkyl moieties are depicted by an ethyl group.

Instead of or in addition to CH2, a phenylene group may be built in, as in the simple snlfonic acid cation exchanger shown schematically, in just two dimensions, in Fig. 26.1. 

The TT-electron system-substituted organodisilanes such as aryl-, alkenyl-, and alkynyldisilanes are photoactive under ultraviolet irradiation, and their photochemical behavior has been extensively studied (1). However, much less interest has been shown in the photochemistry of polymers bearing TT-electron substituted disilanyl units (2-4). In this paper, we report the synthesis and photochemical behavior of polysiloxanes involving phenyl(trimethylsilyl)-siloxy units and silicon polymers in which the alternate arrangement of a disilanylene unit and a phenylene group is found regularly in the polymer backbone. We also describe lithographic applications of a double-layer system of the latter polymers. 

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