Gilch method

The polymerization of l,4-bis(halomethyl)benzenes to PPVs in the presence of a large excess of potassium f-butoxide is referred as the Gilch route [81]. The method was first described for the synthesis of unsubstituted PPV 60, but -unfortunately - this route produces the PPV as an intractable, insoluble powder. However, the adaptation of the Gilch route to the polymerization of l,4-bis(halo-methyl)benzenes possessing solubilizing side groups gives access to soluble PPV materials. 

A general and most widely used method for the synthesis of PPV derivatives was introduced by Gilch and Wheelwright [33]. This method avoids high-temperature conditions and occurs through base-promoted 1,6-elimination of 1,4-/Ys(chloro/bromomethyl)bcnzcncs 7 (Scheme 2.4). For device applications, the as-synthesized PPV materials need to be soluble... 

It should be noted that the Gilch [32] polymerization method using excess potassium f-butoxide at room temperature does not provides us with fully eliminated polymers. Figure 12 compares the UV-vis absorptions of P-8 s with different thermal history and it shows that thermal treatment of the polymer at 150 °C in a vacuum not only moves the absorption position for 7t-7i transition to the longer wavelength side but also increases the absorption intensity for the same... 

Although direct proof was not available until recently, chemical arguments, experimental indications, and the analogy to the aforementioned methods led to the assumption that the Gilch synthesis proceeds according to Scheme 29.3 p-quinodimethane-type species 11 probably are the active monomers, and... 

The most common synthetic routes for traditional PPVs are the Gilch, Witting condensation, and Wessling methods (Figure 11.12) [2]. For multifunctional and... 

Other Routes. Substituted PPV derivatives have also been prepared by several other routes. In cases where the resulting polymers are soluble, these methods are often successful in preparing high molecular weight material. The Gilch route has been used to prepare phenyl and crown ether substituted polymers... 

The firsX(lO) and the second/"//J methods are known to be Wessling-Zimmerman method and Gilch-Wheelwright polymerization, respectively. The last reaction route is practically the same as that is utilized in the synthesis of poly(/ -xylylene) from /7-xylene via the CVD polymerization method. The first two methods have been widely used not only in the synthesis of PPV but also PPV derivatives. Since the methods produce soluble precursor polymers, the final polymer can be obtained in various shapes. 

A common feature of these three methods is the polymerization of 1,4-xylylene intermediates to 1,4-phenyleneethylenes which are then subjected to thermal 1,2-elimination reactions of SR2/HCI [29], HCl [30, 32] or RSOH [31], The Gilch route proved to be very valuable for technical processes. 

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