Etherification phase transfer catalyzed

PECH was modified under similar reaction conditions, except that dimethylformamide (DMF) was used as the reaction solvent. In addition, the phase-transfer-catalyzed etherification of the chloromethyl groups of PECH with sodium 4-methoxy -4 -biphenoxide was used to synthesize PECH with direct attachment of the mesogen to the polymer backbone. Similar notations to those used to describe the functionalized PPO are used for functionalized PECH. In this last case, PPO was replaced with PECH. Esterification routes of both PPO and PECH are presented in Scheme I. 

The major difference between our reaction conditions and the conventional phase transfer catalyzed Williamson etherification (22) is the use of stoichiometric amounts of phase transfer catalyst versus the nucleophilic chain ends in the former case. Under these... 

In conclusion, phase transfer catalyzed Williamson etherification and Wittig vinylation provided convenient methods for the synthesis of polyaromatics with terminal or pendant styrene-type vinyl groups. Both these polyaromatics appear to be a very promising class of thermally reactive oligomers which can be used to tailor the physical properties of the thermally obtained networks. Research is in progress in order to further elucidate the thermal polymerization mechanism and to exploit the thermodynamic reversibility of this curing reaction. 

This reaction would provide completely unique polycondensation kinetics and explain perhaps the peculiarities of several phase transfer catalyzed poly-etherifications. One of these peculiarities observed also in the present case refers to the formation of polyethers at low conversion (Table 1). 

The phase transfer catalyzed reaction of these a,w-di(electrophilic) polyether sulfones with 2-(p-hydroxyphenyl)-2-oxozoline gave a,o)-di(2-oxazo-line) polymers (Scheme 3). The etherification was performed in a two phase liquid-liquid (chlorobenzene, 50% aqueous NaOH) reaction mixture with equimolar amounts of phase transfer catalyst versus phenol groups at room temperature. 

An aromatic polyformal was also prepared from bisphenol-A and methylene chloride by phase-transfer-catalyzed etherification in the presence of 2-(p-hydroxyphenyl)-2-oxazoline as an encapping agent. A polyformal with two oxazoline chain ends was obtained. When a mixture of DMSO and CH2CI2 was used as a solvent rather than only CH2CI2, a pol3nner with both oxazoline and... 

The synthesis strategy for y/alcohols is depicted in Figurel 1,6a and 11.6b. 5/alcohols were converted into monomers or attached to polymer chains by several subsequent reactions. Etherification with allyl bromide resulted in allyl ethers [54] (Figure 11.6c). Phase transfer-catalyzed etherification of y/alcohols and p-(chloromethyl) styrene yielded y/styrene [35] (Figure 11.6d). By reaction with (meth)acryloyl chloride, sf (meth)acrylates were obtained, a method that was widely employed [36, 55, 56] (Figure 11.6e). Besides, the reaction of isocyanatoethyl (meth)acrylate with ... 

Initially, polyethers based chromophore 1 were synthesized to explore the chemistry of the dye and to develop discotic liquid crystalline materials. These materials were prepared by phase transfer catalyzed Williamson etherification (Scheme 1). The first prepared polyether was based on 1 and had a spacer length of four methylene units (n=4, x=0). This demonstrated the chemistry, but the material possessed limited solubility in common organic solvents. Consequently, longer spacers (n=10, x=0) were incorporated to prepare soluble homopolymers of 1. The iH-NMR spectrum confirmed the structure but the polymer displayed a glass transition temperature of 100 °C. Furthermore, the absence of a melting point and a WAXD crystalline structure indicated the materials were amorphous. 

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