Ethynyl monomer

Recently, Kolel-Veetil and Keller have modified this system to produce elastomeric networked polymers. The ambient-condition hydrosilation reactions between monomeric vinyl- or ethynyl-terminated carboranylenesiloxane and three different monomeric branched siloxane cross-linkers in hexane yielding these systems were catalyzed by the Karstedt catalyst.134 The reactions involving the vinyl-carboranylenesiloxane were reported to produce a set of completely hydrosilated networked polymers (105) (Fig. 65). In the case of the ethynyl monomer, the reactions were carried out at two different ratios, yielding a partially (106) and a com-... 

Key to the success of this co-cyclotrimerization procedure is the selection of the appropriate monomers. A co-cyclotrimerization in which one monomer reacts much more rapidly than the other will result in a heterogeneous product as the monomer ratio changes. Moreover, if the mono-ethynyl capping agent reacts much more slowly than the multi-ethynyl monomer, gel formation can occur early in the reaction. Alternatively, if the mono-ethynyl material reacts much more rapidly, it can be exhausted early in the reaction, having produced a non-reactive trimer, and the multi-ethynyl monomers will gel later in the reaction. These problems can be avoided by using monomers of comparable reactivity or by adjusting the feed ratio to compensate for unequal reactivities. With either approach, it is necessary to determine the relative cyclotrimerization rates of each ethynyl monomer. In this paper, we report the initial results of our measurements of these rates. 

The ethynyl monomer is reacted with an oligomeric imide terminated in anhydride groups to yield the ethynyl terminated oligomers as it is shown in Scheme (68). 

The monomer/oligomer mixtures were used In the third step of the reaction sequence, the replacement of bromine with 2-methyl-3-butyn-2-ol by use of the bls(trlphenylphosphlne) palladium chloride catalyst system. This reaction used a trlethylamine/pyridine solvent system to replace the bromines on the ether sulfone with ethynyl groups protected by acetone adducts. The acetone protecting groups were then removed In a toluene/methanol/potasslum hydroxide solvent system. 

Ethynyl Terminated Monomer/Oligomer Mixtures from VI (VII). A mixture of the bis-butynol adduct, VI (3.9 mmol), toluene (40mL) and 10% methanolic K0H (40mL) was heated to reflux under nitrogen. The methanol and toluene were removed by distillation, adding more toluene as needed to maintain the reaction volume at 40mL. After... 

Jegou and Jenekhe [63] have developed a different approach toward di-ethynylated quinoline monomers, as shown in Scheme 10. Reaction of 2-amino-5-bromobenzophenone with 4-bromoacetophenone gave 6-bromo-2-(4 -bro-mophenyl)-4-phenylquinoline, which was alkynylated and deprotected ac-... 

Attempts to elucidate the polymerization or copolymerization kinetics of ethynyl and maleimide-functionalized monomers have been undertaken via vibrational spectroscopy (137). The thermal polymerization of A-(3-ethynyl-phenyl) maleimide (the structure is given in Fig. 48) was studied via IR and Raman spectroscopy. This model compound is interesting because it carries maleimide and ethynyl groups attached to the same aromatic ring. Kinetic studies indicate that both the acetylene and maleimide group react at the same rate, which strongly suggests the formation of a copolymer rather than a mixture of homopolymers. 

N (3-Ethynyl phenyl maleimide is synthesized from 3-ethynylaniline and maleic anhydride in DMAc. The cyclodehydration of the resulting amide acid is performed in the usual way with acetic anhydride and nickel acetate as a base catalyst (138). This AB-type monomer has a melting point of 129-131 °C. The polymerization/copolymerization is extremely exotherm (720 J/g) and proceeds in the 180-220 °C temperature range. Furthermore, JV-(3-ethynyl... 

Oligomeric phenylalkynes, which are potentially interesting as liquid crystals [276] or for the construction of molecular electronic devices [277,278], have been prepared on insoluble supports by strategies such as that outlined in Figure 16.31. Substituted TMS-protected (ethynyl)iodobenzenes were used as monomers in this instance. Oli-gothiophenes have been prepared by a similar synthetic strategy [278]. 

Melissaris and co-workers [46] have studied various novel p-ethynyl-substituted rigid rod monomers by DSC, TG and TG-FTIR and identified the main decomposition products. Void-free neat resin mouldings were made by compression moulding the monomers followed by heating. 

Since there is almost no side-reaction in the polycondensation between metal halides and a, ethynyl compounds (Eqs. 11 and 12), polymers with a degree of polymerization which is nearly equal to that predicted theoretically and base on the monomer ratio, e.g. (31)/(32) in Eq. 11, are obtained. For example, the polycondensation of the system composed of the monomers (PBu3)2 PtCl2 and... 

Following the idea of the first approach, monomers with the l,4-bis[(3 -flu-oro-4 -n-alkoxyphenyl)-ethynyl]benzene mesogens were laterally linked via a CH2-spacer to norbornene, XX-n (n= 1-12). The low molecular mesogens with n>6 showed a k-S -Sc-n-i phase sequence, whereas the norbornene monomers XX-n exhibited only a monotropic or enantiotropic nematic mesophase, respectively [72]. 

One final structure in this series is the bis-TMEDA-solvated bis(phenylethynyl)magnesium species characterized as a monomer (111). ° Note the octahedral geometry of the central magnesium with two axial ethynyl ligands. This series of alkynic structures, (106)-(lil). serves to underscore the unpredictability of carbanion crystal structures. The alkynic carbanions have coordination numbers of one, two or three in these complexes. 

Fig. 5 Structures of the homoditopic (A-A, B-B) nucleobase terminated bis (phenyl-ethynyl)benzene monomers (BP1BP) investigated by Rowan, Mather et al. [63-65]...

Synthsis of High Carbon Materials from Acetylenic Precursors—Preparation of Aromatic Monomers Bearing Multiple Ethynyl Groups... 

Polymerization of propynaldehyde (CH=C-CH=0) is also unique. In dimethylformamide at O °C with sodium cyanide or with tri-n-butyl phosphine catalysts, the reactions yield polymers composed of two different structural units. One is a polyaldehyde and the other is a polyacetylene. The reaction in tetrahydrofuran, however, at -78 °C with sodium cyanide catalyst results in a crystalline poly(ethynyl oxymethylene). Radical initiated polymerizations of this monomer at 60 °C, on the other hand, proceed through the acetylenic group only. 

In addition to the monomers shown in Figure 5.9, decafluorobiphenyl and 3-ethynylphenol can be used. This results in polymers with terminal ethynyl groups [92]. 

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