Oligomers with terminal functional groups

The above-described two-step processes yield polymers that evolve volatiles upon further heating because the condensations continue. To overcome this drawback, prepolymers were developed thatundeigo addition-type reactions at fairly moderate time-temperature schedules. Such prepolymers are terminated by functional groups. The following is an example of one such material, an oligomer, polyquinoxaline-terminated by acetylene groups  

No volatiles can be detected by mass spectrometiy and thermogravimetric analyses during the crosslinking reaction. The thermooxidative stability of the resultant polymers is at least equivalent to polyphenylquioxalines not terminated by acetylene. The crosslinking reaction was shown on a model compound to be an intramolecular cyclization  

Aromatic polyamides with terminal acetylenic groups were formed from 2,2 -diiodo-diphenyl-4,4 -dicarbonyl chloride reacted with aromatic diamines. The phenylethynyl groups were introduced by reacting the iodine moieties with copper phenyl acetylide. Thermal treatment converted the prepolymers to 9-phenyl dibenzanthracene based rigid-rod polymers that fail to melt below 500 

High molecular weight polyquinoxaline polymers were prepared from 3,3, 4,4 -tetraamino-biphenyl that was reacted with aromatic bis(a-diketones) and/or ethynyl-substituted aromatic bis(a-diketones). The polymers contain 0, 5, 10, 30, and 100% pendant groups. Also, ethynyl-substituted diketones were synthesized by the following procedure  

The above reactions yield polymers with high Tg values. The materials, however, exhibited lowered thermooxidative stability. The same was found to be true when the ethynyl moieties were replaced by phenylethynyl groups 

Such prepolymers are terminated by functional groups. Following is an example of one such material, an oligomer, polyquinoxaline terminated by acetylene groups  

It is not necessary for the acetylenic groups to be on the terminal ends of the prepolymers. They can also be located as pendant structures [216]. 

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Polyethylene oligomers with terminal functional groups... 

Oligomers and polymers with reactive functional groups have been used extensively to prepare a great variety of polymeric materials. In many cases the behavior of these functional homopolymers is largely dependent on the nature and number of functional groups. In a number of important applications the functional groups are located at the end of the polymer chain macromolecules with terminal functional groups are usually termed telechelics or macromonomers . To characterize them it is necessary to have information not only about their molar mass but also on their functionality. 

Poly (ary lene ether sulfone)s and poly(arylene ether ketone) have been employed to prepare block and graft copolymers. Generally, the block copolymers can be prepared by reacting functional-group-terminated oligomers with other functional oligomers and monomers. 

A similar procedure was also used for the synthesis of methacrylate functional poly(a-MeS) [80]. Thus, 31 was used in conjunction with SnBr4 in CH2C12 at -78 °C, to obtain the macromonomer with Mns substantially (-50%) higher than the theoretical value. This was probably due to the formation of terminated low MW oligomers with indanyl end group structure. The eliminated proton was as-... 

The telechelic PTHF, with terminal hydroxyl groups, is obtained by the hydrolysis of structure 7.7 with sulfate ester units (reaction 7.8). The products of hydrolysis are sulfuric acid and hydroxy-telechelic PTHF with a practically theoretical functionality (f), of 2 OH groups/mol, without unsaturation. It is very important that the content of cyclic oligomers is extremely low, practically negligible. 

In Chapter 3, the chemistry and technology of the most important oligo-polyols used for elastic polyurethanes fabrication, in fact high MW oligomers (2000-12000 daltons) with terminal hydroxyl groups and low functionality (2-4 hydroxyl groups/mol) were discussed. Polyalkylene oxide polyols (homopolymers of PO or copolymers PO - EO, random or block copolymers), polytetrahydrofuran polyols, filled polyols (graft poly ether polyols, poly Harnstoff dispersion - polyurea dispersions (PHD) and polyisocyanate poly addition (PIPA) polyols), polybutadiene polyols and polysiloxane polyols were all discussed. The elastic polyurethanes represent around 72% of the total polyurethanes produced worldwide. 

ADMET polymerization and depolymerization methods have been used in the synthesis of telechelic oligomers. The metathesis depolymerization of 1,4-polybutadiene is accomplished in the presence or absence of a monofunctional diene by using either of the catalysts presented in Figure 13. Telechelic oligomers with terminal alkene, ester, and silyl ether and imide functional groups may be... 

As result of such a reaction telomere molecules are formed, which differ from the oligomer molecules by their ends. These are laige substituents coming from the decomposition of the solvent molecule (e.g., Cl and such groups as CCI3, CHCl, CH CH Cl, etc.), which exert a decisive influence on the properties of the final product. For this reason, telomeres cannot be equated with oligomers, which do not have reactive terminal functional groups. 

The common synthetic route to bismaleimides or maleimide functionalized oligomers is the condensation of diamines or amino-terminated oligomers with maleic anhydride. Another possibiUty is the use of an AB-type monomer of the following general formula to build the polymaleimide, where X represents a functional group that can be employed in condensation reactions. 

Siloxane Oligomers with Functional Groups Directly Bonded to the Terminal Silicon Atoms (Si—X)... 

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