POLY ETHERS

Polyethers may be obtained from three different classes of monomer, namely carbonyl compounds, cyclic ethers and phenols. These three types of polyether are considered separately in this chapter. 

Polymers of several aldehydes and ketones and halogenated derivatives have been prepared. As yet, only those of formaldehyde have achieved commercial importance these polymers are described in detail in the next section. 

Polymers of aldehydes are commonly termed polyacetals (or acetal resins) since their structure resembles that of polymers obtained by the acetal-forming reaction between aldehydes and diols  

It may be noted that the reaction shown above can actually be used for the preparation of polymers but it does not represent a commercially used method. Similarly, polymers of ketones are sometimes termed polyketals. The aforementioned polymers should not be confused with the poly(vinyl acetal)s and poly(vinyl ketal)s discussed in Chapter 5. 

As mentioned earlier, polymers of formaldehyde are described in the next section. Polymers of higher aliphatic aldehydes and ketones have been extensively investigated but, in general, they do not have the stability necessary for commercial development. For example, acetaldehyde may be polymerized using organometallic initiators at low temperatures, e.g., triethylaluminium at —78 C in this case crystalline isotactic polymer is obtained. Also, the polymerization of acetaldehyde may be effected with cationic initiators at low temperatures (e.g., aluminium chloride at —65°C) or with metal oxides at low temperatures (e.g., alumina at —70°C) in these cases amorphous atactic polymer is obtained. The tacticity of polyacetaldehyde arises because the polymer comprises structural units which contain an asymmetric carbon atom  

There are various procedures for the preparation of polyethers. These procedures typically start with oxirane or oxirane derivatives (e.g. propylene oxide, etc.). Base catalyzed anionic polymerization, acid initiation, or complex coordination catalysis can be used for the reaction [1-3], Not only oxiranes can generate polyethers. Diols also can be used for polyether synthesis. Other source compounds include tetrahydrofuran, which can be polymerized to a polyether using fluorosulfonic acid (HSO3F) as a catalyst, oxetane (trimethylene oxide) or oxetane derivatives, which can be polymerized to generate polyethers with practical applications such as poly[bis(chloromethyl)oxetane], etc. 

Several reports are available In literature regarding thermal decomposition of poly(ethylene oxide) not in flash pyrolysis conditions. One such report indicates that at temperatures between 324° C and 363° C, the polymer generates 9.7% of volatile compounds (at 25° C), 3.9% monomer with smaller amounts of CO2, formaldehyde, ethanol, and saturated C1-C7 compounds [4]. Another report indicates that at temperatures between 225° C and 250° C, the polymer generates CO2, HCHO, 

CH3CHO and (CH3CH2)20. Other reports on PEG are also available in literature. These reports cover various conditions of decomposition, such as low-temperature pyrolysis [5], or thermooxidative degradation of the homopolymer with or without added salts. In thermooxidative degradation PEG forms similar products as in an inert atmosphere [6, 

At 280° C the decomposition products are reported to be diethyl ether, ethyl methyl ether, acetaldehyde, formaldehyde, CO2, CO, ethene, cyclohex-3-ene-1 -one [6]. 

Flash pyrolysis studies on PEO showed that the degradation starts in the range 235-255° C with C-0 and C-C bond scission, leading to a complex mixture of compounds. The possible bond cleavages are the following  

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Properties Unfilled 20% glass-fiber- reinforced Unfilled 20% glass-fiber- reinforced Poly(ether sulfone) Poly(phenyl sulfone)... 

A large variety of newer poly(ether imide)s has been described. Included among these are perfluorinated polymers (96), poly(ester ether imide)s (97), poly(ether imide)s derived from A/,Ar-diamino-l,4,5,8-naphthalenetetracarboxyHcbisimide (98), and poly(arylene ether imide ketone)s (99). In addition, many other heterocyHc groups have been introduced into polyether systems, eg, poly(pyrazole ether)s (100) and poly(aryl ether phenylquinoxaLine)s (101) poly(aryl ether oxazole)s with trifluoromethyl groups (102) and polyethers with other heterolinkages, eg, poly(arylether azine)s (103). 

The effect of a second polymer blended with PPS which causes enhanced nucleation of PPS has been previously observed. It was found that low concentrations (1—2 wt %) of poly(phenylene sulfide ketone) and poly(ether ether ketone), when melt-blended with PPS, function effectively to increase the nucleation density of PPS (149). 

Polyarylether Ketones. The aromatic polyether ketones are tme thermoplastics. Although several are commercially available, two resins in particular, poly ether ether ketone [31694-16-3] (PEEK) from ICI and poly ether ketone ketone (PEKK) from Du Pont, have received most of the attention. PEEK was first synthesized in 1981 (20) and has been well studied it is the subject of numerous papers because of its potential use in high performance aircraft. Tough, semicrystalline PEEK is prepared by the condensation of bis(4-fiuorophenyl) ketone with the potassium salt of bis(4-hydroxyphenyl) ketone in a diaryl sulfone solvent, such as diphenyl sulfone. The choice of solvent is critical other solvents, such as Hquid HE, promote the reaction but lead to premature low molecular-weight crystals, which do not exhibit sufficient toughness (21). 

Crown Esters and Macrocy die Poly ether Lactones... 

Molecules that contain several ether functions are refened to as poly ethers. Polyethers have some novel properties and will appear in Section 16.4. 

When B2H6 is to be used as a reaction intermediate without the need for isolation or purification, the best procedure is to add Et20Bp3 to NaBH4 in a poly ether such as diglyme ... 

These syntheses can be considered as heterocyclic analogue of the poly(ether imide) synthesis... 

Recently, Kricheldorf and Jahnke [108] reported pyridine and pyridazine containing poly(ether-sulfide)s by... 

Mn2(CO)io in a simple photoinitiated free radical polymerization. The antiplatelet activity of these polymers were compared with that of poly(ether-Wrethane) carrying the hydantoin residues in side chains. 

The structural effect of alkyl groups such as methyl, ethyl, and -butyl on the Rp is small. Alkyl 4-methyl-phenylcarbamate can be chosen as a model compound for the hard segment of poly(ether-urethane) (PEU). This group can initiate grafting reaction with Ce(IV) ion and the grafting site was proposed at the hard segment of PEU [3,15] as shown in Scheme (1). 

New Poly ester-Poly ether Binder for Extrusion-Cast Explosives , UCRL-50541, UAEC, Univ of Calif (1968) Ibid, NuclSciAbst 23 (9), 17314 (1969) CA 71,71343 (1969)... 

PAs have also been copolymerized with other polymer systems and, in particular", with polyesters and poly ethers. In the copoly esteramides the crystallinity is decreased by copolymerization, as the crystalline structure of the amide unit is very different from the ester unit. However, alternating polyesteramides behave as homopolymers with a glass ttansition temperature and a melting temperature intermediate to the polyester and the PA polymer (Figs. 3.10 and 3.11).23,24 Polyesters, such as PBT and PET, modified with a small amount of diamide are also copolymers that have a high order.24,73... 

An amine-terminated poly ether (ATPE) is prepared as follows. Charge poly(tetramethylene oxide) diol (PolyTHF 1000, BASF, 75.96 g, 0.0759 m) to a 500-mL three-neck round-bottom flask fitted with a thermocouple, a mechanical stirrer, and a vacuum port. Add tert-butylacetoacetate (24.04 g, 0.1582 m) and apply vacuum. Heat at 175° C for 4 h, Fourier transform infrared (FTIR) analysis should indicate complete loss of the polyol OH absorption at 3300 cm. The room temperature viscosity of the product should be about 520 mPa-s. React this acetoacetylated product (85.5 g, 0.0649 m) with cyclohexylamine (14.5 g, 0.1465 m) at 110° C under vacuum for several hours. Cool the resultant cyclohexylaminocrotonate poly ether product to room temperature (1790 mPa-s at room temperature). 

The AICI3-catalyzed polycondensation of diphenyl ether with a mixture of terephthaloyl chloride and isophthaloyl chloride is a relatively inexpensive route to poly(ether ketone)s. The polymerizations were carried out in chlorinated solvents... 

Scheme 6.9 Synthesis of poly(arylene ether ether ketone) (PEEK) and poly(ether ether ketone ether ketone (PEEKEK) in triflic acid.

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