Poly dimers

Poly(dimercuryimmonium acetylide), 0665 Poly(dimercuryimmonium azide), 4606 Poly(dimercuryimmonium bromate), 0253 Poly (dimer curyimmonium hydroxide), 4416 Poly(dimercuryimmonium iodide hydrate), 4449 Poly (dimer curyimmonium perchlorate), 4006 Poly(dimercuryimmonium permanganate), 4603 See other MERCURY COMPOUNDS, N-METAL DERIVATIVES... 

An example of such a reaction is discussed. Reaction of bis(1,1-diphenyl ethylene) linked by a chain of aliphatic hydrocarbon yields on reduction with alkali metals or suitable electron donors, e,g, naphthalenide, a product of poly-dimerization. For example ... 

Poly(dimer acid co-ethylene glycol), hydrogenated 68855-78-7 Fatty acids, C 18-unsatd., thmers, hydrogenated, polymers with ediylene glycol s Unk... 

The polymer described in the last problem is commercially called poly (phenylene oxide), which is not a proper name for a molecule with this structure. Propose a more correct name. Use the results of the last problem to criticize or defend the following proposition The experimental data for dimer polymerization can be understood if it is assumed that one molecule of water and one molecule of monomer may split out in the condensation step. Steps involving incorporation of the monomer itself (with only water split out) also occur. 

Moreover, where i r-acetjldi- -xyljlene [10029-00-2]( is pyroly2ed, by adjusting temperatures in the deposition region, it is possible to isolate two different polymeric products, ie, poly(acetyl-/)-xylylene) [67076-72-6] (8) and poly(p-xylylene) (PPX) (2). This of course requires the cleavage of the original dimer into two fragments. 

Because lactic acid has both hydroxyl and carboxyl functional groups, it undergoes iatramolecular or self-esterificatioa and forms linear polyesters, lactoyUactic acid (4) and higher poly(lactic acid)s, or the cycUc dimer 3,6-dimethyl-/)-dioxane-2,5-dione [95-96-5] (dilactide) (5). Whereas the linear polyesters, lactoyUactic acid and poly(lactic acid)s, are produced under typical condensation conditions such as by removal of water ia the preseace of acidic catalysts, the formation of dilactide with high yield and selectivity requires the use of special catalysts which are primarily weakly basic. The use of tin and ziac oxides and organostaimates and -titanates has been reported (6,21,22). 

The backbone of poly(phenylene oxide)s is cleaved under certain extreme reaction conditions. Lithium biphenyl reduces DMPPO to low molecular weight products in the dimer and trimer molecular weight range (20) and converts poly(2,6-diphenyl-l,4-phenylene oxide) to 3,5-diphenylphenol in 85% yield (21) (eq. 4). 

Miscellaneous Commercial Applications. Dimer acids are components of "downweU" corrosion inhibitors for oil-drilling equipment (see Petroleum Corrosion and corrosion inhibitors). This may account for 10% of current dimer acid use (71). The acids, alkyl esters, and polyoxyalkylene dimer esters are used commercially as components of metal-working lubricants (see Lubrication). Dimer esters have achieved some use in specialty lubricant appHcations such as gear oils and compressor lubricants. The dimer esters, compared to dibasic acid esters, polyol esters and poly(a-olefin)s, are higher in cost and of higher viscosity. The higher viscosity, however, is an advantage in some specialties, and the dimer esters are very stable thermally and can be made quite oxidatively stable by choice of proper additives. 

More interest has been shown in polymeric flexibilisers, particularly the low molecular weight polyamides from dimer acid (see Chapter 18), the low molecular weight poly sulphides (Chapter 19), polyamines and the polyglycol diepoxides. 

Water-soluble polymers obtained through a radical polymerization [e.g., poly(acrylic acid) PAA] often contain sodium sulfate Na2S04 as a decomposition product of the initiator. The peak of Na2S04 is eluted before the dimer. In the interpretation of the chromatogram, a typical GPC program has to be truncated before the Na2S04 peak, or at a Mpaa value of about 200. The calibration curve in this region can be flattened by an additive small pore column as well, but the principle problem remains unsolved. 

FIGURE 7.30 Poly(a -L-guluroiiate) strands dimerize in the presence of Ca"", forming a structure known as an egg carton. ... 

The phase behavior of several polybibenzoates with oxyalkylene spacers has been reported [11,14,15,20-27]. These spacers include the dimer of trimethylene glycol and different ethylene oxide oligomers. The most noticeable characteristic of these polybibenzoates with ether groups in the spacer is the considerable decrease of the rate of the mesophase-crystal transformation. Thus, Fig. 8 shows the DSC curves corresponding to a sample of poly[oxybis(trimethylene)p,p -bibenzoate], PDTMB, with a structure similar to that of P7MB but with the... 

Similarly, two living polystyrene chains were terminated with the azobisacid chloride ACPC yielding poly-(styrene) with one central azo group [74]. The yield of dimerization was found to be higher when the living chain was treated with 1,1-diphenyl ethylene before reacting it with ACPC. 

This strategy is used for the synthesis of three different exact-mass telechelic oligomers. GPC, NMR, and GC/MS evidence indicates that clean depolymerization chemistry occurs for all three samples. Poly( 1,4-butadiene) (38) is broken down into oligomeric units with two, three, and four repeat units using catalyst 23. Catalyst 14 is more efficient and produces even lower molecular weight oligomers, primarily one and two repeat units. When allylchlorodimethylsilane is used instead of ethylene with 14, telechelic dimers are the only product. 

Recently siloxane-imide copolymers have received specific attention due to various unique properties displayed by these materials which include fracture toughness, enhanced adhesion, improved dielectric properties, increased solubility, and excellent atomic oxygen resistance 1S3). The first report on the synthesis of poly(siloxane-imides) appeared in 1966, where PMDA (pyromellitic dianhydride) was reacted with an amine-terminated siloxane dimer and subsequently imidized 166>. Two years later, Greber 167) reported the synthesis of a series of poly(siloxane-imide) and poly(siloxane-ester-imide) copolymers using different siloxane backbones. However no physical characterization data were reported. 

Other hand, when an equimolar mixture of 2,5-DSP and l OEt is recrystallized from benzene, yellow crystals, comprising 2,5-DSP and l OEt in a molar ratio of 1 2, deposit. In the DSC curve of this crystal, a single endothermic peak is observed at 166°C, which is different from the melting point of either 2,5-DSP (223°C) or l OEt (156°C). Furthermore, the X-ray powder diffraction pattern of the crystal is quite different from those of the homocrystals 2,5-DSP and l OEt. Upon irradiation the cocrystal 2,5-DSP-l OEt affords a crystalline polymer (77i h = 1.0 dl g in trifluoroacetic acid). The nmr spectrum of the polymer coincides perfectly with that of a 1 2 mixture of poly-2,5-DSP and poly-1 OEt. In the dimer, only 2,5-DSP-dimer and l OEt-dimer are detected by hplc analysis, but the corresponding cross-dimer consisting of 2,5-DSP and l OEt is not detected at all (Hasegawa et al., 1993). These observations by nmr and hplc indicate that the photoproduct obtained from the cocrystal 2,5-DSP-l OEt is not a copolymer but a mixture of poly-2,5-DSP and poly-l OEt in the ratio 1 2. 

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