Oligomer small

This, however, is an oversimplification, since these monomeric anions are in rapid equilibrium with oligomers (small polymers) such as the dimer (cf. Fig. 7.2b), cyclic trimer (7.2c), and other small silicate oligomers, 22 of which have been identified by silicon-29 magnetic resonance methods and many of which have no counterparts in solid silicate minerals9 ... 

A more unusual version of the n = 2 form possible is the dimeric complex [(NH3)2Pt(p,-Cl)2Pt(NH3)2]Cl2, where two chloride ions bridge between and link the two metal centres with coordinate covalent bonds. Since the syntheses of the two n = 2 species differ, this is more an intellectual exercise than a difficult case. However, this example does serve to remind us that oligomers (small polymers) are frequently met in coordination chemistry. 

The persistence length model therefore describes the whole spectrum from the more rodlike oligomers (small j) to the well-developed coils (large y). However, the model ignores the finite thickness of the chain, and so it only holds strictly for unperturbed coils. The error due to the finite thickness may be neglected when the persistence length is much greater than the chain thickness. 

Therefore, from these and previous inferences, it may deduced that, at the molecular level, ED/W binary mixtures are very heterogeneous as a consequence of a separation of microphases. This probably implies that the aggregation of different type of clusters, such as tetrahedral or Wj oligomers, small ED homopolymers, and ED/W heteropolymers, should lead to interstitial solvation of one species into the other. Obviously this polyaggregation of clustered species provides the greatest effect corresponding to the hypothetical formation of a 2ED 3W solvent/cosolvent complex, whose existence seems to be still far away from being proven. 

Oligomer Small polymeric molecules generally containing ten or fewer monomer units. 

Oligomer (Section 14 15) A molecule composed of too few monomer units for it to be classified as a polymer but more than in a dimer trimer tetramer etc Oligonucleotide (Section 28 6) A polynucleotide containing a relatively small number of bases Oligosaccharide (Section 25 1) A carbohydrate that gives three to ten monosacchandes on hydrolysis Optical activity (Section 7 4) Ability of a substance to rotate the plane of polanzed light To be optically active a sub stance must be chiral and one enantiomer must be present in excess of the other... 

Hydrocarbons. Synthesized hydrocarbons are the most popular of the synthetic base stocks. These are pure hydrocarbons (qv) and are manufactured from raw materials derived from cmde oil. Three types are used olefin oligomers, alkylated aromatics, and polybutenes. Other types, such as cycloahphatics, are also used in small volumes in specialized apphcations. 

Polymers from either of these homologous series can be made to predominate by usiag a small excess of the diamine or diacid, respectively. In addition to these linear polymers, cycHc oligomers are also formed, though ia this case n... 

The polymer is then dried thoroughly and stored for subsequent processing. Whenever a polyester is made by melt polycondensation, a small amount of cycHc oligomer is formed which is in equiHbrium with the polymer. This can be extracted with solvents from soHd polymer but when the... 

The 4,4 -MDA is sold commercially with a diamine assay of 98 —99%. The major impurity is the 2,4 -MDA isomer, which can be present in amounts up to 3%. PMDA products are normally defined by hydrogen equivalent weight and viscosity. Typical products exhibit a 50 hydrogen equivalent weight and a viscosity of 80 140 mPa-s(=cP) at 70°C. PMDA products normally contain, in addition to the isomers and oligomers of MDA, small amounts of aniline, water, chlorides, and various alkylated amines. AH MDA products should be stored in sealed containers in a cool dry area. 

The ratio of cycHc to linear oligomers, as well as the chain length of the linear sdoxanes, is controlled by the conditions of hydrolysis, such as the ratio of chlorosilane to water, temperature, contact time, and solvents (60,61). Commercially, hydrolysis of dim ethyl dichi oro sil a n e is performed by either batch or a continuous process (62). In the typical industrial operation, the dimethyl dichi orosilane is mixed with 22% a2eotropic aqueous hydrochloric acid in a continuous reactor. The mixture of hydrolysate and 32% concentrated acid is separated in a decanter. After separation, the anhydrous hydrogen chloride is converted to methyl chloride, which is then reused in the direct process. The hydrolysate is washed for removal of residual acid, neutralized, dried, and filtered (63). The typical yield of cycHc oligomers is between 35 and 50%. The mixture of cycHc oligomers consists mainly of tetramer and pentamer. Only a small amount of cycHc trimer is formed. 

Pure D-fmctose is a white, hygroscopic, crystalline substance and should not be confused with the high fmctose com symps (HFCS) which may contain 42—90 wt % fmctose and 23—29% water (8,9). The nonfmctose part of these symps is glucose (dextrose) plus small amounts of glucose oligomers and polymers. Fmctose is highly soluble ia water at 20°C it is 79% soluble, compared with only 47% for glucose and 67% for sucrose. 

Esterification. Esterification of an acid and an alcohol can be catalyzed by small quantities of tetraalkyl titanates (see Esterification). Although the water that forms can hydrolyze and kiactivate the titanate, titanoxane oligomers are cleaved by carboxyHc acids to bicoordinated monomeric acylates. A simplified mechanism is illustrated ... 

The polystyrene-terephthalate copolymer is used as a raw material for transparent bottles of refreshing drinks. It becomes clear that the polymer contains a small amount of oligomer. 

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