Monomer-oligomer

IV Sartomer Monomer/Oligomer Photoinitiator Product Line Literature, Sartomer Co., Exton, Pa., 1991 D. H. Solomon, The Chemistry of Film Fokwot, John Wdey Sons, Inc., New York, 1967. 

Monomer-oligomer equilibria. [Ni(Me-sal)2], mentioned above as a typical planar complex, is a much studied compound. In pyridine it is converted to the octahedral bispyridine adduct (/zsoo = 3.1 BM), while in chloroform or benzene the value of is intermediate but increases with concentration. This is ascribed to an equilibrium between the diamagnetic monomer and a paramagnetic dimer, which must involve a coordination number of the nickel of at least 5 a similar explanation is acceptable also for the paramagnetism of the solid when heated above 180°C. The trimerization of Ni(acac)2 to attain octahedral coordination has already been referred to but it may also be noted that it is reported to be monomeric and planar in dilute chloroform solutions. 

Cleaning fabrics, quartz rods for light guide fibers, residues in microelectronics Removal of monomers, oligomers, and solvent from polymers Fractionation... 

Applications Pressurised fluid extraction (ASE , ESE ) is still in its early stage of development, both for polymeric and other samples. At present, most applications are found in the environmental, food, pharmaceutical and nutraceutical areas. Few reports describe the application of PEE to the extraction of monomers, oligomers and additives from polymers and most work is very recent. An application note [488] has provided some guiding principles for ASE applied to additives in polymers, namely as follows ... 

Explain the differences between monomers, oligomers and polymers. Draw examples of each. 

An alternative to the extraction of intact PHA polymer is the isolation of PHA monomers, oligomers, or various derivatives such as esters [74]. PH As are composed of stereo-chemically pure P-3-hydroxyacids, and therefore can be used as a source of optically pure organic substrates for the chemical and pharmaceutical industry [79]. In this protocol, the defatted cake containing PHA polymer would be chemically treated to obtain the PHA derivatives. For example, transesterification of the meal with methanol would give rise to methyl esters of 3-hydroxyalkanoic acids. The PHA derivatives would then be separated from the meal with appropriate solvents. One potential disadvantage of this method is the potential alteration of the quality of the residual meal if the harsh chemical treatments required for the production of PHA derivatives lead to protein or amino acid breakdown. 

U. Scherf and K. Mullen, Design and synthesis of extended TT-systems monomer, oligomers, polymers, Synthesis. 23-38, 1992. 

Example Procedure for Preparation of Halo-Terminated Intermediate Monomer/Oligomer Mixtures... 

After final chromatographic purification, samples of the AT-systems were cured in air at 288°C (550°F) for eight hours. Samples chosen for curing included pure monomers, monomer/oligomer mixtures produced by the stoichiometry outlined In the previous section, and In one case (the bisphenol-A based resin) pure oligomer. This set of samples was selected to provide data showing the effect of oligomer concentration on thermomechanical properties. 

The second and third steps in the monomer synthesis involve the replacement of bromine with an acetylene protected by an acetone adduct, followed by cleavage of the adduct. These steps will be discussed in more depth later as they are the same for systems containing only monomer or a monomer/oligomer mixture. 

The fact that the incorporation of thiodiphenol into the backbone produced both undesired crystallinity and a low final Tg led to a decision not to synthesize the monomer/oligomer mixture for this system. 

Monomer/Oligomer Synthesis. The first two steps in the four step reaction sequence of Figure 1 are capable of producing both monomer and oligomer. The first step, aromatic nucleophilic substitution, is a polymer forming reaction under the correct stoichiometric conditions. In order to favor the formation of monomer with a small amount of oligomer, the substitution was carried out at a 4 1 ratio of diol to dichlorodiphenyl sulfone. This led to a predominantly monomeric product (IV) with only the requirement that the excess diol be removed from the product to eliminate the potential presence of low molecular weight species in later reactions. 

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. 

Brominated Monomer/Oligomer Mixtures from IV (V). The brominated sulfone monomer/oligomer mixtures were preparedby two different methods. Method A A mixture of pyridine (70mL), IV (11.5 mmol), dibromobenzene (26.96g, 115 mmol), anhydrous potassium carbonate (7.94g, 57.5 mmol) and cuprous iodide (0.13g, 0.7 mmol) was heated at reflux under nitrogen for 24h. After cooling to room temperature, the reaction mixture was acidified with IN HC1 and the aqueous solution extracted with ether. The organic phase was reduced in volume to a brown gum which was washed several times with hexane and then dried to give a 75-95% yield of the dibromo product. 

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... 

---