Residual and Unreacted Starting Materials

Many manufactured polymers contain either unreacted monomer, or low molecular weight polymer (oligomers) in amounts varying from a few parts per million to several percent depending on the manufacturing process used and the type of polymer. Low molecular weight products are particularly prevelent in thermosets. Fiowever, even 

Low pressure polyolefins can in fact contain up to 1 % on a volnme - volnme basis of unreacted monomer, especially when the polymer is newly mannfactnred. 

Indeed, simple monomers, snch as styrene, ethylene, propylene, hexene, vinyl chloride, acrylonitrile and caprolactam, nsnally do occur in the corresponding polymers. In addition to unreacted monomer, any non-polymerisable impnrities in the original monomer feed to the polymerisation conld occur in the final prodnct. Thns, styrene monomers can contain low concentrations of numerous saturated and nnsatnrated hydrocarbons, ethyl benzene being particnlarly prevelent and these, particnlarly the saturated compounds which do not polymerise, will occur in the finished polymer and have implications in the nse of the polymer food packaging. It is not nnknown for compounds as toxic as benzene to occnr at very low concentrations, nsnally less than 10 parts per million in styrene monomer, and this could, therefore, also occur in the polymer. For foodgrades of polystyrene, the monomer content is nsnally nowadays limited to 0.2% maximum. Acrylonitrile monomer may be fonnd in amonnts up to 0.1 % in finished polymer, whilst negligible amounts of monomer are fonnd in polyamide and polymethyl-1-pentene. With thermosets, phenol and formaldelyde are likely to be found even in the most carefully manufactured grades. 

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Under argon, a mixture of 145 (0.046 mmol), 132 (0.046 mmol), Pd(PPli3)4 (0.2 (junol), Cul (0.2 [miol), and diisopropylamine (0.015 mmol) in THF (4 mL) was stirred in the dark at 50°C for 2 days. Ethynylbenzene (0.92 mmol) was then added and stirred at 50°C overnight. After concentration, die residue was dissolved in CHCI3 and filtered. The filtrate was subjected to preparative SEC with CHCI3 as eluent in order to remove catalyst residues and unreacted starting materials. Polymer 42 was obtained as a yellow solid in 85% yield. SEC analysis (THF, polystyrene standards) Mw = 280,000 (PDI = 6.5). 

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