Polycondensations in the Presence of Aromatic Phosphites: Conditions and Reaction Products
Titel:
Polycondensations in the Presence of Aromatic Phosphites: Conditions and Reaction Products
Auteur:
Aharoni, Shaul M.
Verschenen in:
International journal of polymeric materials
Paginering:
Jaargang 26 (1994) nr. 1-2 pagina's 9-17
Jaar:
1994-07-01
Inhoud:
Aromatic phosphites drive two kinds of condensation reactions: amidation and esterification. The amideforming reactions are far more efficient, lending themselves to polymerization as well as chain extension. The ester-forming reactions are significantly more sluggish, limiting their usefulness to the extension, grafting, or block copolymerization of appropriately terminated pre-existing polymer chains. Polyamidations under Yamazaki conditions are most effective over the range of 85 < T < 115°C. Here, in certain aprotic amide solvents such as N,N-dimethylacetamide (DMAc), aromatic amines rapidly, and certain aliphatic amines slowly, condense with carboxylic acids in the presence of aryl phosphites and organic bases to form amide groups. Typical of these phosphites is triphenylphosphite (TPP) and typical of the bases is pyridine. Under these conditions ester formation or breakup do not take place. Examples of the versatility of this procedure are given. Monomers reactive under Yamazaki conditions, and those that fail to react, are listed and discussed. At the temperature interval of 120 < T < 155°C, the efficiency of amidation of aliphatic amines approaches that of aromatic amines. In this case the solvent is DMAc or DMAc/LiCl or N-methyl-2-pyrrolidinone (NMP). TPP and pyridine are present, the latter under reflux. Under these conditions, grafts of high molecular weight aliphatic polyamides were created, reacting aliphatic carboxylic acids with aromatic amines and, conversely, aromatic acids with aliphatic amines. The graft efficiency is rather high. Above the boiling point of the aprotic amide solvents, no solvent or organic base are used. Here, aryl phosphite alone is employed to create aromatic amines, aliphatic amides, polyamide chain extension during extrusion, and block and graft copolymers containing aliphatic amide linkages. Esterification reactions occur at even higher temperatures. Chain extension of poly(ethylene terephthalate) (PET) was achieved in both extruder and melt-processor at temperatures of 265°C and higher, but at rates far slower than for polyamides.
Tijdschrift beschrijving