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Structure–property relationship of blocked diisocyanates: synthesis of polyimides using imidazole‐blocked isocyanates
Author(s) -
Subramani S,
Sultan Nasar A,
Philip Gnanarajan T,
Padmanabha Iyer N,
Radhakrishnan Ganga
Publication year - 2000
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/1097-0126(200006)49:6<546::aid-pi431>3.0.co;2-c
Subject(s) - benzimidazole , imidazole , isophorone diisocyanate , polymer chemistry , isocyanate , polymer , hexamethylene diisocyanate , adduct , toluene diisocyanate , polymerization , materials science , chemistry , polyurethane , organic chemistry
Imidazole, 2‐methylimidazole and benzimidazole‐blocked aromatic and aliphatic diisocyanates have been prepared and polymerized with pyromellitic dianhydride in the presence of a basic catalyst. The polymers are characterized with FTIR, 1 H NMR and 13 C NMR spectroscopy and GPC, DSC and TGA. The structure–property relationship of blocked diisocyanates are discussed in terms of molecular weight of the polyimides obtained. Considering the blocking agent, GPC results show that the benzimidazole blocked adduct yields higher molecular weight polymer than the 2‐methylimidazole‐blocked adduct which, in turn, yields higher molecular weight polymer than the imidazole‐blocked adduct. Considering the structure of the isocyanate, the molecular weight of polymer increases from isophorone diisocyanate to hexamethylene diisocyanate and to toluene diisocyanate (TDI). DSC traces of the polymers derived from TDI show glass transitions ( T g ) in the temperature range 152–180 °C and the values increase from the polymer based on imidazole‐blocked TDI to 2‐methylimidazole‐blocked TDI and to benzimidazole‐blocked TDI. © 2000 Society of Chemical Industry