HETEROGENEOUS NETWORK POLYMERS .11. POLY(L-GLUTAMIC ACID) CROSSLINKED WITH POLYETHER DIISOCYANATES

A series of heterogeneous network polymers [PGA–PEGDI] were synthesized by crosslinking poly(L-glutamic acid) [PGA] with hexamethylenediisocyanate-terminated poly(oxyethylene glycol) [PEGDI] in dimethylacetamide at 70°C, while the solvent was allowed to evaporate slowly. The crosslinking reaction completed before the polymer concentration reached 20 percent. Since this concentration was lower than that of the ‘A’ point, the lyotropic cholesteric liquid-crystal structures involving PGA, which were prevalent in another series of heterogeneous network polymers [PGA–PEG] previously prepared from PGA and poly(oxyethylene glycol) [PEG], were prevented from forming in the PGA–PEGDI casting solutions. Thus, when brought to solid films, PGA–PEGDI was much less ordered than the PGA–PEG in which the ‘solidified’ liquid crystals persisted, as was evidenced by polarizing optical micrographs and X-ray diffraction patterns. The dynamic mechanical as well as the stress–strain behavior of PGA–PEGDI was also consistent with the idea that efficient admixture of the two component polymers could be accomplished in the stress-carrying continuous phase as a result of early crosslinking in the casting solutions. © 1979 The Society of Polymer Science, Japan.