由活性雙官能基Bis-azetidine-2,4-diones中間體快速熔融製備Polymalonamides彈性體及其結構與型態關係之探討

Abstract

Two methods of synthesizing bis-azetidiene-2, 4-dione intermediates have been accomplished in our lab for preparation of three bis-azetidine-2, 4-dione, PBAZ, MBAZ, and LBAZ for our study. Using a thermal process, diethylketene cyclo-adds to aromatic diisocyanates to form aromatic bis-azetidine-2, 4-diones. The yields of bis-aztidine-2, 4-diones from p-phenylene diisocyanate(PPDI) and 4, 4’-dipehnylene diisocyanate (4, 4’-MDI) were found to be 74％ (for PBAZ) and 82% (MBAZ) respectively. Whereas, N, N’-hexamethylene bis-azetidine-2, 4-dione(LBAZ) an aliphatic counterpart, was prepared differently by photolysis of hexamethylene-bis-N-formyl-N-methacrylamides in 71%. Melt-polymerization of bis-azetidine-2, 4-diones with hexamethylene diamine yielded polymalonamides. Similar melt-polymerization has also been extended to synthesize polymolonamide elastomers using Jeffaminer D2000 as the soft-segment component and hexamethylene diamine as the extender with each of the prepared bis-azetidine-2, 4-diones. Elastomers of 35%, 45% and 55% hard-segment contents in each series were prepared. All syntheses were carried out by a two-step process by formation of pre-polymers between individual azetidine-2, 4-diones with Jeffamine* in the first step. The second step to the final product was done with hexamethylene diamine as the extender. Very rapid conversions to the final products were observed universally in less than 150 sec. The polymalonamide elastomers prepared were analyzed by TGA, DSC, DMA, AFM and FE-SEM to characterize morphology of the products. All elastomers prepared from PBAZ and LBAZ are semi-crystalline in nature. Especially, three PBAZ derived elastomers crystallize readily to form distinctive oval island-shape domains as observed by AFM, and are characterized by their sharp Tg,s and Tg,h in DSC and DMA. The domain sizes are uniformly distributed between 200nm to 300nm with increasing larger sizes for higher hard-segment contents. Although semi-crystalline LBAZ-derived elastomers also showed similar phase-segregation in AFM, but their patterns were different and could be influenced greatly by processing techniques. Under high spinning rates of greater than 4000 rpm in spin-coating process, the morphology of LBAZ-elastomers turned into fibrous pattern. Our study indicated that only MBAZ-elastomers are amorphous and showed well mixing between hard and soft segments as indicated by the appearances of Tg,s and new Tg,m at -10~18℃ for the mixed phases in DSC. The physical properties of elastomers have been found to be greatly influenced by morphology and by the hard-segment contents but appeared to be in lesser degrees for the latters.