| The synthesis and properties of semi-aromatic cyclic oligoesters and their corresponding multiblock copolymers are studied. Two series of oligoesters, cyclic oligo(trimethylene terephthalate)s(COTTs) and cyclic oligo(butylene terephthalate)s(COBTs), with different degree of oligomerization(cyclic ring size), were obtained by column chromatography. Some physical and chemical properties of these cyclic oligomers are studied and compared.(PTT-b-PTMO-b-PTT)n multiblock copolymers were synthesized by melt polymerization of COTTs with poly(tetramethylene oxide)(PTMO) macroinitiator, and is characterized by NMR, TEM, SAXS and WAXS. The resilience properties of the multiblock copolymers are tested and the structure-property relationship is revealed. The detailed works are summarized as follows:(1) By careful purification, 7 pure cyclic oligomers with different degree of oligomerization(cyclic ring size) are obtained. The structures are revealed and confirmed by matrix-assisted laser desorption/ionization time of flight(MALDI-TOF) mass spectra and 1H NMR spectra. The melting point, density, and refractive index of these cyclic oligomers are measured, and a special odd-even effect of degree of oligomerization(repeating unit number) on properties is revealed.(2) A series of(PTT-b-PTMO-b-PTT)n alternative multiblock copolymers were synthesized by in-situ condensation polymerization coupling ring-opening polymerization. The block copolymers’ structure was revealed by an improved quantitative 1H NMR technique. The mechanical property of the multiblock copolymers was measured and it reveals that the elongation at break increases with the increasing segment numbers. The largest elongation at break can reach 1800%. By using wide angle X-ray diffraction(WAXD), polarizing optical microscope(POM), small angle X-ray scattering(SAXS) and transmission electron microscope(TEM), the hierarchical structures of the block copolymers are revealed. It shows PTTs form lamella crystals with thickness about 20 nm, while PTMOs form the continuous phase. The domain of phase separation size decreases with increasing segment length. |
