Synthesis,Characterization And Properties Of(PBT-b-PEO-b-PPO-b-PEO-b-PBT)_n Multiblock Terpolymers

We present here the synthesis,characterization and properties of three-component poly(butylene terephthalate)-block-poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide)(PBT-b-PEO-b-PPO-b-PEO-b-PBT)n multiblock terpolymers.A series of(PBT-b-PEO-b-PPO-b-PEO-b-PBT)n multiblock terpolymers were synthesized by the in situ cascade polycondensation-coupling ring-opening polymerization(PROP)method,via a facile one pot melt polymerization process using cyclic oligo(butylene terephthalate)s(COBTs)as monomers,dihydroxyl end-functional PEO-b-PPO-b-PEO as macroinitiator and tetrabutyl titanate(Ti(n-C4H9O)4)as catalyst.The structure of multiblock terpolymers was well characterized by the quantitative 1D-1H NMR and 2D-NMR(1H-1H gCOSY and 1H-13C gHSQC)spectra.The properties of(PBT-b-PEO-b-PPO-b-PEO-b-PBT)n mutiblock terpolymers were measured and the structure-property relationship was studied.Detailed works are summarized as following:(1)A series of(PBT-b-PEO-b-PPO-b-PEO-b-PBT)n mutiblock terpolymers with different PBT content,multiblock segmental number,and/or polyether length were synthesized by PROP method.The peaks in quantitative 'H NMR spectra were assigned accordingly to the whole polymer chain ends,each segmental chain ends,and each segmental blocks,with the assistance of 2D-NMR(1H-1H gCOSY and 1H-13C gHSQC)spectra.The molecular weights in each segmental blocks and total number of segmental blocks were obtained by quantitative 1H NMR.The PROP mechanism was confirmed by the polymerization kinetics studies.(2)Thermogravimetric analysis(TGA)reveals that the 5%weight loss temperature of multiblock terpolymers is around 355 ?,much better(-50 ? higher)than that of PEO-b-PPO-b-PPO macroinitiator.The composition as well as the molecular weights of the multiblock terpolymers has no significant influence on their thermal stability and the thermal stability of EPE segments improve after coupled with PBT.Differential scanning calorimetry(DSC)reveals the double-crystalline properties of the multiblock terpolymers,where the melting point and crystallinity of PBT and PEO segments increase with corresponding PBT and PEO content,due to the confinement effect between lamella crystals.Small angle X-ray scattering(SAXS)and transmission electron microscope(TEM)experiments reveals the microphase-separated morphology of multiblock terpolymers,which is affected by the composition as well as the molecular weights of the multiblock terpolymers.