||This study contains four main parts. Part 1, poly(butylene succinate) (PBSu) rich random copolymers containing ~20% 2-methyl-1,3-propylene succinate (MPS), PBMPSu 80/20. The influence of minor MPS units on thermal properties and crystallization rate was investigated. Part 2, poly(butylene succinate) (PBSu) rich random copolymers containing ~5% 1,4-cyclohexanedimethylene succinate (CHDMS), PBCHDMSu 95/5. The influence of cyclohexane unit on thermal properties and crystallization rate was investigated. Part 3, Poly(butylene succinate) (PBSu) random copolymers containing ~50% 2-methyl-1,3-propylene succinate (MPS), PBMPSu 50/50. Blend of PBSu with poly(2-methyl-1,3-propylene succinate) (PMPSu). The weight ratio of PBSu and PMPSu were 1:1. The crystallization behavior and morphology was compared. Part 4, Poly(ethylene succinate) (PESu) random copolymers containing ~50％ trimethylene succinate (TS), PETSu 50/50. Blend of PESu with poly(trimethylene succinate) (PTSu). The weight ratio of PESu and PTSu were 1:1. The crystallization behavior and morphology was compared.|
Molecular weights of copolymers were measured using capillary viscometer and gel permeation chromatography (GPC). The results indicate that polyesters used in this study have high molecular weights. The chemical composition and the sequence distribution of co-monomers in copolyesters were determined using 1H NMR and 13C NMR. The distribution in these copolyesters was found to be random from the evidence of a randomness value close to 1.0 for a random copolymer. Thermal properties of blends and copolyesters were characterized using differential scanning calorimeter (DSC) and thermogravimeter (TGA). The crystallization kinetics and mleting behaviors was analyzed after isothermal crystallization by DSC. Wide-angle X-ray diffractograms (WAXD) were obtained for specimens after complete isothermal crystallization. The growth rates, morphology were studied using polarized light microscope (PLM). The morphology of specimens after chemical etching was investigated using scanning electron microscope (SEM) and atomic force microscope (AFM).
AS the ratio of MPS units increase, the degree of crystallinity and crystallization rate drop, it was due to decrease of butylene succinate sequence length. The spherulite growth rate of PBCHDMSu 95/5 is much slower compare with PBSu rich copolymers containing 5% TS or MPS. It was due to the steric effect of cyclohexane unit in the polymer chains. The crystalline morphology of PBMPSu 50/50 and PETSu 50/50 were quite different. It was due to the short sequence length of butylene succinate and ethylene succinate. From the analysis results by DSC and observation by PLM and SEM, it indicates that PBSu was miscible with PMPSu while PESu was partial miscible with PTSu.