关键词: 嵌段共聚物, 序列结构分析, 缩聚, 热分析, 力学性能

Abstract: A series of poly(butylene terephthalate-co-cyclohexylene dimethylene terephthalate)-b-poly(ethylene glycol) block copolymers(PBCG) with aromatic moieties PCT molar fraction(x_PCT) varying from 10% to 60% were synthesized and characterized by means of GPC, NMR, thermal analysis and mechanical properties testing. The copolymers exhibit a good symmetric peak in GPC chromatograph with the number average molecular weight more than 3.5×10⁴ and polydispersity less than 1.70. Sequence distribution analysis reveals that the average sequence length of hard segment PBT decreases from 4.02 to 1.41, while that of PCT increases from 1.17 to 2.50 with the increase of x_PCT. The random distribution of the two hard segments is also confirmed in the same way. Microphase-separation structure was demonstrated for the appearance of two glass transition temperatures(T_g,s, T_g,h) and one melting point(T_m,h) belonging to the soft and hard segments, respectively. And the variation of average sequence length and the co-crystallization of two hard segments should be responsible for the minimum of melting point and crystallinity of hard segments at x_PCT being equal to about 20%. The higher thermal stability was justified for increasing decomposition temperature with ascending x_PCT from 10% to 30% in TGA thermograms as well. The mechanical properties testing shows that the lower crystallinity imparts the copolymer higher elongation, while the higher one improves the elastic modulus, tensile strength and yield strength.

Key words: Block copolymer, Sequence structure analysis, Polycondensation, Thermal analysis, Mechanical properties