聚(对苯二甲酸丁二醇酯-co-对苯二甲酸环己烷二甲醇酯)-b-聚乙二醇嵌段共聚物的合成与表征

用熔融缩聚法合成了一系列聚(对苯二甲酸丁二醇酯-co-对苯二甲酸环己烷二甲醇酯)-b-聚乙二醇嵌段共聚物(PBCG),用NMR,GPC,DSC,TGA及力学性能测试等方法表征了材料的结构与性能.GPC分析显示,共聚物分子量均具有较为对称的单峰分布,多分散性指数低于1.70.13CNMR谱结果表明,随PCT摩尔分数(xPCT)从10%增至60%,PBT平均序列长度由4.02降到1.41;而PCT平均序列长度则由1.17升至2.50,二者呈无规分布.受硬段平均序列长度及结晶能力影响,硬段熔点及结晶度在xPCT为20%～30%处均达到最小值,可能是硬段间形成共晶所致.TGA分析显示,引入芳香族聚酯组分PCT确可提高材料的热稳定性.力学性能测试说明,降低结晶度有利于提高材料的断裂延伸率,相反,则有助于增强弹性模量,断裂强度及屈服强度.

Synthesis and Characterization of Poly(butylene terephthalate-cocyclohexylene dimethylene terephthalate)-b-poly(ethylene glycol) Block Copolymers

A series of poly(butylene terephthalate-co-cyclohexylene dimethylene terephthalate)-b-poly(ethylene glycol) block copolymers(PBCG) with aromatic moieties PCT molar fraction(xPCT) 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 xPCT. 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(Tg,s, Tg,h) and one melting point(Tm,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 xPCT being equal to about 20%. The higher thermal stability was justified for increasing decomposition temperature with ascending xPCT 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.