【作者】 边界；

【导师】 封麟先； 叶胜荣；

【作者基本信息】 浙江大学 ， 高分子化学与物理， 2002， 博士

【摘要】 本文通过缩聚反应合成了不同分子量的聚对苯二甲酸乙二酯（PET）；聚对苯二甲酸（乙二醇/丁二醇）酯（P（ET/BT））、聚（对苯二甲酸/间苯二甲酸）乙二醇酯（P（ET/EI））和聚（对苯二甲酸己二酸）乙二醇酯（P（ET/EA））等系列的无规共聚酯以及PET/PBG（聚丁二醇）和PET/PEG（聚乙二醇）等系列的嵌段共聚酯，并采用DLI（解偏振光强度法）、DSC、WAXD、IR和NMR等实验技术着重研究了它们的结晶行为与共聚酯的序列结构。在此基础上，对PET及其共聚酯的结晶机理、“成核”添加剂对聚酯的促进机理、Avrami方程相关参数的物理意义及玻璃化转变的本质作了一定的探索。 首次发现了PET的分子量大小影响其结晶行为的规律，以及不同分子量的PET链各自形成晶区的现象。通过结晶动力学测试、DSC分析、WAXD对晶体结构的测定和FTIR对链末端氢键结构的研究，首次提出，低分子量PET（M，≤6170）与高分子量PET（M，≥12600）结晶行为的差异源于它们晶体结构的不同，而PET分子链末端的游离羟基形成氢键是其结晶时所必须经历的一个过程，故不同类型氢键的形成是导致不同晶体结构产生的主要原因。 首次用解偏振光法（DLI）证实了玻璃态PET中一定程度有序性的存在，但它有别于晶态PET中的有序，在15～70℃之间，其有序程度随温度的升高而下降，并与温度之间有着一一对应关系（记忆效应），红外分析表明，该有序仍由含反式亚甲基的链段组成。有序程度随温度的升高而下降源于分子链段间距离的增加。在15～50℃范围内，玻璃态PET有序度随温度变化的转变为一级转变，用Arrhenius方程计算得该转变所需的活化能为22.56KJ/mol。 非晶态PET中的有序结构可起“胚核”的作用，起始结晶前胚核的大小及活动性将导致PET结晶过程的差异，故起始状态不同（已、未结晶样品从熔融态；冰水淬火、室温无水乙醇淬火样品从玻璃态以及恒温退火样品），PET试样的半结晶时间(t_1/2)、Avrami指数（n）值随结晶温度的变化规律也不相同。这一发现对阐明PET结晶过程的微观机理有重要作用。 不同成核添加剂对PET结晶影响的实验结果表明，在PET的结晶过程中，不 摘要太可能存在真正的异相成核剂，添加剂对结晶过程的影响主要源于门)与熔融的聚酯大分于链发生化学反应，使 ET链段构象转变的活化能降低；（2）与聚酯形成配键以起到固定PET分子链的作用，当形成配键的量过多时，因破坏了分子链的对称性使 PET的结晶能力下降；（3）当添加剂或添加剂与聚酯反应后的产物在晶体结构上相互匹配时，通过吸附作用可增加聚酯链段间的相互作用及链段的有序程度。 根据实验结果和理论分析提出，导致聚合物结晶过程Avri指数n值不为整数的原因有：（）有效胚核在晶核附近的分布并不对称，使晶核的结晶生长点不为偶数；（2）有效胚核向晶核的转化概率处于中间状态；（3）不同的结晶机制可同时存在于某一等温结晶过程中。故n值的大小代表着聚合物结晶时，晶核中生长点的数目，而结晶生长点与有效胚核数＊)和生长核数或晶核数（M）的比值有关，即11。NfM。 首次将H3IUllan的PBC周期键链理论应用于聚酯结晶过程的研究，提出聚合物的结晶过程应为晶片h维生长，其n值介于2～3之间，该结论符合多数实验结果。对于n＜2的聚合物结晶过程，是由于晶核周围胚核数的减少（或转化为晶核，或不能发生大规模的分子链运动）所致，而－n＞3的过程则是由于晶核周围过多的胚核数使晶核生长时，二个或多个胚核可同时进入同一生长点，即晶片的分枝生长造成的。聚合物结晶后期的“二次结晶”现象，即偏离AVrallll线性的结晶过程同样是由于结晶生长点的减少所致。这一理论的运用较好地解释了聚酯结晶过程的各种复杂现象，形成了一个较为统一的理论模型。 系统地研究了共聚酯的序列结构与结晶行为之间的关系，提出PET类共聚酯的结晶性能除与引入链段的含量、规整性、柔顺性有关外，还取决于引入链段本身的结晶能力，该结论可较好地解释共聚酯的结晶行为。在 PpeTST)共聚酯中，因 BT链段结晶所需的活化能较小，故在整个组分变化范围内均可结晶，而ET链段在它的含量小于50％时，则几乎无法形成自己的晶区，当ET链段和BT链段的组成比为6535（序列分布：LEE。2．85；LBB。1．55）时，共聚酯的结晶能力最弱。在P（ET／E）共聚酯中，柔性EA链段不能形成自己的晶区，规整性和柔顺性两者的共同作用使EA链段在分子链中的含量约为20％时，结晶速率出现最大值。而引入刚性链段的P（ET／EI）共聚酯，则随EI链段含量的增加，结晶能力降低，结晶速率减小。 且且 浙江 大学博士学位论文 无规共聚酯的熔点均随“杂质”链段引入量的增加而降低，这是由于晶粒尺寸减小以及结晶链段间的距离h和b轴方向的重复长度)增加，即结晶密度下降引起的。在晶态P爬TffiA)和PaT／EI冲，C轴明显较“纯”PET的短，该结果表明，完全更多还原

【Abstract】 The crystallization behavior of polyethylene terephthalate(PET); random poiy (ethylene /tetramethylene terephthalate) (P(ET/BT)); poly(ethylene terephthalate/ isophthalate) (P(ET/EI)) and poly(ethylene terephthalate/adipate) (P(ETIEA)) copolyesters; and block polyethylene terephthalate/polyethylene glycol (PET/PEG) and polyethylene terephthalate/polytetramethylene glycol (PET/PBG) were studied by DLI (depolarized light intensity); DSC,WAXD;PLM and IR technique. Their crystallization and nucleating mechanism; the physics meaning of Avrami exponent and glass transition were investigated.The crystallization behavior of PET with lower viscosity average molecular weight (M, ~6l70) is significantly different from which with higher molecular weight(M1 i~ 12600). Their crystal structure also exists some difference. When the molecular weight of PET is about 7500, the crystallizing process in which the PET chains with different molecular weight formed their own crystallization regions taken palace. And the phenomena of double crystallization regions in DSC and WAX]) analysis appear. The formation of hydrogen bond between free hydrocarbyl at the ends of the chains and oxygen atoms is a necessary process when amorphous PET crystallizes and the double regions result from the different type of hydrogen bond.It was demonstrated that some level of order exists in glassy poly(ethylene terephthalate) by depolarized light intensity (DLI) technique, but this order is different from that in crystalline PET. The degree of order in glassy PET decrease with the increasing temperature between 1 5-~70 ’C. The IIIR analysis indicated that this order relates to gauche structure of the ethyleneglycol fragments. The decrease of order with temperature comes from the increase of distance between the order segments.In term of Avrami equation, the influence of different initial state (from the melt; quenched in ice-water; quenched in alcohol at room temperature) on crystallization kinetics of PET were studied using depolarized light intensity (DLI) technique. It wasivshown that the regularities of half-crystallization time and Avrami exponent values vs. isothermal crystallization temperature are different. The various dimension and mobility of the germ nuclei, the clusters of order segments whose sizes are less than one critical value, result in this difference.The results of the influence of various nucleating additive on the PET crystallization process indicated that there may not be a really heterogeneous nucleating agent for PET and its copolyesters crystallization. The influences of the additive on the crystallization arise from (I) the reaction with the molten macromolecular chains of PET; (2) the formation of coordination bonds with PET chains and fixation them when PET crystallizing. The crystallization ability would decrease when too many these bonds formed for the regularity and symmetry were destroyed; (3) the increasing in the degree of order and the interaction between the order ET segments when the crystal structure of PET and additive or its reaction products is matching. And one additive can possess the different acceleration mechanisms.The reason why Avrami exponents in the crystallization processes of polymer are not integer caused by (I) the distribution of effective germ nuclei around the growth nuclei are not symmetric and thus result in the odd growth points in the crystal nuclei; (2) the probability of the formation from germ nuclei to growth nuclei is in the intermediate state; (3) the difference mechanism which can exit in the same isothermal crystallization process. So Avrami exponent indicate the number of growth points in one crystal nucleus and it is a function of the ratio of the effective number of the germ nuclei (N) to the number of growth nuclei (M) namely nocNlM.In term of the PBC (periodic bond chain vector) theory of P. Hartman, the crystallization morphology of polymer was predicted should be crystal lamellar (disk-like or two dimension’s growth), and the values o更多还原