POLYMORPHISM IN POLY(ARYL ETHER KETONE)S
POLYMORPHISM IN POLY(ARYL ETHER KETONE)S
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DOI：
10.1016/0032-3861(94)90763-3
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发表时间：
1994-01-01
期刊：
影响因子：
4.6
通讯作者：
FARON, KL
中科院分区：
文献类型：
--
作者：
GARDNER, KH;HISAO, BS;FARON, KL
用x射线衍射研究了聚芳醚酮（PEKs）的化学结构和结晶条件对其多态性的影响。研究了两种类型的化学变化：(1)酮/醚键的摩尔比（以%酮键表示）从33%变化到67%，使用完全的1,4取代形式的聚芳基醚醚酮（PEEK）， PEK，聚芳基醚酮醚酮酮（PEKEKK）和聚芳基醚酮酮（PEKK）；(2) 1,4取代的苯基残基部分取代它们的1,3取代的PEKK和PEKEKK。采用熔融结晶法、冷结晶法和二氯甲烷暴露诱导结晶法（溶剂结晶法）制备了as聚合聚合物和材料。对于所研究的所有聚合物，在熔融结晶制备的样品中观察到称为形式1的传统结构。相反，对于在其他条件下结晶的聚合物，有时会观察到第二种多晶，称为形式2。通过改变1,3-取代/1,4-取代异构体的比例和/或在结晶过程中改变醚/酮的键比和分子迁移率，系统地改变了链的刚度。随着链刚度的增加和结晶迁移率的降低，第二晶型的形成能力显著增强。聚芳醚酮的多态性可能是由于成核控制：稳定的1型相具有较慢的成核速率，因此比亚稳定的2型相具有更高的晶体表面自由能。
Polymorphism in poly(aryl ether ketone)s (PEKs) has been studied by X-ray diffraction as a function of the chemical structure and the crystallization conditions. Two types of chemical variations were investigated: (1) the molar ratio of the keto/ether linkages (expressed as % ketone linkages) was varied from 33 to 67% using the wholly 1,4-substituted forms of poly(aryl ether ether ketone) (PEEK), PEK, poly(aryl ether ketone ether ketone ketone) (PEKEKK) and poly(aryl ether ketone ketone) (PEKK) and (2) the partial replacement of 1,4-substituted phenyl residues with their 1,3-substituted counterparts of PEKK and PEKEKK. As-polymerized polymers and materials prepared by melt crystallization, cold crystallization and crystallization induced by exposure to methylene chloride (solvent crystallization) were used. For all of the polymers investigated, the conventional structure, known as form 1, was observed in samples prepared by melt crystallization. In contrast, for polymers crystallized under one of the other conditions, the second polymorph, known as form 2, was sometimes observed. The occurrence of form 2 was found to be dependent on chain stiffness, which was systematically modified by changing the 1,3-substituted/1,4-substituted isomer ratio and/or by changing the ether/keto linkage ratio and molecular mobility during crystallization. With the increase of chain stiffness and the decrease of crystallization mobility, the ability to form the second polymorph was significantly enhanced. Polymorphism in poly(aryl ether ketone)s may be due to the nucleation control: the stable, form 1 phase has a slower nucleation rate, and thus a higher crystal surface free energy than the metastable form 2 phase.