等规聚1-丁烯结构转变调控

By establishing gelation networks of organic small molecules in isotactic polybutene (iP-1-B) to provide iP-1-B molecular chains with confined spacial environment and by applying shear under high pressure to iP-1-B, the formation of the crystal structures and crystal transitions of iP-1-B would be investigated via in-line or off-line synchrotron radiation WAXS/SAXS combined with shear heating stage together with XRD, FTIR and DSC. The effects of the confined spacial environments and the shears under high pressures on the selective formation of the crystal forms directly from iP-1-B melt during crystallization process, the crystal structures and II-I transitions of iP-1-B would be discussed in detail on the basis of the concept of tunable pre-ordering conformational structure of mesophase which appears before and would be developed as crystals. The effective acceleration method of II-I transition and even the selective formation of stable crystal structures of form I or form I' directly from iP-1-B melt while processing would be focused on with the balance of the mechanical properties of the materials and the adaptations to polymer processing process and applications carefully considered. At the same time, the mechanism of II-I transition and that of the selective formation of stable form I and form I' directly from iP-1-B melt would be discussed on the levels of molecular chains with helix conformations. The final purpose of this project is to provide experimental and theoretical supports to improvement of design, manufacturing, and applications of iP-1-B-based materials with its advantages as “golden plastics”.

以不同化学结构有机小分子化合物等在等规聚1-丁烯（iP-1-B）中形成凝胶网络结构空间受限环境，并以PVT测量仪等对iP-1-B施加不同高压/剪切作用，采用离/在线同步辐射WAXS/SAXS联用剪切热台并结合XRD、FTIR、DSC等表征iP-1-B结晶结构形成及转变，研究iP-1-B在所形成受限空间环境和高压/剪切等作用下基于链行为乃至构象有序mesophase调控的结晶过程、结晶结构选择性形成及II-I转变过程的调控作用及调控规律，探索有效加速iP-1-B的II→I转变的方法乃至直接从熔体选择性形成稳定I或I'晶的方法，同时兼顾材料力学性能平衡和加工成型应用适应性，并通过与受限调控条件下iP-1-B的链行为关联，从分子链水平探讨相关机理，为真正发挥出iP-1-B “塑料黄金”的性能优势，推进iP-1-B材料设计、制备和应用发展提供实验和理论依据。

等规聚丁烯-1（iPB-1）是一种多晶型高分子，因耐高温蠕变等优异性能被称“塑料黄金”，但1954年首次合成后推广应用一直受限，原因之一在于，iPB-1加工成型过程中经熔融结晶先在动力学上形成热力学亚稳态晶型II，随后在室温需经一周乃至更长时间才能完成II-I转变得到热力学稳态晶型I并达到产品尺寸和性能稳定。理论上，II-I转变为成核控制固固转变的传统观点已广为接受，但iPB-1晶型选择机理尚不清楚；II-I转变促进技术多有研究，但工业适用技术缺乏。. 我们首先尝试在iPB-1中引入有机小分子化合物以凝胶网络化，考察其基于iPB-1链运动调控对iPB-1晶型选择和II-I转变的影响，随后在这一工作启发下，基于温度、溶剂、压力等因素协同，从iPB-1侧乙基引起熵变能垒决定其链构象选择角度，提出了iPB-1晶型选择机理并重新考虑了II-I转变过程，发展了相关调控技术。. 实验发现，引入有机小分子化合物以凝胶网络化未改变iPB-1熔融结晶晶型选择，但相容性好的有机小分子化合物可明显促进II-I转变；不同于晶型I只能由晶型II转变得到的传统观点，实验发现iPB-1熔体降温到Tcr=35 oC以下可依温度直接形成少量晶型I；增加压力可显著加快晶型II向更致密晶型I转变，而消弱iPB-1链间作用则可在熔融结晶时形成比晶型II更疏松的晶型III；特定溶剂作用下较高温形成晶型II，较低温形成晶型I’，相容性适当的溶剂和低温可显著加快II-I转变，且行为上难以用传统成核控制固固转变观点解释。可见，低温、压力、溶剂等有利于缩小iPB-1链间距进而增加链间作用的因素，有利于iPB-1链克服熵变能垒形成熵低而致密稳定3/1螺旋构象及晶型I；反之，有利于形成熵较高较疏松11/3螺旋构象及晶型II，甚至形成熵更高更疏松4/1螺旋构象及晶型III。iPB-1晶型选择取决于链间作用是否能克服熵变能垒而跨过不同螺旋构象能量陷阱并由此选择相应螺旋构象，进而决定iPB-1晶型选择和II-I转变，iPB-1熔体表现为“强液体”且II-I转变是“晶型II-致密中介相”控制的“晶型II-致密中介相-晶型I”过程。优选相容性适合的添加剂，可将II-I转变缩短至36小时，适于工业应用。