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以不同臂(Arm)数的星形聚氧化乙烯(PEO)为对象,系统地研究了其在不同温度下结晶的晶体冰花图案.实验中采用的星形PEO样品,其臂数分别为3,4和8(3-arm-PEO,4-arm-PEO和8-arm-PEO)且每臂的分子量均为5000,线形PEO其分子量为5000.显然,随着星形PEO分子臂数的增加,分子拓扑形状的各向异性不断减小.在单层片晶冰花图案研究中发现,随着结晶温度逐渐向平衡熔点靠近,这些PEO样品的结晶冰花图案具有从树枝状晶体转变为海藻状晶体,然后转变为非规整的紧凑形晶体,最后变成多面晶体的变化规律.对细节的分析进一步表明,随着星形PEO分子臂数的增加,由于分子的各向异性减小,导致冰花状晶体的各向异性程度不断减弱,因此从树枝状晶体到海藻状晶体和从树枝状晶体到多面晶体的转变温度也都逐渐降低.将这些转变温度对臂数作图获得的一张形态相图(morphology diagram)说明了星形PEO结晶图案的分子形状依赖性,也阐明了冰花图案形成的大分子拓扑形状效应.
In this paper, the crystal ice crystal pattern crystallized at different temperatures was systematically studied with different numbers of arm-shaped PEO.The star-shaped PEO samples used in this experiment have arm numbers of 3, 4 and 8 (3-arm-PEO, 4-arm-PEO and 8-arm-PEO) and each arm has a molecular weight of 5000 and linear PEO has a molecular weight of 5000. It is clear that as the number of arms of the ascending PEO molecule increases , The anisotropy of the molecular topography shape decreases continuously.It has been found in the study of single-layer crystal ice pattern that as the crystallization temperature gradually approaches the equilibrium melting point, the crystalline ice pattern of these PEO samples has the transition from dendrite to seaweed-like crystal , And then transformed into non-regular compact crystals, and finally changed into a polygonal crystal.Detailed analysis of the details further shows that with the increase of the number of arms of the star PEO molecules, due to the decrease of the anisotropy of the molecules, The degree of anisotropy of the crystal is declining, so the transition temperatures from dendrites to seaweed crystals and from dendrites to polyhedral crystals also decrease gradually. A phase diagram obtained by mapping these transition temperatures to the number of arms The morphology diagram illustrates the star PEO Molecular shape dependence crystalline pattern, but also illustrates the topology of macromolecules Ice pattern formed shape effect.