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为了更好控制结晶的形态、大小以及产率,系统地研究了各种控制因素对自晶种方法制备PS-bPLLA嵌段共聚物单晶及复合单晶的影响,并考察了晶体在溶液和本体状态的热力学稳定性.通过调控成核温度(Ts)、成核时间(ts)和结晶温度(Tc)等参数,成功制备了不同尺寸、形状和厚度的单晶.随着Ts和ts的增加,晶体尺寸增加并且尺寸分布变窄.随着Tc的增加,单晶形状由菱形转变为截顶菱形.同时还利用两步法分别制备和表征了PS-b-PLLA/PLLA复合单晶.DSC热扫描实验表明,溶液生长的片状晶体在本体状态下处在热力学亚稳态,在升温熔融过程中出现明显的重结晶现象.但是晶体在不同温度下退火并不能增强其稳定性,从而证明了PLLA片晶厚度不能通过分子链在晶体内沿着链轴方向滑移而增厚.
In order to better control the morphology, size and yield of the crystals, the influence of various control factors on the preparation of PS-bPLLA block copolymer single crystal and composite single crystal from the seed crystal system was systematically investigated. The thermodynamic stability of the bulk state has been investigated. Single crystals with different sizes, shapes and thicknesses were successfully prepared by controlling the nucleation temperature (Ts), nucleation time (ts) and crystallization temperature (Tc) The crystal size increases and the size distribution becomes narrower.With the increase of Tc, the single crystal shape changes from rhombus to truncated rhombus.The PS-b-PLLA / PLLA composite single crystal is also prepared and characterized by two-step method. DSC thermal scanning experiments show that the solution-grown flake crystals are thermodynamically metastable in the bulk state and have obvious recrystallization during the temperature rising and melting process, but the crystals annealed at different temperatures do not enhance the stability It is proved that the thickness of PLLA lamellae can not be thickened by the molecular chain sliding in the crystal along the chain axis.