Formation of BaSO4 fibres with morphological complexity in aqueous polymer solutions.
Formation of BaSO4 fibres with morphological complexity in aqueous polymer solutions.
复制标题
在聚合物水溶液中形成形态复杂的 BaSO4 纤维。
作者：
L. Qi;H. Cölfen;M. Antonietti;M. Li;J. Hopwood;A. J. Ashley;S. Mann
在聚丙烯酸酯和部分单膦化聚环氧乙烷嵌段聚甲基丙烯酸添加剂的水溶液中，通过简单沉淀反应制备了形态复杂的BaSO4纤维。对于聚丙烯酸酯，纤维沉积物的形成强烈依赖于过饱和度(S)和Ba2+：聚合物摩尔比(R)的水平。在S = 60 ~ 80, R = 3 ~ 14时，虽然产率很低，但几周后形成了由BaSO4纳米丝束组成的高度各向异性的结晶纤维。在S = 80时，纳米丝也被组织成锥形聚集体，在较低的R值下，这些纳米丝形成由多个锥对锥组成的高阶结构，具有显著的自相似性。在研究的摩尔比范围内，增加过饱和度会产生卵形或十字形枝晶颗粒。相比之下，在部分膦化嵌段共聚物的存在下，BaSO4结晶得到了高产量的BaSO4纤维，长度可达100微米，由直径30纳米的无缺陷单晶纳米纤维束组成，具有均匀的生长尖端。提出了一种基于无定形前驱体粒子、矢量定向力和范德华引力的无缺陷生长BaSO4纳米丝的模型。
BaSO4 fibres with morphological complexity were formed in aqueous solution with polyacrylate and partially monophosphonated poly(ethyleneoxide)-block-poly(methacrylic acid) additives by a simple precipitation reaction. For polyacrylate, formation of the fibrous deposits was strongly dependent on the level of supersaturation (S) and Ba2+:polymer molar ratio (R). At S = 60 to 80, and R = 3 to 14, highly anisotropic crystalline fibres consisting of bundles of BaSO4 nanofilaments were formed after several weeks, although the yield was low. The nanofilaments were also organized into cone-shaped aggregates at S = 80, and at lower R values these formed higher-order structures that consisted of multiple cone-on-cone assemblies with remarkable self-similarity. Increasing the supersaturation produced ovoid or cross-shaped dendritic particles for the range of molar ratios studied. In contrast, BaSO4 crystallisation in the presence of a partially phosphonated block copolymer gave a high yield of BaSO4 fibres up to 100 microm in length, and consisting of co-aligned bundles of 30 nm-diameter defect-free single-crystal nanofilaments with a uniform growth tip. A model for the defect-free growth of BaSO4 nanofilaments in aqueous polymer solutions based on amorphous precursor particles, vectorially directing forces and van der Waals attraction is proposed.