Formation of BaSO_4 Fibres with Morphological Complexity in Aqueous Polymer Solutions

摘要

BaSO_4 fibres with morphological complexity were formed in aqueous solution with polyacrylate and partially monophosphonaced 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 Ba_(2+):polymer molar ratio (R).At S-60 to 80,and R=3 to 14,highly anisotropic crystalline fibres consisting of bundles of BaSO_4 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 particlds for the range of molar ratios studied.In contrast,BaSO_4 crystallisation in the presence of a partially phosphonated block copolymer gave a high yield of BaSO_4 fibres up to 100 #mu#m in lentgh,and consisting of co-cligned bundles of 30 nm-diameter defect-free single-crystal nanofilaments with a uniform growth tip.A mode for the defect-free growth of BaSO_4 nanofilaments in aqueous polymer particles,vectorially directing forces and van der Waals attraction is proposed.