The Distribution Of Dye And SiO₂ Nanoparticles In Semi-crystalline Polymers

Semicrystalline polymer is one of the most important materials in modern society.Their structure and morphology have caused extensive attention.Polymer spherulites are the key features of morphology of semicrystalline.However,almost invariably they were observed in thin films or thin sections of the bulk polymer.Of necessity in these studies the thickness of the film or section was considerably smaller than the spherulite diameter.Thus what was observed were disks rather than spheres growing from the melt,and polygons rather than polyhedra in set solids after the aggregates impinged on one another.The shape of the 3-D object has then been merely extrapolated from the 2-D form by implication.Here we present a new approach aimed at imaging spherulites using fluorescence microscopy?FM?of fluorescent dye-doped polymers for the first time based on complexation of semicrystalline polymers with Nile Red-modified SiO₂nanoparticles.We concentrate on visualizing in semicrystalline polymers not only the distribution of fluorescent compounds,but also of labelled nanoparticles in order to gain better insight into these materials.The main contents are as follows:1.Construction of Nile Red-modified SiO₂ nanoparticles?Nile Red-SO₂ NPs?.On one hand,using tetraethyl orthosilicate as silicon materials,SiO₂ nanoparticles with uniform particle size distribution?35 nm and 200 nm respectively?were successfully synthesized based on the method of amino acids.Compared with the traditional method of ammonia,such method is highly controlled,which is helpful to obtain nanoparticles with controlled uniform size.On the other hand,using m-diethylaminophenol as reagent,triethoxysilane-substituted Nile Red compounds were synthesized through four chemical reactions.Finally,triethoxysilane-substituted Nile Red was reacted with SiO₂ nanoparticles,and Nile Red-SO₂ NPs were subsequently obtained with size of 35 nm and 200 nm,respectively.2.Fabrication of blends of different polymers with suitable fluorescent dyes and investigation of their structure evolution in-situ using a combination of fluorescence and polarized microscopy.By using freeze-dry technique,a series of polymer blends were obtained based on Nile Red-SO₂ NPs and IPP,PE,PEO and PLA,respectively.Meanwhile,Nile Red and ZnSe/ZnS quantum dot were complexed with polymers as control.It is indicated that,compared with 35 nm Nile Red-SO₂ NPs,200 nm Nile Red-SO₂ NPs in the polymer blends are more helpful for observing their structure evolution,because their nucleation rate is slower and the spherulite morphology and texture are clearer.Furthermore,it provided a 2-D technique for determining nanoparticle distribution on a large scale.It will develop new ways of introducing compatible fluorescent labelled nanoparticles into engineering plastics.The visualization method developed will allow investigation into the neglected problem of intra-and interspherulitic cavitation,microcrack formation and substrate delamination,potentially degrading mechanical and optical properties of semicrystalline polymers and nanocomposites.