Study On Emulsion Polymerization Technology And Relations Of Structure And Properties Of Organosilicon/acrylate Based Composite Copolymers

Emulsion polymerization is a reaction system which can be characterized as a low-viscosity, good-heat-transference, and at the same time, the environment friendly. Therefore, it is being widely used to prepare paints, vanishes, adhesives, rubbers and controlled drug release systems. Acrylate latex is one of the most important polymers, and it is well known for its good adhesivity, anticorrosion and weatherability properties. However, acrylate based polymers possess poor higher and lower temperature resistance and poor waterproofness due to their macromolecular structures. The utilization of organosilicon which has higher bond energy and lower surface energy to modify the acrylate latex can markedly improve and enhance those properties mentioned above for acrylate polymers, and to date, it has become one of the most important research directions in this field.In this thesis, the development of emulsion polymerization theory and related new technologies are comprehensively reviewed, and the synthetic technologies of acrylate latex modified by organosilicon both at home and abroad are also reviewed. Based on the current development and research in this field, attentions of this study are focused on three ways for preparing novel acrylate latexes modified by organosilicons, that is, 1) The acrylate monomers are copolymerized with unsaturated silicons by emulsion copolymerization; 2) a new latex with microphase separation morphology is synthesized, which shows a core-shell structure character; 3) Soap-free polymerization is explored for preparing a higher-performance latex using an unsaturated silicon monomer, different acrylates and a reactive emulsifier.By using techniques of delaying addition of organosilicon monomer and a hydrolysis inhibitor, the hydrolysis and condensation of 3-(trimethoxysilyl) propyl methacrylate during polymerization can be effectively prevented, as a result, organosilicon content in the macromolecular chain is increased. The molecular structure of the copolymer is characterized by infrared spectroscopy and differential scanning calorimetry. The mechanical and hydroscopicity tests indicate that the physical properties of organosilicon-acrylate copolymer from mechanical, thermal to waterproof ability are much better than that of pure acrylate based polymers.According to the principles of molecular design, two new types of organosilicon monomers with slower rate of hydrolysis are synthesized by an alcohol exchange reaction. The reactants include 3-(triethoxysilyl) propyl and 3-(tri-2-propoxysily) propyl methacrylates. The structures of monomers synthesized are characterized andconfirmed by NMR. It is proved that organosilicon -acrylate latex with higher silicon content can be prepared by using these novel silicone monomers, and the polymer products have excellent mechanical and waterproof properties.Using the semi-batch synthesis techniques, a grafting reaction mechanism is adopted to prepare a core-shell composite latex of siloxane/acrylate based copolymer. The infrared spectroscopy, transmission electron microscopy, light scattering and X-ray photoelectron spectroscopy are used to characterize the polymer structure and the morphology of the latex particles. The results demonstrate that composite latex with core/shell morphology is indeed successfully prepared. The mechanical and water-proof tests for the films of the polymer indicate that it is the morphology of core/shell structure that contributes the excellent physical properties for the copolymers. The thermodynamic calculation is conducted for the latex particles with different morphology, and date analysis shows that the key technique to prepare core/shell composite latex is to reduce the interfacial tension between polysiloxane based core and polyacrylate shell.A Soap-free latex of acrylate modified with organosilicon is prepared by soap-free copolymerization. The effects of monomer component, initiator concentration, monomer concentration, ionic strength and organosilicon content on the emulsifier-free copolymeri...