Preparation Of Styrene-maleimide Copolymer Microsphere And Its Application In Constructing Hydrophobic Surfaces

Polymer microspheres have large surface area,low density,high dispersion and mobility,and are widely used in drug delivery,chromatographic analysis,catalysis,liquid crystal display,material modification and other fields.Styrene-maleimide copolymer(SMI)has good heat resistance and chemical stability,and is commonly used as a heat resistant modifier for resin.The current methods for the synthesis of SMI microspheres mainly use the expensive maleimide monomer copolymerized with styrene,which lacks the cost advantage.Although SMI can also be prepared by first synthesizing styrene-maleic anhydride copolymer(SMA),then ammonolysis and further imidization,this route is not suitable for the synthesis of microspheres.Therefore,it is still necessary to develop new low-cost methods for preparing SMI microspheres.Based on this background,a new approach was proposed to prepare water-dispersible nano-scale SMI microspheres by imidization reaction of styrene-maleamic acid copolymer aqueous solution under high temperature and high pressure,and the resulted SMI microspheres were used to construct hydrophobic surfaces.The main research contents and results of this thesis are as follows:1.A method for in-situ preparation of SMI microspheres by imidization reaction in styrene-maleamic acid copolymer aqueous solution was developed.Firstly,a series of copolymers of maleamic acid with different structures were prepared by aminating SMA with different reagents including methylamine-ammonia,ethylamine-ammonia and amylamine-ammonia.By studying the imidization reaction of maleamic acid copolymers with different structures under high temperature and high pressure,it is found that the emulsion of SMI microsphere can be prepared from aqueous solution of maleamic acid copolymer directly when the proportion of methylamine,ethylamine and amylamine is greater than 50%,60%and 70%,respectively.The particle size of the product increased from tens of nanometers to hundreds of nanometers with the increase of the amount of alkyl amine,and the Zeta potential gradually increased from-50 m V to about-20 m V.SMI microspheres with 10%～90%anhydride groups were prepared by imidizing maleamic acid copolymer that prepared by partly aminating SMA with ethylamine.It was found that the microspheres could be prepared in the range of 50～1300 nm when the amount of ethylamine was10%～90%of anhydride.The surface was negatively charged and the potential increased from-42 m V to-15 m V with the increase of ethylamine dosage.The effects of reaction temperature,solid content and SMA molecular weight on the preparation of microspheres were studied.The results showed that the emulsion obtained at the reaction temperature of 160~oC,solid content of 10 wt%and SMA molecular weight of 2800～190,000 had the best stability.In the process of microsphere formation,the degree of imide and the yield of microsphere gradually increased.After 5 h,the degree of imide and the yield of microsphere reached 92.6%and 95.7%,respectively,and then leveled off.2.Hydrophobic coatings were constructed on the surface of glass and paper using the prepared SMI microspheres.The morphology and hydrophobicity of microsphere emulsion at different concentrations and drying temperatures were investigated on the surface of hydroxylated glass.The results showed that the solid content of emulsion and drying temperature were positively correlated with the hydrophobicity of coating surface.When the solid content of emulsion was 20 wt%and was dried at 120~oC,the hydrophobicity of coating was the best,and the contact angle reached 124.2°and the roughness is 19.3 nm.The hydrophobic coating was constructed on the surface of the paper by using the microsphere emulsion,which has a good toughening and hydrophobic modification effect on the paper.The effects of hot pressing temperature and emulsion solid content on the hydrophobicity and mechanical properties of the coating were studied.The results showed that the optimal solid content was 5wt%and the impregnation amount was 3.56 g/m~2 when the microsphere emulsion was coated on the surface of the paper.When the hot pressing temperature is above 80~oC,the hydrophobicity tends to be stable,and the maximum contact angle is 124.2°.With the increase of hot pressing temperature,the tensile load of the modified paper first increases and then decreases,reaching the maximum value of 76.4 N at 140~oC,which is about 2.5 times higher than that of the blank sample.The elongation at break decreased from 0.966 to0.102.Scanning electron microscopy(SEM)showed that the space between the paper fibers was filled and the microspheres were tightly bonded to the paper fibers.