The Synthesis Of Polymeric Surfactants In The Emulsion Polymerization Reaction Applied Research

In this thesis, we focus on the preparation of polymeric surfactant and their applications in emulsion polymerization. The main contents embrace three aspects which are summarized as follows:1. The preparation of alkali soluble polymeric surfactant and its application in emulsion polymerizationAlkali soluble polymeric surfactant (ASPS), poly(methacrylic acid-co-n-butyl methacrylate), with certain molecular weight and relatively narrow molecular weight distribution, was prepared by the cleavage of the tert-butyl groups in poly(n-butyl methacrylate-co-tert-butyl methacrylate) which was obtained by RAFT polymerization induced byγ-ray irradiation. The obtained ASPS was used as polymeric surfactant in emulsion polymerization of styrene. The results show that this type of polymeric surfactant within a large-region of molecular weight and carboxyl content displays a good performance in the stabilization of styrene emulsion with a large-region of molecular weight and carboxyl content. The carboxyl content in ASPS shows obvious effects on the stabilization of emulsion, polymerization rate, viscosity of emulsion and morphology of final latex particles. The particle size distribution was affected by the molecular weight distribution of ASPS. In general, micron scale latex with a quite narrower particle size distribution could be easily obtained by the emulsion polymerization stabilized by this kind of polymeric surfactant, and the particle size of latex could be adjusted by the molecular weight or carboxyl content of ASPS prepared with the method of RAFT living radical polymerization induced byγ-ray irradiation.2. The applications of polymeric surfactant in miniemulsion polymerization induced by ray irradiation1) Polystyrene (PS) latex particles with narrow particle size distribution (PSD) (PDI=1.008) were successfully obtained byγ-ray irradiation induced miniemulsion polymerization stabilized by ASPS, and the particle size could be controlled between 50 nm and 250 nm by adjusting the concentration of HD or ASPS. Kinetics of polymerization revealed that the polymerization process could not be simply divided into three intervals as conventional emulsion polymerization. The reaction rate rapidly rose to a maximum and then decreased with time. In addition, total absorbed dose and dose rate could also strongly affect the particle size and PDI of PS latexes.2) A facile route for preparing monodispersed PS latexes with relatively smaller particle diameters viaγ-ray initiated miniemulsion polymerization using waterborne polyurethane (WPLJ) as surfactant was presented. By varying the amounts of WPU and HD we achieved to control the particle diameters in the region from 30 to 50 nm. Furthermore, for this system, the familiar disadvantage of secondary nucleation was avoided, which was almost inevitable in the case with SDS as the surfactant when its concentration was higher than CMC in the miniemulsion.3) PS nanocapsules were successfully prepared by y-ray-initiated miniemulsion polymerization stabilized by ASPS. The formation of hollow particles could be attributed to the relatively low reaction temperature, the combination of mutual static and steric repulsion of polymeric surfactant, and especially the grafting reaction between polystyrene and surfactant inγ-ray induced heterophase polymerization, which promotes the encapsulation process by affecting the kinetic factors.3. The preparation of carboxyl functionalized polymeric nanoparticles and its application in seeded emulsion polymerizationThe polymeric nanoparticles, poly(methacrylic acid-co-butyl methacrylate-co-styrene) (PMBS), were prepared by the soap-free emulsion polymerization of MAA, BMA and St. The XPS analysis and IR spectrum of PMBS showed that the PMBS particles were functionalized by carboxyl. TEM and DLS were used to characterize the morphology and particle size of PMBS particles. The content of the "film" shape materials in PMBS latexes decreases with the increase of monomer content, and the particle size almost keeps constant. However, the increase of monomer content widens the PSD of final PS latex particles. The study on the effect of MAA content in feed showed that the particle size of PMBS latexes decreased with the increase of MAA content, and the PSD of PMBS latexes became broad. However, the increase of MAA content did not broaden the PSD of final PS latexes. In addition, the ratio of BMA to St also affected the particle size and PSD of PMBS latexes and the final PS latexes. PS particles with very narrow particle size distribution could be obtained when the ratio of BMA to St was in the range from 1:1 to 1:3 for the seed making. Finally, a possible stabilization mechanism of PMBS particles was proposed based on the investigations.