Study Of Polystyrene Microspheres Based On Hyperbranched Polymer Vesicles As Templates

Monodisperse microspheres have attracted wide interest due to their extensiveapplications such as calibration standards, separation media, microelectronics,coatings, and biotechnology. In all applications, uniform cross linked polystyreneparticles play a crucial role in obtaining better efficiency and meeting their originalrequirements by virtue of their surface characteristics and high sorption capacity.For the production of uniform polystyrene (PS) microspheres, several classicaltechniques have been developed in the past, including emulsion polymerization,seed emulsion polymerization, dispersion polymerization, emulsifier-free emulsionpolymerization. However the above methods have various problems such asdifficult control, tedious reaction steps, high surfactant residues, or use of hazardoussolvents. In this dissertation, we report a novel approach to prepare monodisperseparticles which can overcome these limitations.For this purpose, firstly, a new type of polymer vesicle named “branchedpolymersomes”(BPs), is prepared through the aqueous self-assembly of amphiphilichyperbranched multi-arm copolymer coined HBPO-star-PEO. Subsequently, thephoto-induced polymerization of styrene monomers that were solubilized within thehydrophobic region of bilayer of the pre-established vesicles was conducted byusing UV light (365nm) as well as a hydrophobic photo-initiator (DMPA). Finally,styrene-divinylbenzene (St-DVB) copolymer colloidal particles with perfectspherical shape and narrow size distributions were successfully prepared, which arerequired for subsequent formation of high quality colloidal crystals. With themonomer concentration increasing, the size of microspheres grows to a certainextent, then slightly reduces. The diameter of the copolymer colloidal particles canbe controlled from50to200nm by changing monomer proportion.Optimum conditions and proportions which affect the morphology of thesynthesized microspheres were investigated by TEM, SEM, DLS and microscope.The results indicate that the copolymerization takes place in the vesicle templateswith constant thickness, and longer time intervals would promote the phaseseparation of vesicles and monodisperse microspheres. In order to verify thetemplate polymerization, both rhodamine labeled HBPO-star-PEO and pyren-1-ylmethyl acrylate were synthesized. The copolymerization with styrene inthe vesicles bilayer and blending with the rhodamine-labeled vesicles further testifythe proposed mechanism.