材料綜合實驗：Lab I Emulsion polymerization of styrene

1、South University of Science and Technology of China Department of Materials Science and Engineering Comprehensive Experiment of MaterialsLab I:Emulsion polymerization of styreneObjectives1. Understanding the fundamental of emulsion polymerization method.2. Learning the mechanism of free radial polym

2、erization.3. Gaining handon experience on synthesis of polymers through polymerization.IntroductionPrinciple of emulsion polymerization: HYPERLINK /wiki/Emulsion_polymerization /wiki/Emulsion_polymerizationAt the beginning of an emulsion polymerization, three phases are present: a continuous aqueous

3、 phase containing the initiator; suspended droplets of monomers, kept from coagulating to a continuous organic phase by agitation; and soap (emulsifier) micelles containing a small portion of monomer. Initiator fragments enter some of the micelles, where polymerization takes place at certain tempera

4、ture, supplied with monomers by diffusion from the monomer droplets through the aqueous phase. As these micelles (now more properly called monomerpolymer particles) grow, they are stabilized by more soup at the expense of uninitiated micelles, which eventually disappear. The polymerization rate depe

5、nds on the number of micelles, and this in turn on the concentration of the soap.Reaction mechanism free radical polymerizationGeneral equationReaction Mechanism ChainInitiating steps:ExperimentalMaterialsMonomer Styrene, reagent gradeInitiator Potassium Peroxydisulfate, K2S2O4, reagent grade.Emulsi

6、fier Sodium lauryl sulfate.Coagulation agent Sodium Chloride, NaCl, reagent grade.Washing solvent hot water.Medium solvent Deionized, distilled, and degassed water.ApparatusHotplate with magnetic stirring.Oil bath.250 mL threenecked glass flask.Condenser with cooling water.Beakers, glass rods, and m

7、agnetic stirring bar.Filter.ProceduresIn the flask, add 50 mL deionized, distilled, and degassed water, 0.30 g sodium lauryl sulfate.Add a stirring bar into the flask, place the flask with the condenser and emerge the flask into the oil bath on the top of the hotplate.Prepare a solution containing 0

8、.30 g Potassium Peroxydisulfate and 10 ml DI water in a beaker.Start stirring and increasing the reaction temperature to 80 oC.Put the K2S2O4 solution of step III and 10 ml styrene into the flask.Rapidly increase the temperature to 89 oC with stirring and keep the temperature at 89 oC .After 1.5 hou

9、r, close the hotplate, remove the flask and transfer the emulsion solution into a beaker,Add 5g NaCl into the beaker with vigorous stirring.Add 150ml hot water into the beaker and filter. Wash twice with hot water in the filter.Dry the polymer in an oven at 50 60 oC, and weigh the product to determi

10、ne the yield.ReportDescribe the goal, introduction, materials, apparatus, and experimental in your own words.Report the yield and analyze the possible reasons that could affect the finial yield.Answer the following questions:How does temperature affect the polymerization?How do impurities affect the

11、 polymerization?Why the reaction solution is light blue during the polymerization?ReferencesOdian, G. Principles of Polymerization, 4th Ed. John Wiley&Sons, Inc. 2004Flory, P.J. Principles of Polymer Chemistry, Ithaca, Cornell University Press 1953./wiki/Emulsion_polymerizationCautionsThe initiator and monomer should be added after the emulsion was completely dissolved.Do not change the stirring speed during the reaction, usually the spee