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<p>Slide 1</p> <p>Polymer SynthesisCHEM 421</p> <p>Odian Book: Chapter 4</p> <p>Polymer SynthesisCHEM 421</p> <p>Emulsion PolymerizationsEconomically importantWestern countries 108 tons/year30% of all polymers made by free radical methodsemulsion polymers accounts for 40-50% of thisFirst employed during WWII for production of synthetic rubberToday: MMA, VC, vinylidene chloride, styrene, fluoropolymers, vinyl acetate, EVA, SA, SBR, chloroprene, etc</p> <p>Polymer SynthesisCHEM 421</p> <p>Emulsion Polymerization RecipeWater (continuous phase)Water-insoluble monomerWater-soluble initiatorSurfactant (detergent)</p> <p>Polymer SynthesisCHEM 421</p> <p>SurfactantsHydrophobic /Lipophilic core</p> <p>Polymer SynthesisCHEM 421</p> <p>SurfactantsTypes- Anionic - Cationic - Amphoterics - Non-ionics</p> <p>Polymer SynthesisCHEM 421</p> <p>Emulsion Polymerization Recipe</p> <p>Polymer SynthesisCHEM 421</p> <p>Emulsion PolymerizationsPolymzRateSurfactant Concentration</p> <p>Polymer SynthesisCHEM 421</p> <p>Kinetics of Emulsion PolymerizationPercentConversionTimeIIIIII</p> <p>Polymer SynthesisCHEM 421</p> <p>Kinetics of Emulsion PolymerizationRate% ConversionIIIIII</p> <p>Polymer SynthesisCHEM 421</p> <p>Before InitiationIIIIIIIIIMMMMMMMMMMMMMMMMMMMMonomer Dropletca. 1 micron diameterconc = 1011/mLstabilized by soapMicelle Containing Monomerca. 75 diameterconc = 1018/mLRelative surface area1 : 560Initiation of micelles statistically favored</p> <p>Polymer SynthesisCHEM 421</p> <p>Interval One: 0 15 % ConversionI IIIIII IIMMMMMMMMMMMMMPPMMMicellesContaining MonomerActivelatex particle</p> <p>MicellesContaining MonomerMicellesContaining MonomerActivelatex particles</p> <p>Inactivelatex particles</p> <p>Inactivelatex particles</p> <p>Polymer SynthesisCHEM 421</p> <p>Qualitative Details</p> <p>ConversionMicellesMonomerDropletsParticleNumberParticleSizeCommentsI0 15%presentpresentincreasesincreasesNucleation period, Increasing RpIIIII</p> <p>Polymer SynthesisCHEM 421</p> <p>Interval Two: 15 80% ConversionIIIII IIMMMMMMMMMPPInactivelatex particles</p> <p>Inactivelatex particles</p> <p>Inactivelatex particles</p> <p>Activelatex particles</p> <p>Activelatex particles</p> <p>I IMPActivelatex particles</p> <p>No micellesNumber of particles constant, thereforeRp = constant</p> <p>Polymer SynthesisCHEM 421</p> <p>Kinetics of Emulsion PolymerizationNumber ofMicellesTimeIIIIIINumber ofPolymerParticles1018010150</p> <p>Polymer SynthesisCHEM 421</p> <p>Qualitative Details</p> <p>ConversionMicellesMonomerDropletsParticleNumberParticleSizeCommentsI0 15%presentpresentincreasesincreasesNucleation period, Increasing RpII15 80%absentpresentconstantincreasesConstant # of particles,Cp = constantIII</p> <p>Polymer SynthesisCHEM 421</p> <p>Interval Three: 80 100% ConversionIIIII IMMMMMMMPPI MPMPI No monomer dropletsNo micelles</p> <p>Polymer SynthesisCHEM 421</p> <p>Qualitative Details</p> <p>ConversionMicellesMonomerDropletsParticleNumberParticleSizeCommentsI0 15%presentpresentincreasesincreasesNucleation period, Increasing RpII15 80%absentpresentconstantincreasesConstant # of particles,Cp = constantIII80 100%absentabsentconstantroughly constantConstant # of particles,Cp = decreasing</p> <p>Polymer SynthesisCHEM 421</p> <p>Emulsion Polymerization KineticsOnce inside a particle, radical propagates as rp = kp[M]Overall rate: Rp = kp[M][P.][P.] = N (where N = the sum of micelle and particle concentrations and = average # of radicals per particle)Therefore,Increase N to increase rate!</p> <p>Polymer SynthesisCHEM 421</p> <p>Emulsion Kinetics, cont.Smith-Ewart Kinetics:Case 2: = 0.5 (MOST CASES!)1 radical per particleHalf of the particles active, half not activeCase 1: 0.5Termination constant is lowHigh viscosity, initiator; large particles</p> <p>Polymer SynthesisCHEM 421</p> <p>Emulsion Polymerization KineticsHow to increase Rp? Increase N to increase rateIncrease surfactant concentration to increase N</p> <p>Polymer SynthesisCHEM 421</p> <p>Molecular Weight in Emulsion PolymerizationsMolecular weight determined by rate of growth of a chain divided by rate of radical entry (ri) How to increase molecular weight?DPrp = ri</p> <p>Polymer SynthesisCHEM 421</p> <p>Free Radical Solution PolymerizationsRecall To increase molecular weightIncrease monomer concentrationDecrease initiator concentrationTo increase Rate of PolymerizationIncrease monomer concentrationIncrease initiator concentrationCant do both!Rp = kp [M] (kd f [I] / kt)1/2</p> <p>**********************</p>


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