Synthesis of styrene and acrylic emulsion polymer systems by semi-continuous seeded ...

Synthesis of styrene and acrylic emulsion polymer systems by semi-continuous seeded ...

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particles by semi-continuous seeded emulsion polymerization processes was . The critical factor in our choice of emulsion polymerization, however 

Synthesis of styrene and acrylic emulsion polymer systems by semi-continuous seeded ... free download

R oc heste r I ns titut e of T echn olog y R IT Sc hol ar W ork s The se s The sis/Di sse rta tion C olle ct ion s 512004 S yn thesi s of s ty re ne a nd a crylic e mulsion p olyme r sys te ms b y semicon tin uou s seeded p olyme riz a tion pr oces ses L ynle y H G uckia n F ollo w thi s and a ddition al w orks at: h tt p://s chola rw ork sr it edu/the se s Thi s The sis i s br ought to y ou for f re e a nd ope n acce ss b y the The sis/Di sse rta tion C olle ct ion s at R IT S chola r W orks I t h as be en a cce pt ed for inclusion in The se s b y a n a uthor iz e d a dmini str ator of R IT Schola r W orks F or mor e information, p leas e c onta ct r its cho la rw ork [email protected] itedu R ecomme nded Citation G uck ia n, L ynley H, " Syn the sis of s ty re ne a nd a crylic e mulsion po lyme r syste m s b y semi con tin uous s eede d po lyme riza tion pr oc esse s" (2004) The sis R oche ste r I nstitut e of T echno logy Ac ce sse d f rom SynthesisofStyrene andAcrylic Emulsion PolymerSystems by Semicontinuous SeededPolymerization Processes Lynley H Guckian May, 2004 THESIS Submitted in partial fulfillment ofthe requirements forthe degree of Master ofScience in Materials ScienceandEngineering APPROVED: Grazyna KmiecikLawrynowicz Thomas W Smith Project Advisors Department Head Rochester InstituteofTechnology Rochester, NewYork 14623 Center forMaterial Science & Engineering SynthesisofStyrene andAcrylic Emulsion PolymerSystems by Semicontinuous SeededPolymerization Processes I,Lynley H Guckian,herebygrantpermission tothe Wallace Memorial Library, of RIT,toreproduce mythesis in whole or in partAnyreproduction willnotbefor commercial useofprofit Lynley H Guckian Date Abstract The synthesis of monodisperse styrene and acrylic coreshell polymer particles by semicontinuous seeded emulsion polymerization processes was investigated 120 and 140 nm homopoly(styrene) seed particles were made for each batch and monodisperse 300 and 400 nm coreshell particles were synthesized therefrom Divinylbenzene and poly(dimethylsiloxane) were compositional variables that were studied as part of the synthesis The addition of DVB significantly increased the gel content of the particles The incorporation of poly(dimethylsilocane) appeared to plasticize the particles The particle size, morphology, surface charge, molecular weight, percent gel content, and glass transition characteristics of the particles were evaluated Itwas found that the surface charge of the particles was affected by increasing particle size and by incorporating poly(dimethylsiloxane) or acrylic functionality in the shell Acknowledgements Iwould like to extend my deepest gratification to my advisors, Professor Thomas W Smith and Dr Grazyna KmiecikLawrynowicz of Xerox Corporation, for their guidance and patience throughout the extent of my project The knowledge Igained through working with them is indispensable Iwould like to thank Professor Andreas Langner for his help in understanding and examining zeta potential and for contributing to the writeup of my project Iwould like to thank Maura A Sweeney and Robert D Bayley of Xerox Corporation for their help in synthesizing the latex particles Iwould also like to thank Witold Niedzialkowski, KimLander, Mike Mehan, Dennis Stearns, and Mark Monachino for their help in analyzing the latex particles Lastly, Iwould like to thank my husband Ryan for his endless love and support Table of Contents I Introduction 1 1 1Experimental 10 i Materials 10 ii Latex Synthesis 10 iii Latex Characterization 16 III Results 21 IV Discussion 34 V Conclusions 44 Endnotes 45 References 46 m List of Tables Table 1Recipes for Semicontinuous Seeded Emulsion Polymerization of Styrene, Styrene/MMA and MMA Systems 12 Table 2 Characterization of Semicontinuous Seed Emulsion Polymers 22 Table 3Characterization of Incorporation of PDMS Macromer in PS and PS/PMMA Particles 28 IV List of Figures Figure 1Schematic Representation of Emulsion Polymerization as Described by Harkins 4 Figure 2 Course of an Emulsion Polymerization as Described by Harkins Model 5 Figure 3 Emulsion Polymerization Reactor Systems 7 Figure 4 SEM of 292 nm polystyrene particles 23 Figure 5SEM of 411 nm polystyrene particles 23 Figure 6 Differential scanning calorimetry thermogram of 300 nm PS control latex 24 Figure 7 Differential scanning calorimetry thermogram of 400 nm PS control latex 24 Figure 8SEM of 304 nm polystyrene particles crosslinked with 14% DVB 26 Figure 9 SEM of 415 nm polystyrene particles crosslinked with 14% DVB 26 Figure 10 Differential scanning calorimetry thermogram of 300 nm PS/DVB latex 26 Figure 1 1 Figure 12 Differential scanning calorimetry thermogram of 400 nm PS/DVB latex 27 Figure 12 SEM of 351 nm polystyrene particles 29 Figure 13 SEM of 342 nm polystyrene/PDMS particles 29 Figure 14 Differential scanning calorimetry thermogram of 350 nm PS latex 29 Figure 15 Differential scanning calorimetry thermogram of 350 nm PS/PDMS latex 30 Figure 16 SEM of 318 nm polystyrene/PMMA core/shell particles 31 Figure 17 SEM of 319 nm polystyrene/PMMA/PDMS core/shell particles 31 Figure 18 Differential scanning calorimetry thermogram of 320 nm PS/PMMA core/shell latex 32 Figure 19 Differential scanning calorimetry thermogram of 320 nm PS/PMMA/PMMAPDMS core/shell latex 32 Figure 20 SchematicRepresentation of Oligomer Precipitating to Form a New Particle 35 I Introduction Large monodisperse polymer particles havemany applications including coatings, finishes1, photonic crystals2, chromatographic columns3, and biomedical devices4 The synthesis of particles, ranging in size from 005 to 2000 um, has been atopic of interest in both academic and industrial laboratories Polymer particles in this size range may be synthesized by suspension, dispersion, or emulsion polymerization Suspension polymerization entails the polymerization of asuspension of monomer droplets in a medium in which the monomer is not soluble Typically it involves the polymerization of an "oilsoluble monomer" dispersed in water with the agency of a polymeric protective colloid or particulate suspension aid, initiating with an oilsoluble, freeradical catalyst Suspension polymerization typically produces particles ranging from 50 to 2000 um in size5 The locus of polymerization in suspension polymerization systems is the monomer droplet and kinetics in suspension polymerization reactions, in which the polymer is soluble in the monomer, are identical to polymerization in bulk Suspension polymerization yields readily isolable polymer particles that may be directly used in molding and extrusion of plastics Suspension polymerization allows for facile dissipation of heat reaction and can be readily scaled up in batch and continuous reactor schemes A disadvantage of suspension polymerization is that the protective colloid or particulate suspension aid most often has to be removed in a post polymerization processing reaction Dispersion polymerization has been described by Barrett6 as aspecial case of precipitation polymerization in which flocculation is prevented and particle size is controlled by an amphipathic graft or block copolymer dispersant The polymerization occurs predominantly in the polymer particle and the resulting particles are typically 01 to 10 urn in size Dispersion polymerization is capable of producing monodisperse particles A potential disadvantage of dispersion polymerization is that organic solvents are generally used as the reaction medium when polymerizing oilsoluble monomers Classic emulsion polymerization involves an oilsoluble monomer in water mediated by asurfactant and awatersoluble initiator The polymerization can be viewed as being initiated in micelles with the bulk of the polymerization occurring in monomerswollen latex particles Emulsion polymerization, in a batch process, typically produces particles that range in size from 005 to 03 um7 The locus and kinetics of polymerization differentiate emulsion polymerization from suspension and dispersion As compared to suspension and dispersion polymerization systems, emulsion polymerization offers the fastest polymerization rate and yields the highest molecular weight polymers The degree and rate of polymerization are determined by the number of polymer particles8, DP = kpN[M]/p and Rp= 103Nnkp[M]/NA where kp is the propagation rate constant, N is number of particles per milliliter (typically 1014), [M] is the monomer concentration, p is the rate of radical production, nis the average number of radicals per micelle, and Na is Avogadro's number The initiallyformed particles are very small (typically 2050 nm in diameter) Given the rapid diffusion rates for freeradicals in solutions, two radicals in any volume element of this size will immediately couple Accordingly, there is, on average, only one radical per particle and thus, termination by recombination is suppressed Emulsion polymerization systems can generally be driven to nearly quantitative conversion of monomer to polymer This leadsto reduced production costs and in many cases the resulting latex can be directly used in commercial applications9 Of the three polymerization processes described above, emulsion polymerization was chosen as our preferred method of synthesis Specifically, we were interested in creating monodisperse polymer particles in the 0205 um size range Suspension polymerization is particularly suited to produce much larger particles and thus was not aviable process While dispersion and emulsion polymerization are both capable of producing particles in the desired size range, dispersion polymerization of oilsoluble monomers with slight solubility in water is typically carried out in nonaqueous media The use of volatile and sometimes toxic organic solvents requires substantial investment in systems to control emissions and is typically avoided in the modern industrial environment The critical factor in our choice of emulsion polymerization, however, was that itis capable of producing particles in our desired size range The kinetics of emulsion polymerization were first described in the literature by Wendall Smith and Roswell Ewart10 The SmithEwart theory describes the kinetics of initiation and propagation in the polymerization of an oil soluble monomer, in water, initiated by awater soluble free radical initiator and mediated by a micellar surfactant In 1945, William Harkins reported a broadly applicable mechanism or model for emulsion polymerization11,12 The Harkins model describes three distinct intervals or stages during the course of an emulsion polymerization Interval Iis the nucleation phase wherein polymer particles are first formed, ostensibly being nucleated in monomer swollen micelles Interval IIbegins when particle nucleation stops and micelles are consumed Monomer is still found in droplets and polymer particles and there are aconstant number of particles in the system Interval III is the final stage of the reaction and in this phase monomer droplets are no longer present Monomer is only found in the polymer particles and the particle size is constant as the rest of the monomer is consumed These mechanistic features were exploited in our seeded growth ofpolymer particles Figure 1 Schematic Representation of Emulsion Polymerization as Described by Harkins (From Polymer Chemistry, BVollmert, SpringerVerlag, 1973, p 155) MonuiTwi iln>nlfii "3y_> MS <\ vWS^ oo5, h ^|:gg;;^^ * \s I laicx particle iiiiiiiinvirii mnHtculcs Figure 2 Course of an Emulsion Polymerization as Described by Harkins Model (From The Elements of Polymer Science and Engineering, A Rudin, Academic Press, 1982, p 248) 100 o o o 60 40 INTERVAL II NO UICEILAR SOAP MONOMER INDROPLETS MONOMER IN POLYMER PARTICLES CONSTANT NUMBER OF PARTICLES NTERVALHI NO DROPLETS MONOMER INPOLVMER PARTICLES CONSTANT NUMBER OF PARTICLES INTERVAL I MONOMER INMICELLES (dtom ~100A"j MONOMER INDROPLETS (diom 1005A*) MONOMER INPOL> VEF PARTICLES GROWING NUMBER OF POL'MER PARTICLES _L TIME (hr) The SmithEwart theory describes three cases In case 1, n<05 and pVN k0a/v n is the number of free radicals per reaction locus, p' is the rate of entrance of free radicals, N is the number of reaction loci, k0 is the rate constant, a is the interfacial area of loci, vis the volume of loci, and kt is the termination rate constant Case 1would be operative when radical desorption and termination in the aqueous phase are predominant In case 2, n=05 and k0a/v pVN < k/v Thus, at any given time half of the polymer particles containa living freeradical and are active Case 2 kinetics will typically predominate during interval IIwhen the particle size is too small to accommodate more than one radical In case 3, n>05 and pVN k/v Case 3would be operative when the particle size is large or the termination rate constant is low Case 3type kinetics may be used to describe seeded polymerization processes in which relatively large particles are being formed Since the seminal work of Harkins and Smith and Ewart, ithasbecome understood that nucleation processes in emulsion polymerization can take place by two mechanisms, micellar13 and homogeneous14 nucleationcapture Micellar nucleation is the classic mechanistic picture used to describe an emulsion polymerization In micellar nucleation, primary and oligomeric radicals in the aqueous phase enter the surfactant micelles Residual monomer dissolved in the aqueous phase also migrates into the micelles where itencounters initiating radicals As the monomer is converted to polymer, the micelles become polymer particles In homogeneous nucleation, free radicals react with monomer that is dissolved in the aqueous phase The growing oligomeric radicals become insoluble and precipitate from solution to form primary particles These primary particles typically undergo accretive growth increasing in volume until absorbed surfactant or ionizable surface species on the particle surface can produce charge stabilization Homogeneous nucleation is the probable mechanistic process for the polymerization of monomers with appreciable water solubility (>1% by weight), surfactantfree systems, and systems wherein the concentration of surfactant is well below the critical micelle concentration15 Three reactor systems (batch, semicontinuous, and continuous) are commonly used in industrial emulsion polymerization, these are schematically shown in Figure 3 Batch reactors usually consist of astirred tank equipped with a heat removal device such as ajacket or a reflux condenser All of the ingredients are added at or near the beginning of the reaction and the reaction is carried out to conversion Batch reactors are commonly used to make small latex batches, typically less than 1000 gallons in size The heat given off in a very short interval of time in polymerization reactions is quite large and despite the high heat capacity of water, the exotherm in large batch reactorscan exceed the cooling capacity of stateoftheart jacketed reactors Batch reactors are thus suitable for the preparation of relatively small commercial volumes of polymer Figure 3 Emulsion Polymerization Reactor Systems V J "^ >, \ J A Batch Reactor B Semicontinuous Reactor CO 12 q 11 o _ O CO LO LO CM G> CM CM CD t T_l > d CM LO d O CO O LO CM _ CD CM LO CD t 0)1 05d ^ OO LOCO d O CO O LO o CO| CT) CM LO CO rj" > O CM "* O O LO T_ d O CD O LO O r^l o> cm lo co lo 05 d CM "* O LO d O CO O LO o CD| 05 CM LO CO Tj 05 d ^ O LO LO ^ d ci O CO O LO o LOI CD C\l LO CO LO > d LO LO d d O CD O CM r O) CM LO CO ^^ ^ O CM OCO d O CO O CM CM CO CO| ^ CM LO CD ^ _J J!o CM N 3*c o E< 1 2 d C to COCDCo coDO CD fc ^ CD < fc 03 CO CO CO cj) _i J c Q ac >_>iCL ' c co c Q_ O Q "O CDCD CD CD CO U 0) Batch 1:300nm Polystyrene Control Deionized (Dl) water, 1170 g, and 026 g SLS were charged in the reactor The reaction mixture was subjected to a nitrogen purge to displace the oxygen for a minimum of 30 minutes and was simultaneously heated to 75C The reactor was then charged with 50 gstyrene monomer and stirred for 10 minutes to disperse the monomer droplets in the water phase 262 g KPS dissolved in 20 mL Dl water was added to initiate the polymerization Within minutes of initiation, the appearance of a milky white emulsion mademanifest the start of the polymerization The initial 30 minute period of the polymerization was the seeding stage After the seed particles reached 140 nm in size, 81 g styrene monomer was fed in over a period of 34 minutes After monomer addition was complete, the polymerization was allowed to continue for 2 hours to complete conversion of monomer to polymer The resulting particles were 29234 nm in size Batch 2: 400nm Polystyrene Control The same procedure was followed for the synthesis of seed particles as described for the 300 nm polystyrene control (Batch 1) After the seed particles reached 140 nm in size, 212 gstyrene monomer was fed in over a period of 96 minutes The monomer feed was stopped and the mixture was continually stirred for an additional 100 minutes After the 100 minutes, the monomer feed was started againand an additional 100 gstyrene monomer was fed in over a period of 50 minutes After the second monomer addition was complete, the polymerization was allowed to continue for 2 hours to complete conversion of monomer to polymer Due to a larger size particle, more surfactant was needed to provide stabilization An additional 0135 g SLS was added to the reaction mixture at three time intervals: 70 minutes after the end of the first monomer feed, at the start of the second monomer feed, and 60 minutes after the end of the second monomer feed The resulting particles were 41 145 nm in size 13 Batch 3: 300nm Polystyrene/DVB Latex The same procedure was followed as described for the 300 nm polystyrene control (Batch 1)except that instead of using exclusively styrene, asolution of 18 g DVB and 131g styrene was used The resulting particles were 30433 nm in size Batch 4: 400nm Polystyrene/DVB Latex The same procedure was followed as described for the 400 nm polystyrene control (Batch 2) except that instead of using exclusively styrene, asolution of 49 g DVB and 362 g styrene was used The resulting particles were 41546 nm in size Batch 5: 350nm Polystyrene Control The same procedure was followed for the synthesis of seed particles as described for the 300 nm polystyrene control (Batch 1) except that 265 g KPS was used After the seed particles reached 119 nm in size, 550 gstyrene monomer was fed in over a period of 250 minutes After monomer addition was complete, the polymerization was allowed to continue for 2 hours to complete conversion of monomer to polymer An additional 025 g SLS was added to the reaction mixture at two time intervals: 180 minutes after start of monomer feed and at the end monomer feed An additional 05 g KPS was added to the reaction mixture 60 minutes after the end of monomer feed The resulting particles were 351 38 nm in size Batch 6: 350nm Polystyrene/PDMS Latex The same procedure was followed as described for the 350 nm polystyrene control (Batch 5) with the addition of 10 g PDMS macromer to the last 100 gof monomer feed (10 g PDMS: 90 gstyrene) The resulting particles were 34240 nm in size 14 Batch 7: 320nm Polystyrene/PMMA Latex The same procedure was followed for the synthesis of seed particles as described for the 350 nm polystyrene control (Batch 5) After the seed particles reached 121 nm in size, 450 g MMA monomer was fed in over a period of 212 minutes After monomer addition was complete, the polymerization was allowed to continue for 2 hours to complete conversion of monomer to polymer An additional 05 g SLS was added to the reaction mixture at two time intervals: 40 and 100 minutes after start ofmonomer feed An additional 05 g KPS was added to the reaction mixture 60 minutes after the end of monomer feed The resulting particles were 31851 nm in size Batch 8: 320nm (Polystyrene/PMMA)/PDMS Latex The same procedure was followed as described for the 320 nm PS/PMMA latex (Batch 7) with the addition of 10 g PDMS macromer to the last 100 gof monomer feed (10 g PDMS: 90 g MMA) The resulting particles were 31925 nm in size Batch 9: 174 nm PMMA Latex Dl water, 990 g, and 026 g SLS were charged in the reactor The reaction mixture was subjected to a nitrogen purge to displace the oxygen for a minimum of 30 minutes and was simultaneously heated to 75C The reactor was then charged with 50 g MMA monomer and stirred for 10 minutes to disperse the monomer droplets in the water phase 265 g KPS dissolved in 20 mL Dl water was added to initiate the polymerization Within minutes of initiation, the appearance of a milky white emulsion made manifest the start of the polymerization The initial 30 minute period of the polymerization was the seeding stage After the seed particles reached 81 nm in size, 312 g MMA monomer was fed in over a period of 153 minutes After monomer addition was complete, the polymerization was allowed to continue for 2 hours to complete conversion of monomer to polymer An additional 0135 gSLS was added to the reaction mixture 34 minutes after start of monomer feed The resulting particles were 17428 nm in size 15 Batch 10: 250nm PMMA Latex The same procedure was followed as described for the 174 nm PMMA latex (Batch 9) with the following exceptions: 25 g MMA was initially charged to the reactor resulting in 77 nm seed particles and an additional 05 g SLS was added to the reaction mixture 100 minutes after start of monomer feed The resulting particles were 25031 nm in size Batch 11:260nm PMMA Latex The same procedure was followed as described for the 174 nm PMMA latex (Batch 9) with the following exceptions: 127 g MMA was initially charged to the reactor resulting in 60 nm seed particles and an additional 05 g SLS was added to the reaction mixture 30 and 120 minutes after start of monomer feed The resulting particles were 26235nm in size Batch 12: 250nm PMMA Latex II The same procedure was followed as described for the 260 nm PMMA latex (Batch 11) with the exception that the reaction temperature was lowered to 65C The resulting particles were 24835 nm in size iii Latex Characterization Size of particles was evaluated by scanning electron microscopy (SEM) and light scattering Compositional homogeneity was examined by differential scanning calorimetry (DSC) Molecular weight and polydispersity index was investigated by gel permeation chromotography (GPC) Percent total gel was determined by gravimetric filtration Particle surface charge was monitored by zeta potential Surface and particle composition were probed by xray photoelectron spectroscopy (XPS) and inductively coupled plasma (ICP) The polymer or copolymer was isolated before performing DSC, GPC, % total gel, and surface and particle composition analyses (XPS and ICP) by lyophilization 16 Particle Analysis: The SEM analysis' was performed in a Hitachi S4500 fieldemission scanning electron microscope (FESEM) at 5 keV probe voltage Samples were prepared for analysis bydropping undiluted latex from a pipette onto doublecoated carbon conductive adhesive tabs affixed to aluminum sample studs The samples were dried at room temperature Dry samples were sputter coated with 150 A gold in vacuo to eliminate electrostatic charging Dynamic light scattering was performed using a Microtrac UPA 150 Using a pipette 13 drops of sample was added to the sample compartment and diluted with Dl water to an internal loading factor of 100 1The samples were each run four times at 300s Instrument settings were particle transparency, absorptive; particle shape, spherical; and fluid refractive index, 133 Each run directly gave a histogram of counts as afunction of the scattered light The mean particle diameter is reported as three separate quantities: mv, the volume distribution, mn, the number distribution, and ma, the area distribution We report the particle size as mv in all cases and also report the standard deviation as calculated Latex samples were removed from the reactor using a pipette at intermittent time intervals and analyzed to measure seed particles, monitor particle growth through out the polymerization, and measure final particle size Compositional Analysis: The glass transition temperatures (Tg's) of the latex polymers were measured with a differential scanning calorimeter (DSC; model Q1000, TA Instruments, New Castle, DE)n 10 mg of sample was used and two heat cycles were performed over atemperature range of 0to 150C at aheating rate of 10C/min All data was tabulated from the second heat cycle 17 Molecular Weight Analysis: The averagemolecular weight and polydispersity of polymers were determined by gel permeation chromatography (GPC, model 2690, Waters, Boston, MA)m A mobile phase of THF and six Waters Styragel columns (HR6, HR5, HR4,HR3, HR2, HR1) were used The samples were dissolved in THF, filtered through 02 micron Teflon filters and injected into the GPC system Polystyrene standards ranging from 4,230,000 to 1,260 g/mol were used for the calibration Percent Total Gel: The % total gel was determined by gravimetric filtration Approximately 40 mg (W1) of each sample was weighed into ascintillation vial and 20 mL toluene was added The samples were allowed to shake on a box shaker for 4 hours Two filters, one Whatman Filter Paper 425 cm type GF/A and one MSI Micro Teflon Filter 47mm type PTEF, were placed in an aluminum pan and their weight recorded (W2) A filtration apparatus was assembled using a 1Liter vacuum flask with vacuum pump and trap, ceramic filter support, and aWhatman 3piece filter funnel The Teflon filter was placed shinny side down on to the filter support and the Whatman filter was placed on top The filter funnel was clipped to the filter support and the filters were wet with toluene The contents of the vial were emptied onto the filter and the vial rinsed with 2 mL toluene The wet filters were removed from the filter apparatus using forceps and the filters were allowed to air dry in the aluminum dish overnight The weight of the aluminum filter dish was recorded the next day (W3) The % total gel was calculated using: (W3W2)/W1 x100 Surface Charge Analysis: The zetapotential of the latex were measured with aZeta Reader (Mark 21 ,ZPi Inc, Bedminster, NJ) Approximately 05 gof each sample was added to 500 mL deionized water The sample was introduced to the instrument by cycling it through the sample accessory using the automated sample pumps At this time the sample was injected into the capillary sample cell using similar automated pumps The cell image was scanned by a high resolution color ccd camera and displayed on a high resolution color monitor When avoltage was applied, the particles moved across the capillary cell Vertical scan lines, with 25 micron line spacing, were manually adjusted to mimic the movement of the particles and the zeta potential was manually recorded for aminimum of ten sample injections per latex batch The voltage was set at 20 V/cm and the camera was operated in the darkfield mode Surface Composition: The samples were analyzed for surface composition using a Physical Electronics 5800 ESCA Xray Photoelectron Spectrometer (XPS)iv A region about 800 microns in diameter was analyzed The samples were presented to the xray source by depositing the polymers onto doublebacked conductive copper adhesive tape adhered to astainless steel sample holder The limits of detection of the technique are about 01 atom percent for the top 25 nm The samples were analyzed for composition on aTJA IRIS ICP (inductively coupled plasma) using matrixmatched standardsv The samples were prepared for analysis by weighing 10 gram of dried latex into a platinum crucible and 06 grams of 50/50 Lithium Tetraborate/Lithium Metaborate flux were added to the sample The sample was placed in afurnace with afluxing program (300 C/1hrs, 600 C/4hrs, 950 C/40min) 15 ml of 50 % HCI was added and heated on a hot plate until dissolved The sample was transferred to a 100 mL plastic volumetric, 05 mL of concentrated HF was added, and itshook overnight 75 mL of 4% H3B03 solution was added to neutralize any excess HF 1mL of 5% Triton X100 was added as awetting agent and the sample was brought to volume with Dl water Analysis of Residual PDMS Macromer in the Aqueous Phase: Sample preparation: 30 mL of each latex sample was placed in a PTFE ultracentrifuge tube The samples were placed in a Beckman L60 19 Ultracentrifuge and ran at 20,000 rpm for 1hour under vacuum at <200 mTorr at ambient temperature The samples were then removed from the centrifuge and the aqueous phase was collected via pipette for analysis A silicon standard and blank were also prepared A 50 pg/mL silicon standard was prepared by the following procedure: pipet 50 mL of the 1000 ug/mL silicon solution into a 100 mL volumetric flask, add 20 mL of a 1% Triton X100 solution, add 20 mL cone HN03, and dilute with Dl water to volume A blank was prepared by the following procedure:pipet 20 mL of a 1% Triton X100 solution into a 100 mL volumetric flask, add 20 mL cone HN03, and dilute with Dl water to volume Sample analysisvl: The standard, blank, and sampleswere ran on aThermo Jarrell Ash IRIS ICP The instrument was calibrated at the silicon wavelength, 2516 nm, using the standard and blank solutions A solution containing 20 ug/mL of lutetium was split into the standard, blank, and sample solution lines and used as an internal standard (a ratio of analyte to internal standard intensity was applied to compensate for fluctuations due to sample introduction and matrix differences) The lutetium wavelength of 2615 nm was used The sample solutions were introduced to the instrument by direct aspiration to obtain avalue for Si concentration in pg/mL 20 III Results As described in detail in the experimental section, eight different batches ofpolystyrene core latex were synthesized The relevant characteristics of these 8 batches (seed size, particle size, zeta potential, weight average molecular weight, molecular weight polydispersity, gel content, and glass transition temperature) are summarized in Table 2 Monodisperse seed latexes of two sizes were made, 140 nm for batches 1through 4 and 120 nm for batches 5 through 8 Reactions 1and 2were styrene controls Both reactions entailed the polymerization of styrene onto 140 nm seed particles The gel content and glass transition temperatures were unaffected by the change in particle size Figures 6 and 7display DSC scans for the 300 and 400 nm particles The glass transition curve had a smooth sigmoidal shape indicative of awellformed polymer, and the onset Tg of 981 00C is close to that reported in the Polymer Handbook for poly(styrene) The change in particle size affected the molecular weight, polydispersity, and zeta potential The molecular weight of the 400 nm control was double that seen in the 300 nm control The PDI also increased with size The absolute value of the zeta potential was lower in the 400 nm particles As seen in Figures 4 and 5, both reactions produced spherical and relatively monodisperse particles 21 ^_CO CO^CMt^^COCMCM c cicNioT^dd^ci o +1 +1 +1 +1 +1 +1 +1 +1 oa, > COWCONSCOCNO cdaicdcdi^cdLodNLOr^LOCOI^LOCD (0 i i i **0)N O CO oo co off c^r^^^cpco^^ ^ ^ ^ t CM O O 'I T_ **C ^ a> ** cocoin^LOSoos d> coco^^oqoooooo O """ CMCMCDOOCM'r'dd o a aiLqjojracostO'^; 0 'tCDCCSSCOCO ^_^a> p oq p cp lo ^t 5 (AQ LOh^r5c5'>!tooLdr^t^O C C 00 C) CT> O t Tt LO "tf t CM *' o "3LOCOCOCOOCMLO u o ^CO^OO'^CO'vl'^CM \S N E +1 +1 +1 +1 +1 +1 +1 +1 t_ 2 c CMt^LOtCMCOCT) <_ OtOtLOtItt Q cm^jco^oococooo (DOMrNCDCDO) a> S ^* CMOOOOOOtttt+1 +1+1 +1 +1 +1 +1 +1 S cocrjTscDnTo to w COCO^OOtCMCMCM CM o^ "t "* CO CO ^ _J CM __ p^ ? ^ O Op CD sSS CO ( 0) E E Ecoto E_:w| oQ LOCO c 0 TCMCO^LOCOI^00 Figure 4 SEM of 292 nm polystyrene Figure 5 SEM of 41 1nm polystyrene particles particles 23 Sample BBL2771364 Size 67500 mg Method Tgto 150C Comment EAlatex Bob Baytey /Lynley Guckjan DSC File ZVDSC Q100\lman\aug03\0308M 005 Operator kirn Run Date 05Aug03 1148 Instrument DSC Q100 V73Build 249 [i 1024B*C 1 1 I J 10249C L J ~~ __|7 92X \ ; 0 0 a Temperature iC) 160 ijnivp", al v'38E1Lirilnjrrienu Figure 6 Differential scanning calorimetry thermogram of 300 nm PS control latex Sample BBL2771366 Size 92780 mg Method Tgto 150C Comment EAlate Bob Bayley /Lynley Guckjan DSC File ZSC Q100\lmaniaug03\030804 006 Operator kirn Run Date 05Aug03 1339 Instrument DSC Q100V73Build 249 10465C r~ 1CW66>: I I ~~ ______ 9972C \ 60 80 100 Temperature |C> iirnvfisal1,'] hh[AinT'ii'titTilv Figure 7 Differential scanning calorimetry thermogram of 400 nm PS control latex 24 In batches 3and 4, the effect of the addition of DVB was evaluated 14% weight percent DVB was incorporated in the monomer feed for reactions 3and 4 and the particles were grown to nominally 300 and 400 nm in size, respectively The incorporation of DVB had little effect on the particle size, glass transition temperature, and zeta potential The glass transition curves, shown in Figures 10 and 11had the same shape characteristics as the controls; the absolute value of the onset Tg was minimally elevated As expected the gel content of the polymer was dramatically affected by the incorporation of adifunctional monomer The gel content was greater than 85% in both materials The incorporation of DVB does not appear to have had asignificant affect on the morphology of the particles The particles, shown in Figures 8 and 9, appear to be relatively monodisperse in size 25 Figure 8 SEM of 304 nm polystyrene Figure 9 SEM of 415 nm polystyrene particles crosslinked with 14% DVB particles crosslinked with 14% DVB Sample BBL2771368 Size 72930 mg Method SPARTg DSC File Z\DSC Q1000\]man\April04\040428 004 Operator km Run Date 28Apr04 1356 Instrument DSC 01000 V73Build 249 6 0I O 60 80100 Temperature 04 20 55 Instrument DSC Q1000 V73Build 249 I / ~^_ 10565C ! "T^L 10565X | ~~~~^ 110077K 302 _,i Temperature |C) 16C Universal V386TAlnsl'ijrrifint= Figure 14 Differential scanning calorimetry thermogram of 350 nm PS latex 29 Sample BBL2772570 Size7 7650 mg Method Tgto 150C DSC File ZtDSCQ1000Vman\Feb04\040220 014 Operator km Run Date 21Feb04 0128 Instrument DSC 01000 V73Build 240 /^ V \ 60 30100 Temperature (Cj 160VJ8B TAInstruments Figure 15 Differential scanning calorimetry thermogram of 350 nm PS/PDMS latex In reactions 7and 8, 320 nm PS/PMMA and (PS/PMMA)/PDMS core/shell particles were made The particle size, molecular weight, polydispersity, and gel content were similar for the two reactions The glass transition and zeta potential were perturbed by the addition of a PMMA and PMMAPDMS shell The DSC curves of the particles from both reactions, shown in Figures 18 and 19, exhibited long, broad transition zones as compared with the styrene homopolymers Such broad transitions are indicative of asubstantially miscible mixture of copolymers of differing composition and molecular weight One might interpret the data as being indicative of two glass transitions; one at 100 and another at 115C The zeta potential measurements gave two significant results First, with the addition of PDMS to the reaction, the absolute zeta potential was increased by 5 mV Second, the zeta potential was lower for the PS/PMMA particles than for similar PS particles The (PS/PMMA)/PDMS latex was similar to the PS/PDMS latex in that XPS was unable to detect silicon in the top 25 nm of the surface ICP 30 analysis confirmed the presence of silicon in the particles at 01% and in the aqueous phase at 44 ppm As seen in Figures 16 and 17 the core/shell particles were spherically shaped, but the surface does not appear as smooth as those in the PS controls However, the particles still appear monodisperse and to some degree still arrange in a structured lattice Figure 16 SEM of 31 8 nm polystyrene/PMMA core/shell particles Figure 17 SEM of 319nm polystyrene/PMMA/PDMS core/shell particles 31 Sample BBL2772566 Size 92860 mg Method Tgto 150 C DSC File ZOSCQ1000Vman\Feb04\040220012 Operator kirn Run Date 20Feb04 2339 Instrument DSC Q1000 V73Build 240 &*" s&f ~~~^7 97C O Temperature iC) 160 Universal V3BEiTAinstruments Figure 18 Differential scanning calorimetry thermogram of 320 nm PS/PMMA core/shell latex Sample BBL2772568 Size 85900 mg Method Tgto 150C DSC File ZSCQ1000\JmantFeb04\040220 013 Operator km Run Date 21Feb04 0034 Instrument DSC O1000 V73Build 240 Temperature tCj

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