Film forming hybrid acrylic/ZnO latexes with excellent UV absorption capacity

Film o ming hyb id ac ylic/ZnO la exes wi h excellen UV abso p ion capaci y Mi en Agui e a, Ma iano Ba ado b, Maide I u ondobei ia c, Ana Oka iz d, Te esa Gu aya c, Ma ia Paulis a, Jose Ramon Leiza a a POLYMAT, Kimika Aplika ua saila, Kimika Zien zien Fakul a ea, Uni e si y o he Basque Coun y UPV/EHU, Joxe Ma i Ko a Zen oa, Tolosa Hi ibidea 72, 20018 Donos ia-San Sebas ián, Spain b SGIke , Uni e si y o he Basque Coun y UPV/EHU, Joxe Ma i Ko a Zen oa, Tolosa Hi ibidea 72, 20018 Donos ia-San Sebas ián, Spain c eMERGE and Depa men o Mining and Me allu gical Enginee ing and Ma e ials Science, Uni e si y o he Basque Coun y UPV/EHU, P_ Ra ael Mo eno Pi xi xi, 3, 48013 Bilbao, Spain d eMERGE and Depa men o Applied Physics I, Uni e si y o he Basque Coun y UPV/EHU, P_ Ra ael Mo eno Pi xi xi, 3, 48013 Bilbao, Spain Abs ac Ac ylic/ZnO hyb id la exes we e syn hesized h ough a wo-s ep emulsion polyme iza ion p ocess. Fi s , a hyb id seed was syn hesized by miniemulsion polyme iza ion, which con ained all he hyd ophobically modi ied ZnO nanopa icles. Subsequen ly, his hyb id seed was employed in a seeded semiba ch emulsion copolyme iza ion yielding high solids con en hyb id la exes (40 w %). C yo- ansmission elec on mic oscopy (c yo-TEM) demons a ed ha he dispe sion o he ZnO nanopa icles in he ini ial miniemulsion was no homogeneous, which led o a hyb id seed wi h wo popula ions, polyme pa icles con aining ZnO and p is ine polyme pa icles. A e he second s ep o polyme iza ion ba ely he same mo phology was ob ained. Ne e heless, i was p o ed by elec on omog aphy (3D-TEM) ha he ZnO nanopa icles we e encapsula ed in he polyme pa icles. The hyb id ilms con aining ZnO p esen ed a supe io UV abso p ion capaci y han hei coun e pa hyb id ac ylic/CeO2 p epa ed ollowing he same s a egy. This is he accep ed manusc ip o he a icle ha appea ed in inal o m in Chemical Enginee ing Jou nal 270 : 300-308 (2015), which has been published in inal o m a h ps://doi.o g/10.1016/j.cej.2015.02.025. © 2015 Else ie unde CC BY-NC-ND license (h p:// c ea i ecommons.o g/licenses/by-nc-nd/4.0/) 1. In oduc ion In he las wo decades he inco po a ion o nanosized ino ganic ma e ials in o o ganic polyme ma ix has a ac ed he in e es o scien is s in academia and indus y. This is mainly due o he syne ge ic e ec s obse ed when combining he p ope ies o he ino ganic ma e ials (ine ness, chemical esis ance, empe a u e esis ance, wea he and UV esis ance, ha dness..) wi h he polyme ic ones (p ocessabili y, lexibili y, oughness, gloss, cu ing…) [1]. Miniemulsion polyme iza ion is a powe ul echnique o ob ain hyb id o ganic–ino ganic ma e ials wi h encapsula ed mo phology. This mo phology is a ac i e due o he ad an ages ha i p o ides o he inal hyb id ma e ial. Fo ins ance, be e dispe sion o he ino ganic ma e ial in he polyme ic ma ix, imp o ed s abili y agains agg ega ion o he nano ille s, p o ec ion o he ille om he ou side componen s (en i onmen ) o imp o emen s in many p ope ies such as mechanical, op ical o ba ie [2], [3], [4], [5], [6]. Howe e , he e a e h ee main aspec s o ake in o conside a ion when encapsula ing ino ganic nanopa icles by miniemulsion polyme iza ion. The i s one is he we abili y o he nanopa icles in he monome phase. This equi es he modi ica ion o he na u ally hyd ophilic su ace o he ino ganic ma e ial. The second one is he emulsi ica ion p ocess, which will de ine he size o he monome d ople s. And he las one, he aspec a io and he size o he nano ille [7], [8], [9], [10], [11]. The encapsula ion o he ino ganic ma e ial by miniemulsion polyme iza ion is no always achie ed; i s success being go e ned by he modynamic and kine ic conside a ions [12], [13]. Recen ly, we ha e shown ha CeO2 nanopa icles we e success ully encapsula ed in o high solids con en ac ylic la ex binde s by means o a wo-s ep semiba ch polyme iza ion s a egy [14]. The i s s ep consis ed on he p oduc ion o a hyb id seed by ba ch miniemulsion polyme iza ion using hyd ophobically modi ied CeO2 nanopa icles, and he second s ep comp ised a seeded semiba ch p ocess whe e he eed was ei he a p eemulsion o monome , o low CeO2 loadings [14], [15], o a hyb id miniemulsion, o highe CeO2 loadings [16]. This wo-s ep semiba ch polyme iza ion s a egy can be used o encapsula e o he me al oxides o ino ganic ma e ials wi h po en ial applica ions in ields ha include UV- blocking clea coa s, sola cells and an ico osi e coa ings among o he s. Ano he in e es ing me al oxide nanopa icle ha can be inco po a ed in o polyme ma ices is zinc oxide (ZnO). ZnO nanopa icles p esen a wide band gap ene gy (3.4 eV) and la ge exci a ion binding ene gy (60 mV), which make hem ideal o ca aly ic, op ical and elec ical applica ions [17], [18], [19], [20], [21]. ZnO nanopa icles ha e been inco po a ed in o o ganic–ino ganic nanocomposi e wa e bo ne dispe sions using di e en polyme iza ion s a egies and polyme ic ma ices [19], [22], [23], [24], [25], [26] and o a wide ange o applica ions. Dhoke e al. [25] di ec ly added a dispe sion o ZnO nanopa icles o an aqueous comme cial alkyd esin dispe sion and obse ed ha small amoun s (0.01–0.03 w %) o ZnO nanopa icles imp o ed co osion and mechanical p ope ies (sc a ch and ab asion esis ances). Xiong e al. [26] blended s y ene/bu yl ac yla e la exes and nanoZnO dispe sions in subs an ially highe amoun s (up o 9 w %) and analyzed he e ec o ZnO pa icle size on mechanical and op ical (UV and NIR shielding) p ope ies. They ound ha he be e he dispe sion o ZnO in he ma ix and he smalle he size o ZnO nanopa icles, he be e he p ope ies achie ed by he hyb id composi e ma e ials. O he au ho s used ZnO nanopa icles as Picke ing s abilize s in oil-in-wa e dispe sions. Thus, Chen e al. [23] showed ha he mo phology o ZnO/PS hyb id dispe sions changed depending on he hyd ophilici y o he ini ia o used (KPS s AIBN), esul ing in Picke ing s abilized pa icles when AIBN was used. Upon d ying he hyb id la exes showed a pH-bu e ing abili y. Also o pH-bu e ing applica ions Jeng e al. [24] syn hesized oil-in-wa e Picke ing s abilized polyanyline dispe sions using THF o Toluene as oil-phase. Modi ied ZnO nanopa icles ha e been also inco po a ed in o polyme ic dispe sions using miniemulsion polyme iza ion. Zhang e al. [22] used ZnO nanopa icles modi ied wi h me hoxyp opyl silane (MPS) in he miniemulsion polyme iza ion o s y ene. Low solids con en hyb id la exes wi h encapsula ed and homogeneous dis ibu ions o ZnO in he polyme pa icles we e ob ained, when a high enough amoun o MPS was used o modi y he ZnO. When lowe MPS amoun s we e used he nanopa icles emained a he polyme pa icle-aqueous phase in e ace like in Picke ing s abilized sys ems. Bo h mo phologies p esen ed luminescence p ope ies ha we e no p esen when ba e ZnO nanopa icles we e dispe sed in a PS la ex. Lu e al. [19] syn hesized also hyb id PS/ZnO la exes by miniemulsion polyme iza ion using ac ylic acid as comonome and compa ibilize o he ZnO nanopa icles wi h he PS. In e es ingly, he au ho s ound ha when he polyme iza ion was done in he p esence o co on ab ic, he UV-blocking capaci y o he co on ab ic was subs an ially imp o ed, wi h espec o blends o he ab ic and he hyb id la ex o he ab ic and ZnO nanopa icles. The inc eased pe o mance was a ibu ed o he in e ac ion o he ca boxylic g oups o he hyb id pa icles and he hyd oxyl g oups o he co on. In his wo k hyd ophobically modi ied ZnO was inco po a ed in o a ilm o ming clea coa ac ylic la ex binde by he wo-s ep seeded semiba ch polyme iza ion s a egy de eloped ecen ly by ou g oup o CeO2. La exes wi h 40 w % solids con en we e p oduced and he UV-blocking capaci y o he anspa en hyb id ilms cas ed was assessed and compa ed wi h ac ylic/CeO2 ilms. Fu he mo e, he mo phology o he hyb id pa icles was assessed by elec on omog aphy (3D-TEM) and unlike in p e ious wo ks, i was unambiguously p o ed ha mos o he ZnO agg ega es we e encapsula ed in he polyme pa icles. 2. Expe imen al 2.1. Ma e ials The hyd ophobic ZnO nanopa icles dispe sion (in me hoxyp opyl ace a e) was kindly supplied by Al ana (Ge many) wi h 40 w % o nanopa icles. The dispe sion was d ied (a 60 °C o 2 days) and he esul ing powde g inded. Me hyl me hac yla e, MMA (Quimid oga) and n-Bu yl ac yla e, BA (Quimid oga) we e used as ecei ed. Po assium pe sul a e (KPS, Ald ich) ini ia o was used as supplied. Dodecyl diphenyloxide disul ona e (Dow ax 2A1 45%, Dow Chemical) and n-Oc adecyl ac yla e (OA, 97%, Ald ich) we e used as an anionic emulsi ie and as a co-s abilize , espec i ely. Deionized wa e (MiliQ quali y) was used in he miniemulsions and hyd oquinone (Ald ich) was used o s opping he eac ion in he samples wi hd awn om he eac o . 2.2. Cha ac e iza ion me hods ZnO nanopa icle, polyme pa icle and monome d ople size dis ibu ions we e measu ed by Dynamic Ligh Sca e ing (DLS) using a Ze asize Nano Se ies (Mal e n Ins umen ). Fo his analysis, a ac ion o la ex (o miniemulsion) was dilu ed wi h deionized wa e , whe eas in he case o he ZnO nanopa icles dispe sions hey we e measu ed as ecei ed. The epo ed a e age pa icle size (d ople size) alues ep esen an a e age o wo epea ed measu emen s. The s abili y o he miniemulsions was s udied by measu ing he ligh backsca e ed a 60° in he Tu biscan Lab expe equipmen . Con e sion was measu ed by g a ime ic analysis. The mo phology and pa icle size dis ibu ion (PSD) o he la ex pa icles as well as he mo phology o he ilms cas ed om he la exes we e analyzed by T ansmission Elec on Mic oscopy (TEM), TECNAI G2 20 TWIN (FEI), ope a ing a an accele a ing ol age o 200 keV in a b igh - ield image mode. The samples we e dilu ed and d ied using a UV lamp. The ilms cas ed a oom empe a u e we e immed using an ul amic o ome de ice a −40 °C (Leica EMFC6) equipped wi h a diamond kni e. The ul a hin sec ions (100 nm) we e placed on 300 mesh coppe g ids and we e obse ed wi hou u he s aining. 500 polyme and ZnO pa icles we e coun ed and measu ed using a comme cially a ailable so wa e (Image P o Plus 7.0). The p epa a ion o he miniemulsion samples o c yo-TEM, in ol ed i s a i i ica ion p ocedu e on a FEI Vi obo Ma k IV (Eindho en, The Ne he lands). One d op o he sample solu ion (∼3 μL) was deposi ed in a coppe g id (300 mesh Quan i olis, hyd ophilized by glow-discha ged ea men jus p io o use) wi hin he en i onmen al chambe o he Vi obo and he excess liquid was blo ed away. The sample was sho in o mel ing (liquid) e hane and ans e ed o a Single Til C yo-Holde . The C yo- Holde was p e iously p epa ed by 655 Tu bo Pumping S a ion o main ain he sample bellow – 170 °C and o minimize he he mal de i e. The sample was examined in he TECNAI G2 20 TWIN (FEI) men ioned abo e, ope a ing a an accele a ing ol age o 200 keV in a b igh - ield and low-dose image mode. In o de o assess he deg ee o encapsula ion o he ZnO, a 3D omog aphic econs uc ion o a ep esen a i e a ea o he sample was ca ied ou using mic og aphs acqui ed in a JEOL JEM-1230 he mionic emission TEM mic oscope a 100 keV wi h a digi al came a in low dose condi ions. The il se ies was acqui ed om −60° o +60° e e y 2°, a nominal magni ica ion o ×20 K and ×30 K. The images we e hen aligned using he IMOD 4.3.4 so wa e package [27]; and he aligned il se ies we e econs uc ed using he WBP econs uc ion algo i hm wi h he TOMO3D so wa e [28]. A e he econs uc ion, a pos -p ocessing o he images was ca ied ou in Fiji [27]. 2.3. Miniemulsion p epa a ion and seeded semiba ch polyme iza ion In a ypical o mula ion 8.7 g o ZnO dispe sion (5 weigh based on monome s pe cen , wbm%, o ZnO) was added o MMA (30 g), BA (30 g) and OA (2.47 g) o p oduce he oil phase; i was s i ed o 15 min unde magne ic agi a ion. On he o he hand, he wa e phase was p oduced by mixing 1.33 g o Dow ax 2A1 wi h 140 g o wa e . Then bo h phases we e mixed o 15 min and soni ied o 15 min (ope a ing a 8-ou pu con ol and 80% du y cycle in an ice ba h and unde magne ic s i ing) o p oduce he miniemulsion. The p e iously p epa ed 30 w % solids con en (SC) miniemulsions we e polyme ized ba chwise in a 1 L glass jacke ed eac o i ed wi h a e lux condense , sampling de ice, N2 inle and a s i e o a ing a 150 pm. The miniemulsion was cha ged in he eac o and a e eaching he desi ed empe a u e (75 °C) a sho o KPS ini ia o (0.3 g) was added. The eac ion was ca ied ou o hal an hou . Once he seed was p oduced, ano he sho o KPS (1 g) was added o he eac o and he eeding o a p eemulsion (81.4 g MMA, 81.4 g BA, 3.6 g Dow ax 2A1 and 187.2 g o wa e ) con aining he es o he monome needed o each 40 w % SC was s a ed. The p eemulsion was ed o 4 h and he eac ion mix u e was cooked o one mo e hou a 90 °C. 3. Resul s and discussion 3.1. ZnO nanopa icles we abili y As i has been explained in he in oduc ion, he we abili y o he nanopa icles in he monome mix u e is a key aspec a ec ing conside ably he inal mo phology o he hyb id ma e ial. Fo ha , 1 wbm% o ZnO nanopa icles we e dispe sed in he monome mix u e composed o MMA/BA (50/50 w %). Fig. 1 p esen s he hyb id dispe sion ob ained. Fig. 1. Dispe sion o he ZnO nanopa icles in MMA/BA 50/50 w % monome mix u e. ZnO nanopa icles did no sedimen in he bo om o he lask, bu as i can be seen he dispe sion was opaque. The eason can be ound in he ZnO pa icle size. Acco ding o he DLS, he a e age diame e o he ZnO nanopa icles was 75 nm. Fig. 2 p esen s he TEM mic og aphs o his dispe sion. The mic og aphs show ha indi idual ZnO nanopa icles (25–35 nm) agg ega ed o o m la ge size en i ies in ag eemen wi h he a e age alue measu ed by DLS. Fig. 2. TEM mic og aphs o 1 w % ZnO nanopa icles in MMA/BA (50/50 w %). 3.2. Polyme iza ion o he hyb id la exes The p e iously desc ibed wo-s ep seeded semiba ch emulsion copolyme iza ion s a egy was applied o p oduce hyb id ac ylic/ZnO la exes. In o de o p oduce hyb id la exes wi h he highes ZnO nanopa icle inco po a ion e iciency and he lowes coagulum con en , se e al p ocess a iables we e a ied such as he way ZnO nanopa icles we e inco po a ed (di ec ly as ecei ed; dispe sed in me hoxyp opyl ace a e o as powde a e d ying ou o 2 days a 60 °C) o he emulsi ie amoun used in he seed polyme iza ion (1 o 2 wbm%). The ob ained coagulum alues we e in good ag eemen wi h he miniemulsion s abili y measu emen s (see Suppo ing In o ma ion), showing ha he eac ion ca ied ou wi h 1 wbm% o Dow ax in he seed and adding he ZnO di ec ly as ecei ed (in he dispe sion wi h me hoxyp opyl ace a e) p esen ed good miniemulsion s abili y and no coagulum in he inal la ex. The inal a e age polyme pa icle size o he hyb id la ex (measu ed by DLS) was 392 nm, almos 100 nm highe han he one ha should ha e been ob ained om an homogeneous dis ibu ion o he ed monome among he seed pa icles (dpseed: 152 nm). This is an indica ion o pa icle agg ega ion/coagula ion du ing he eeding s ep ha is analyzed below wi h he help o TEM measu emen s. Ano he in e es ing esul was ha he gel con en was 31% in he inal la ex. P e ious wo ks ha e shown ha o a ypical seeded semiba ch emulsion polyme iza ion o mula ion o MMA/BA 50/50 w %, a e he cooking pe iod he gel con en ha dly exceeds 10–15% [29], [30]. The highe gel con en ob ained in his p ocess may be associa ed o he abo e men ioned pa ial coagula ion o pa icles (i.e., la ge sizes o he polyme pa icles), which would inc ease he a e age numbe o adicals pe pa icle, he p obabili y o bimolecula e mina ion and hence o gel o ma ion [31]. 3.3. Mo phology o he ac ylic/ZnO hyb id la exes Fig. 3 p esen s he TEM mic og aphs o he polyme iza ion discussed abo e. The mic og aphs p esen he hyb id MMA/BA/ZnO hyb id nanod ople dispe sion (a), he seed hyb id la ex (b) and he inal hyb id la ex a e he semiba ch addi ion o he p eemulsion (c). Fig. 3. (a) C yo-TEM mic og aph o he ac ylic/ZnO hyb id miniemulsion, (b) TEM mic og aph o he hyb id ac ylic/ZnO seed and (c) TEM mic og aph o he hyb id ac ylic/ZnO inal la ex. As i can be seen, he monome d ople size dis ibu ion was e y b oad (Figs. 3 and 4a). O e all, 50% (see Fig. 3a) o he d ople s con ained ZnO nanopa icles o agg ega es. ZnO nanopa icles appea ed agg ega ed as had al eady been seen in he monome mix u e (see Fig. 2). The e o e he sonica ion p ocess led o a e y he e ogeneous dis ibu ion o he ZnO agg ega es; bo h la ge and small d ople s can be iden i ied wi h and wi hou ZnO. Bou gea -Lami e al. [32] obse ed a simila ype o dis ibu ion o silica nanopa icles in MMA and BA monome s. They s a ed ha a d ople wi h nanopa icles can be agmen a ed gi ing smalle d ople sizes, which some o hem migh con ain he nanopa icles and o he s no . No e ha he p oduc ion o a nanod ople dispe sion wi h each d ople con aining one nanopa icle o agg ega e o he ino ganic ma e ial is no an easy ask. Ma ching he numbe o d ople s and he numbe o ino ganic nanopa icles equi es an accu a e con ol o he size o he nanod ople s, which is con olled by a la ge numbe o p ocess a iables (e.g., he ene gy applied o he coa se emulsion, he iscosi y o he o ganic phase, he s abili y o he o med nanod ople s wi h espec o Os wald ipening and coalescence ha depends on he composi ion o he o ganic phase (e.g., cos abilize and hyd ophobe used) and he su ac an amoun and ype) ha makes his ask challenging in many ci cums ances. In compa ison wi h he mo phology o hyb id miniemulsions p epa ed wi h CeO2 [33], [34], hese ob ained wi h ZnO showed a less homogeneous dis ibu ion o he ZnO and a highe agg ega ion o he nanopa icles. Fig. 4. PSD measu ed using TEM mic og aphs o he (a) miniemulsion d ople s, (b) seed pa icles and (c) inal pa icles. Fig. 3b p esen s he mo phology o he hyb id seed pa icles ob ained a e polyme izing he miniemulsion o 30 min. Two main popula ions can be dis inguished, a popula ion o la ge polyme pa icles con aining ZnO and a popula ion wi h smalle pa icles wi hou ZnO. The compa ison o he miniemulsion d ople size dis ibu ion (Fig. 4a) and he PSD o he seed la ex (Fig. 4b) indica es ha a subs an ial ac ion o small d ople s did no nuclea e, bu deg aded (di using he monome o he exis ing pa icles) inc easing he size o he exis ing polyme pa icles. The numbe o pa icles con aining ZnO was smalle (33%) han he numbe o monome d ople s ha con ained ZnO, which is an indica ion ha in addi ion o he ans e o monome om small d ople s o la ge ones (due o Os wald ipening), he e was also coagula ion be ween d ople s con aining ZnO agg ega es. Figs. 3c and 4c p esen he TEM mic og aph and PSD o he inal la ex. The igu es clea ly indica e ha g ow h occu ed by polyme iza ion o he en e ing monome in he seed pa icles and coagula ion/agg ega ion o he pa icles. The a e age pa icle size was well abo e ha expec ed in absence o coagula ion and he TEM analysis (Fig. 4c) shows he p esence o e y la ge pa icles (600–1000 nm) con aining ZnO. The pe cen age o hese polyme pa icles (21%) was sligh ly smalle han hose ound in he seed pa icles p o ing ha he coagula ion among polyme pa icles con aining ZnO occu ed. The mo phology o he polyme pa icles con aining ZnO was analyzed in u he de ail by using elec on omog aphy (3D-TEM). This assessmen will allow o unambiguously de e mine he loca ion o he ZnO nanopa icle agg ega es in he inal la ex; namely, i he agg ega es a e ully encapsula ed in he polyme pa icles o no . Two di e en a eas o he hyb id la ex we e analyzed. In he i s one, a single polyme pa icle was analyzed which con ained mo e han one ZnO nanopa icle (see Fig. 5a), whe eas in he second egion nine polyme pa icles wi h ou ZnO agg ega es (Fig. 5b) we e s udied. Each agg ega e has been numbe ed o simpli y he ollowing discussion. Fig. 5. TEM mic og aphs o wo selec ed a eas o he hyb id ac ylic/ZnO la ex. (a) Specimen wi h a single polyme pa icle con aining ZnO. (b) Specimen wi h nine polyme pa icles and h ee o hem con aining ZnO. Tomog aphic econs uc ions a e desc ibed in he OXYZ coo dina es (Fig. 6). The OZ axis coincides wi h he di ec ion o he beam and he OX axis is he il ing axis. In o de o isualize his 3D objec , di e en 2D sec ions a e ep esen ed in he Fig. 7, Fig. 8, Fig. 9, Fig. 10. Aiming a he de e mina ion o he loca ion o he ZnO nanopa icles inside he polyme pa icle, hei posi ion in di e en 2D sec ions o planes, commonly known as o hoslices was analyzed. Fig. 6. Schema ic ep esen a ion o he X, Y and Z axis posi ion, elec on beam di ec ion, he di ec ion in which he sample was il ed and he dimension o he chosen sample’s a ea. Fig. 7. O hogonal sec ions o he econs uc ed single pa icle o Fig. 5a. OXY sec ions co esponding o he planes indica ed in he OYZ sec ion wi h whi e lines. (a) Z = 26 nm; (b) Z = 86 nm; (c) Z = 156 nm; (d) Z = 229 nm; (e) Z = 298 nm; ( ) Z = 367 nm; (g) Z = 420 nm. Sci. 90 (2003) 1923–1931. [27] J.R. K eme , D.N. Mas ona de, J.R. McIn osh, Compu e isualiza ion o h eedimensional image da a using IMOD, J. S uc . Biol. 116 (1996) 71–76, h p:// dx.doi.o g/10.1006/jsbi.1996.0013. [28] J.I. Agullei o, J.J. Fe nandez, Fas omog aphic econs uc ion on mul ico e compu e s, Bioin o ma ics 27 (2011) 582–583, h p://dx.doi.o g/10.1093/ bioin o ma ics/b q692. [29] I. Gonzalez, J.M. Asua, J.R. Leiza, The ole o me hyl me hac yla e on b anching and gel o ma ion in he emulsion copolyme iza ion o BA/MMA, Polyme 48 (2007) 2542–2547, h p://dx.doi.o g/10.1016/j.polyme .2007.03.015. [30] O. Elizalde, G. A zamendi, J.R. Leiza, J.M. Asua, Seeded semiba ch emulsion copolyme iza ion o n-bu yl ac yla e and me hyl me hac yla e, Ind. Eng. Chem. Res. 43 (2004) 7401–7409. [31] M.J. Ba andia an, J.C. De la Cal, J.M. Asua, Emulsion polyme iza ion, in: J.M. Asua (Ed.), Polym. Reac . Eng., Blackwell Publishing, 2007, pp. 233–269. [32] E. Bou gea -Lami, G.A. Fa zi, L. Da id, J.-L. Pu aux, T.F.L. McKenna, Silica encapsula ion by miniemulsion polyme iza ion: dis ibu ion and localiza ion o he silica pa icles in d ople s and la ex pa icles, Langmui 28 (2012) 6021– 6031, h p://dx.doi.o g/10.1021/la300587b. [33] M. Paulis, J.R. Leiza, Encapsula ion wi h miniemulsion polyme iza ion, in: S. Kabayashi, K. Mullen (Eds.), Encycl. Polym. Nanoma e ., Sp inge -Ve lag, 2014. 10.1007/987-3-642-36199-9_261-1. [34] M. Agui e, M. Paulis, M. Ba ado, M. I u ondobei ia, A. Oka iz, T. Gu aya, e al., E olu ion o pa icle mo phology du ing hyb id ac ylic/CeO2 nanocomposi es p oduced by miniemulsion polyme iza ion, J. Polym. Sci. Pa A: Polym. Chem.53 (2015) 792– 799, h p://dx.doi.o g/10.1002/pola.27504.