Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2009. / Thesis submitted in partial fulfillment of the requirements for the degree of Master of Science (Polymer Science) at University of Stellenbosch. / ENGLISH ABSTRACT: The preparation of poly(acrylonitrile/methyl acrylate) [poly(AN-co-MA)] copolymers and poly(AN-co-MA)/clay nanocomposites, via emulsion polymerization, their characterisation, and the relationships between their molecular structures and physical properties are described. The copolymer composition was varied, and the properties of the products were analysed and correlated to copolymer composition. The free volume properties of the copolymer were dependent on the glass transition temperature (Tg), which is dependant on the copolymer composition. The copolymer crystallinity decreased with increasing MA content. The decrease in crystallinity and increase in both o-Ps lifetime and o-Ps intensity with decreasing Tg was caused by the enhanced chain mobility brought about by the incorporation of methyl acrylate. The poly(acrylonitrile-co-methyl acrylate)/clay nanocomposites with 60% AN:40% MA (mol:mol) ratio were prepared using montmorillonite clay modified via adsorption, using 2-acrylamido-2-methyl-1-propanesulphonic acid (AMPS), via in-situ intercalation polymerization. The poly(AN-co-MA)/clay nanocomposites with different clay loadings showed no difference in morphology. They exhibited improved thermomechanical properties and higher thermal stability than the neat copolymers. The melt rheology results of these nanocomposites showed an improved storage modulus as well as increased shear thinning behaviour with increasing clay content. However, the nanocomposites exhibited long-time relaxation behaviour and their chemical structures evolved during analysis. This was attributed to cyclisation reactions taking place at the temperature used during the oscillatory tests. The sorption isotherms of water vapour in these nanocomposites followed a dualmode sorption behaviour (BET type II mode). Hysteresis was observed in sorption/desorption isotherms of these nanocomposites. The equilibrium water uptake was higher in the nanocomposites compared to the neat copolymers, and it increased with increasing clay content, especially at high water activities (0.8). Although diffusion and permeability decreased with increasing clay content the solubility increased due to the hydrophilic nature of the clay. Despite the decrease in diffusion and permeability parameters the free volume hole radius of the nanocomposites remained constant, but a slight decrease in free volume hole number was observed. / AFRIKAANSE OPSOMMING: Die bereiding van poli(akrilonitriel/metielakrilaat) [poli(AN-ko-MA)] kopolimere en poli(AN-ko-MA)/klei nanosamestellings deur middel van emulsiepolimerisasie, hul karakterisering asook die ooreenkoms tussen hul molekulêre strukture en fisiese eienskappe is beskryf. Die kopolimeersamestelling is gevarieer, en eienskappe is geanaliseer en dan gekorreleer met die kopolimeersamestelling. Die vrye-volume eienskappe van die kopolimeer was afhanklik van die glasoorgangstemperatuur (Tg) wat weer afhanklik is van die kopolimeersamestealling. Die kristalliniteit van die kopolimeer het verminder met die hoeveelheid MA teenwoordig. Die afname in kristalliniteit en toename in beide die o-Ps leeftyd en o-Ps intensiteit met afname in Tg is veroorsaak deur die beter kettingbeweegbaarheid wat veroorsaak is deur die byvoeging van metielakrilaat. Die poli(akrilonitriel-ko-metielakrilaat)/klei nanosamestellings met 60% AN:40% MA (mol:mol) verhouding is berei deur die gebruik van montmorillonietklei, gemodifiseer deur die adsorpsie van 2-akrielamido-2-metiel-1-propaansulfoonsuur (AMPS) deur middel van 'n in-situ interkaleringspolimerisasie. Die poli(AN-ko-MA)/klei nanosamestellings het, ten spyte van die verskillende hoeveelhede klei wat gebruik is, geen verandering in morfologie getoon nie. Hulle het wel beter termodinamiese eienskappe en hoër termiese stabiliteit as die oorspronklike kopolimere getoon. Die smeltreologie resultate van hierdie nanosamestellings het ‘n beter stoormodulus getoon, sowel as toenemende skuifverdunningsgedrag met 'n verhoogde klei inhoud. Tog het die nanosamestellings lang tyd-ontspanningsgedrag getoon en die chemiese struktuur het verander tydens analise. Dit word toegeskryf aan die sikliese reaksies wat plaasvind by die temperatuur wat gebruik is tydens die ossillatoriese toetse. Die sorpsie isoterme van waterdamp in hierdie nanosamestellings het ‘n dubbel-styl sorpsiegedrag gevolg (BET tipe II styl). Histerese is waargeneem in sorpsie/desorpsie isoterme van hierdie nanosamestellings. Die ewewig in wateropname van die nanosamestellings was hoër as vir dié van die oorspronklike kopolimere en dit het toegeneem met 'n toenemende klei inhoud, veral by hoë humiditeit (0.8). Al het die diffusie en deurlaatbaarheid afgeneem met 'n toename in die klei inhoud, het die oplosbaarheid toegeneem as gevolg van die hidrofiliese karakter van die klei. Ten spyte van die afname in diffusie en deurlaatbaarheidsparameters, het die radius van die vryevolume openinge van die nanosamestellings konstant gebly, maar ‘n klein afname in die aantal vrye-volume openinge is gevind.

Thesis (PhD)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Fully exfoliated polystyrene-clay nanocomposites were prepared via free radical polymerization in dispersion polymerization, in a mixture of ethanol and water. Sodium montomorillonite clay (MMT) was pre-modified using 3-(trimethoxysilyl) propyl methacrylate (MPTMS) before being used in a dispersion polymerization process. The particles obtained were not completely stable and TEM images showed that most of the clay platelets were distributed in the dispersing phase. A second objective included, the preparation of low molecular weight of polystyrene (PS) and amphiphilic block copolymers of poly(styrene-b-2-hydroxyethyl acrylate) (PS-b-PHEA)using reverse iodine transfer polymerization (RITP) living/controlled free radical polymerization.The reaction kinetic profile of the RITP process for styrene and 2-Hydroxyethyl acrylate (HEA) was also studied. The formation of the block copolymer PS-b-PHEA was confirmed by GPC and gradient HPLC. The resulting PS-I and (PS-b-PHEA)-I were chemically modified by dimethylethylamine and triethylamine respectively, ended with PS and PS-b-PHEA has quaternary ammonium end-chain functionality (PS-cationic and (PS-b-PHEA)-cationic). The obtained functional polymers (PS-cationic) and (PS-b-PHEA)-cationic) were then grafted onto MMT via a simple ion-exchange process to offer MMT with polymer chains on the surface (PS-MMT) and (PS-b-PHEA)-MMT). Furthermore, the ability of the interaction ofPS-b-PHEA with MMT by adsorption via several functional groups was also investigated. The third objectiveincluded the use of this new class of pre-modified clay PS-MMT in the preparation of PCNs as stabilizers, the clay particles were encapsulated into PS latexes with a partially exfoliated structure at 100% CEC, upon stoppage of the polymerization process, and the final dispersion found to be stable for up to 5 wt% of clay filler loading. The thermal and thermo-mechanical properties of PS-nanocomposites were found to be dependent on both nanocomposites morphology, and clay loading. (PS-b-PHEA)-MMT was also used as stabilizers in the preparation of PS via dispersion polymerization. PS colloidal particles obtained were found to be armoured by (PS-b-PHEA)-MMT layers, with particles sizes in the micro-size range, with fair stability were obtained for clay loadings up to 5%. Analysis of the structure and thermo-mechanical properties of the resulting PCNs revealed the efficiency of the clay surface pre-modification in stabilizing the system throughout the heterophasic polymerization process.The melt flow properties of final PCNs were found to be strongly dependent on the clay loading, with shift observed from liquid-like viscoelastic to solid-like viscoelastic behaviour as the clay content increased due to percolation of the clay network within the PS matrix taking place upon film formation above Tg. / AFRIKAANSE OPSOMMING: Die eerste doelwit was die voorbereiding van ten volle geëksfolieerde polistireen-klei nanosamestellings deur vrye radikaal polimerisasie in dispersie-polimerisasie, in 'n mengsel van etanol en water. Natrium montmorilloniet klei (MMT) is gemodifiseer deur gebruik te maak van 3-(trimetoksiesiliel) propiel metakrilaat (MPTMS), voordat dit gebruik is in die dispersie-polimerisasie. Die bekomde partikels was nie heeltemal stabiel nie. Transmissie elektronmikroskopie (TEM) resultate het getoon dat die meeste van die klei plaatjies in die dispersie-fase versprei is. Die tweede doelwit was die voorbereiding van polistireen (PS) met 'n lae molekulêre massa, gevolg deur die vorming van amfifiliese blok kopolimere van poli(stireen-b-2-hidroksie-etiel akrilaat) (PS-b-PHEA) met behulp van omgekeerde jodium oordrag polimerisasie (RITP) lewendige/gekontroleerde vrye radikaal polimerisasie. Die reaksie kinetiese profiel van die RITP proses was bestudeer met betrekking tot stireen en 2-hidroksie-etiel akrilaat (HEA). Die vorming van die blok kopolimeer PS-b-PHEA is bevestig deur GPC en gradiënt HPLC. Die gevolglike PS-I en (PS-b-PHEA)-I was chemies gewysig deur onderskeidelik dimetieletielamien en trietielamien, waardeur PS en PS-b-PHEA een kwaternêre ammonium ketting-endfunksionaliteit bekom het (PS-kationies en (PS-b- PHEA)-kationies). Laasgenoemde twee funksionele polimere was toe gekoppel aan MMT deur 'n eenvoudige ioon-ruilingsproses wat MMT met polimeerkettings op die oppervlak (PS-MMT) en (PS-b-PHEA)-MMT) tot gevolg het. Die interaksie van PS-b-PHEA met MMT deur middel van adsorpsie van verskeie funksionele groepe is ook ondersoek. Die derde doel was gerig op die gebruik van hierdie nuwe klas gemodifiseerde klei PS-MMT as stabiliseerders vir die voorbereiding van polimeer-klei-nanosamestellings (PCNs). Die 100% CEC gemodifiseerde klei deeltjies is ge-inkapsuleer in die PS emulsies met 'n gedeeltelik geëksfolieërde struktuur, na afloop van die polimerisasie proses. Die finale dispersie was stabiel tot en met 'n klei inhoud van 5 wt%. Daar is gevind dat die termiese en termo-meganiese eienskappevan die PS-nanosamestellings afhanklik is van beide die morfologie en die klei inhoud. (PS-b-PHEA)-MMT was ook gebruik as stabiliseerder in die voorbereiding van PS deur dispersie polimerisasie. Daar is gevind dat die PS kolloïdale partikels wat verkry is, versterk was deur (PS-b-PHEA)-MMT lae. Partikel groottes was in die mikro-grootte gebied, en voldoende stabiliteit is verkry vir 'n klei inhoud van tot 5%. Analise van die struktuur en die termo-meganiese eienskappe van die bekomde PCNs het getoon dat die vooraf modifisering van die klei oppervlak doeltreffend was in die stabilisering van die sisteem gedurende die heterofase polimerisasie proses. Daar is ook gevind dat die smelt vloei eienskappe van die finale PCNs sterk afhang van die klei inhoud; 'n verskuiwing vanaf vloeistof-agtige viskoelastiese tot vaste-agtige viskoelastiese gedrag is waargeneem soos die klei-inhoud verhoog. Hierdie verskynsel was te danke aan perkolasie van die klei netwerk binne die PS matriks wat plaasvind tydens film vorming by 'n hoër temperatuur as die glasoorgangstemperatuur (Tg).

Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The use of co-sonication (ad-miniemulsion) polymerisation for the preparation of highly filled polymer/clay hybrid latexes is described. Laponite (Lap) content levels in the range of 10–50 wt% were effectively encapsulated in both polystyrene (PS) and polystyrene-co-butyl acrylate nanoparticles (PSBA). The latex and film morphological features of these highly filled hybrid materials were evaluated using both transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). PS/Lap latexes exhibited mixed particle morphologies from armoured particles at low clay content (10 wt%) to encapsulated particles at high clay content (50 wt%). However, PSBA/Lap hybrid latexes exhibited predominantly crumpled particle morphologies through the clay content studied. The resultant polymer/clay nanocomposites (PCNs) of PS/Lap and PSBA/Lap exhibited either partially or fully exfoliated structures. It was found that generally these PCNs exhibited superior properties than the neat polymers except for thermal stability properties. As much as 5000% storage modulus improvement was observed for both PS/Lap and PSBA/Lap relative to the neat polymers. The Tg of PSBA/Lap showed a 14 ºC shift towards higher temperature. Rheology tests showed that the resultant PCNs exhibited solid-like viscoelastic behaviour. The encapsulation of montmorilonite clay (MMT) using the ad-miniemulsion procedure was found to be ineffective. The MMT platelets remained adhered onto the polymer particles surfaces. Ineffective encapsulation of MMT platelets was attributed to their dimensions which were either large or equal to those of the polymer particles. Despite the ineffective encapsulation, the MMT platelets were completely exfoliated within the final PCNs as shown by both SAXS and TEM. Overall, the ad-miniemulsion was found to be an effective method for the preparation of highly filled water based polymer/clay hybrid latexes. However, the clay encapsulation in polymer particles and the extent of clay exfoliation were found to be dependent on clay dimensions relative to the polymer particles, monomer/clay compatibility and clay modifier reactivity. It was found that clay dimensions and use of clay modifier that improve monomer/clay compatibility enhances encapsulation. On the other hand, the modifier reactivity influenced the extent of clay exfoliation in the final PCN, irrespective of clay encapsulation in the polymer particles. These findings were based on comparative studies conducted on the use of Lap versus MMT and non-reactive modifier versus reactive modifier during ad-miniemulsion polymerisation. / AFRIKAANSE OPSOMMING: Die gebruik van mede-sonikasie (ad-miniemulsie) polimerisasie vir die voorbereiding van die hoogsgevulde polimeer/klei hibriedlatekse word beskryf. Laponiet (Lap) vlakke in hoeveelhede van 10-50 gew% is effektief ge-inkapsuleer in beide polistireen (PS) en polistireen-ko-butielakrilaat nanopartikels (PSBA). Die morfologiese eienskappe van die latekse en films van hierdie hoogsgevulde hibried materiale is geëvalueer deur beide transmissie-elektronmikroskopie (TEM) en klein-hoek X-straal-verstrooiing (SAXS). PS/Lap latekse het gemengde partikel morfologieë getoon, bv. vanaf gepantserde partikels by lae kleihoeveelhede (10 gew%) tot ge-inkapsuleerde partikels by hoë kleihoeveelhede (50 gew%). Daarteenoor het PSBA/Lap hibriedlatekse „n oorwegend verkreukelde partikelmorfologie getoon vir die reeks kleihoeveelhede wat bestudeer is. Die gevolglike polimeer/klei nanokomposiete (PKNs) van PS/Lap en PSBA/Lap het, óf gedeeltelike, óof ten volle geëksfolieerde strukture getoon. Oor die algemeen is bevind dat hierdie PKNs beter eienskappe as die suiwer polimere getoon het, behalwe vir die termiese stabiliteit eienskappe. Verbeteringe van soveel as 5000% in die stoormodulus is waargeneem vir beide PS/Lap en PSBA/Lap met betrekking tot die suiwer polimere. Die Tg van PSBA/Lap het „n 14°C verskuiwing na „n hoër temperatuur getoon. Reologiese toetse het getoon dat die gevolglike PKNs vastestofagtige visko-elastiese gedrag getoon het. Die inkapsulering van montmorilonietklei (MMT), deur middel van die ad-miniemulsieproses, was ondoeltreffend. Die MMT plaatjies het agtergebly op die oppervlaktes van die polimeerpartikel. Oneffektiewe inkapsulering van MMT plaatjies is toegeskryf aan hul grootte, wat óf groter, óf gelyk was aan dié van die polimeerpartikels. Ten spyte van die oneffektiewe inkapsulering was al die MMT plaatjies in die finale PKNs geëksfolieer soos deur beide SAXS en TEM aangedui. Oor die algemeen is bevind dat ad-miniemulsie „n effektiewe metode is vir die voorbereiding van hoogsgevulde waterbasis polimeer/klei hibriedlatekse. Daar is egter bevind dat klei inkapsulering in polimeerpartikels asook die omvang van klei eksfoliëring, afhanklik is van die klei afmetings in verhouding tot die polimeerpartikels, monomeer/klei verenigbaarheid en die reaktiwiteit van die kleiwysiger. Daar is bevind dat die klei afmetings en die gebruik van „n kleiwysiger wat die monomeer/klei verenigbaarheid verbeter, inkapsulering bevorder. Aan die ander kant het die reaktiwiteit van die kleiwysiger die omvang van klei eksfoliëring in die finale PKNs beïnvloed, ongeag van klei inkapsulering in die polimeerpartikels. Hierdie bevindings is gebaseer op vergelykende studies van die gebruik van Lap teenoor MMT en nie-reaktiewe wysiger teenoor reaktiewe wysiger gedurende ad-miniemulsiepolimerisasie.

Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: In materials chemistry, surface-initiated reversible deactivation radical polymerisation (SI-RDRP) has emerged as one of the most versatile routes to synthesising inorganic/organic hybrid materials consisting of well-defined polymers. The resultant materials often exhibit a remarkable improvement in bulk material properties even after the addition of very small amounts of inorganic modifiers like clay. A novel cationic reversible addition–fragmentation chain transfer (RAFT) agent with the dual purpose of modifying the surface of Laponite clay and controlling the polymerisation of monomer therefrom, was designed and synthesised. Its efficiency to control the polymerisation of styrene was evaluated and confirmed through investigating the molar mass evolution and chain-end functionality. The surface of Laponite clay was modified with the cationic chain transfer agent (CTA) via ion exchange and polymerisation performed in the presence of a free non-functionalised CTA. The addition of the non-functionalised CTA gave an evenly distributed CTA concentration and allowed the simultaneous growth of surface-attached and free polystyrene (PS). Further analysis of the free and grafted PS using analytical techniques developed and published during the course of this study, indicated that the free and grafted PS chains were undergoing different polymerisation mechanisms. For the second monomer system investigated n-butyl acrylate, it was apparent that the molar mass targeted and the monomer conversions attained had a significant influence on the simultaneous growth of the free and grafted polymer chains. Additional analysis of the grafted polymer chains indicated that secondary reactions dominated in the polymerisation of the surface-attached polymer chains. A new approach to separating the inorganic/organic hybrid materials into their various components using asymmetrical flow field-flow fractionation (AF4) was described. The results obtained not only gave an indication of the success of the in situ polymerisation reaction, but also provided information on the morphology of the material. Thermogravimetric analysis (TGA) was carried out on the polymer-clay nanocomposite samples. The results showed that by adding as little as 3 wt-% of clay to the polymer matrix, there was a remarkable improvement in the thermal stability. / AFRIKAANSE OPSOMMING: Oppervlakgeïnisieerde omkeerbare deaktiveringsradikaalpolimerisasie (SI-RDRP) is een van die veelsydigste roetes om anorganiese/organiese hibriedmateriale (wat bestaan uit goed-gedefinieerde polimere) te sintetiseer. Die produk toon dikwels ʼn merkwaardige verbetering in die makroskopiese eienskappe – selfs na die toevoeging van klein hoeveelhede anorganiese modifiseerders soos klei. ʼn Nuwe kationiese omkeerbare addisie-fragmentasie kettingoordrag (RAFT) middel met die tweeledige doel om die modifisering van die oppervlak van Laponite klei en die beheer van die polimerisasie van die monomeer daarvan, is ontwerp en gesintetiseer. Die klei se doeltreffendheid om die polimerisasie van stireen te beheer is geëvalueer en bevestig deur die molêre massa en die funksionele groepe aan die einde van die ketting te ondersoek. Die oppervlak van Laponite klei is gemodifiseer met die kationiese kettingoordragmiddel (CTA) deur middel van ioonuitruiling en polimerisasie wat uitgevoer word in die teenwoordigheid van ʼn vrye nie-gefunksionaliseerde CTA. Die toevoeging van die nie-gefunksionaliseerde CTA het ʼn eweredig-verspreide konsentrasie CTA teweeggebring en die gelyktydige groei van oppervlak-gebonde en vry polistireen (PS) toegelaat. Verdere ontleding van die vrye- en geënte PS met behulp van analitiese tegnieke wat ontwikkel en gepubliseer is gedurende die verloop van hierdie studie, het aangedui dat die vry- en geënte PS-kettings verskillende polimerisasiemeganismes ondergaan. n-Butielakrilaat is in die tweede monomeer-stelsel ondersoek en dit was duidelik dat die molêre massa wat geteiken is en die geënte polimeerkettings. ʼn Nuwe benadering tot die skeiding van die anorganiese/organiese hibriedmateriale in hulle onderskeie komponente met behulp van asimmetriese vloeiveld-vloei fraksionering (AF4) is beskryf. Die resultate wat verkry is, het nie net 'n aanduiding gegee van die sukses van die in-situ polimerisasiereaksie nie, maar het ook inligting verskaf oor die morfologie van die materiaal. Termogravimetriese analise (TGA) is uitgevoer op die polimeer-klei nanosaamgestelde monsters. Die resultate het getoon dat daar 'n merkwaardige verbetering in die termiese stabiliteit was na die toevoeging van so min as 3 wt% klei by die polimeermatriks.

This thesis explores ideas of everydayness, the mundane, and the repetitive emptiness of consumer culture. It looks at the malaise that plagues everyday life and examines several attempts throughout history to break from its grips which revolve around a search for a more ideal state. This research includes utopias of modernism, the transcendental, the communal living of Shakers and Early Christians, ascetic monks and The Desert Fathers. These ideas have shaped my studio practice as I construct installations based on worlds which allude to the eternal, the otherworldly, and the fragility of our physical world when compared to more eternal spiritual archetypes.

Cette étude porte sur des films composites à base d'amidon de manioc plastifié au glycérol et d'une argile kaolinique, comme charge minérale. L'origine et les mécanismes des interactions argile-amidon et leur rôle sur les propriétés des films ont été examinés. Pour vaincre le caractère non-expansible de la kaolinite, l'analyse du mécanisme de son exfoliation a été effectuée par insertion du diméthylsulfoxyde suivi d'un échange en milieux acétate d'éthyle et acétate d'ammonium. Une forte déstructuration de l'édifice cristallin de la kaolinite suite à l'échange est observée. La réassociation des feuillets après échange est désordonnée et permet d'escompter une meilleure dispersion de la kaolinite intercalée au sein d'un polymère. Ceci est confirmé par les analyses comparées de microscopies et de diffraction des rayons X sur des films incorporant diverses doses d'argile brute ou intercalée. L'abaissement de la température de transition vitreuse et du module élastique, ainsi que l'accroissement des effets de barrières à la décomposition thermique, à la diffusion de vapeur d'eau et à la transmission des UV visibles confirme la dispersion meilleure de la kaolinite intercalée. L'orientation des chaînes d'amidon et la diffusion du plastifiant transporté à l'interface par l'argile sont les mécanismes qui justifient l'effet plastifiant apporté par l'argile. L'interférence des interactions amidon-argile sur les interactions chaîne-chaîne au sein de l'amidon participe à la plasticité des films en diminuant la cristallinité. Les interactions amidon-argile se sont avérées faibles du fait des répulsions électrostatiques associées à des interactions associatives de type pont hydrogène / In this study, composites films made from glycerol plasticized cassava starch and a kaolinite clay, as mineral filler, were studied. The origin and mechanisms of clay-starch interactions and their role on films properties are examined. To deal with the unexpandable nature of kaolinite, an analysis of its exfoliation mechanism was done through dimethylsulfoxide (DMSO) intercalation followed by DMSO displacement using ethyl acetate and ammonium acetate. The crystalline structure of kaolinite is deeply disordered upon DMSO displacement because of a random reassociation of the clay layers. A better dispersion of the intercalated kaolinite within a polymer matrix is then expected. This expectation was confirmed by the comparison of microscopes and X-ray diffraction analyses on films charged with various dosages of raw or DMSO intercalated kaolinite. The lowering of the glass transition temperature and the elastic modulus together with the increase of barrier effects to thermal decomposition, water vapour diffusion and visible UV transmission, confirmed that the intercalated kaolinite is better dispersed. The starch chain orientation coupled to increase starch/glycerol miscibility due to the transportation of glycerol at the interface by clay particles are the two mechanisms that better explained plasticization effect induced by the filler. The interference of starch-kaolinite interactions on starch chain-chain interactions caused a decrease of starch matrix cristallinity that contribute to increase plasticization. The starch-kaolinite interactions are found to be weak due electrostatic repulsion associated to some weak associative forces due to hydrogen bonds

Materiais nanocompósitos híbridos polímero-argila nos quais lamelas nanométricas de argila montmorilonita são encapsuladas e dispersas em matriz polimérica são em geral mais rígidas, tenazes e resistentes do que os materiais poliméricos convencionais e tem o potencial de aplicações em revestimentos e filmes com propriedades de barreira. Dentre as várias técnicas de preparação de nanocompósitos poliméricos, as técnicas de polimerização \"in-situ\" em emulsão e mini-emulsão vem sendo empregada na síntese de látices híbridos com lamelas de argilas encapsuladas pelo polímero. Neste trabalho foram preparados látices híbridos de poliestireno e argila montmorilonita esfoliada através de dois métodos: no primeiro, a polimerização em emulsão e miniemulsão convencional na presença de argila modificada com sal quaternário de amônio é realizada com surfatante catiônico; no segundo método, um surfatante aniônico reativo foi usado para modificar uma argila natural sódica e empregada na polimerização em emulsão. Os resultados obtidos tanto para a polimerização em emulsão como em miniemulsão empregando idênticos reagentes (argila organofílica modificada e surfatante catiônico) mostraram boa conversão, aumento na velocidade de polimerização com aumento da concentração de surfatante e de argila, aumento na temperatura de pico na máxima velocidade de decomposição (TG), aumento no módulo de armazenamento no patamar vítreo e no patamar borrachoso (DMTA) com aumento da concentração de argila, encontrando um valor mínimo em ambos a 5% de argila. Apesar dessas características positivas, não foi obtida a encapsulação das lamelas da argila que era o objetivo principal do trabalho. Por outro lado, o método de polimerização em emulsão não convencional com surfatante reativo mostrou baixa eficiência na conversão mas que se mostrou eficaz na encapsulação das lamelas da argila para os látices com baixa conversão e elevado diâmetro de partícula. / Polymer-clay nanocomposite materials, in which nanometer-thick layers of clay dispersed in polymers, are generally stiffer, stronger, and tougher than normal polymeric materials and can be potentially useful in a variety of applications. These polymer-clay nanocomposites can be prepared in several ways, namely by emulsion \"in-situ\" polymerisation where polymer chains are coagulated on silicate layers producing capped silicate layers are more or less uniformly dispersed in aqueous medium. The objective of this work is to prepare polymer-clay hybrid latexes with exfoliated clay platelets encapsulated inside latex particles in order to improve the exfoliation of the clay platelets in the final polymeric film. To achieve this objective two separate approaches have been investigated, first by conventional emulsion polymerization and miniemulsion polymerization in the presence of montmorillonite clay modified by cationic surfactant and in the other approach a reactive anionic surfactant was used to modify the natural montmorillonite clay layers by emulsion polymerization. The results for both the emulsion polymerization as in miniemulsion using identical reagents (organoclay modified and cationic surfactant) showed good conversion, polymerization rate increased with increasing concentration of surfactant and clay, increased peak temperature at maximum speed decomposition (TG), an increase in storage modulus in the glassy plateau and the rubbery plateau (DMTA) with increasing concentration of clay, finding a minimum value in both the 5% clay. Despite these positive characteristics, encapsulation was not obtained from lamellar clay that was the main objective. Moreover, the method of emulsion polymerization with non-conventional reactive surfactant showed low conversion efficiency but has proved effective in the encapsulation of the lamellae of the clay for the lattices with low conversion and high particle diameter.

Materiais nanocompósitos híbridos polímero-argila nos quais lamelas nanométricas de argila montmorilonita são encapsuladas e dispersas em matriz polimérica são em geral mais rígidas, tenazes e resistentes do que os materiais poliméricos convencionais e tem o potencial de aplicações em revestimentos e filmes com propriedades de barreira. Dentre as várias técnicas de preparação de nanocompósitos poliméricos, as técnicas de polimerização \"in-situ\" em emulsão e mini-emulsão vem sendo empregada na síntese de látices híbridos com lamelas de argilas encapsuladas pelo polímero. Neste trabalho foram preparados látices híbridos de poliestireno e argila montmorilonita esfoliada através de dois métodos: no primeiro, a polimerização em emulsão e miniemulsão convencional na presença de argila modificada com sal quaternário de amônio é realizada com surfatante catiônico; no segundo método, um surfatante aniônico reativo foi usado para modificar uma argila natural sódica e empregada na polimerização em emulsão. Os resultados obtidos tanto para a polimerização em emulsão como em miniemulsão empregando idênticos reagentes (argila organofílica modificada e surfatante catiônico) mostraram boa conversão, aumento na velocidade de polimerização com aumento da concentração de surfatante e de argila, aumento na temperatura de pico na máxima velocidade de decomposição (TG), aumento no módulo de armazenamento no patamar vítreo e no patamar borrachoso (DMTA) com aumento da concentração de argila, encontrando um valor mínimo em ambos a 5% de argila. Apesar dessas características positivas, não foi obtida a encapsulação das lamelas da argila que era o objetivo principal do trabalho. Por outro lado, o método de polimerização em emulsão não convencional com surfatante reativo mostrou baixa eficiência na conversão mas que se mostrou eficaz na encapsulação das lamelas da argila para os látices com baixa conversão e elevado diâmetro de partícula. / Polymer-clay nanocomposite materials, in which nanometer-thick layers of clay dispersed in polymers, are generally stiffer, stronger, and tougher than normal polymeric materials and can be potentially useful in a variety of applications. These polymer-clay nanocomposites can be prepared in several ways, namely by emulsion \"in-situ\" polymerisation where polymer chains are coagulated on silicate layers producing capped silicate layers are more or less uniformly dispersed in aqueous medium. The objective of this work is to prepare polymer-clay hybrid latexes with exfoliated clay platelets encapsulated inside latex particles in order to improve the exfoliation of the clay platelets in the final polymeric film. To achieve this objective two separate approaches have been investigated, first by conventional emulsion polymerization and miniemulsion polymerization in the presence of montmorillonite clay modified by cationic surfactant and in the other approach a reactive anionic surfactant was used to modify the natural montmorillonite clay layers by emulsion polymerization. The results for both the emulsion polymerization as in miniemulsion using identical reagents (organoclay modified and cationic surfactant) showed good conversion, polymerization rate increased with increasing concentration of surfactant and clay, increased peak temperature at maximum speed decomposition (TG), an increase in storage modulus in the glassy plateau and the rubbery plateau (DMTA) with increasing concentration of clay, finding a minimum value in both the 5% clay. Despite these positive characteristics, encapsulation was not obtained from lamellar clay that was the main objective. Moreover, the method of emulsion polymerization with non-conventional reactive surfactant showed low conversion efficiency but has proved effective in the encapsulation of the lamellae of the clay for the lattices with low conversion and high particle diameter.

Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / The search for more productive seeds and with better transport and storage conditions has developed the interest of companies and researchers. In this section, nanotechnology, in particular, polymer / clay nanocomposites has proved to be an excellent alternative. By means of these nanomaterials it is possible to transport assets that allow the plant to better growth, productivity and germination rates, through the transport of fertilizers, agrochemicals or even essential micronutrients. The aim of this work was to synthesize and study nanocomposites polymer / clay; poly (hydroxyethyl methacrylate), pure laponite (pHEMA / Lap) and enriched with manganese micronutrients (pHEMA / LapMn). These materials aim to provide water and concomitantly provide nutrients to the seeds. The best formulation for the samples, amounts of polymer and clay was studied, and from this the micronutrient was incorporated into the formulation. The materials were characterized by absorption spectroscopy in the infrared region (FTIR), X-ray diffractometry (XRD) and thermogravimetry (TG). In addition, the water uptake capacity of the samples was evaluated. TG results showed an increase in thermal stability due to the interaction of the polymer chain with the clay. The XRD study showed that pure Lap and Lap Mn presented similar basal spacing to that found in the literature and that the nanocomposite had an exfoliated structure of the materials. The observation of the degree of swelling of the samples showed that the nanocomposites showed a capacity of water absorption 10% higher than the pure hydrogel. The seed coating affected the germination rate of the seeds, showing an optimization of this process. / A busca por sementes mais produtivas e com melhores condições de transporte e armazenamento tem desenvolvido o interesse de empresas e pesquisadores. Nesta vertente, a nanotecnologia, em especial, os nanocompósitos polímero/argila tem se mostrado uma excelente alternativa. Por meio destes nanomateriais é possível transportar ativos que possibilitem a planta melhor crescimento, produtividade e taxas de germinação, por meio do transporte de fertilizantes, agroquímicos ou até micronutrientes essenciais. Neste trabalho buscou-se sintetizar e estudar nanocompósitos polímero/argila; poli(metacrilato de hidroxietila) (pHEMA), laponita pura (pHEMA/Lap) e enriquecida com micronutrientes manganês (pHEMA/LapMn). Estes materiais tem por objetivo fornecer água e concomitantemente fornecer nutrientes para as sementes. Estudou-se qual a melhor formulação para as amostras, quantidades de polímero e de argila e a partir desta incorporou-se o micronutriente a formulação. Os materiais foram caracterizados por espectroscopia de absorção na região do infravermelho (FTIR), difratometria de raios X (DRX) e termogravimetria (TG). Além disso, a capacidade de absorção de água das amostras foi avaliada. Houve aumento da estabilidade térmica decorrente da interação da cadeia polimérica com a argila. O estudo por DRX mostrou que a Lap pura e a Lap Mn apresentaram espaçamento basal similar ao encontrado na literatura e que o nanocompósito apresentou estrutura esfoliada dos materiais. A observação do grau de intumescimento das amostras mostrou que os nanocompósitos apresentaram uma capacidade de absorção de água 10% superior à do hidrogel puro. O revestimento das sementes prejudicou a taxa de germinação das mesmas mostrando-se necessário uma otimização deste processo. / São Cristóvão, SE