Branching in poly(methyl methacrylate) (PMMA) is produced by incorporating a pre-prepared polymeric chain transfer agent (PCTA) into a single stage radical polymerisation. Samples of PCTA having a range of transfer functionalities and molar masses were synthesised by modifying a methacrylate-based copolymer. Control of branching in PMMA has been studied as a function of transfer functionality and molar mass in the PCT A and a function of MMA and initiator concentrations in the MMA polymerisation. The branched samples of PMMA have been characterised by size exclusion chromatography (SEC) with multi-detectors to determine Mark–Houwink and other parameters to assess levels of branching. Some PCTA samples have been prepared with a UV chromophore to facilitate characterisation by SEC-UV.

Les polymères de grande masse molaire sont couramment utilisés comme viscosifiants par l’industrie pétrolière. Ils peuvent se présenter sous la forme d’une poudre qui doit être dissoute dans l’eau le plus rapidement possible avant d’être pompée dans le puits. Cette étude porte sur la compréhension des mécanismes qui entrent en jeu lors de la dissolution de la poudre d’un polyélectrolyte appelé GP. Bien qu’étant solubles dans l’eau, les grains de GP présentent un comportement hydrophobe lorsqu’ils sont mis en contact avec l’eau. Le mouillage est défavorable. Une couche de gel viscoélastique gonfle et bouche les pores entre les grains, provoquant la formation de grumeaux qui augmentent le temps de dissolution. Nous avons montré que c’est la cinétique de gonflement du gel qui contrôle la cinétique de dissolution du GP. Le gonflement du gel est un processus diffusif gouverné par la pression osmotique due à la présence des contre-ions du GP. La reptation ne joue aucun rôle dans le désenchevêtrement des chaines, qui survient uniquement lorsque la concentration en polymère dans le gel devient inférieure à la concentration critique de recouvrement c* du GP. La disparition du gel peut être accélérée en imposant une vitesse d’agitation ω dans le mélange eau/GP qui génère un cisaillement à l’interface gel/solution. La couche de gel est alors érodée lorsque la concentration en polymère dans le gel devient inférieure à la concentration critique d’érosion cer, supérieure à c* et qui augmente avec ω. Nous avons montré que la cinétique de dissolution du GP est alors contrôlée par l’érosion de la couche de gel et que le temps de dissolution varie comme ω à la puissance -1.2. / Polymers of large molar mass are often used as fluids viscosifiers in the Oil and Gas industry. Ideally, the polymer powder must mix with water and totally dissolve as fast as possible before being pumped in the well. This study focuses on the understanding of the mechanisms at stake during the dissolution of a polyelectrolyte called GP. Even if they are hydrosoluble, GP grains exhibit a hydrophobic behavior when they are put in contact with water, which is responsible for a poor wetting. A viscoelastic gel layer forms and clogs the pores between GP grains, leading to the formation of lumps which increases the dissolution time. We demonstrate that the GP dissolution kinetics is controlled by the gel swelling kinetics. Gel swelling is a diffusive process governed by GP counter-ions osmotic pressure. Gel dissolution is not controlled by a reptation process but occurs when the polymer concentration inside the gel reaches c*, the overlap concentration of the GP. Dissolution is accelerated by stirring the polymer/water mix. The shear at the gel/solvent interface is responsible for the gel erosion. Erosion occurs when the polymer concentration inside the gel reaches the critical erosion concentration cer > c*, which increases with the mixing velocity ω. We demonstrate that GP dissolution kinetics is thus controlled by the erosion of the gel layer and that the dissolution time varies as ω to the power -1.2.

yes / Fluorescence spectroscopy on a series of aqueous solutions of poly(acrylic acid) containing a luminescent label showed that polymers with molar mass, Mn < 16.5 kDa did not exhibit a pH responsive conformational change, which is typical of higher molar mass poly(acrylic acid). Below this molar mass, polymers remained in an extended conformation, regardless of pH. Above this molar mass, a pH-dependent conformational change was observed. Diffusion-ordered nuclear magnetic resonance spectroscopy confirmed that low molar mass polymers did not undergo a conformational transition, although large molar mass polymers did exhibit pH-dependent diffusion. / Engineering and Physical Sciences Research Council (EPSRC) funded CASE award PhD. Part funded by flocculant manufacturer SNF (UK) Ltd.

Os polímeros com propriedades luminescentes, e mais especificamente, os eletroluminescentes, tem atraído muita atenção devido a sua possível aplicação em dispositivos ópticos e eletrônicos do tipo LEDs (light-emitting diodes). Grande parte das pesquisas realizadas no campo da eletroluminescência se baseia em estudos sobre poli (arilenos-vinilenos), como o poli-(p-fenileno vinileno), PPV, e seus derivados. No processo de polimerização de tais polímeros, a influência de algumas variáveis são importantes em suas propriedades finais. Este trabalho descreve a exploração da influência de diversas variáveis no processo de polimerização do derivado do PPV, o poli-(2-metoxi-5-hexiloxi-p-fenileno-vinileno) MH-PPV. Além disso, com o intuito de verificar a influência da presença de aditivos na massa molar dos polímeros foram realizadas polimerizações utilizando-se os aditivos 4-metoxifenol, cloreto de tercbutila e cloreto de benzila durante o processo de polimerização. Também foram realizados estudos sobre o modo de adição e temperatura de polimerização utilizando o aditivo cloreto de benziIa. Todos os produtos foram caracterizados por HPSEC (Cromatografia de Exclusão por Tamanho) para determinação das massas molares dos polímeros. Observou-se que a temperatura e a velocidade de adição da base no meio reacional são variáveis que influenciam significativamente no processo de polimerização e, conseqüentemente, na distribuição na massa molar dos polímeros. Foi constatado que o uso de aditivos no processo de polimerização previne a formação de géis; fornece polímeros com baixa massa molar, aumentando a solubilidade dos polímeros em solventes orgânicos como clorofórmio e THF. A análise térmica dos polímeros revelou que além da Tg em tomo de 160oC, todos os polímeros apresentaram uma transição em tomo de 75oC. Os espectros de absorção e emissão não foram afetados de forma significativa dentro dos valores de massas molares médias obtidas. Foi possível também obter uma relação entre os valores de massa molar obtidos por HPSEC e valores de viscosidade relativa, que pode ser utilizada para estimar valores de Mw através de medidas de tempo de escoamento / Electroluminescent polymers have been widely investigated due to its potential applications in optoelectronic devices such as polymer light-emitting diodes (PLEDs). Most of the polymers suitable for application in PLEDs are related to the poly(arylenes-vinylene) polymers, including the poly(p-phenylene-vinylene) (PPV) and its derivatives, which are of special interest. Such materials can exhibit significant differences on their final properties upon changes on specific synthesis parameters. In this work it is described the influence of three different additives, viz. 4-methoxyphenol, terc-butyl chloride and benzyl chloride, on the polymerization process of the derivative poly(2-methoxy-5-hexyloxy-p-phenylenevinylene) MHPPV. Size Exclusion Chromatography analyses revealed that the type and rate of incorporation of the additives to the polymerization reaction largely affects the molecular weight of the polymers. In addition, it was observed that the use of additives leads to the synthesis of low molecular weight polymers, increasing their solubilities in common organic solvents, eg. chloroform and tetrahydrofuran. The glass transition temperature (Tg) of the polymers was determined by differential scanning calorimetry (DSC) to be ca. 160oC. Interestingly, all the polymers presented an additional transition point at ca. 75oC. Neither the electronic absorption nor the emission spectra were affected by the differences on the molecular weight of the polymers. Finally, it was possible to establish correlations between the molecular weight analyses (from HPSEC) and viscosity experiments, which can be useful for Mw determination

Made available in DSpace on 2017-07-21T20:42:41Z (GMT). No. of bitstreams: 1 Carlos Alberto Silva de LIma.pdf: 3634642 bytes, checksum: 8583be31697ada29693d8e5c36b484b5 (MD5) Previous issue date: 2014-01-07 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nowadays, polymeric nanocomposites are well established in terms of their importance. However, there is still a long way to be investigated, since its methods for obtaining, processing and characterization, as there are many variables to be changed to optimize the responses. There is need in understanding the behavior of such materials when subjected to degradative processes, such as nanoparticles influence responses, and maximize or minimize the occurrence of these effects. In this work the behavior of neat polypropylene, polypropylene with organically modified montmorillonite, with and without the presence of a coupling agent (polypropylene-graft-maleic anhydride) when subjected to reprocessing in a twin screw extruder. It was investigated the effect of molar mass of the polypropylene matrix. For this purpose, three types of polypropylenes (high, middle and low molar mass) were processed one, or up to five times. Compositions were prepared neat or with 5% by weight montmorillonite, with and without the presence of coupling agent in the ratio 3:1. The properties is going to be investigated by the techniques of X-ray diffraction, scanning electron microscopy, rheology, infrared spectroscopy by Fourier transform, thermogravimetry, differential scanning calorimetry, tests of Izod impact and colorimetry. First of all, it was proved the presence of iron in the nanoclay, which affects the color of the sample due to oxidation of the iron cation. It was found that the samples became darker, redder, and more yellow because of the presence of the nanoparticles, iron and degradation. These results agreed with the changes observed by infrared spectroscopy, which generally showed low occurrence of the degradation rates of carbonyl and unsaturation, concluding that the greatest degradation occurred by the reduction in molar mass due to the β -scission process, confirming the reduction the values of complex viscosity. It was possible to monitor via rheology by different modes narrowing of the distribution of molar masses and the reduction in molar mass. Along with this information the values and behaviors of the slopes of the curves allowed us to infer the possible microstructure formed state of dispersion and distribution. XRD results indicated the formation of only a sample with an increase in the interlayer spacing, while the rheological results suggest that there is more than one sample with intercalated structure. Thus, there was a little difficulty using just one technique among them to state what actually occurred, concluding that it is essential to perform the technique of transmission electron microscopy. Addition of MMT and MMT / PP - g-MA afforded more thermally stable samples compared to pure PP, this was attributed to the effect of labyrinth. Finally, the impact resistance by the addition of montmorillonite was greater, it means that the clay did not act as stress concentrators, but as energy absorbers and hindered propagation of microcracks. But with PP-g-MA had a fracture behavior intermediate between PP and PP/MMT, with intermediate values of impact resistance. The fracture analysis was possible via SEM and allows to observe the morphology of the different samples. / Nanocompósitos poliméricos são materiais bem estabelecidos do ponto de vista da sua importância, mas ainda há um longo caminho a ser investigado, desde seus métodos de obtenção, processamento e caracterização, pois existem muitas variáveis a serem alteradas para otimização das respostas apresentadas por esses materiais. Há também uma necessidade em compreender o comportamento de tais materiais quando submetidos a processos degradativos, como as nanocargas influenciam o comportamento, bem como maximizar ou minimizar determinados desempenhos. Neste trabalho, foi estudado o comportamento das composições de polipropileno puro, polipropileno com montmorilonita, com e sem agente compatibilizante (polipropileno graftizado com anidrido maleico) quando submetidos a múltiplas extrusões em extrusora dupla rosca; investigando ainda o efeito da massa molar da matriz polimérica. Para tanto, três tipos de polipropilenos com diferentes massas molares (baixa, média e alta) foram processados uma, ou em até cinco vezes. As composições elaboradas foram puras ou com 5% de montmorilonita em peso, com e sem a presença de agente compatibilizante na razão 3:1. Em seguida, as amostras foram investigadas por meio das técnicas de difração de raios X, microscopia eletrônica de varredura, reometria de placas paralelas, espectroscopia de infravermelho por transformada de Fourier, termogravimetria, ensaios de impacto Izod com entalhe e colorimetria. Primeiramente comprovou-se a presença de ferro na nanoargila, o qual afetou a coloração das amostras, devido à oxidação do cátion de ferro. Verificou-se que as amostras tornaram-se mais escuras, mais vermelhas e mais amarelas, por causa da presença das nanopartículas, do ferro e da degradação. Estes resultados concordaram com as variações observadas por espectroscopia de infravermelho, que em geral revelou pouca ocorrência de degradação pelos índices de carbonila e insaturação, concluindo que a maior degradação ocorreu pela redução na massa molar, devido ao processo de cisão-β, comprovado pela redução nos valores de viscosidade complexa. Foi possível via reologia acompanhar por diferentes modos o estreitamento da distribuição de massas molares e a redução na massa molar. Juntamente com essas informações os valores das inclinações e comportamentos das curvas permitiram inferir sobre a possível microestrutura formada, estado de dispersão e distribuição. Os resultados de DRX indicaram a formação de apenas uma amostra com aumento no espaçamento interlamelar, enquanto que os resultados reológicos apresentaram indícios de haver mais de uma amostra com estrutura intercalada. Deste modo, ocorreu uma pequena dificuldade em utilizar apenas uma técnica entre elas para afirmar o que de fato ocorreu, concluindo que é imprescindível a realização da técnica de microscopia eletrônica de transmissão. A adição de MMT ou MMT/PP-g-AM permitiu obter amostras termicamente mais estáveis em relação ao PP puro, isso se atribuiu ao efeito de labirinto. Finalmente, a resistência ao impacto com a adição de montmorilonita foi maior, ou seja, não atuaram como concentradores de tensão, mas auxiliaram na absorção de energia e dificultando a propagação de microfissuras. Já com PP-g-AM ocorreu um comportamento de fratura intermediário entre PP e PP/MMT, apresentando valores intermediários de resistência ao impacto. A análise da fratura foi possível via MEV, além de permitir observar a morfologia das diferentes amostras.

La cellulose est un biopolymère naturel et très abondant. Selon son origine et son mode d’extraction, elle présente des propriétés de cristallinité et de longueur de chaînes variables. Les interactions hydrogène entre les chaînes de cellulose sont en grande partie responsables de son organisation et forment un réseau très dense qui limite sa solubilité. Sa dissolution, complète et non-dégradante, est donc compliquée et dépend de la capacité du solvant à rompre ces liaisonshydrogène intermoléculaires. L’analyse de la cellulose par chromatographie d’exclusion stérique (SEC) pour suivre l’évolution des distributions de masses molaires (DMM) au cours des procédés de transformation est donc toujours problématique. Le système de solvant le plus commun estactuellement le chlorure de lithium/N,N-diméthylacétamide (LiCl/DMAc) qui est extrêmement toxique. L’objectif de ce travail est le développement d’une méthode d’analyse des DMM de la cellulose dans des conditions moins toxiques et adaptée à tous les types de cellulose. Parmi les nombreux systèmes de solvant décrits dans la littérature, 3 systèmes, plus verts et nondérivatisants, ont été sélectionnés afin d’identifier un système de solvant permettant la dissolution,sans dégradation, d‘échantillons de cellulose de cristallinité et de masse molaire moyenne variables afin de remplacer LiCl/DMAc. Les analyses thermogravimétriques et les mesures viscosimétriques ont permis d’évaluer et de comparer les modifications de 4 échantillons de cellulose dissous dans ces 3 systèmes et dans le LiCl/DMAc. LiCl/DMAc dégrade les celluloses de plus haute masse molaire (-cellulose et Vitacel), réduisant de 50 % les longueurs de chaîne après dissolution. Le système tétrabutylammonium/diméthylsulfoxide (TBAF/DMSO) permet une dissolution rapide des 4 échantillons de cellulose sans dégradation ou modification majeure. Le système TBAF/DMSO a, par la suite, été privilégié pour la caractérisation des échantillons en SEC. Du fait d’interactions possibles entre les groupements aromatiques composant la phase stationnaire et les molécules de TBAF, le système complet n’a pas pu être utilisé comme éluant. L’éluant choisi a donc été le DMSO mais qui, seul, ne solubilise pas les échantillons cellulosiques. Les molécules de TBAF sont cependant indispensables au mécanisme de dissolution et laconcentration en TBAF dans le DMSO a dû être adaptée en fonction des échantillons. Pour les échantillons cellulosiques de faible masse molaire, une concentration en TBAF de l’ordre de 1 %(m/v) est suffisante et permet de réaliser une analyse des masses molaires satisfaisantes. Pour les échantillons de plus haut poids moléculaire, cette concentration n’est plus suffisante pour les dissoudre convenablement. Or, avec des concentrations plus élevées, des phénomènesd’agrégation provoque l’élution d’une partie importante des macromolécules dans le volume mort, comme observé avec l’analyse de standards de pullulane. / Cellulose is a very abundant natural biopolymer. According to its origin and to its extraction mode, it presents various cristallinity rate and molar mass. Its organization relies mainly on intermolecular hydrogen bonds that form a strong network and thus limitating cellulose solubility. Complete andnon-degradative dissolution is then complicated and depends on the solvent ability to disrupt these hydrogen bonds. Analysis of the molar mass distribution (MMD) of cellulose by size exclusion chromatography (SEC) of cellulose is consequently problematic while the study of the evolution of cellulose molar mass during transformations could be extremely useful in many processes. The most common solvent used in SEC is lithium chloride/N,N-dimethylacetamide (LiCl/DMAc), which is extremely toxic. The aim of this PhD study is then to develop a new analytical method to characterize cellulose MMD using safer solvents and adapted to all kinds of cellulosic sample. Among the numerous non-derivatizing solvent systems described in the literature, three of themhave been selected. Greener and less toxic than LiCl/DMAc, their ability to dissolve cellulosic sample of various cristallinity and average molar mass without degradation was then tested. Thermogravimetric analyses and viscosimetric studies allowed to evaluate and to compare the modifications involved by the dissolution for four different cellulosic samples. LiCl/DMAc degraded the samples of higher molar mass (-cellulose and Vitacel) decreasing their degree ofpolymerization by 50 % after dissolution. Tetrabutylammonium/dimethylsulfoxide (TBAF/DMSO) system allows rapid dissolution of the 4 cellulose samples, without major degradation or modification. TBAF/DMSO system was then studied as solvent for SEC analysis of these cellulose samples. Due to the interactions between the aromatic groups composing the stationary phase with TBAF molecules, the complete system could not be used as eluant. Chosen eluant was then DMSO alone. However, as the TBAF molecules are mandatory for the dissolution of cellulose, TBAF concentration was adapted according to the cellulose nature for the preparation of the samples. For low molar mass cellulose samples, a TBAF concentration of 1 %(w/v) was sufficient and allowed to performed correctly the chromatographic analysis. For the samples of higher molar mass, this concentration was not high enough to complete the dissolution. Using, higher concentrations caused aggregation phenomena resulting in the elution of a large amount of the macromolecules in the dead volume, as observed with the analysis of pullulan standards.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Hyaluronic acid (HA) is a linear, unbranched polymer, composed by simple disaccharide units, whose molar mass may range in a wide interval of distribution (104-107 Da). It is used in pharmaceutical and cosmetic applications depending on its average molecular mass. The fractionation of macromolecules of the order of magnitude of the HA may be performed by gel permeation or size-exclusion chromatography (GPC). The objective of this work is to study the characterization, purification and fractionation of microbial HA by using GPC. HA was supplied by the Department of Biotechnological Processes (DPB/FEQ/UNICAMP), having been produced by microorganisms â Streptococcus zooepidemicus â in synthetic culture media. After being centrifuged from the fermentation broth, HA was precipitated with ethanol and then dissolved in saline solution, this pre-purification procedure being performed up to four times. The presence of proteic contaminants was identified by electrophoresis in polyacrylamide gel under denaturant conditions (SDS-PAGE) and quantified by the Bradford method. For the HA sample which had been precipitated in ethanol and dissolved in 0.1 M NaNO3 four times, protein concentration was found to be nearly 100 &#956;g/mL. The sodium salt of commercial (Sigma Aldrich - EUA) microbial HA was used as standard in order to measure a calibration curve to assess HA concentration in the samples. For the sample precipitated in ethanol and dissolved in 0.1 M NaNO3 four times, AH concentration was found to be approximately 780 &#956;g/mL. Molar mass distribution of HA samples was assessed by GPC, both in analytical and semi-preparative scale, using refractive index (RI) and UV/Vis (280 nm) detectors, 0.1 M NaNO3 as mobile phase, flow rate 0.8 mL/min and tracers dextran and pullulan (polymers of similar hydrodynamic volume as compared to HA) as molar mass standards. The samples showed molar mass distributions in the range of 103 to 107 Da, after being precipitated and dissolved four times. For these samples, the average molar mass was found to be in the order of magnitude of 105 Da. In the semi-preparative column Superose, it was possible to separate HA fractions, with molar mass above 105 Da, and free of proteic contaminants, in an elution interval of 10 minutes / O Ãcido HialurÃnico (AH) à um polÃmero linear, nÃo ramificado, composto por unidades dissacarÃdicas simples, cuja massa molar pode se distribuir num largo intervalo (104-107 Da). à usado em aplicaÃÃes farmacÃuticas e cosmÃticas dependendo de sua massa molar mÃdia. A separaÃÃo de macromolÃculas da ordem de grandeza do AH à possÃvel atravÃs da Cromatografia de permeaÃÃo em gel (GPC). Este trabalho tem como objetivo estudar a caracterizaÃÃo, purificaÃÃo e fracionamento do AH produzido por microorganismos, utilizando GPC. O AH, cedido pelo Departamento de Processos BiotecnolÃgicos (DPB/FEQ/UNICAMP), foi obtido por cultivo de microorganismos - Streptococcus zooepidemicus - em meio de cultura sintÃtico. ApÃs centrifugaÃÃo do caldo de fermentaÃÃo, o AH foi precipitado com etanol e ressuspenso em soluÃÃo salina, sendo esta etapa de prÃ-purificaÃÃo executada atà quatro vezes. A presenÃa de contaminantes protÃicos foi identificada por eletroforese em gel de poliacrilamida sob condiÃÃes desnaturantes (SDS-PAGE) e quantificada pelo mÃtodo de Bradford, obtendo-se 97,20 &#956;g/mL, para a amostra de AH apÃs quatro precipitaÃÃes em etanol e ressuspensÃes em NaNO3 0,1 M. Para as determinaÃÃes de concentraÃÃo de AH nas amostras estudadas, utilizou-se o sal sÃdico de AH microbial comercial (Sigma Aldrich - EUA) como padrÃo. Quantificando-se a amostra de AH apÃs quatro precipitaÃÃes em etanol e ressuspensÃes em NaNO3 0,1 M, obteve-se 783,70 &#956;g/mL. A distribuiÃÃo da massa molar do AH foi avaliada por GPC, em escala analÃtica, utilizando coluna Shodex OHPak-SB806M-HQ e, em escala semi-preparativa, a coluna Superose 6, detectores de Ãndice de refraÃÃo e UV/Vis (280 nm), NaNO3 0,1 M como fase mÃvel, vazÃo de 0,8 mL/min e padrÃes de Dextrana e Pullulan (polÃmeros de volume hidrodinÃmico semelhante ao AH) como marcadores de massa molar (5,2x103 - 7,9x106 Da e 5,8x103 â 8,53x105 Da, respectivamente). A amostra apresentou uma distribuiÃÃo polimÃrica na faixa de 103 a 107 Da, apÃs quatro precipitaÃÃes em etanol e ressuspensÃes em NaNO3 0,1 M, sendo sua massa molar mÃdia da ordem de 105 Da. Foi possÃvel separar fraÃÃes de AH, acima de 105 Da, livre de contaminantes protÃicos, num intervalo de aproximadamente 10 minutos, na coluna Superose 6

In this thesis, size-exclusion chromatography (SEC) of woodpolymers dissolved in lithium chloride/N,N-dimethylacetamide(LiCl/DMAc) has been used to characterize the molar massdistributions (MMD) of wood polymers in pulp fibers afterchemical degradation. Characterization of birch kraft pulps subjected to ozonedegradation and acid hydrolysis, respectively, rendereddifferent changes in the MMD. Ozone degradation resulted inlarge redistributions of the original MMD, observed as thedevelopment of a distinct fraction of cellulose withintermediate molar mass. Acid hydrolysis resulted in minorchanges of the original MMD compared to ozonation. Fiberssubjected to acid hydrolysis were considerably weaker thanozonated fibers. These results indicated that there aredifferences in how the two chemicals degrade the fiber. The solubility of softwood kraft pulp fibers was enhanced byderivatization of the fiber polymers with ethyl-isocyanateduring simultaneous dissolution in LiCl/DMAc. Thederivatization made it possible to achieve reliable estimationsof the MMD, and hence molar masses, of softwood kraft pulps.The derivatization procedure made it possible to dissolve 90 %of softwood kraft pulps with kappa numbers over 50. Severe alkaline degradation of birch and Norway spruce woodchips was studied both by varying the pulping time and byvarying the initial alkali concentration. Differences werefound in the MMD of the two fiber types, and the alkalinedegradation was found to affect polymers in the entire MMD. Multi-angular laser light scattering (MALLS) was used as adetection technique with SEC on cellulosic samples. The MMD andaverage molar masses obtained through directstandardcalibration with commercial standards were compared with MMDand molar masses as obtained by MALLS-detection. Largediscrepancies were found, and two methods of correcting forthese discrepancies were developed. Theoretical simulations of polymer degradation wereperformed. Random, or homogeneous degradation was used as amodel for alkaline cellulose chain scission, and a resemblancewith experimental data was observed. End-wise depolymerizationof cellulose was also simulated and the results are discussedin the light of experimentally observed MMD. <b>Keywords:</b>cellulose, kraft pulp, birch, spruce,ozonation, acid hydrolysis, degradation, MMD, sizeexclusionchromatography, light scattering, molar mass, chainscission

Träbaserade cellulosananofibriller är intressanta som förstärkande fas i polymera nanokompositer; detta främst på grund av den kristallina cellulosans höga styvhet och på grund av nanofibrillernas förmåga att bilda nätverk. Cellulosananofibriller kan användas i form av mikrokristallin cellulosa, MCC, som har lågt längd/diameter förhållande, eller i form av mikrofibrillerad cellulosa, MFC, med högt längd/diameter förhållande. Målet med det här arbetet är att studera struktur-egenskapsförhållanden för nanofibrillnätverk och kompositer. Nanokompositer baserade på MCC och termoplastisk polyuretan tillverkades genom in-situ polymerisation. Cellulosafibrillerna var väl dispergerade i matrisfasen och kompositen visade ökad styvhet, styrka samt brottöjning. Dessa förbättningar antas bero på stark interaktion mellan polyuretan och cellulosananofibrillerna. En metod som underlättar mikrofibrillering av massafiberns cellvägg under homogenisering har utvecklats. Massan förbehandlades med ett enzym innan homogenisering. Den här metoden förenklade mikrofibrilleringen och mekanismerna diskuteras. De resulterande MFC-nanofibrillerna hade högt längd/diameter förhållande. Filmer har tillverkats av MFC-nanofibriller och filmernas struktur samt mekaniska egenskaper har studerats. Röntgendiffraktion och SEM visar att nanofibrilerna är mer orienterade i planet än i rymden. SEM och densitetsmätningar visar även att filmerna har en porös struktur. Resultaten från dragprovning visade att filmernas brottstyrka är beroende av molekylvikten för cellulosan. Nanofibrillerna med högst molekylvikt visade en E-modul på 13.2 GPa, brottstyrkan var 214 MPa och brottöjningen 10.1%. Kompositer med hög fiberhalt har tillverkats genom tillsats av melaminformaldehyd till MFC-filmer. Dessa kompositer visar ökad styvhet och styrka på bekostnad av brottöjningen. Kompositer har också tillverkats genom impregnering av MFC-nätverk med en hyperförgrenad polymer som tvärbands. DMA visar två Tg för kompositerna med 0.26 och 0.43 volymfraktion nanofibriller; matrisens Tg samt ytterligare ett Tg vid högre temperatur. Detta motsvarar molekyler med lägre mobilitet på grund av ökad interaktion med nanofibrillernas ytor. / The cellulose nanofibril from wood is an interesting new material constituent that can provide strong reinforcement in polymer nanocomposites due to the high stiffness of the cellulose crystals and the network formation characteristics of the nanofibrils. Cellulose nanofibrils can be used either in the form of low aspect ratio microcrystalline cellulose, MCC, or as high aspect ratio microfibrillated cellulose, MFC. The objective is to study structure-property relationships for cellulose nanofibril networks and composites. Nanocomposites based on MCC and thermoplastic polyurethane were prepared by in-situ polymerization. The cellulose nanofibrils were successfully dispersed in the matrix and the composites showed improvements in stiffness, strength, as well as in strain-to-failure. Cellulose nanofibrils reinforce the physical rubber network by strong molecular interaction with the rubber. A method that facilitates microfibrillation of the pulp cell wall during homogenization has been developed. The pulps were treated with a combination of beating and enzymatic treatment prior to homogenization. The enzymatic pretreatment was found to facilitate the microfibrillation and the mechanisms are discussed. The resulting MFC nanofibrils were of high aspect ratio. Cellulose nanofibril networks of high toughness were prepared from MFC and studied with respect to the structure and mechanical properties. These films have a porous structure and the nanofibrils are more in-plane than in-space oriented. Tensile testing showed that the strength is dependent on the average molecular weight of the cellulose. The MFC of the highest molecular weight showed a modulus of 13.2 GPa, tensile strength as high as 214 MPa and 10.1% strain-to-failure, at a porosity of 28%. Composites of high fiber content have been prepared by addition of melamine formaldehyde to MFC films. These composites show increased stiffness and strength, at the cost of strain-to-failure. Composites were also prepared by impregnating MFC nanofibril networks with a hyperbranched polymer. The matrix was crosslinked and strong interactions with the nanofibrils were formed. By DMA two Tg’s were observed for the composites with 0.26 and 0.43 volume fraction nanofibrils. The Tg of the matrix was observed as well as a Tg at higher temperatures. This corresponds to molecules with constrained mobility by increased interactions with the cellulose nanofibril surfaces. / QC 20100810

<p>In this thesis, size-exclusion chromatography (SEC) of woodpolymers dissolved in lithium chloride/N,N-dimethylacetamide(LiCl/DMAc) has been used to characterize the molar massdistributions (MMD) of wood polymers in pulp fibers afterchemical degradation.</p><p>Characterization of birch kraft pulps subjected to ozonedegradation and acid hydrolysis, respectively, rendereddifferent changes in the MMD. Ozone degradation resulted inlarge redistributions of the original MMD, observed as thedevelopment of a distinct fraction of cellulose withintermediate molar mass. Acid hydrolysis resulted in minorchanges of the original MMD compared to ozonation. Fiberssubjected to acid hydrolysis were considerably weaker thanozonated fibers. These results indicated that there aredifferences in how the two chemicals degrade the fiber.</p><p>The solubility of softwood kraft pulp fibers was enhanced byderivatization of the fiber polymers with ethyl-isocyanateduring simultaneous dissolution in LiCl/DMAc. Thederivatization made it possible to achieve reliable estimationsof the MMD, and hence molar masses, of softwood kraft pulps.The derivatization procedure made it possible to dissolve 90 %of softwood kraft pulps with kappa numbers over 50.</p><p>Severe alkaline degradation of birch and Norway spruce woodchips was studied both by varying the pulping time and byvarying the initial alkali concentration. Differences werefound in the MMD of the two fiber types, and the alkalinedegradation was found to affect polymers in the entire MMD.</p><p>Multi-angular laser light scattering (MALLS) was used as adetection technique with SEC on cellulosic samples. The MMD andaverage molar masses obtained through directstandardcalibration with commercial standards were compared with MMDand molar masses as obtained by MALLS-detection. Largediscrepancies were found, and two methods of correcting forthese discrepancies were developed.</p><p>Theoretical simulations of polymer degradation wereperformed. Random, or homogeneous degradation was used as amodel for alkaline cellulose chain scission, and a resemblancewith experimental data was observed. End-wise depolymerizationof cellulose was also simulated and the results are discussedin the light of experimentally observed MMD.</p><p><b>Keywords:</b>cellulose, kraft pulp, birch, spruce,ozonation, acid hydrolysis, degradation, MMD, sizeexclusionchromatography, light scattering, molar mass, chainscission</p>