Cellulose is one of the most abundant biopolymers found in nature. Cellulose based derivatives have a number of advantages including recyclability, reproducibility, biocompatibility, biodegradability, cost effectiveness and availability in a wide variety of forms. Due to the benefits of cellulose based systems, this research study was aimed at developing novel cellulosic nanoparticles with potential pharmaceutical and personal care applications. Two different cellulosic systems were evaluated, each with its own benefits and proposed applications. The first project involves the synthesis and characterization of polyampholyte nanoparticles composed of chitosan and carboxymethyl cellulose (CMC), a cellulosic ether. EDC carbodiimide chemistry and inverse microemulsion technique was used to produce crosslinked nanoparticles. Chitosan and carboxymethyl cellulose provide amine and carboxylic acid functionality to the nanoparticles thereby making them pH responsive. Chitosan and carboxymethyl cellulose also make the nanoparticles biodegradable and biocompatible, making them suitable candidates for pharmaceutical applications. The synthesis was then extended to chitosan and modified methyl cellulose microgel system. The prime reason for using methyl cellulose was to introduce thermo-responsive characteristics to the microgel system. Methyl cellulose was modified by carboxymethylation to introduce carboxylic acid functionality, and the chitosan-modified methyl cellulose microgel system was found to be pH as well as temperature responsive. Several techniques were used to characterize the two microgel systems, for e.g. potentiometric and conductometric titrations, dynamic light scattering and zeta potential measurements. FTIR along with potentiometric and conductometric titration was used to confirm the carboxymethylation of methyl cellulose. For both systems, polyampholytic behaviour was observed in a pH range of 4-9. The microgels showed swelling at low and high pH values and deswelling at isoelectric point (IEP). Zeta potential values confirmed the presence of positive charges on the microgel at low pH, negative charges at high pH and neutral charge at the IEP. For chitosan-modified methyl cellulose microgel system, temperature dependent behaviour was observed with dynamic light scattering. The second research project involved the study of binding interaction between nanocrystalline cellulose (NCC) and an oppositely charged surfactant tetradecyl trimethyl ammonium bromide (TTAB). NCC is a crystalline form of cellulose obtained from natural sources like wood, cotton or animal sources. These rodlike nanocrystals prepared by acid hydrolysis of native cellulose possess negatively charged surface. The interaction between negatively charged NCC and cationic TTAB surfactant was examined and it was observed that in the presence of TTAB, aqueous suspensions of NCC became unstable and phase separated. A study of this kind is imperative since NCC suspensions are proposed to be used in personal care applications (such as shampoos and conditioners) which also consist of surfactant formulations. Therefore, NCC suspensions would not be useful for applications that employ an oppositely charged surfactant. In order to prevent destabilization, poly (ethylene glycol) methacrylate (PEGMA) chains were grafted on the NCC surface to prevent the phase separation in presence of a cationic surfactant. Grafting was carried out using the free radical approach. The NCC-TTAB polymer surfactant interactions were studied via isothermal titration calorimetry (ITC), surface tensiometry, conductivity measurements, phase separation and zeta potential measurements. The major forces involve in these systems are electrostatic and hydrophobic interactions. ITC and surface tension results confirmed two kinds of interactions: (i) electrostatically driven NCC-TTAB complexes formed in the bulk and at the interface and (ii) hydrophobically driven TTAB micellization on the NCC rods. Conductivity and surface tension results confirmed that the critical micelle concentration of TTAB (CMCTTAB) shifted to higher values in the presence of NCC. Phase separation measurements allowed us to identify the formation of large aggregates or hydrophobic flocs depending on the TTAB concentration. Formation of NCC-TTAB complexes in aqueous solutions was confirmed by a charge reversal from negative to positive charge on the NCC rods. The effect of electrolyte in shielding the negative charges on the NCC was observed from ITC, surface tensiometry and phase separation experiments. Several mechanisms have been proposed to explain the above results. Grafting of PEGMA on the NCC surface was confirmed using FTIR and ITC experiments. In phase separation experiments NCC-g-PEGMA samples showed greater stability in the presence of TTAB compared to unmodified NCC. By comparing ITC and phase separation results, an optimum grafting ratio (PEGMA : NCC) for steric stabilization was also proposed.

O amido, encontrado abundantemente na natureza, é formado por dois polímeros: a amilopectina e a amilose. Ambos polímeros possuem excelentes qualidades industriais tais como, a biodegradabilidade e o baixo custo de obtenção. Entretanto, a amilopectina possui baixa solubilidade em solução aquosa. Para expandir a gama de aplicações deste polímero como, por exemplo, a produção de filmes biodegradáveis solúveis em água e que possam ser usados como revestimento de proteção no transporte de alimentos, ainda se fazem necessários alguns estudos. Um deles é tentar correlacionar como a funcionalização do seu esqueleto polimérico pode afetar a reação de formação destes filmes. Neste sentido, o objetivo desta Dissertação de Mestrado foi estudar a síntese da carboximetil amilopectina (CMAm) variando-se a pressão, temperatura e razão entre água e solvente orgânico. Sintetizamos várias CMAm a partir da amilopectina de milho ceroso, por meio de uma reação heterogênea utilizando hidróxido de sódio e ácido cloroacético. Empregou-se uma mistura de dimetilsulfóxido (DMSO) e água como solvente, com uma proporção variável entre 0 a 50% de água, para as pressões ambiente (758,3 mmHg) e reduzida (80 ± 20 mmHg) e para as temperaturas 70 e 80 ºC. Para cada uma das condições sintéticas estudadas, obtivemos CMAm com graus de substituição (GS) diversos. Os GS foram determinados por titulações condutimétricas com hidróxido de amónio e para as amostras sintetizadas com 0 a 40% de água foram confirmados por cromatografia líquida de alta eficiência (HPLC), obtendo-se uma boa correlação entre estes valores (R2 de 0,94263). Atribuiu-se os picos referentes às estruturas monossubstituídas (2-; 3- ou 6-mono-O-carboximetil glicose), dissubstituídas (2,3-; 2,6- ou 3,6-di-O carboximetil glicose) e trissubstituídas (2,3,6-tri-O-carboximetil glicose) por meio da cromatografia líquida acoplada a espectrometria de massa (LC-MS). A síntese realizada a 70 oC, pressão reduzida apresenta uma distribuição de CMAm substituída mais homogênea do que as demais condições sintéticas estudadas. Por medidas de potencial zeta em função do pH, determinaram-se para as CMAm de GS 0,86 e 0,43 o ponto isoelétrico no pH de 3,6 e 4,6; respectivamente. O espalhamento dinâmico de luz mostrou que a funcionalização da amilopectina com grupos carboximetílicos levou a abertura da sua estrutura inicial, extremamente ramificada, permitindo a formação de agregados maiores em solução aquosa para as amostras sintetizadas a 80 ºC sob pressão reduzida. Em contraste, as sínteses a 70 ºC nas pressões ambiente e reduzida provocaram uma diminuição no tamanho dos agregados em solução aquosa em função do GS. Por fim, a análise por microscopia ótica e eletrônica de varredura dos filmes de CMAm sintetizadas neste trabalho mostraram que são totalmente dependentes do GS, tipo de substituinte e o tamanho dos agregados em solução aquosa. / Starch is abundant in nature and composed by two polymers: amylopectin and amylose. Both biopolymers have excellent industrial characteristics, such as biodegradability and low cost. However, amylopectin has a very low solubility in aqueous solution. In order to expand the uses this biopolymer, for instance, the production of aqueous soluble and biodegradable films for food packing, there are still many open fields to study. One of them is to find the correlation between how the functionalization of the polymer backbone can affect the film formation process. For this reason, the goal of this work was to study the synthesis of carboxymethyl amylopectin (CMAm) varying the employed pressure, temperature and the ratio of water and organic solvent. Several CMAm were synthetized using amylopectin from maize, by means of an heterogeneous reaction using sodium hydroxide and chloroacetic acid. We have used a mixture of dimethyl sulfoxide (DMSO) and water as reaction solvent with variable ratio of 0 to 50% of water, employed ambient (758,3 mmHg) or reduced (80 ± 20 mmHg) pressure and temperatures of 70 and 80 ºC. The degree of substitution (DS) were determined for every synthetic condition studied in this work. The DS were determined through conductometric titration with ammonium hydroxide. The DS of the samples synthesized with 0 to 40% of water, were confirmed by high performance liquid chromatography (HPLC), with good correlation between these values (R2 of 0,94263). The peaks of the monosubstituted structures (2-; 3- ou 6-mono-O-carboxymethyl glucose), disubstituted (2,3-; 2,6- ou 3,6-di-O carboxymethyl glucose) e trisubstituted (2,3,6-tri-Ocarboxymethyl glucose) were attributed by liquid chromatography coupled with mass spectrometry (LC-MS). The synthesis made at 70 oC, reduced pressure, showed a more even distribution of substituted CMAm than the other synthetic conditions analyzed in this work. The isoelectric point of CMAm of DS of 0.86 and 0.43 were determined by zeta potential as function of pH. They were, respectively of pH 3.6 and 4.6. The dynamic light scattering showed that the funcionalization of the amylopectin with carboxymethyl groups has opened the initial branched polymer backbone, for samples synthesized at 80 ºC under reduced pressure, forming large aggregates in aqueous solution. On the other hand, the synthesis at 70 ºC at ambient and reduced pressures has caused a reduction of the aggregates sizes in aqueous solution as function of increasing DS. The optic and electronic scan microscopies of the CMAm films showed that they are completely dependent on DS, sort of susbstituents and sizes of the aggregates in aqueous solution.

Content: Developing novel tanning agents from renewable biomass is regarded as an effective strategy for sustainable leather industry. In this study, a series of dialdehyde carboxymethyl cellulose (DCMC) were prepared by periodate oxidation of carboxymethyl cellulose (CMC) with varying degrees of substitution (DS: 0.7, 0.9 and 1.2). The structural properties of DCMC were characterized. Size Exclusive Chromatography measurements showed that CMC underwent severe degradation during periodate oxidation, resulting in the decline of weight-average molecular weight from 250,000 g/mol to around 13,000 g/mol. FT-IR analysis illustrated that aldehyde group was successfully introduced into DCMC. The aldehyde group content of DCMC decreased from 8.38 mmol/g to 2.95 mmol/g as the DS rose from 0.7 to 1.2. Interestingly, formaldehyde was found to be produced in DCMC, and its content was 159.4, 151.7 and 38.4 mg/L, respectively when the DS of CMC was 0.7, 0.9 and 1.2, respectively. Further analysis by HPLC found that fructose was formed during oxidative degradation, and was subsequently oxidized to generate formaldehyde. This was in accordance with the fact that higher DS resulted in lower formaldehyde content in DCMC. The whole reaction mechanism is still under investigation at the moment. Tanning trials showed that the shrinkage temperature and thickening rate of DCMC tanned leather decreased as the DS increased. This should be due to the difference in aldehyde content of DCMC. Leather tanned by DCMC-0.7 (DS of CMC was 0.7) had the highest shrinkage temperature of 81°C and thickening rate of 76%. It was noteworthy that the formaldehyde content in DCMC tanned leather was only 0.11-0.40 mg/kg even though DCMC contained a small amount of formaldehyde. In general, we hope the work on dialdehyde tanning agent derived from CMC could provide some essential data for the development of sustainable tanning material and process. Take-Away: 1. Higher degree of substitution (DS) of CMC resulted in lower aldehyde group content of DCMC. 2. The formaldehyde content of DCMC was negatively correlated with DS. 3. The tanning performance of DCMC with lower DS was better.

Plant cell wall polysaccharides are abundant natural polymers making them potential sources for sustainable and biodegradable materials. Interfacial behavior, including adsorption and enzymatic degradation, of several plant cell wall polysaccharides and their derivatives were studied with a quartz crystal microbalance with dissipation monitoring (QCM-D), surface plasmon resonance (SPR) and atomic force microscopy (AFM). Xyloglucan adsorption isotherms were obtained to probe how cellulose-hemicellulose interactions were affected by the type of cellulose substrate and molar mass of xyloglucan. Xyloglucan as small as a heptasaccharide still adsorbed irreversibly onto cellulose. Carboxymethyl cellulose (CMC) adsorption onto cellulose and viscoelastic properties and water contents of the adsorbed CMC layers were obtained from a combination of QCM-D and SPR data. The CMC samples formed hydrated and viscoelastic layers compared to the relatively rigid xyloglucan layer. Pectin model surfaces were prepared by pectin adsorption from citric phosphate buffer onto gold substrates. These pectin model surfaces were used for subsequent interaction studies with xyloglucan and enzymatic degradation behavior. There is a strong correlation between the degree of esterification (DE) and film resistance to degradation with the high DE being the most susceptible to degradation. The adsorption of two mixed linkage glucans (MLG), barley and lichen MLG, onto regenerated cellulose (RC) surfaces in the absence and presence of other matrix polysaccharides was studied. Viscoelastic properties of the resulting layer were compared as a function of the proprotion of '-(1''3) linkages with lichen MLG forming softer gel-like layers on RC. The lichen MLG layers were further used for enzymatic degradation studies with respect to enzyme concentration, temperature, pH and ionic strength. These studies show that polymer adsorption is a promising strategy to modify material surfaces and provides fundamental understanding of interactions and biodegradation of cell wall polysaccharides at solid/liquid interfaces. / Ph. D.

O nebivolol é um fármaco anti-hipertensivo, comercializado na forma de uma mistura equimolar dos enantiômeros RSSS e SRRR-nebivolol. Esses dois enantiômeros possuem propriedades farmacológicas distintas, o que sugere uma farmacocinética diferente entre ambos. Sendo assim, foram desenvolvidos dois métodos para a análise do nebivolol por eletroforese capilar (CE), um aquiral e outro quiral. O primeiro consistiu em um método para análise de forma farmacêutica comercial de comprimidos de nebivolol. Foram definidas as seguintes condições analíticas: capilar de sílica fundida 50 ?m de diâmetro interno (d.i) e 38 cm de comprimento efetivo (c.ef), eletrólito de corrida composto por tampão acetato de sódio 50 mM, pH 4,0, temperatura de 30 °C, tensão de 30 kV e detecção a 200 nm. O método desenvolvido permitiu a análise rápida e eficiente de comprimidos comerciais de nebivolol, sendo simples, seletivo, preciso e exato, está em conformidade com o guia de validação de métodos analíticos da ANVISA (2003), e foi aplicado para quantificação de comprimidos comerciais de nebivolol. O segundo método teve como objetivo realizar a análise enantiosseletiva da ligação do nebivolol à albumina humana do soro (HSA). Após a avaliação de diversos parâmetros, foram estabelecidas as seguintes condições analíticas: capilar de sílica fundida 50 ?m d.i e 38 cm c.ef, eletrólito de corrida composto por tampão acetato de sódio 50 mM, carboxi-metil-?-ciclodextrina 12,5 mM, 1% acetonitrila, pH 4,0, temperatura de 25 oC, tensão de 25 kV e detecção a 200 nm; e como técnica de stacking foi utilizada field amplified sample injection com plug de água (5 psi, 5 s) e injeção eletrocinética 5 kV por 30 s. Nesta condição foi obtida uma resolução de 1,58 e tempo de análise inferior a 25 minutos. No estudo de ligação à HSA foi observado que há enantiosseletividade na ligação, porém, este estudo ainda precisa ser melhor delineado em relação às concentrações de proteína e analito, bem como tempo de incubação e procedimento de filtração para separação das frações livre e ligada / Nebivolol is an anti-hypertensive drug, commercialized as a racemic mixture of RSSS and SRRR-nebivolol. Both enantiomers have distintict pharmacological properties, what suggests a different pharmacokinectis between them. Therefore, it was developed two methods for the nebivolol analysis by capillary electropforesis (CE), one of them is achiral and the other is chiral. The first method aimed the analysis of tablets. The analytical conditions were determined: silica fused capillary 50 ?m internal diameter (i.d.) and 38 cm effective length (ef. l.), running electrolyte composed by 50 mM sodium acetate buffer, pH 4.0, 30 °C temperature, 0 kV applied voltage and 200 nm UV detection. The developed method allowed a quickly and efficient tablets analysis, being simple, selective, accurate and precise, and it is also in accordance with ANVISA (2003) analytical methods validation guide, and it was applied to the quantification of nebivolol in tablets. The second method aimmed to analyze the enantiosselective nebivolol binding to HSA. After the evaluation of many parameters, it was stabilished the following analytical conditions: 50 ?m i.d. and 38 cm ef.l. fused silica capillary, running electrolyte composed by 50 mM sodium acetate buffer, 12.5 mM carboxymethyl- ?-cyclodextrin, acetonytrile 1%, pH 4.0, 25 oC, 25 kV applied voltage and 200 nm UV detection; and as stacking technique it was applied field amplified sample injection with water plug(5 psi, 5 s) and 5 kV por 30 s eletrokinect injection. At this condition, it was possible to achive 1.58 resolution and less than 25 minutes of analysis. At the HSA binding study, it was observed an enantiosselectivity on the binding; however this study still needs better desing in conserne to analyte and protein concentration, as well as, incubation time and filtration proceadure to the separion of binded and free fractions.

Degradation of peroral administered drugs by various enzymes in the gastrointestinal tract has proven to be troublesome for the absorption' and bioavailability of protein and peptide drugs. Mucoadhesive polymers such as poly(acrylates) have proven to inhibit protease enzymes responsible for initiating digestion of peptide drugs. Enzyme inhibitors have unique chemical properties enabling it to interact with enzymes to form complexes with such enzymes prohibiting it from functioning properly. Anionic carboxymethylated chitosan derivatives such as N,N-dicarboxymethyl chitosan and N, O-carboxymethyl chitosan display unique structural similarities to enzyme inhibitors being anionic polymers that may interact with bi-valent cations... / Thesis (M.Sc. (Pharm.))--North-West University, Potchefstroom Campus, 2004.

Degradation of peroral administered drugs by various enzymes in the gastrointestinal tract has proven to be troublesome for the absorption' and bioavailability of protein and peptide drugs. Mucoadhesive polymers such as poly(acrylates) have proven to inhibit protease enzymes responsible for initiating digestion of peptide drugs. Enzyme inhibitors have unique chemical properties enabling it to interact with enzymes to form complexes with such enzymes prohibiting it from functioning properly. Anionic carboxymethylated chitosan derivatives such as N,N-dicarboxymethyl chitosan and N, O-carboxymethyl chitosan display unique structural similarities to enzyme inhibitors being anionic polymers that may interact with bi-valent cations... / Thesis (M.Sc. (Pharm.))--North-West University, Potchefstroom Campus, 2004.

O nebivolol é um fármaco anti-hipertensivo, comercializado na forma de uma mistura equimolar dos enantiômeros RSSS e SRRR-nebivolol. Esses dois enantiômeros possuem propriedades farmacológicas distintas, o que sugere uma farmacocinética diferente entre ambos. Sendo assim, foram desenvolvidos dois métodos para a análise do nebivolol por eletroforese capilar (CE), um aquiral e outro quiral. O primeiro consistiu em um método para análise de forma farmacêutica comercial de comprimidos de nebivolol. Foram definidas as seguintes condições analíticas: capilar de sílica fundida 50 ?m de diâmetro interno (d.i) e 38 cm de comprimento efetivo (c.ef), eletrólito de corrida composto por tampão acetato de sódio 50 mM, pH 4,0, temperatura de 30 °C, tensão de 30 kV e detecção a 200 nm. O método desenvolvido permitiu a análise rápida e eficiente de comprimidos comerciais de nebivolol, sendo simples, seletivo, preciso e exato, está em conformidade com o guia de validação de métodos analíticos da ANVISA (2003), e foi aplicado para quantificação de comprimidos comerciais de nebivolol. O segundo método teve como objetivo realizar a análise enantiosseletiva da ligação do nebivolol à albumina humana do soro (HSA). Após a avaliação de diversos parâmetros, foram estabelecidas as seguintes condições analíticas: capilar de sílica fundida 50 ?m d.i e 38 cm c.ef, eletrólito de corrida composto por tampão acetato de sódio 50 mM, carboxi-metil-?-ciclodextrina 12,5 mM, 1% acetonitrila, pH 4,0, temperatura de 25 oC, tensão de 25 kV e detecção a 200 nm; e como técnica de stacking foi utilizada field amplified sample injection com plug de água (5 psi, 5 s) e injeção eletrocinética 5 kV por 30 s. Nesta condição foi obtida uma resolução de 1,58 e tempo de análise inferior a 25 minutos. No estudo de ligação à HSA foi observado que há enantiosseletividade na ligação, porém, este estudo ainda precisa ser melhor delineado em relação às concentrações de proteína e analito, bem como tempo de incubação e procedimento de filtração para separação das frações livre e ligada / Nebivolol is an anti-hypertensive drug, commercialized as a racemic mixture of RSSS and SRRR-nebivolol. Both enantiomers have distintict pharmacological properties, what suggests a different pharmacokinectis between them. Therefore, it was developed two methods for the nebivolol analysis by capillary electropforesis (CE), one of them is achiral and the other is chiral. The first method aimed the analysis of tablets. The analytical conditions were determined: silica fused capillary 50 ?m internal diameter (i.d.) and 38 cm effective length (ef. l.), running electrolyte composed by 50 mM sodium acetate buffer, pH 4.0, 30 °C temperature, 0 kV applied voltage and 200 nm UV detection. The developed method allowed a quickly and efficient tablets analysis, being simple, selective, accurate and precise, and it is also in accordance with ANVISA (2003) analytical methods validation guide, and it was applied to the quantification of nebivolol in tablets. The second method aimmed to analyze the enantiosselective nebivolol binding to HSA. After the evaluation of many parameters, it was stabilished the following analytical conditions: 50 ?m i.d. and 38 cm ef.l. fused silica capillary, running electrolyte composed by 50 mM sodium acetate buffer, 12.5 mM carboxymethyl- ?-cyclodextrin, acetonytrile 1%, pH 4.0, 25 oC, 25 kV applied voltage and 200 nm UV detection; and as stacking technique it was applied field amplified sample injection with water plug(5 psi, 5 s) and 5 kV por 30 s eletrokinect injection. At this condition, it was possible to achive 1.58 resolution and less than 25 minutes of analysis. At the HSA binding study, it was observed an enantiosselectivity on the binding; however this study still needs better desing in conserne to analyte and protein concentration, as well as, incubation time and filtration proceadure to the separion of binded and free fractions.

This thesis deals with the preparation of chemically and/or enzymatically modified cellulose. This modification can be either irreversible or reversible. Irreversible modification is used to prepare cellulose derivatives as end products, whereas reversible modification is used to enhance solubility in the preparation of regenerated cellulose. The irreversible modification studied here was the preparation of carboxymethyl cellulose (CMC) using extended mercerization of a spruce dissolving pulp. More specifically the parameters studied were the effect of mercerization at different proportions of cellulose I and II in the dissolving pulp, the concentration of alkali, the temperature and the reaction time. The parameters evaluated were the degree of substitution, the filterability and the amount of gel obtained when the resulting CMC was dissolved in water. Molecular structures of CMC and its gel fractions were analysed by using NIR FT Raman spectroscopy. It was found that the alkali concentration in the mercerization stage had an extensive influence on the subsequent etherification reaction. FT Raman spectra of CMC samples and their gel fractions prepared with low NaOH concentrations (9%) in the mercerization stage indicated an incomplete transformation of cellulose to Na-cellulose before carboxymethylation to CMC. Low average DS values of the CMC, i.e. between 0.42 and 0.50 were obtained. Such CMC dissolved in water resulted in very thick and semi solid gum-like gels, probably due to an uneven distribution of substituents along the cellulose backbone. FT Raman spectra of CMC samples and their gel fractions mercerized at higher alkaline concentration, i.e. 18.25 and 27.5% in the mercerization stage, indicated on the other hand a complete transformation of cellulose to Na-cellulose before carboxymethylation to CMC. Higher average DS values of the CMC, i.e. between 0.88 and 1.05 were therefore obtained. When dissolved in water such CMC caused gel formation especially when prepared from dissolving pulp with a high fraction of cellulose II. The reversible modification studied was the dissolution of cellulose in NaOH/ZnO. Here the effect of enzyme pretreatment was investigated by using two mono-component enzymes; namely xylanase and endoglucanase, used in consecutive stages. It was found that although the crystallinity and the specific surface area of the dissolving pulp sustained minimal change during the enzymatic treatment; the solubility of pulp increased in a NaOH/ZnO solution from 29% for untreated pulp up to 81% for enzymatic pretreated pulp. / Baksidetext Cellulose can be chemically and/or enzymatically modified. Irreversible modification is used to prepare cellulose derivatives as end products, reversible modification to enhance solubility in the preparation of regenerated cellulose. The irreversible modification studied here was the preparation of carboxymethyl cellulose (CMC) using extended mercerization of a spruce dissolving pulp. More specifically the parameters studied were the effect of mercerization at different proportions of cellulose I and II in the dissolving pulp, the concentration of alkali, the temperature and the reaction time. It was found that the alkali concentration in the mercerization stage had an extensive influence on the subsequent etherification reaction. The content of cellulose II had little effect on degree of substitution (DS) at low NaOH concentration, but tended to decrease DS at higher NaOH concentration in both cases compared with cellulose I. It was also found that the content of cellulose II correlates with the gel formation obtained when the CMC is dissolved in water. The reversible modification studied was the dissolution of cellulose in NaOH/ZnO. Here the effect of enzyme pretreatment was investigated by using two mono-component enzymes; namely xylanase and endoglucanase, used in consecutive stages. It was found that the solubility of pulp increased in a NaOH/ZnO solution from 29% for untreated pulp up to 81% for enzymatic pretreated pulp.

Cellulose nanofibrils (CNFs) are nanoscale fibers of high aspect ratio that can be isolated from a wide variety of cellulosic sources, including wood and bacterial cellulose. With high strength despite of their low density, CNFs are a promising renewable building block for the preparation of nanostructured materials and composites. To fabricate CNF-based materials with improved inherent rheological and mechanical properties and additional new functionalities, it is essential to tailor the surface properties of individual CNFs. The surface structures control the interactions between CNFs and ultimately dictate the structure and macroscale properties of the bulk material. In this thesis we have demonstrated different approaches, ranging from non-covalent adsorption and covalent chemical modification to modification of cellulose biosynthesis, to tailor the structure and surface functionalities of CNFs for the fabrication of advanced materials. These materials possess enhanced properties such as water-redispersibility, water absorbency, dye adsorption capacity, antibacterial activity, and mechanical properties. In Paper I, CNFs were modified via the irreversible adsorption of carboxymethyl cellulose (CMC). The adsorption of small amounts of CMC onto the surface of CNFs prevented agglomeration and co-crystallization of the nanofibrils upon drying, and allowed the recovery of rheological and mechanical properties after redispersion of dried CNF samples. In Paper II, CNFs bearing permanent cationic charges were prepared through quaternization of wood pulp fibers followed by mechanical disintegration. The activation of the hydroxyl groups on pulp fibers by alkaline treatment was optimized prior to quaternization. This optimization resulted in individual CNFs with uniform width and tunable cationic charge densities. These cationic CNFs demonstrated ultrahigh water absorbency and high adsorption capacity for anionic dyes. In Paper III, via a similar approach as in Paper II, CNFs bearing polyethylene glycol (PEG) were prepared by covalently grafting PEG to carboxylated pulp fibers prior to mechanical disintegration. CNFs with a high surface chain density of PEG and a uniform width were oriented to produce macroscopic ribbons simply by mechanical stretching of the CNF hydrogel network before drying. The uniform grafted thin monolayer of PEG on the surface of individual CNFs prevented the agglomeration of CNFs and facilitated their alignment upon mechanical stretching, thus resulted in ribbons with ultrahigh tensile strength and modulus. These optically transparent ribbons also demonstrated interesting biaxial light scattering behavior. In Paper IV, bacterial cellulose (BC) was modified by the addition of chitin nanocrystals (ChNCs) into the growing culture medium of the bacteria Acetobacter aceti which secretes cellulose in the form of entangled nanofibers. This led to the in situ incorporation of ChNCs into the BC nanofibers network and resulted in BC/ChNC nanocomposites exhibiting bactericidal activity. Further, blending of BC nanofibers with ChNCs produced nanocomposite films with relatively lower tensile strength and modulus compared to the in situ cultivated ones. The bactericidal activity increased significantly with increasing amount of ChNCs for nanocomposites prepared by direct mixing of BC nanofibers and ChNCs. In Paper V, CNFs were isolated from suspension-cultured wild-type (WT) and cellulose-binding module (CBM) transformed tobacco BY-2 (Nicotiana tabacum L. cv bright yellow) cells. Results from strong sulfuric acid hydrolysis indicated that CNFs from transgenic cells overexpressing CBM consisted of longer cellulose nanocrystals compared to CNFs from WT cells. Nanopapers prepared from CNFs of transgenic cells demonstrated significantly enhanced toughness compared to CNFs of WT cells. / <p>QC 20141103</p> / CARBOMAT