Chemical modification of cellulose has been of growing interest, owing to the abundance and processing challenges of natural cellulose. To date, etherification and esterification are the most effective strategies to modify physicochemical properties of cellulose and append new functionalities. However, they typically require relatively harsh conditions, thus limiting introduction of new functional groups. An alternative strategy to synthesize novel cellulose derivatives is to append a good leaving group to cellulose backbone, followed by nucleophilic substitution reaction. Though tosylation and bromination of cellulose are frequently used, they have drawbacks such as chemo- and regioselectivity issues, high cost, and difficulty in purification. We have successfully developed a method to chemo- and regioselectively chlorinate cellulose esters using MsCl. Compared to bromination of cellulose typically used, this chlorination method has many advantages, including low cost of reagents and ease of separation. The chlorinated cellulose esters are useful intermediates for appending new functionalities by displacement reactions. We have synthesized a library of cellulose ester derivatives by this chlorination/nucleophilic substitution strategy, including cationic and anionic cellulose ester derivatives. These cellulose ester derivatives possess great potentialiii for various applications, including amorphous solid dispersion, tight junction opening, anionic drug delivery, and gas separation membranes. / MS

Cette thèse s'inscrit dans le contexte de la Chaire Industrielle Bioplastiques, financé par MINES ParisTech et cinq entreprises partenaires : Arkema, L'Oréal, Nestlé, PSA Peugeot-Citroën et Schneider Electric, qui vise à développer de nouveaux matériaux biosourcés durables. L'objectif global de la thèse est de trouver de nouvelles propriétés à une ancienne famille de plastiques biosourcés – les esters de cellulose – en les mélangeant avec une polyoléfine. Nous avons débuté l'étude par une étape de screening qui nous a permis de caractériser l'ester de cellulose retenu (acétobutyrate de cellulose ou CAB) et de définir l'objectif de la thèse : améliorer la résistance au choc du CAB en y ajoutant une phase polyoléfinique finement dispersée. Le CAB est, en effet, particulièrement fragile : sa résilience est inférieure à 2 kJ/m² lors d'un choc Charpy entaillé. Pour diminuer la taille de nodules de la phase dispersée et la distance qui les sépare, deux approches ont été utilisés. Premièrement, plusieurs mélanges de CAB et de polyéthylènes (PE) de densités différentes ont été préparés par mélangeur interne. Des compatibilisants maléisés ont été utilisés pour diminuer la tension interfaciale entre les phases. Les tailles des nodules, mesurées par microscopie électronique à balayage se sont classées suivant les rapports de viscosité et d'élasticité (PE/CAB), mesurés par rhéométrie dynamique. La résilience de ces mélanges a été augmentée par rapport au CAB mais n'a pas dépassé 6 kJ/m². Dans la seconde approche, des polyoléfines fonctionnalisées (maléisées) ont été utilisées comme unique phase dispersée. La fonctionnalité accrue a permis d'améliorer l'adhésion interfaciale. La taille des nodules et leur espacement ont été considérablement réduits. Les mélanges sélectionnés ont été préparés par extrusion bi-vis et les éprouvettes de résistance au choc ont été préparées par injection. Pour quelques formulations, une longueur moyenne de ligaments de matrice (séparant deux nodules voisins) particulièrement petite (0,1 µm) a permis d'atteindre la transition fragile-ductile du matériau et une résilience supérieure à 60 kJ/m². / This work has been funded by the Industrial Chair in Biopalstics, financed by MINES ParisTech and fives industrial partners: Arkema, L'Oréal, Nestlé, PSA Peugeot-Citroën and Schneider Electric, whose objective is to develop new durable biobased materials. The aim of this thesis is to find new properties for an old-fashioned biobased plastic – cellulose esters – by blending with polyolefins. We started the project with a screening of the cellulose ester (cellulose acetate butyrate or CAB) properties. Thus, we were able to define the goal of the project: improving impact resistance of CAB by adding a finely dispersed polyolefin phase. Indeed, CAB is very brittle: its notched Charpy resilience is below 2 kJ/m². To decrease the size and the spacing of dispersed phase nodules, we developed two different approaches. First, several blends between CAB and polyethylenes (PE) with various densities have been prepared by internal mixer. Maleinated compatibilizers have been used to decrease interfacial tension between phases. Nodules sizes, measured from scanning electron microscope images ranked according to the viscosity and elasticity ratios (PE/CAB). Those ratios have been measured by dynamic rheometry. Blends resilience increased compared to CAB but did not exceed 6 kJ/m². In the second approach, functionalized (maleinated) polyolefins have been used as a single dispersed phase. Increased functionality led to improved interfacial adhesion. Nodules size and their spacing have been significantly decreased. Selected blends were prepared by twin-screw extrusion and impact bars were injected. For some formulations, a small (near 0.1 µm) mean matrix ligaments thickness (distance between two neighboring nodules) was obtained and led to the brittle-ductile transition of the material, with a resilience higher than 60 kJ/m².

Esta tese apresenta o estudo do efeito do solvente acetato de etila e acetona no comportamento em solução dos polímeros acetato butirato celulose (CAB) e acetato butirato carboximetil celulose (CMCAB) e nas características dos seus filmes finos obtidos pela técnica de revestimento rotacional ou por adsorção. As medidas de viscosidade e espalhamento de raio-X a baixo ângulo (SAXS) mostraram que o acetato de etila é um melhor solvente para CAB e CMCAB do que a acetona. A caracterização dos filmes foi feita através de medidas de elipsometria, microscopia de força atômica (AFM), espectrocospia vibracional por geração de soma de freqüências (SFG) e medidas de ângulo de contato. Os filmes de CMCAB obtidos por revestimento rotacional são mais espessos quando preparado em acetona do que em acetato de etila. Imagens de AFM mostraram que os filmes de CMCAB oriundos de soluções em acetato de etila são mais homogêneos e lisos do que aqueles preparados a partir de acetona. Medidas de SFG comprovaram a forte afinidade da acetona com SiO2/Si, mostrando que esse solvente cria uma nova camada para os filmes de CAB e CMCAB. Os valores de energia superficial calculados para CAB e CMCAB foram semelhantes ~ (49,0 ± 0,5) mJ/m², sendo a contribuição da componente dispersiva maior que a da componente polar. A adsorção das proteínas lisozima, albumina do soro bovino (BSA), concanavalina A e jacalina foram mais pronunciadas sobre os filmes de CMCAB do que sobre CAB. Indicando que a presença do grupo carboximetil (CM) contribui significativamente no processo de adsorção das biomoléculas. O efeito da rugosidade dos filmes de CAB e CMCAB sobre o processo de adsorção das proteínas foi estudado. No caso do CMCAB, a adsorção das proteínas foi mais pronunciada sobre o filme rugoso do que sobre o filme mais liso. Entretanto, para os filmes de CAB a rugosidade não teve um efeito significativo na adsorção das proteínas / The effect of ethyl acetate and acetone on the solution behavior of cellulose acetate butyrate (CAB) and carboxymehtylcellulose acetate butyrate (CMCAB) and on the characteristics of films obtained either by spin coating or adsorption was investigated. Viscosity and small angle X-ray scattering (SAXS) measurements showed that ethyl acetate is a better solvent than acetone for CAB e CMCAB. Films were characterized by means of ellipsometry, atomic force microscopy (AFM), sum frequency generation (SFG) and contact angle measurements. Spin-coated films of CMCAB from ethyl acetate solutions were thicker than those deposited from acetone solutions. AFM images revealed that CMCAB spin coated films from ethyl acetate solutions were homogeneous and flat. However, films obtained from solutions in acetone were very rough. SFG spectra showed that acetone binds strongly to SiO2/Si wafers, creating a new surface for CAB and CMCAB films. Surface energy values determined for spin-coated CAB and CMCAB were similar ~ (49,0 ± 0,5) mJ/m² with the dispersive component larger than the polar component. The adsorption of lysozyme, bovine serum albumin (BSA), concanavalin A and jacalin was more pronounced onto CMCAB films than that onto CAB films. Indicating that carboxymethyl group favored the adsorption process. The influence of surface roughness of CAB and CMCAB on protein adsorption has been investigated. In the case of CMCAB, protein adsorption was morepronounced onto rough films than that onto flat films. However, the roughness of CAB films exerted no significant influence on proteins adsorption

Esta tese apresenta o estudo do efeito do solvente acetato de etila e acetona no comportamento em solução dos polímeros acetato butirato celulose (CAB) e acetato butirato carboximetil celulose (CMCAB) e nas características dos seus filmes finos obtidos pela técnica de revestimento rotacional ou por adsorção. As medidas de viscosidade e espalhamento de raio-X a baixo ângulo (SAXS) mostraram que o acetato de etila é um melhor solvente para CAB e CMCAB do que a acetona. A caracterização dos filmes foi feita através de medidas de elipsometria, microscopia de força atômica (AFM), espectrocospia vibracional por geração de soma de freqüências (SFG) e medidas de ângulo de contato. Os filmes de CMCAB obtidos por revestimento rotacional são mais espessos quando preparado em acetona do que em acetato de etila. Imagens de AFM mostraram que os filmes de CMCAB oriundos de soluções em acetato de etila são mais homogêneos e lisos do que aqueles preparados a partir de acetona. Medidas de SFG comprovaram a forte afinidade da acetona com SiO2/Si, mostrando que esse solvente cria uma nova camada para os filmes de CAB e CMCAB. Os valores de energia superficial calculados para CAB e CMCAB foram semelhantes ~ (49,0 ± 0,5) mJ/m², sendo a contribuição da componente dispersiva maior que a da componente polar. A adsorção das proteínas lisozima, albumina do soro bovino (BSA), concanavalina A e jacalina foram mais pronunciadas sobre os filmes de CMCAB do que sobre CAB. Indicando que a presença do grupo carboximetil (CM) contribui significativamente no processo de adsorção das biomoléculas. O efeito da rugosidade dos filmes de CAB e CMCAB sobre o processo de adsorção das proteínas foi estudado. No caso do CMCAB, a adsorção das proteínas foi mais pronunciada sobre o filme rugoso do que sobre o filme mais liso. Entretanto, para os filmes de CAB a rugosidade não teve um efeito significativo na adsorção das proteínas / The effect of ethyl acetate and acetone on the solution behavior of cellulose acetate butyrate (CAB) and carboxymehtylcellulose acetate butyrate (CMCAB) and on the characteristics of films obtained either by spin coating or adsorption was investigated. Viscosity and small angle X-ray scattering (SAXS) measurements showed that ethyl acetate is a better solvent than acetone for CAB e CMCAB. Films were characterized by means of ellipsometry, atomic force microscopy (AFM), sum frequency generation (SFG) and contact angle measurements. Spin-coated films of CMCAB from ethyl acetate solutions were thicker than those deposited from acetone solutions. AFM images revealed that CMCAB spin coated films from ethyl acetate solutions were homogeneous and flat. However, films obtained from solutions in acetone were very rough. SFG spectra showed that acetone binds strongly to SiO2/Si wafers, creating a new surface for CAB and CMCAB films. Surface energy values determined for spin-coated CAB and CMCAB were similar ~ (49,0 ± 0,5) mJ/m² with the dispersive component larger than the polar component. The adsorption of lysozyme, bovine serum albumin (BSA), concanavalin A and jacalin was more pronounced onto CMCAB films than that onto CAB films. Indicating that carboxymethyl group favored the adsorption process. The influence of surface roughness of CAB and CMCAB on protein adsorption has been investigated. In the case of CMCAB, protein adsorption was morepronounced onto rough films than that onto flat films. However, the roughness of CAB films exerted no significant influence on proteins adsorption

Biodegradable thermoplastic composites were prepared using high modulus lyocell fibers and cellulose acetate butyrate (CAB). Two reinforcement fiber types: fabric and continuous fiber tow were used. Fabric had advantages of uniform alignment and easier processing, but lacked the use as a unidirectional reinforcement and a continuous method of matrix application. Three different matrix application methods were screened for both fiber types. Matrix application by suspension of particles in water was not feasible because of particle sizes > 15 &micro m. The other disadvantages were high moisture absorption during matrix application and void formation during consolidation. Melt processing technique using alternating sandwich structure of fabrics and CAB films produced composites with impressive appearance, low void contents and low moisture absorption. However, SEM results revealed interfacial failure and extensive fiber pull out. Relatively larger fiber and matrix regions were present on the scale of 10^-3m. Solution prepregging technique using methyl ethyl ketone (MEK) as a solvent for CAB and continuous fibers as reinforcement produced composites with uniform matrix distribution, high tensile strengths and high modulus, and even wetting of fibers by CAB. A maximum tensile modulus of 21.5 GPa and a maximum strength of 251.7 MPa were achieved for a continuous fiber reinforced composites at a volume fraction of 66.5% compared to 0.8 GPa and 76 MPa for the matrix, respectively. Void contents and water absorption were relatively high compared to comparable carbon fiber composites. / Master of Science

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第19197号 / 農博第2136号 / 新制||農||1034(附属図書館) / 学位論文||H27||N4943(農学部図書室) / 32189 / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 西尾 嘉之, 教授 木村 恒久, 教授 髙野 俊幸 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

No description available.

Esta tese está dividida em duas partes. Na Parte I, blendas de polietileno maleado (M-PE) e butirato acetato de celulose (CAB) (5-50% em massa) e compósitos de polietileno (PE) ou M-PE e 20% em massa de celulose, acetato de celulose (CA), propionato acetato de celulose (CAP) ou CAB foram preparados em um misturador. As estruturas e propriedades das misturas foram estudadas através de ensaios mecânicos, calorimetria exploratória diferencial, microscopia eletrônica de varredura, extração com solvente seletivo seguida de espectroscopia FTIR e difração de raios-X (XRD). As blendas M-PE/CAB e os compósitos PE/polissacarídeo e M-PE/polissacarídeo não apresentaram mudanças significativas nos valores da temperatura de fusão (Tm) quando comparados aos valores de Tm do PE e do M-PE. Dados de XRD mostraram que a adição das cargas não causou mudança na estrutura cristalina do PE ou M-PE, mas aumentou a região amorfa dos materiais, indicado que a miscibilidade ocorre na parte amorfa do PE. Compósitos preparados com M-PE apresentaram tensão no escoamento e elongação superiores do que os preparados com PE, evidenciando o efeito compatibilizante do anidrido maléico. Na parte II, o efeito de dois bons solventes, acetona e acetato de etila, nas características e propriedades superficiais dos filmes finos (50nm&#60;espessura<200nm) e ultrafinos (espessura<6nm) de CA, CAP ou CAB preparados por revestimento rotacional ou adsorção, respectivamente, foram caracterizados por elipsometria, microscopia de força atômica (AFM) e medidas de ângulo de contato. Os resultados foram discutidos baseados na taxa de evaporação do solvente e na energia de interação substrato-solvente. Os efeitos do recozimento e do tipo de éster de celulose na espessura, morfologia e molhabilidade da superfície foram investigados. Após o recozimento, os filmes ultrafinos de ésteres de celulose tornam-se hidrofóbicos, indicando uma reorientação molecular na interface sólido-ar. Os filmes ultrafinos preparados a partir de soluções de acetona são estáveis, enquanto que os preparados a partir de soluções de acetato de etila apresentaram dewetting. A estabilidade dos filmes foi monitorada por AFM e explicada pelos valores da constante de Hamaker, determinados pela primeira vez para estes materiais. A imobilização de lipase sobre os filmes ultrafinos estáveis de CA, CAP e CAB com e sem recozimento foi quantificada para avaliar a possibilidade de aplicação destes filmes como substratos para biomoléculas. A adsorção de lipase sobre os filmes de CA e CAP com recozimento foi mais pronunciada do que nos mesmos filmes sem recozimento. A atividade enzimática da lipase foi avaliada com medidas espectrofotométricas do produto formado a partir da hidrólise do para-nitrofenol dodecanoato. A lipase imobilizada sobre os filmes mais hidrofóbicos apresentou uma atividade maior do que a lipase livre e manteve a atividade alta após três usos. As amostras foram estocadas por até 30 dias. A lipase imobilizada sobre os filmes mais hidrofóbicos manteve 70% da sua atividade, e a lipase imobilizada sobre os filmes mais hidrofílicos manteve apenas 30% da atividade. Estes resultados indicaram que preservação da estrutura conformacional da enzima foi favorecida pela hidrofobicidade do substrato polimérico e interações entre os resíduos polares da lipase e as partes de glucopiranosil dos ésteres de celulose. / This thesis is divided into two parts. In the first part, blends of maleated polyethylene (M-PE) and cellulose acetate butyrate (CAB) (5-50wt%) and composites of polyethylene (PE) or M-PE and 20wt% of cellulose, cellulose acetate (CA) or cellulose acetate propionate (CAP) were prepared in an laboratory mixer. The mixtures structures and properties have been studied by means of tensile testing, differential scanning calorimetry, scanning electron microscopy, X-ray diffraction (XRD) and extraction with a selective solvent followed by Raman spectroscopy. No significant change on the melting temperature (Tm) values obtained for M-PE/CAB blends or PE/polysaccharides or M-PE/polysaccharides composites could be observed, when compared with the Tm values obtained for PE and M-PE. X-ray diffraction showed that the addition of the polysaccharides had no influence on the lattice constants of PE or M-PE, but it increased the PE amorphous region, indicating that the miscibility happens on the amorphous region of the PE. Composites prepared with M-PE presented yield stress and elongation values higher than those prepared with PE, showing the compatibilizer effect of maleic anhydride. In the second part, the effect of two good solvents, acetone and ethyl acetate, on the characteristics and surface properties of thin (30nm&#60;thickness<200nm) and ultrathin (thickness<6nm) cellulose ester films obtained by spin coating or adsorption, respectively, has been investigated by means of ellipsometry, atomic force microscopy (AFM) and contact angle measurements. The results were discussed in the light of solvent evaporation rate and interaction energy between substrate and solvent. The effects of annealing and type of cellulose ester on film thickness, film morphology and surface wettability were also studied. Upon annealing, ultrathin films of cellulose ester became hydrophobic, evidencing molecular re-orientation at the solid-air interface. Ultrathin films prepared from acetone solutions are stable, but the ones prepared from ethyl acetate solutions presented dewetting. Film stability was followed by AFM and explained with basis on the Hamaker constant values, calculated for the first time for CA, CAP and CAB. The adsorption of lipase onto stable ultrathin films of cellulose esters, with and without annealing, was quantified in order to evaluate the possibility of applying such films as support for biomolecules. Lipase adsorption onto annealed CA and CAP films was more pronounced than that onto CA and CAP untreated films. Enzymatic activity was evaluated by the spectrophotometric measurement of the product formed from the hydrolysis of para-nitrophenyl dodecanoate. Lipase immobilized onto more hydrophobic films presented higher activity than free lipase and could be reused three times retaining activity at a high level. The effect of storing time on the activity of immobilized lipase was studied. Lipase immobilized onto more hydrophobic films retained 70% of activity after one month, reaching the same level of activity of free lipase, and lipase immobilized onto more hydrophilic films retained just 30% of activity after 30 days. These results indicated that enzyme preservation was favored by polymeric substrate hydrophobicity and by the interactions between the polar residues of lipase and the glucopyranosyl moieties of cellulose ester.

Esta tese está dividida em duas partes. Na Parte I, blendas de polietileno maleado (M-PE) e butirato acetato de celulose (CAB) (5-50% em massa) e compósitos de polietileno (PE) ou M-PE e 20% em massa de celulose, acetato de celulose (CA), propionato acetato de celulose (CAP) ou CAB foram preparados em um misturador. As estruturas e propriedades das misturas foram estudadas através de ensaios mecânicos, calorimetria exploratória diferencial, microscopia eletrônica de varredura, extração com solvente seletivo seguida de espectroscopia FTIR e difração de raios-X (XRD). As blendas M-PE/CAB e os compósitos PE/polissacarídeo e M-PE/polissacarídeo não apresentaram mudanças significativas nos valores da temperatura de fusão (Tm) quando comparados aos valores de Tm do PE e do M-PE. Dados de XRD mostraram que a adição das cargas não causou mudança na estrutura cristalina do PE ou M-PE, mas aumentou a região amorfa dos materiais, indicado que a miscibilidade ocorre na parte amorfa do PE. Compósitos preparados com M-PE apresentaram tensão no escoamento e elongação superiores do que os preparados com PE, evidenciando o efeito compatibilizante do anidrido maléico. Na parte II, o efeito de dois bons solventes, acetona e acetato de etila, nas características e propriedades superficiais dos filmes finos (50nm&#60;espessura<200nm) e ultrafinos (espessura<6nm) de CA, CAP ou CAB preparados por revestimento rotacional ou adsorção, respectivamente, foram caracterizados por elipsometria, microscopia de força atômica (AFM) e medidas de ângulo de contato. Os resultados foram discutidos baseados na taxa de evaporação do solvente e na energia de interação substrato-solvente. Os efeitos do recozimento e do tipo de éster de celulose na espessura, morfologia e molhabilidade da superfície foram investigados. Após o recozimento, os filmes ultrafinos de ésteres de celulose tornam-se hidrofóbicos, indicando uma reorientação molecular na interface sólido-ar. Os filmes ultrafinos preparados a partir de soluções de acetona são estáveis, enquanto que os preparados a partir de soluções de acetato de etila apresentaram dewetting. A estabilidade dos filmes foi monitorada por AFM e explicada pelos valores da constante de Hamaker, determinados pela primeira vez para estes materiais. A imobilização de lipase sobre os filmes ultrafinos estáveis de CA, CAP e CAB com e sem recozimento foi quantificada para avaliar a possibilidade de aplicação destes filmes como substratos para biomoléculas. A adsorção de lipase sobre os filmes de CA e CAP com recozimento foi mais pronunciada do que nos mesmos filmes sem recozimento. A atividade enzimática da lipase foi avaliada com medidas espectrofotométricas do produto formado a partir da hidrólise do para-nitrofenol dodecanoato. A lipase imobilizada sobre os filmes mais hidrofóbicos apresentou uma atividade maior do que a lipase livre e manteve a atividade alta após três usos. As amostras foram estocadas por até 30 dias. A lipase imobilizada sobre os filmes mais hidrofóbicos manteve 70% da sua atividade, e a lipase imobilizada sobre os filmes mais hidrofílicos manteve apenas 30% da atividade. Estes resultados indicaram que preservação da estrutura conformacional da enzima foi favorecida pela hidrofobicidade do substrato polimérico e interações entre os resíduos polares da lipase e as partes de glucopiranosil dos ésteres de celulose. / This thesis is divided into two parts. In the first part, blends of maleated polyethylene (M-PE) and cellulose acetate butyrate (CAB) (5-50wt%) and composites of polyethylene (PE) or M-PE and 20wt% of cellulose, cellulose acetate (CA) or cellulose acetate propionate (CAP) were prepared in an laboratory mixer. The mixtures structures and properties have been studied by means of tensile testing, differential scanning calorimetry, scanning electron microscopy, X-ray diffraction (XRD) and extraction with a selective solvent followed by Raman spectroscopy. No significant change on the melting temperature (Tm) values obtained for M-PE/CAB blends or PE/polysaccharides or M-PE/polysaccharides composites could be observed, when compared with the Tm values obtained for PE and M-PE. X-ray diffraction showed that the addition of the polysaccharides had no influence on the lattice constants of PE or M-PE, but it increased the PE amorphous region, indicating that the miscibility happens on the amorphous region of the PE. Composites prepared with M-PE presented yield stress and elongation values higher than those prepared with PE, showing the compatibilizer effect of maleic anhydride. In the second part, the effect of two good solvents, acetone and ethyl acetate, on the characteristics and surface properties of thin (30nm&#60;thickness<200nm) and ultrathin (thickness<6nm) cellulose ester films obtained by spin coating or adsorption, respectively, has been investigated by means of ellipsometry, atomic force microscopy (AFM) and contact angle measurements. The results were discussed in the light of solvent evaporation rate and interaction energy between substrate and solvent. The effects of annealing and type of cellulose ester on film thickness, film morphology and surface wettability were also studied. Upon annealing, ultrathin films of cellulose ester became hydrophobic, evidencing molecular re-orientation at the solid-air interface. Ultrathin films prepared from acetone solutions are stable, but the ones prepared from ethyl acetate solutions presented dewetting. Film stability was followed by AFM and explained with basis on the Hamaker constant values, calculated for the first time for CA, CAP and CAB. The adsorption of lipase onto stable ultrathin films of cellulose esters, with and without annealing, was quantified in order to evaluate the possibility of applying such films as support for biomolecules. Lipase adsorption onto annealed CA and CAP films was more pronounced than that onto CA and CAP untreated films. Enzymatic activity was evaluated by the spectrophotometric measurement of the product formed from the hydrolysis of para-nitrophenyl dodecanoate. Lipase immobilized onto more hydrophobic films presented higher activity than free lipase and could be reused three times retaining activity at a high level. The effect of storing time on the activity of immobilized lipase was studied. Lipase immobilized onto more hydrophobic films retained 70% of activity after one month, reaching the same level of activity of free lipase, and lipase immobilized onto more hydrophilic films retained just 30% of activity after 30 days. These results indicated that enzyme preservation was favored by polymeric substrate hydrophobicity and by the interactions between the polar residues of lipase and the glucopyranosyl moieties of cellulose ester.