Coating urea to prepare controlled release N-fertilizer has been considered as an effective way to increase its nutrient use efficiency, thus reduce its waste and the consequent harmful environmental impacts. Inorganic sulphur and synthetic polymers have been used in the industry as coating materials together with utilization of various types of expensive coating equipment which commonly requires also complicated technical setup and controls. As development trends, biopolymers are attention-grabbing to replace the synthetic polymers. Alternative simple coating technique is also desired. So far, polylactic acid (PLA) has been reported as a more promising biopolymer than several synthetic polymers for coating. On the other hand, highly purified industrial softwood kraft lignin (SKL) produced after LignoBoost process is now available in a large quantity, which should also be a promising biopolymer for the coating application. Aiming at increase of the efficiency of PLA-coated urea and development of alternative coating technique to generally make the preparation of control-released fertilizer more effective, economic and environmentally sustainable, in this study, SKL has been used in a PLA-SKL blending form as complex coating material and simple dip-coating technique has been investigated and applied. In order to lower the wettability of PLA-SKL coat layer, four different anhydrides, namely acetic anhydride, palmitic anhydride, lauric anhydride and trifluoroacetic anhydride, were used to esterify SKL to form AcSKL, PaSKL, LauSKL and TFASKL respectively before its utilization. NMR and FTIR analyses showed that the esterification reactions have been completed for AcSKL and PaSKL. LauSKL was partly esterified due to the low charge of lauric anhydride regent, while TFASKL was not esterified expectantly due to the steric hindrance between the three F atoms and polymeric SKL. In order to obtain organically bound nitrogen structure to also create slow-release type of N-fertilizer, Mannich reaction on SKL using diethylamine was also conducted to prepare ManSKL. The reaction was completed as shown by NMR and FTIR spectroscopy. To bring further functionality of metal chelation to open the possibility to also bring essential trace element into the final fertilizer, ethylenediaminetriacetic acid (ED3A) was synthesized and further used via Mannich reaction to modify SKL to form ED3ASKL. ED3A is not commercially available and it was synthesized successfully with an environmentally friendly method from commercial EDTA and the structure was verified by NMR spectroscopy. However, the Mannich reaction using ED3A was not very successful as shown by product’s NMR and FTIR spectra. In a comparison experiment using vanillyl alcohol as a lignin model structure, ED3A was successfully coupled onto the vanillyl alcohol structure as shown by NMR and FTIR spectra. Apparently there was a severe steric hindrance from SKL for the Mannich reaction using the larger molecule of ED3A than diethylamine for Mannich reaction. For utilization of dip-coating technique, dichloromethane(DCM) and tetrahydrofuran (THF) were chosen to dissolve PLA and SKL or the modified SKL respectively. Cast films of PLA/modified lignin complex were prepared using Teflon Petri-dishes. The optimal concentration of PLA in DCM and the effect of DCM/THF ratios on the prepared cast film which expectantly represents the quality of the complex coat in the coated urea were compared with SEM images and contact angle determination. It has been found that a 30 wt% of PLA in DCM was the best and this solution mixed with modified lignin solution (6 % in THF) in a ratio of DCM/THF =3/2 (v/v) had the best film performances and water barrier properties. Generally, the cast films from PLA/modified lignin complexes showed better properties compared with the neat PLA cast film. No pores and cracks were found on the surface. Comparatively, the LauSKL film showed the most homogeneous surface. But the AcSKL film had the best water barrier properties. The PLA/modified lignin complex coated urea was then prepared by dip-coating process. The coat thickness and weight increase showed statistically positive correlations against the repeating times of the dip-coating process. The coating layer also showed one single layer structure. The speed of urea releasing for coated urea was tested and the results showed that it was much slower than the un-coated or PLA-coated urea. The single-layered PLA/AcSKL and PLA/ManSKL were both observed with sound properties in delaying the release of urea cores in water. Conclusively, the PLA/modified SKL coated urea fertilizers prepared by dip-coating technique demonstrated in this study have highly efficiency with better effects of water barrier, organically N slow release, and nitrification inhibiting (due to free phenolic functional groups) properties. Both SKL and the dip-coating technique are promising in the fertilizer applications. / Att ytbelägga urea för att skapa kontrollerad frisläppning av kväverika gödningsmedel har ansetts vara en effektiv metod för att öka användandet av näringsämnena från urea och dessutom minska den möjliga miljöpåverkan urea har. Kommersiellt har oorganiskt svavel och syntetiska polymerer använts för att ytbelägga olika material och detta är kopplat till olika typer av dyra ytbeläggningsutrustningar som ofta kräver komplicerade tekniska lösningar och kontroller. För att förbättra dagens lösningar är en intressant trend användandet av biopolymerer och en annan viktig aspekt är att utveckla nya enklare ytbeläggningstekniker än vad som finns på marknaden idag. Polylaktid (PLA) har till exempel rapporterats som en mer lovande förnybar polymer än flera av de syntetiska polymererna för ytbeläggnig. En annan intressant förnybar polymer är lignin, som idag tillverkas med hög renhet industriellt som barrveds kraft lignin (SKL) ur LignoBoost processen. Med målet att öka effektiviteten hos urea belagd med PLA och att utveckla en alternativ ytbeläggningsmetod för att göra den generellt mer effektiv, ekonomisk och miljövänlig har SKL använts i en PLA-SKL blandning för att ytbelägga med urea och en enkel doppbeläggningsmetod utvecklats och applicerats. För att minska vätbarheten av PLA-SKL ytbeläggningen har fyra anhydrider, ättiksyraanhydrid, palmitisk anhydrid, lauric anhydrid, och trifluoroacetisk anydrid, använts för att esterifiera SKL och bilda AcSKL, PaSKL, LauSKL och TFASKL. NMR och FTIR användes för att verifiera esterifieringsreaktionerna. Fullständig reaktion kunde konstateras för AcSKL och PaSKL, LauSKL hade bara delvis esterifierat pga den låga mängd lauric anydrid som användes medan TFASKL inte ledde till den tilltänkta esterifieringen pga steriska hinder mellan de tre flor-atomerna och SKL polymeren. För att tillverka en organiskt bunden kvävestruktur, som dessutom har en långsam frisättning av N-rika gödningsmedel genomfördes en Mannich-reaktion på SKL med dietylamin som katalysator för att framställa ManSKL. Reaktion gick till full omsättning, enligt NMR- och FTIR-spektroskopi. För att få ytterligare funktionalitet såsom metallkelation, vilken öppnar möjligheten att tillföra väsentliga spårämnen till gödningsmedlet, syntetiserades och användes etylendiamintriättiksyra (ED3A) för att modifiera SKL för att bilda ED3ASKL. ED3A finns inte kommersiellt tillgängligt utan syntetiserades framgångsrikt med en miljövänlig metod från kommersiell EDTA, varefter strukturen verifierades genom NMR-spektroskopi. Mannich-reaktionen på SKL med ED3A var emellertid inte särskilt framgångsrik, vilket NMR- och FTIR-spektra av produkten visade, Som modellexperiment användes vaniljalkohol som en ligninmodellstruktur till vilken ED3A framgångsrikt kopplades. Orsaken till denna stora skillnad i reaktivitet tros vara steriska hinder från SKL. För att utveckla en doppbeläggningsteknik valdes diklormetan (DCM) och tetrahydrofuran (THF) som lösningsmedel för att lösa upp PLA, SKL och den modifierade SKL. Gjutna filmer av PLA/modifierat lignin tillverkades i Teflon Petri-skålar. Den optimala koncentrationen av PLA i DCM och effekten av DCM/THF-förhållandet på filmens morfologi förväntas representerar kvaliteten för den framtida ytbeläggningen på urea, därför jämfördes filmernas SEM-bilder och kontaktvinkel. Det kunde konstateras att en 30 vikt% PLA i DCM var optimal och att denna lösning blandad med modifierad ligninlösning (6% i THF) i ett förhållande av DCM/THF = 3/2 (v/v) hade den bästa filmprestanda och vattenbarriäregenskaper. Generellt visade filmer av PLA/modifierade lignin bättre egenskaper jämfört med den rena PLA-filmen då inga porer och sprickor hittades på ytan. LauSKL-filmen uppvisade den mest homogena ytan medan AcSKL-filmen hade de bästa vattenbarriäregenskaperna. Urea ytbelagdes med PLA och PLA/modifierade lignin genom en doppbeläggningsprocessen. Beläggningstjockleken och viktökningen visade statistiskt positiva korrelationer gentemot antalet upprepningar av doppbeläggningsprocessen. Beläggningsskiktet visade också en enda skiktstruktur. Hastigheten det tog för urea att frigöra sig från den ytbelagda urean undersöktes och resultaten visade att den var mycket långsammare än den obehandlade urean eller den PLA-belagda urean. Enkelskiktad PLA/AcSKL och PLA/ManSKL uppvisade båda goda fördröjningsegenskaper för frisättningen av urea i vatten. Sammanfattningsvis kan man säga att PLA/modifierade SKL-belagda ureagödningsmedel framställda genom en utvecklad doppbeläggningsteknik, uppvisar hög effektivitet med bättre egenskap som vattenbarriär, långsam frisättning av organiskt kväve och nitrifikationshämmande egenskaper (beroende på fria fenoliska funktionella grupper). Både SKL och doppbeläggningstekniken är lovande i för gödningsmedelstillämpningarna.

Polylactide homopolymers with pendent carboxylic acid functional groups have been designed and synthesized to be studied as magnetite nanoparticle dispersion stabilizers. Magnetic nanoparticles are of interest for a variety of biomedical applications including magnetic field-directed drug delivery and magnetic cell separations. Small magnetite nanoparticles are desirable due to their established biocompatibility and superparamagnetic (lack of magnetic hysteresis) behavior. For in-vivo applications, it is important that the magnetic material be coated with biocompatible organic materials to afford dispersion characteristics or to further modify the surfaces of the complexes with biospecific moieties. The acid-functionalized silane endgroup was utilized as the dispersant anchor to adsorb onto magnetite nanoparticle surfaces and allowed the polylactide to extend into various solvents to impart dispersion stability. The homopolymers were complexed with magnetite nanoparticles by electrostatic adsorption of the carboxylates onto the iron oxide surfaces, and these complexes were dispersible in dichloromethane. The polylactide tailblocks extended into the dichloromethane and provided steric repulsion between the magnetite-polymer complexes. The resultant magnetite-polymer complexes were further incorporated into controlled-size nanospheres. The complexes were blended with poly(ethylene oxide-b-D,L-lactide) diblock copolymers to introduce hydrophilicity on the surface of the nanospheres with tailored functionality. Self-assembly of the PEO block to the surface of the nanosphere was established by utilizing an amine terminus on the PEO to react with FITC and noting fluorescence. / Ph. D.

Le sujet de cette étude consiste en la synthèse de nouveaux copolymères, associatifs en milieux aqueux, susceptibles d'encapsuler une protéine. Ces copolymères doivent être biocompatibles et biorésorbables pour une application biomédicale éventuelle et doivent de plus être amphiphiles. Le but de ce manuscrit est ainsi de décrire la synthèse de copolymères à blocs amphiphiles. L'association des blocs hydrophobes du copolymère doit en effet permettre la formation de particules en émulsion aqueuse. La partie hydrophobe des copolymères à blocs est constituée de polylactide synthétisé par polymérisation par ouverture de cycle du L-lactide. Le bloc hydrophile est constitué de poly(acide glutamique), peptide obtenu en deux étapes. On synthétise le poly(glutamate de benzyle) lors de la première étape par polymérisation par ouverture de cycle d'un anhydride de Leuchs, le N-carboxyanhydride de L-glutamate de benzyle. On déprotège ensuite les fonctions acide de ce polymère encore hydrophobe, le poly(glutamate de benzyle), pour obtenir le poly(acide glutamique), hydrophile. L'architecture du copolymère à blocs est obtenue à l'aide d'un amorceur difonctionnel qui amorce dans un premier temps la polymérisation du L-lactide. Le premier bloc de polylactide ainsi synthétisé possède en bout de chaîne un groupement susceptible d'amorcer la polymérisation du N-carboxyanhydride de L-glutamate de benzyle. On synthétise donc dans un deuxième temps le copolymère à blocs hydrophobes et on déprotège les fonctions acide du deuxième bloc pour obtenir le copolymère à blocs amphiphiles.

Le rotomoulage est une technique de transformation des polymères thermoplastiques qui souffre encore aujourd'hui d'un certain empirisme. Depuis de nombreuses années, la simulation du procédé de rotomoulage est considérée comme une nécessité à l'introduction de nouveaux matériaux et à l'élargissement de ses domaines applications. Ces travaux s'inscrivent à la suite de nombreuses études visant à développer un logiciel de simulation permettant de prédire le comportement de la matière en condition de mise en œuvre.L'objectif de cette thèse est de s'intéresser plus particulièrement à la simulation de la phase de refroidissement. Pour cela, il est nécessaire de mettre au point un modèle décrivant la cinétique de cristallisation et pouvant tenir compte des contraintes liées aux conditions thermiques extrêmes dans lequel se déroule le procédé (température, présence d'oxygène, temps de cycle long), lesquelles peuvent avoir une influence sur la thermostabilité du polymère. Dans le cadre de cette étude, le choix s'est porté sur le Polylactide (PLA). Le PLA présente une faible stabilité thermique et une cinétique de cristallisation lente, ce qui facilite l'observation de ces deux phénomènes. Dans un premier temps, la thermodégradation du PLA a été étudiée et un modèle visant à décrire son évolution dans des conditions proches de celles du procédé, a été mis en place. Puis, une étude de cristallisation considérant l'influence de la masse moléculaire et du polymorphisme du PLA, a été réalisée afin de modéliser sa cinétique. Enfin, un couplage des deux modèles a été envisagé dans l'optique de les intégrer à une simulation globale des transferts thermiques impliqués dans le procédé de rotomoulage.

Une série de complexes à base de titane porteurs de ligands aminodiols de différentes configuration (mélange de diastéréoisomère, meso, racémique ou chiral) ont été synthétisés et caractérisés par différentes techniques spectroscopiques. Ces complexes ont ensuite été utilisés comme amorceurs pour la polymérisation par ouverture de cycles de différents monomères hétérocycliques (L/rac-lactide, caprolactone, butyrolactone et triméthylène carbonate) via un mécanisme de coordination-insertion. Tous les complexes se sont révélés efficaces pour la polymérisation des lactides que ce soit en solution à 70°C ou en masse à 130°C avec un bon contrôle. Lors de la polymérisation du rac-lactide, le complexe porteur du ligand racémique a permis d‟obtenir un polylactide partiellement heterotactique, alors que tous les autres complexes n‟ont conduit qu‟à des polymères atactiques. Tous les complexes se sont également révélés très actifs pour la polymérisation de la caprolactone aussi bien en solution qu‟en masse à 70°C avec un bon contrôle. Des études cinétiques réalisées en solution ont permis de mettre en évidence un ordre cinétique unitaire en monomère. De bonnes activités ont également été obtenues pour la polymérisation de la butyrolactone et du triméthylène carbonate. De plus, le bon contrôle de ce type de la polymérisation a permis de synthétiser des copolymères à blocs du L/rac-lactide et de caprolactone. Enfin, la copolymérisation aléatoire de ces 2 monomères a permis de mettre en évidence une réactivité inversée par rapport aux réactions d'homopolymérisation. / A series of titanium isopropoxides complexes coordinated by enantiopure, racemic, meso and diastereomeric aminodiol ligands have been prepared and characterized by spectroscopic techniques. The complexes were tested as initiators for the ring opening polymerization (ROP) of cyclic esters such as L/rac-lactide, caprolactone, butyrolactone and trimethylene carbonate via coordination-insertion mechanism. In lactide polymerizations, all complexes showed significant activity both in solution at 70°C and in bulk at 130°C with a good control. The complex derived from rac-aminodiol ligand gave partially heterotactic polylactide in ROP of rac-lactide, whereas all other complexes yielded atactic polylactides. For caprolactone polymerizations, all complexes were found to be effective initiators under both solution and bulk conditions (up to 60% monomer conversion was reached within 10 min in bulk condition at 70°C), again with good control. Kinetic studies of ROP of lactides and caprolactone in solution conditions have been investigated and showed a first kinetic order in monomer. Significant activities were also observed for (ROP) of butyrolactone and trimethylene carbonate. Block copolymers of caprolactone and lactides were successfully synthesized with these catalytic systems by sequential polymerization techniques. The complexes were also tested as initiators for the production of random copolymers containing caprolactone and lactides and a reverse order of reactivity was observed between lactide and caprolactone compared to homopolymerization.

The work focuses on new processes for the preparation of lactic acid derivatives. The main objective was to verify the feasibility of preparing high molecular weight polylactide using ethyl lactate as a precursor of lactide synthesis. Part of the work is devoted to the new ethyl lactate synthesis method. The experimental part of the thesis is divided into partial key steps on the way from the lactic acid to the high molecular polylactide. The preparation of anhydrous ethyl ester of lactic acid (EtLA) was solved in an innovative way using alcoholysis of the oligomeric lactic acid. A kinetic model for isothermal alcoholysis and equimolar reactants ratio was derived from this method. The ethyl lactate was oligomerized by transesterification into the low and high molecular weight oligomer with the help of newly found catalysts suitable for the reaction medium. Stannous lactate was used as catalyst for oligomerization of the low molecular weight polymer suitable for the preparation of lactide (Mn 1000 g.mol-1). Experimental polymerization of ethyl lactate into high molecular weight product in tens of kDa has been investigated with newly synthesized tetraethyllactoyl titanate, Ti(EtLA)4. The laboratory method was derived for the depolymerization of the oligomer into lactide. Optimal conditions found for lactidation are as follow: temperature 225 ° C, pressure 2 kPa, catalysis 0,05 mol% of stannous lactate (with respect to oligomer lactate units). The prepared lactide was refined to polymer grade purity by distillation and subsequent recrystallization from ethyl acetate and toluene. The method for the preparation of high molecular weight PLA through ROP polymerization of lactide has been optimized. By optimization, suitable catalyst concentration was found in combination with the polymerization temperature and the polymerization length. An equimolar mixture of Tin 2-ethylhexanoate and 1-decanol was used as the catalytic system. The optimal ROP conditions for achieving the maximum molecular weight and suppressed polymer coloration (yellowing) are: catalyst concentration 0,01 mol%, temperature 160 °C, and polymerization length 4 hours. PLA with molecular weight Mw= 447 ± 7,8 kg.mol-1 was prepared at these conditions and good repeatability of the result was achieved. The effect of naturally occurring lactide contaminants and their influence on the course and ROP result was experimentally verified on the optimized polymerization system. The purpose was to explore the effect of lactide contamination with water and ethanol as natural lactide contaminants. The results clearly confirm the orderly lower sensitivity of the polymerization system for the presence of ethanol as compared to water contamination. In the case of the presence of water, the course and the result of the polymerization in terms of both the conversion and achieved molecular weights are negatively affected, even when the water content is in the order of 0,001%. Conversely, the presence of ethanol has a positive effect on lactide conversion and polymer polydispersity. Lactides with an alcohol content of about one-tenth of a percent are suitable to reach molecular weights of PLA similar to commercially available products. This difference shoves a significant advantage in the proposed technology of preparing PLA from ethyl lactate, especially for easier purification of crude lactide into polymer grade purity.

The theoretical part of the diploma thesis is focused on the funcionalization of polyolefins in order to accelerate their degradation and to increase their carbon content from renewable resources with focus on hydroxyacids. The experimental part is focused on preparing samples and studying the properties of the polypropylene and polyethylene blends with the polylactide with different contents of the initiator and the maleic anhydride. Samples were evaluated by determining the degree of conversion maleic anhydride, differential scanning calorimetry, infrared spectroscopy, melt flow index and mechanical properties.

El propósito de esta tesis doctoral fue evaluar la influencia de los diferentes procesos de gestión de residuos, tales como la valorización material, energética y biológica de dos poliésteres clave de la industria del embalaje: el actual no-renovable poli (tereftalato de etileno) (PET) y el potencial candidato para sustituirlo en un futuro próximo, la polilactida (PLA) de base renovable. Se utilizaron diversas plantas piloto para simular las condiciones de la degradación sufrida por PET y PLA en el reciclado mecánico, la pirólisis, la combustión y el enterramiento en suelo. Los cambios fueron monitorizados por calorimetría diferencial de barrido (DSC), análisis dinámico-mecánico-térmico (DMTA), análisis termogravimétrico (TGA), espectrometría infrarroja con transformada de Fourier (FTIR), espectroscopia de correlación 2D-IR para el análisis de gases (EGA), espectrometría de masas MALDI-TOF, microscopía electrónica de barrido (SEM), índice de fluidez de masa fundida (MFR), ensayos de tracción e impacto Charpy y viscosimetría. Se han propuesto, desarrollado y aplicado diversas estrategias y procedimientos analíticos para establecer parámetros fiables para ser utilizados como indicadores de la degradación y por tanto controlar la influencia de cada proceso de valorización en la calidad del material. El comportamiento de PET y PLA reciclados mecánicamente se evaluó en base a sus propiedades químicas, microestructurales, mecánicas y térmicas. Se observó una pérdida general de prestaciones de PET y PLA reprocesado una vez y dos veces, respectivamente. Además, las propiedades de los materiales reciclados de PLA fueron mejores en términos relativos a los productos reciclados de PET. Las descomposiciones térmica y termo-oxidativa causadas por los procesos de pirolisis y combustión se evaluaron sobre la estabilidad térmica, gases emitidos y cinéticas de descomposición. Se destaca el uso de la combustión controlada para ambos polímeros, ya que se necesita menos energía para iniciar la descomposición, y la mezcla de gases que se desprenden es más homogénea. / Badía Valiente, JD. (2011). Strategies and analytical procedures for a sustainable plastic waste management. An application to poly (ethylene terephthalate) and polylactide in the packaging sector [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/12890 / Palancia

Syftet med detta examensarbete var att utveckla ett hållbart ersättningsmaterial till akrylnitrilbutadienstyren plast (ABS), genom att applicera principerna för grön kemi och teknik. ABS är en icke-nedbrytbar plast som till exempel används i slagtåliga produkter för hyttinteriörer. Att utveckla ett nytt material baserat på en kravspecifikation med en specifik produkt i åtanke är av stor betydelse då en initial teoretiska utvärdering kan ge resultat som driver ytterligare innovation och säkerställer en god överensstämmelse med förväntningarna på produkten. Baserat på den genomförda litteraturutvärderingen och kravspecifikationen för produkten valdes polylaktid (PLA) som matrismaterial och blandades med nanofibrer av lignocellulosa (LCNF) och naturgummi (NR), där maleinsyraanhydrid (MA) användes som kompatibilisator. Denna modifieringsstrategi syftade till att förbättra PLAs styrka och minska dess sprödhet. Flera olika parametrar undersöktes, vilka inkluderar olika torkningsmetoder för LCNF:en och olika metoder för MA tillsats före bearbetningen av blandningen. Termisk analys av blandningarna visade att tillsatsen av LCHF och NR inte påverkar nedbrytningstemperaturen för PLA-matrisen i någon större utsträckning, men att kristalliniteten påverkades av dem och de olika behandlingsmetoderna. Styvheten hos de PLA-baserade materialen var likvärdig ABS, medan elasticitet var generellt likvärdig PLA och där tillsatsen av naturgummi förbättrade materialens deformationskapacitet. SEM bilder indikerade att de tre komponenterna var kompatibiliserade, då fibrösa strukturer och sammanflätade nätverk av LCNF och NR i PLA-matrisen kunde observeras. SEM bilderna visade också att NR agglomererade då stora agglomerat och porösa strukturer uppstod, vilket understryker vikten av att optimera framtida blandningsstrategier. En livscykelbedömning (LCA), enligt en vagga-till-graven metod, förväntas visa lägre koldioxidutsläpp för det föreslagna alternativet jämfört med ABS tack vare tillämpningen av principerna för grön kemi vid produktutformningen. Detta bekräftar den ursprungliga hypotesen om en ökad miljövänligheten hos PLA-baserade ersättningsmaterial jämfört med ABS. / This thesis aims to develop sustainable replacement for Acrylonitrile Butadiene Styrene (ABS) in high-impact applications within construction equipment’s Cab interior. Adhering to the principles of Green Chemistry and Engineering, the study focused on developing and accessing an environmentally friendly substitute for ABS, a commonly used non-biodegradable plastic. Investigating novel materials with a tailored requirements list is vital in materials science and engineering. Theoretical approaches can yield results which drive further innovation, ensuring comprehensive alignment with application expectations through a holistic approach to address critical factors. Following this guideline, the chosen alternative was Polylactide (PLA), fortified with a blend of lignocellulose nanofibers (LCNFs) and natural rubber (NR) at a 10 wt.% concentration, with the addition of Maleic Anhydride (MA) as a compatibilizer. This modification strategy aimed to enhance PLA's strength and reduce its brittleness. The investigation encompassed various parameters, including different LCNF drying methods and variations in additive treatment before melt-mixing with PLA. The outcomes from thermal analysis indicated that the inclusion of reinforcements does not significantly affect the degradation temperature of the PLA matrix. Crystallinity, on the other hand, was found to be influenced by the presence of lignocellulose reinforcements and natural rubber, with intriguing nuances emerging from the interplay of these components and different treatment methods. PLA-based alternatives performed similarly to low grade ABS and had similar stiffness levels. In terms of elasticity, most materials behaved similarly to neat PLA, but the addition of natural rubber enhanced their deformation capacity. Successful compatibilization between lignocellulose reinforcements, natural rubber, and PLA was assumed from the observed fibrous structures and interwoven networks within the PLA matrix. Additionally, the presence of aggregates and porous structures highlighted the challenges posed by rubber agglomeration. Finally, the observation of larger agglomerates beyond typical interphase sizes raised concerns about brittle behavior, emphasizing the need for optimizing blend toughening strategies. The input for a Life Cycle Assessment (LCA), following a cradle-to-gate approach, is anticipated to show lower carbon emissions for the proposed alternative in comparison to ABS due to the principles of Green Engineering applied in the product design, denoting the environmental viability of the PLA-based substitute.

The phase behavior of chiral block copolymers (BCPs*), namely, BCPs with at least one of the constituent block is formed by chiral monomers, is studied both experimentally and theoretically. Specifically, the formation of a unique morphology with helical sense, the H* phase, where the chiral block forms nanohelices hexagonally embedded in the matrix of achiral block, is investigated. Such unique morphology was first observed in the cast film of polystyrene-b-poly(L-lactide) (PS-b-PLLA) from a neutral solvent dichloromethane at room temperature with all the nanohelices being left-handed, which would switch to right-handed if the PLLA block changes to PDLA. Further studies revealed that such morphology only forms when the chiral PLLA block possesses certain volume fraction (from 0.32 to 0.36), and the molecular weight exceeds certain critical value (around 20,000 to 25,000 g/mol). Achiral phases such as lamellae, gyroid, cylinder, and sphere will form if the above criteria are not satisfied. Even though the unique H* phase has been extensively studied and utilized for many applications, many fundamental and important questions remain unanswered for such BCP* system. Specifically, how does the molecular level chirality transfer from the several-angstrom scale of the lactide monomer to the tens-of-nanometer size scale of the H* domain morphology? Why is the chirality transfer not automatic for this BCP* system? Is H* phase a thermodynamic stable or metastable phase? Are there other novel phases other than the H* phase that could form within the BCP* system? We aimed at providing answers to the abovementioned questions regarding the formation of chiral H* phase, which is no longer limited to the PS-b-PLLA/PDLA system. We divided our studies into both experimental and theoretical parts. In the experiments, we studied the effect of solvent casting conditions, including solvent removal rate and polymer-solvent interactions, on the formation of the H* phase in PS-b-PLLA/PDLA BCPs*. In addition, we monitored the morphological evolution during solvent casting using time-resolved x-ray scattering technique. We found that good solubility towards both PS and PLLA/PDLA blocks are required for the formation of the H* phase, and microphase separation has to happen prior to crystallization of chiral block. Most importantly, we found that crystalline ordering is not necessary for the H* phase formation. This result led us to propose melt-state twisted molecular packing as the underlying driving force for such helical phase to form, and began our work on the theory for BCPs*. First we built the theoretical tool by incorporating the orientational segmental interactions into the self-consistent field theory (SCFT) for BCPs. As a demonstration, we constructed the phase diagrams for one-dimensional (1D) and two-dimensional (2D) phases, for achiral BCPs with different orientational stiffness. We found that orientational stiffness could serve as another parameter to introduce asymmetry into BCP systems, in addition to conformational and architectural asymmetry. This model was further applied to study the phase behavior of BCPs*, and two phase diagrams were constructed. Another chiral phase, wavy lamellae (L* phase), was observed for BCPs*. The H* phase was found to be a thermodynamic stable phase, as long as the segregation strength ����and chiral strength ��! exceed certain critical values. Energetically favorable cholesteric texture was observed for the chiral segment packing inside the H* phase, which is believed to drive such unusual morphology to form. A simple geometrical argument based on bending of cylindrical microdomain and twisted packing of the bended microdomain can be given to explain the nonlinear chiral sensitivity of BCP* morphology, which further explains the non-automatic feature of chirality transfer in such system.