The context of this thesis is a research project focused on the investigation of a renewable biopolymer-poly(lactic acid) (PLA) as a potential replacement of petroleum-based polymers in advanced nanocomposites reinforced with Microfibrillated cellulose (MFC). MFC is extracted from wood, which is a renewable, sustainable, carbon neutral and recyclable material. This advanced MFC-PLA bio- based composite material is expected to allow for the substitution of petroleum-based plastics in various markets and applications. The specific objectives of the thesis are: 1) to describe the morphological characterization of MFC used for prototype MFC-PLA composites, and 2) to determine the mechanical properties of the prototype MFC-PLA nanocomposites formulation generated in form of thin transparent films. In order to meet this objective it was necessary to: 2.1) develop a methodology for optical strain measurement in transparent thin films; and 2.2) develop an effective methodology for obtaining multiple mechanical properties from small number of specimens of prototype materials subjected to tensile tests. Two types of MFC, one obtained by courtesy of University of Maine and the other purchased from Innventia AB company, were investigated under a field emission scanning electron microscopy (FESEM). The micrographs obtained from FESEM showed that both types of MFC were of complex hierarchical structures, which did not allow qualitative characterization of the morphological features in terms of particulate composites nor cellular solids. Since prototype formulations of MFC-PLA composites were generated in small amounts (typically one Petri dish) in a form of thin transparent films, there was a need for quick and efficient assessment of their key mechanical properties that would provide feedback and guide further prototyping work. An optical measurement method based on digital image correlation (DIC) principle was developed to measure the deformation and strains of the tensile film samples. In our study, the accuracy and precision of the measurement of deformation were ±1.5 µm and 0.4 µm respectively. The corresponding accuracy and precision in terms of strains were ±30 µstrain and 75 µstrain respectively. This method can be successfully used to determine the critical mechanical properties, such as elastic modulus, toughness and Poisson's ratio, of transparent thin films by a single tensile test, all of which require precise strain measurement. In addition, this optical measurement method makes it possible to significantly simplify the testing for measuring essential work of fracture (EWF), an important material property of thin transparent films. In traditional method, measurement of EWF requires large amount of notched specimens. However, our study showed that only a small amount of notched specimens were needed to measure the EWF of a material. This method could not be successfully used to determine EWF from un-notched tensile specimens. / Graduation date: 2012 / Folder labeled "UMaine MFC aerogel" contains SEM micrographs of MFC from University of Maine (referred as type A MFC in the thesis). Two pieces of leaf-like flakes at different locations were cut by Focused Ion Beam (FIB) in order to observe the internal structure of the flakes. Folder "FIB_01 ": a series of SEM micrographs of FIB-cut flake at different magnification levels. Folder "FIB_02 ": another series of SEM micrographs of FIB-cut flake at various magnification levels. Folder labeled "Swedish MFC aerogel" contains SEM micrographs of MFC from Innventia AB company, Sweden (referred as type B MFC in the thesis). There is a series of SEM micrographs of type B MFC aerogel at various magnification levels in this folder.

The objective of this research project was to evaluate the mechanical, morphological, and permeability properties of electrospun blends of polydioxanone and poly(lactic acid) for application as vascular grafts. Mechanical analysis was performed by uniaxial tensile testing to examine the peak load, peak stress, elastic modulus, and strain at break of the fibrous materials. The morphological characteristics of the polymer blends were analyzed using phase contrast microscopy, scanning electron microscopy, and image analysis software. Scanning electron microscopy and image analysis software were used to assess fiber diameter and pore size of electrospun scaffolds. Scaffold permeability measurements were also used to calculate fiber diameter and pore size, and the values were compared to those obtained using image analysis. The material property results acquired from the research suggest that the electrospun polymer blends have potential for use in vascular graft applications.

The blending of lignin as a component in a thermoplastic blend poses a challenge in the form of dispersion and compatibility. Polyesters such as poly(lactic acid) and poly(butylene adipate-co-terephthalate) offer the best opportunity of compatibility in melt blending with lignin due to their ability to form hydrogen bonds. The fractionation of lignin into more homogeneous fractions offers better dispersion and more consistent properties, retaining the toughness of the original polymer in addition to bridging stress transfer between PLA and PBAT. Functionalization of lignin was done by lactic acid grafting. The resulting blend of PLA/PBAT/modified fractionated lignin showed improved interaction between lignin and PLA, but reduced compatibility between lignin and PBAT. This thesis provides a deeper understanding on the effect of lignin heterogeneity, its fractions, and the functionalization of lignin on lignin and bioplastic blends to further the use of a largely produced industrial by-product in high value applications. / Natural Sciences and Engineering Research Council (NSERC) – Lignoworks Biomaterials and Chemicals Strategic Research Network, Canadian Foundation for Innovation (CFI), Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA)

Le poly(acide lactique), PLA, est un polymère biocompatible et biodégradable, qui peut être produit à partir de ressources renouvelables. En conséquence, il a soulevé une attention toute particulière en tant que remplacement éventuel des polymères à base de pétrole. C’est un polyester aliphatique ayant des propriétés telles que module élevé, haute résistance, biocompatibilité et est donc un matériau prometteur pour diverses applications telles que les implants, l’encapsulation de médicaments et l'emballage. A cause de sa faible température de transition vitreuse, le PLA a une faible résistance thermique et les applications sont donc limitées à celles qui ne sont pas associées à des températures élevées. En outre, ce polymère souffre d'un faible degré de cristallinité. L'augmentation du taux de cristallinité dans de nombreuses techniques de mise en forme, telles que le moulage par injection, est nécessaire. Il y a plusieurs façons d'augmenter le niveau de cristallinité du PLA. Ces procédés comprennent l'utilisation d'agents nucléants, de plastifiants, ou de combinaisons d'agents plastifiants et de nucléation. La cristallisation du PLA à l'état fondu se présente sous deux formes cristallines légèrement différentes connues sous les noms α et α'. Cette étude compare la capacité d'auto-nucléation de ces deux formes cristallines par auto-nucléation. Ceci est réalisé en comparant les températures de cristallisation lors du refroidissement des échantillons préalablement cristallisés à diverses températures, puis de nouveau chauffé à une température dans la plage de fusion partielle du PLA. Dans la deuxième étape, l'effet des paramètres cinétiques et le poids moléculaire du PLA sur l'efficacité de nucléation des PLA phases cristallines a été étudié. Cette partie de l’étude ouvre une nouvelle voie pour comprendre le rôle des modifications cristallines du PLA qui mènent aux conditions optimales pour la cristallisation du PLA. La mise en forme des polymères implique des contraintes de cisaillement et d’élongation, ce qui implique une cristallisation induite par l’écoulement et la solidification qui s’en suit. Les propriétés mécaniques des produits finals dépendent du degré de cristallisation et de la nature des cristaux formés. Par conséquent, l'optimisation du procédé nécessite une bonne compréhension de la façon dont l’écoulement influence la cristallisation. Le type d'écoulement peut jouer un rôle important sur la cristallisation. Par exemple, l'écoulement élongationnel provoque l’orientation et l’étirement des molécules dans le sens de l'extension, comme dans le cas de la mise en forme de fibres et le soufflage de film, en aidant le processus de cristallisation induite par l'écoulement. Une littérature abondante existe sur la ii cristallisation des thermoplastiques classiques induite par l'écoulement. Cela dit, moins d'attention a été accordée à l'effet de l'écoulement de cisaillement et d'allongement sur la cristallisation du PLA. Comme étudié dans la dernière partie de ce document, l'effet du poids moléculaire sur la cristallisation induite par cisaillement du PLA est rapporté. Pour cela, trois différents PLA à faible, moyen et haut poids moléculaire ont été préparés par réaction d'hydrolyse. Ensuite, en utilisant un rhéomètre oscillatoire, l’effet du cisaillement sur la cinétique de cristallisation du PLA a été examiné. / Abstract : Poly(lactic acid), PLA, is a biocompatible and biodegradable polymer that can be produced from renewable resources. As a result, it has raised particular attention as a potential replacement for petroleum-based polymers. It is an aliphatic polyester with properties such as high modulus, high strength, and biocompatibility and is thus a promising material for various applications such as implants, drug encapsulation, and packaging. In the wake of low glass transition temperature, PLA has a low heat resistance and its application is limited to those not associated with high temperatures. In addition, this polymer suffers from a low degree of crystalinity. Increasing the crystallization rate in many processing operations, such as injection molding, is required. So far, many routes have been found to improve the crystallinity of PLA. These methods include using nucleating agents, plasticizers, and combination of nucleating agents and plasticizers together. PLA crystallization in the melt state results in two slightly different crystalline forms known as α and α’forms. This thesis compares the self-nucleation ability of these two crystal forms by self-nucleation. This is achieved by comparing crystallization temperatures upon cooling for samples previously crystallized at various temperatures and then re-heated to a temperature in the partial melting range for PLA. In the second step, we study the effect of molecular weight of PLA on the nucleation efficiency of PLA crystalline phases. This part of the investigation opens a new pathway to understand the role of PLA crystalline phases on the optimal condition for its crystallization kinetics. Polymer processing operations involve mixed shear and elongational flows and cause polymer molecules to experience flow-induced crystallization during flow and subsequent solidification. The mechanical properties of the final products are significantly dependent upon the degree of crystallization and types of formed crystals. Therefore, optimization of any polymer process requires a good understanding of how flow influences crystallization. The type of flow can play a significant role in affecting crystallization. For example, elongational flow causes molecules to orient and stretch in the direction of extension, as in the case of fiber spinning and film blowing, helping the process of flow-induced crystallization. An extensive body of literature exists on flow-induced crystallization of conventional thermoplastics. Having said that, less attention has been paid to the effect of shear and elongational flow on the PLA crystallization kinetics. As investigated in the final part of this thesis, the effect of iv molecular weight on the shear-induced crystallization of PLA is reported. For this, low, medium and high molecular-weight PLAs were prepared from a high molecular weight one by a hydrolysis reaction. Next, by means of a simple rotational rheometry, effect of the shear flow was examined on the crystallization kinetics of these three PLAs.

Doctor of Philosophy / Department of Grain Science and Industry / X. Susan Sun / Poly(lactic acid) (PLA), a synthetic biopolymer, is a promising substitute of some petroleum-based polymers due to its mechanical and biodegradable properties. But, because of the high cost of PLA (compared to those petroleum plastics for disposable application), starch has been incorporated into PLA to reduce cost and accelerate the biodegradability rate of the composites. But, the addition of starch as filler to PLA decreased mechanical performance of the composite. The addition of methylenediphenyl diisocyanate (MDI) into PLA/starch blends improved drastically the mechanical properties of the composite. Results from thermal-degradation analysis showed that PLA had the highest Arrhenius activation energy and strongest thermal endurance of all samples, followed by PLA/starch/MDI and PLA/starch. Aged samples exposed to fluctuating humidity storage conditions significantly decreased their performance. But, storing the samples in plastic bags could minimize degradation of properties. PLA and its composites with starch would not significantly affect application function when they are stored in controlled environment. PLA and PLA/starch based composites sealed in plastic bags can be stored in fluctuating humidity conditions (30-90% RH) for up to 30 days. Tensile strength, elongation, and damping increased with average particle size of starch granules (APS). But, declination of these properties was detected with APS larger than 45 mm. Crystallinity increased as the APS decreased. Young’s modulus, storage modulus, and moisture absorption were not significantly affected by the starch APS. The use of MDI as a coupling agent altered the role of starch APS on those properties of poly(lactic acid)/starch composite. The oxidation of the primary alcohol group on C6 of starch molecules up to 10% degree of substitution did not significantly affect the mechanical properties of PLA/starch/MDI, but the composites showed a reduced inelastic deformation (tensile curve) and significant increase in storage modulus and damping. Results suggest that a substitution of hydroxyl group on C6 of starch molecules for carboxyl group (up to 10%) increased the strengthening effect of MDI enough to reduce inelastic deformation of the composites upon load, but not enough to enhance mechanical properties.

Le psoriasis est une dermatose inflammatoire chronique affectant 2 à 3 % de la population européenne. Les cytokines pro-inflammatoires ont un rôle crucial dans la pathogénèse du psoriasis. Parmi les voies de signalisation cytokinique, l'étude de la voie JAK/STAT a conduit au développement de traitements systémiques efficaces. Cependant, les essais cliniques évaluant les inhibiteurs JAK/STAT impliquent en grande majorité des administrations orales, la voie topique restant marginale. Le développement de formulations innovantes pour application topique contenant des inhibiteurs JAK/STAT semble être une stratégie prometteuse dans le cadre du psoriasis. Les nanoparticules de poly(acide lactique) (NP PLA) développées au laboratoire ont été étudiées pour la délivrance topique de principes actifs. Ce sont des vecteurs efficaces, qui s'accumulent dans les follicules pileux. De plus, l'encapsulation d'actifs dans des NP PLA permet une libération spécifique au niveau du site d'action, et donc une réduction de la toxicité. L'objectif de ce travail est d'élaborer des formulations semi-solides de NP PLA contenant un inhibiteur JAK/STAT pour le traitement topique du psoriasis, tout en caractérisant un modèle in vivo de psoriasis induit par applications d'Imiquimod. Cette caractérisation des lésions psoriasiformes permettra l'évaluation in vivo des nanoformulations topiques contenant des inhibiteurs JAK/STAT. Cinq formulations ont été élaborées puis caractérisées afin de répondre aux attentes galéniques pour une application topique. L'intégrité des NP PLA a été vérifiée, et la pénétration/perméation de molécules modèles à travers de la peau de souris inflammée a été évaluée / Psoriasis is a chronic inflammatory skin disease, affecting 2 to 3 % of European population. Inflammatory cytokines play a crucial role in the pathogenesis of psoriasis. Among cytokines signaling pathways, JAK/STAT pathway has been widely investigated, leading to the development of efficient systemic agents. However, current clinical trials evaluating JAK/Sat inhibitors mainly involve oral administrations, with few investigations on topical route. Developing innovative drug delivery systems for topical application of JAK/STAT inhibitors seems a promising strategy for psoriasis treatment. Poly(lactic acid) nanoparticles (PLA NPs) developed in the laboratory have been widely investigated for topical drug delivery and are efficient carriers for local dermatotherapy, especially through hair follicles. Moreover, drug encapsulation in PLA NPs for topical delivery allows a specific delivery to the site of action, and thus a decreased toxicity.The aim of this work was to elaborate semi-solid formulations of PLA NPs containing JAK/STAT inhibitors for topical treatment of psoriasis, while characterizing an in vivo model of Imiquimod-induced psoriasis in mice. This characterization of psoriasis-like skin lesions in Imiquimod treated mice provided key tools for in vivo evaluation of topical nanoformulations containing JAK/STAT inhibitors. Five formulations have been developed and then characterized in order to meet galenic criteria for topical drug administration. PLA NPs integrity was assessed, and penetration/permeation profiles of model dugs through inflamed mice skin were determined

Orientadores: Ana Rita Morales, Otávio Cavalett / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-27T19:01:47Z (GMT). No. of bitstreams: 1 CosatedeAndrade_MarinaFernandes_M.pdf: 2991365 bytes, checksum: df7e463a288c5c88feea3df3157d956a (MD5) Previous issue date: 2015 / Resumo: Este projeto teve como objetivo realizar uma Avaliação do Ciclo de Vida comparando três formas de destinação do poli(ácido láctico) (PLA) e estudar a reciclagem deste polímero, que pode ser mecânica ou química. A reciclagem mecânica foi realizada por duas extrusões do PLA. No segundo processamento, o polímero proveniente da primeira extrusão foi dividido em duas partes, sendo que uma porção recebeu adição de um extensor de cadeia comercial. As amostras obtidas foram caracterizadas por Calorimetria Diferencial Exploratória (DSC), Cromatografia por Permeação em Gel (GPC), Índice de Fluidez, Análise Termogravimétrica (TGA), ensaio de resistência ao impacto Izod e ensaio de tração. Os resultados obtidos mostraram que o número de extrusões diminuiu a massa molar, o índice de fluidez e a estabilidade térmica e aumentou a cristalinidade do polímero. A presença do extensor de cadeia causou a recuperação dessas propriedades. Além disso, o módulo de elasticidade e o alongamento na ruptura sofreram alterações importantes com o aumento da cristalinidade do material. A reciclagem química foi realizada pela hidrólise do PLA, que gera ácido láctico, e posteriormente pela polimerização do ácido láctico, em que é obtido novamente PLA, através da policondensação direta. O ácido láctico foi caracterizado por Cromatografia Líquida de Alta Eficiência (HPLC) e o rendimento da reação obtido foi acima de 95%. O PLA polimerizado foi identificado por Espectroscopia do Infravermelho por Transformada de Fourier (FTIR) e sua massa molar foi medida por Cromatografia por Permeação em Gel (GPC). Os resultados da Avaliação do Ciclo de Vida para os métodos e categorias estudados mostraram que a reciclagem mecânica apresentou o menor impacto ambiental, seguida pela reciclagem química e pela compostagem. Dentre as formas de reciclagem, o insumo mais importante foi o consumo de energia elétrica / Abstract: This project aimed to conduct a Life Cycle Assessment comparing three forms of poly(lactic acid) (PLA) disposal and to study the mechanical and chemical recycling of this polymer. Mechanical recycling was performed by two extrusions of PLA. In the second extrusion, part of the material was processed with a commercial chain extender. The samples were characterized by Differential Scanning Calorimetry (DSC), Gel Permeation Chromatography (GPC), Melt Flow Index, Thermogravimetric Analysis (TGA), Izod test and Tensile test. The results showed that the molecular weight, Melt Flow Index and thermal stability decreased and the crystallinity degree of the polymer increased with the extrusion number. The presence of a chain extender recovered these properties. Furthermore, Young modulus and elongation at break undergo important changes with the crystallinity increase. The chemical recycling was performed by hydrolysis reaction, which produced lactic acid. PLA was obtained through the direct condensation polymerization from lactic acid monomer. Lactic acid was characterized by High Performance Liquid Chromatography (HPLC) and the reaction yield was above 95%. The polymerized PLA was identified by Fourier Transform Infrared Spectroscopy (FTIR) and Gel Permeation Chromatography (GPC). Considering the methods and impact categories studied, the Life Cycle Assessment showed that mechanical recycling had the lowest environmental impact, followed by chemical recycling and composting. Among the forms of recycling, the most important input was the electricity consumption / Mestrado / Ciencia e Tecnologia de Materiais / Mestra em Engenharia Química

Teoretická část předložené dizertační práce popisuje princip radikálového roubování a faktory ovlivňující reakční průběh. Radikálové roubování poly(mléčné kyseliny) (PLA) reaktivní modifikací je vhodnou technikou přípravy biodegradabilních polymerních materiálů s rozličnými vlastnostmi. Současný stav problematiky modifikace poly(mléčné kyseliny) radikálovým roubováním v tavenině je obsahem literární rešerše včetně možných aplikací. Experimentální část se zabývá modifikací PLA anhydridem kyseliny itakonové (IAH) radikálovým roubováním v tavenině. Reakce byla iniciována 2,5-bis(tert-butylperoxy)-2,5-dimethylhexanem (L101). V první části je průběh radikálového roubování pozorován “in situ” pomocí diferenciální kompenzační kalorimetrie (DSC) a termogravimetrické analýzy (TGA). Exotermní pík na DSC záznamu odpovídá průběhu radikálové reakce, na jehož základě lze definovat aktivační energii reakce. Průběh TGA křivky “in situ” radikálové reakce umožňil detekovat vedlejší produkty vznikající v průběhu radikálové modifikace. Ve druhé části byla PLA funkcionalizována reakcí v diskontinuálním laboratorním mixéru za reakčních podmínek navržených dle poločasu rozpadu zvoleného iniciátoru a zpracovatelských podmínek PLA. Reakční teplota 190 °C byla stanovena výpočtem z Arrheniovy rovnice pro reakční čas 6 min. Uvedené reakční parametry byly zvoleny s ohledem na kinetiku rozkladu L101 a potlačení degradace PLA. Infračervená spektroskopie (FTIR) potvrdila navázání IAH na PLA řetězec na základě výskytu –CH2 vibrací s absorpčními pásy při vlnočtu 2860 a 2920 cm-1. Vzrůstající intensita absorpčního pásu 1750 cm-1 potvrdila přítomnost minoritních C=O vibrací anhydridového kruhu překrytých dominantními C=O vibracemi PLA řetězce. Nukleární magnetická rezonance (1H-NMR) nepotvrdila roubování oligomerního IAH na PLA. Koncentrace reaktantů ve zvoleném rozsahu (0.5–10 hm % IAH, 0.1–2 hm % L101) byla použita pro posouzení jejího vlivu na obsah naroubovaného IAH a míru vedlejších reakcí, např. -štěpení, větvení a síťování. Při vysoké koncentraci IAH a L101 byla potvrzena homopolymerace IAH i přes její zanedbávání v tématicky podobných studiích. Tvrzení o IAH homopolymeraci bylo podpořena výsledky kolorimetrické analýzy, charakterizací vzorků připravených polymerací IAH za podmínek radikálového roubování a termickou stabilitou frakcí extrahovaných z PLA-g-IAH. Radikálovou modifikací PLA došlo ke zvýšení flexibility polymerních řetězců díky objemné struktuře IAH navázané na PLA řetězci, což se projevilo poklesem teploty skelného přechodu (Tg). Zvýšený obsah amorfní fáze, hydrofilní chování, rozvětvená struktura a štěpení řetězců má pozitivní vliv na zvýšenou biodegradabilitu PLA-g-IAH v porovnání s nemodifikovanou PLA. Neradikálová degradace, probíhající v průběhu zpracování PLA, byla prokázána změnou tokových vlastností taveniny. Tento nežádoucí jev byl potlačen přídavkem tzv. “prodlužovače řetězců” obsahujícího reaktivní epoxy skupiny. Reakce mezi epoxy skupinami a karboxylovými skupinami byla potvrzena pomocí FTIR a změnou reologických vlastností PLA-g-IAH.

The relationship between polymer chain architecture, crystallization behavior, and morphology formation was investigated. The structures formed are highly dependent on chain configuration and crystallization kinetics. Poly(lactic acid) (PLA) and Poly(ethylene-co-vinyl acetate) (EVA) random copolymers were studied. Sample characterization was performed using a variety of techniques, including spectroscopy, scattering, and calorimetry. In PLA, structural differences between α’ and α crystalline phases were analyzed using cryogenic infrared and Raman spectroscopy. Compared to the  crystal, the ’ crystal has slightly looser packing and weaker intermolecular interactions involving carbonyl and methyl functional groups. Simulations in conjunction with Raman scattering analyzed the conformational distortion of the α’ phase. The conformation of an α’ chain was determined to have tg’t-103 conformation with tg’t-31 units randomly distributed along the chain. Departure of the O-C α dihedral angle was also confirmed. The structural disorder leads to different thermal properties for α’ and α crystalline forms, which was quantified by measuring the enthalpic change at melting for both crystals ( = 57 ± 3 J/g and =9 6 ± 3 J/g). The transformation from α’ to α and the mechanism of order formation in PLA were also elucidated. The relationship between chain configuration of EVA random copolymers and crystallization behavior was established. For three different EVA samples, the distribution of methylene sequences was calculated and compared to a distribution of crystallite sizes formed. This comparison revealed that only a small fraction of the total methylene segments present actually crystallized. Cocrystallization with highly mobile oligomers was explored to enhance the crystallization of EVA copolymers. When blended, EVA28 (28 weight percentage) cocrystallizes with C36H74 n-alkane resulting in faster crystallization kinetics and a higher degree of crystallinity. The observed increase in degree of crystallinity was directly related to the chain configuration. Compositional mapping using Raman spectroscopy provided evidence for oligomer nucleation. The cocrystallization kinetics and morphology of EVA and n-alkane blends was found to depend on the chain length of oligomer. In both systems studied, crystallization kinetics determines the morphologies formed, which are undoubtedly related to the details of molecular architecture.

Yes / The shape memory effect of highly oriented long‐chain‐branched poly(lactic acid) (LCB‐PLA) prepared through solid‐phase die drawing technology was studied by comparison with PLA. When the recovery temperature increased from 60°C to 120°C, for PLA, only one‐step recovery at about 80°C can be observed and the recovery ratio was below 21.5%, while, for LCB‐PLA, multiple recovery behavior with high recovery ratio of 78.8% can be achieved. For oriented PLA, the recovery curve of the final sample showed the same trend with that of sample suffering just free drawing; while for oriented LCB‐PLA, the recovery curve of the final sample showed the same trend with that of sample suffering just die drawing. After shape recovery, the mechanical properties of LCB‐PLA showed a linear downward trend with the recovery temperature. Together with amorphous phase, the oriented mesomorphic phase, which formed during solid die drawing, can act as switching domains. And thus, upon heating, the chain segment of amorphous phase relaxed at first and triggered the first macroscopical shape recovery, leading to the decrease of long period (Lac) and the thickness of the amorphous layer (La). Then, with further increasing temperature, the oriented mesomorphic phase gradually relaxed resulting subsequently multi‐shape recovery, and the Lac and the La further decreased. Therefore, by regulating the recovery temperature of oriented LCB‐PLA, the shape recovery ratio and mechanical strength can be controlled effectively, and thus the self‐reinforced and self‐fastening effect can be achieved simultaneously for PLA as bone fixation material.