Resumo: A Biologia Sistêmica visa a compreensão da vida através de modelos integrativos que enfatizem as interações entre os diferentes agentes biológicos. O objetivo é buscar por leis universais, não nas partes componentes dos sistemas mas sim nos padrões de interação dos elementos constituintes. As redes complexas biológicas são uma poderosa abstração matemática que permite a representação de grandes volumes de dados e a posterior formulação de hipóteses biológicas. Nesta tese apresentamos as redes biológicas integradas que incluem interações oriundas do metabolismo, interação física de proteínas e regulação. Discutimos sua construção e ferramentas para sua análise global e local. Apresentamos também resultados do uso de ferramentas de aprendizado de máquina que nos permitem compreender a relação entre propriedades topológicas e a essencialidade gênica e a previsão de genes mórbidos e alvos para drogas em humanos / Abstract: Systems Biology aims to understand life process through integrative models that emphasize the interactions among biological agents. The goal is to search for universal laws, not in the description of systems parts, but on interactions patterns among systems elements. Biological networks are a powerful mathematical abstraction that allows the representation of large experimental datasets and the formulation of biological hypothesis. In this thesis we investigate biological networks that assemble information of: metabolism, protein interaction and regulation. We discuss the network construction methodology and mathematical tools to describe its local and global properties. We also present results, obtained through machine learning tools, expressing the implication of topological properties on gene essentiality, morbidity, and drugability on human genes

Polymer-based drug delivery systems have fantastic potential in chemotherapy as they can reduce drug side effects, help in patient compliance and provide targeting. Nanoprecipitation is used to encapsulate small drug molecules into polymer nanoparticles to form a drug delivery system. A major obstacle in polymer-based drug delivery systems reaching the clinic is their inability to load sufficient drug molecules. Little is known about the processes involved in the encapsulation of drug molecules into these delivery systems. An insight into the processes that govern the formation of these particles and encapsulation of small drug molecules within them is therefore desirable. We used molecular dynamics to model nanoprecipitation by simulating the dispersion of an acetone drop, containing polymer, into water containing drug. To allow sufficient dispersion of acetone a large amount of water is required, thus coarse-graining becomes mandatory. However, we maintain accuracy for our polymer-drug interactions by using a multiscale force field. Atomistic polymer and drug molecules contain coarse-grain virtual sites which facilitate interactions with the coarse-grain solvent molecules. We also employed fully atomistic reference simulations via resolution transformation to optimise our multiscale force field. This thesis details the theory and design behind this model of nanoprecipitation including how other techniques produced inferior results. Initial simulations with our multiscale model matched an experimental trend and were shown to be accurate relative to atomistic reference simulations. We also analysed a fully atomistic simulation of nanoprecipitation that took several months to complete. This atomistic simulation was used as a reference to update the multiscale force field. The updated force field improved on some aspects of the simulation but there are still areas that need improvement. Insight from the simulations provides an understanding of the experimental results and trends. The transferability of the model should help in designing more efficient polymer-based drug delivery systems in the future. We conclude with future work on modelling polymer-based drug delivery systems including alternate methods to gain understanding of not only drug incorporation but also drug release.

Development of novel biodegradable polymers from renewable resources has attracted attention due to the limitations associated with polymers obtained from petroleum resources. The objective of the work presented in this thesis was to develop various novel biodegradable amphiphilic block copolymers from commercially available sustainable feedstocks for drug delivery applications. Synthesis was performed using a reported method under mild reaction conditions. Renewable δ-decalactone was chosen as a key monomer to synthesise novel amphiphilic block copolymers via ROP using PEG as initiator. A diblock (i.e. mPEG-b-PDL) and a triblock (i.e. PDL-b-PEG-b-PDL) copolymer of poly(decalactone) (PDL) was synthesised and purified successfully. Additionally, a novel triblock copolymer (i.e. mPEG-b-PDL-b-PPDL) was synthesised using ω-pentadecalactone as monomer and mPEG-b-PDL as initiator via ROP to generate a copolymer with different physical properties. Further, a di-block copolymer of ε-caprolactone (i.e. mPEG-b-PCL) was synthesised for comparative studies with novel block copolymers. Micelles of synthesised block copolymers were fabricated using a reported nanoprecipitation method. Micelles fabricated from these novel block copolymers were of sizes <200nm and possessed low critical micelle concentration (CMC) values. Curcumin and Amphotericin B were successfully encapsulated in the novel block copolymer micelles via nanoprecipitation method. The results obtained from curcumin loading and release studies suggested that these novel PDL block copolymers could perform in similar fashion when compared with poly(caprolactone) (PCL) block copolymer micelles. However, in subsequent study micelle of mPEG-b-PDL gave high loading content compared to mPEG-b-PCL micelles when amphotericin B was used as a drug. Further, a preliminary in vitro degradation study of mPEG-b-PDL micelles was performed and the results proposed that the ester linkage of PDL chain were susceptible to hydrolytic degradation in physiological condition. Additionally, in vitro cytotoxicity studies performed on HCT-116 human colon cancer cells revealed that the novel mPEG-b-PDL micelles have similar toxicity profiles when compared to the well-established mPEG-b-PCL micelles. Ligand mediated targeting efficiency of novel diblock copolymer micelles was also studied for potential future applications in cancer therapy. Amphiphilic block copolymers using PEG and PDL were synthesised via click chemistry to generate functionalised block copolymers. Folic acid and rhodamine B were used as targeting ligand and tracker dye respectively. Mixed micelles fabricated from functionalised block copolymers (i.e. FA-PEG-b-PDL, RhB-PEG-b-PDL and mPEG-b-PDL) were tested on folate receptor positive (MCF-7 FR+ve) and folate receptor negative (A549 FR-ve) human cancer cell lines for receptor mediated endocytosis. The acquired confocal images demonstrated the nonspecific uptake of the PEG-b-PDL micelles formulations (targeted and non-targeted) in both cell lines selected in current study. The results obtained from this thesis study suggested that the synthesised novel PDL block copolymer micelles have potential to act as a novel drug delivery system. However, further studies have been proposed to explore the possible applications of these renewable block copolymers.

CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior / Neste trabalho um modelo atmosfÃrico de resoluÃÃo de nuvens e um modelo da camada superior do oceano sÃo usados, isolados e acoplados, com a finalidade de se estudar, em duas dimensÃes (plano xz) a circulaÃÃo de Walker. As simulaÃÃes com o modelo oceÃnico, forÃadas por ventos zonais sÃo utilizadas para imitar o perfil climatolÃgico das temperaturas no Oceano PacÃfico Equatorial e obter a influÃncia da convecÃÃo sobre a temperatura da superfÃcie do oceano na parte equatorial oeste do PacÃfico. No modelo atmosfÃrico, a convecÃÃo atmosfÃrica Ãmida e o fluxo de grande-escala sÃo impulsionados por um gradiente linear de grande-escala da temperatura da superfÃcie do mar. As caracterÃsticas bÃsicas da circulaÃÃo de Walker e a realimentaÃÃo de ondas curtas das nuvens sobre a temperatura da superfÃcie sÃo estudadas. O acoplamento entre os modelos oceÃnico e atmosfÃrico à forÃado somente pelo perfil de temperatura das Ãguas mais quentes na parte oeste e Ãguas frias na parte leste da bacia oceÃnica. Algumas caracterÃsticas reais de processos fÃsicos de grande e de pequena-escala, tal como a correlaÃÃo entre salinidade e temperatura, sÃo relativamente bem reproduzi das em um modelo bidimensional acoplado.

Para investigar o efeito de diferentes sistemas de manejo do solo no estoque de carbono e na composição química da matéria orgânica ao longo do perfil do solo e sobre sua capacidade de retenção de carbono, foram desenvolvidos dois estudos em Latossolos subtropicais. No primeiro estudo, foi investigada a influência do sistema de plantio direto (PD) e do sistema de preparo convencional (PC) do solo sobre o estoque de carbono e qualidade da matéria no perfil do solo e nas frações leve livre (FLL), leve oclusa (FLO) e pesada (FP) até 20 cm de profundidade de um Latossolo Bruno (LB) e de um Latossolo Vermelho (LV). No segundo, foi estudado o efeito de sistema de manejo do solo (PD e PC) sobre a capacidade de retenção de carbono nas frações silte e argila dos mesmos Latossolos do estudo I. Para tais finalidades, foram coletadas amostras deformadas de solo nas camadas de 0-2,5; 2,5-5; 5-10; 10-20; 20-30; 30-40; 40-60; 60-80 e 80-100 cm e indeformadas nas profundidades 0-5; 5-10 e 10-20 cm. O teor de carbono do solo e das frações foi determinado por combustão seca e a composição química da matéria orgânica foi analisada por técnicas espectroscópicas. Sob PD, o estoque de C foi superior (9,7 e 12,2 Mg ha-1 nas camadas de 0-2,5 cm e de 2,5-5 cm respectivamente) ao observado sob PC até 5 cm de profundidade (6,4 e 8,5 Mg ha-1 nas camadas de 0-2,5 cm e de 2,5-5 respectivamente) no LB e até 2,5 cm no LV (5,6 Mg ha-1 sob PD e 4,7 Mg ha-1 sob PC). A subsuperfície do solo armazenou 69% (no LB) e 75% (no LV) do carbono aportado anualmente ao perfil do solo em virtude do manejo do solo sob PD. Tanto no solo inteiro quanto nas frações (FLL, FLO e FP), o PD favoreceu a preservação de estruturas orgânicas lábeis e tal efeito foi mais pronunciado no LB em comparação ao LV. O LB apresentou maior retenção de C nas frações silte (52 g kg-1 sob PD e 41 g kg-1 sob PC) e argila (61 g kg-1 sob PD e 54 g kg-1 sob PC) do que o LV (Csilte = 32 g kg-1 sob PD e 31 g kg-1 sob PC e Cargila = 25 g kg-1 sob PD e sob PC), independente do manejo de solo. No LB, o sistema PD promoveu maior retenção de C nas frações comparativamente ao PC, enquanto no LV, a capacidade de retenção de C das frações não diferiu em função do manejo. Em ambos os Latossolos, a retenção de C pode ser explicada por dois processos principais de sorção; interação organo-mineral e auto-associação da matéria orgânica em estruturas tipo micelares. No LV, este último processo parece ser predominante, ao passo que no LB, ambos os mecanismos contribuem igualmente para o sequestro de carbono. / Two studies were developed in Oxisols for investigating the effect of different management systems on soil C stocks and on chemical composition of organic matter along the profile, and on the carbon retention capacity. In the first study, we investigated the the effect of no-tillage (NT) and conventional tillage (PC) on C stocks and composition of organic matter of the soil profile and of the free light fraction (FLF), occluded light fraction (OLF) and heavy fraction (HF) to 20 cm depth of a Brown Oxisol (BO) and a Red Oxisol (RO). In the second study, we investigated the C retention capacity in the silt and clay fractions of the Oxisols used in the first study. For these purposes, soil samples were collected in soil layers of 0-2.5, 2.5 to 5, 5-10, 10-20, 20-30, 30-40, 40-60, 60-80 and 80 -100 cm and undisturbed soil samples in the depth of 0-5, 5-10, 10-20 cm. The C content in soil and fractions was determined by dry combustion and chemical composition of organic matter was analyzed by spectroscopic techniques. Under NT, C stock was greater (9.7 e 12.2 Mg ha-1 in surface layers 0-2.5 cm and 2.5-5 cm respectively) than that found under CT (6.4 e 8.5 Mg ha-1 in surface layers 0-2.5 cm and 2.5-5 cm respectively) in the BO and up to 2.5 cm in the RO (5.6 Mg ha-1 under NT and 4.7 Mg ha-1 under CT). The subsoil stored 69% (in BO) and 75% (in RO) of carbon added annually to the soil profile due to soil management under NT system. In bulk soil and in the fractions (FLF, OLF and HF) as well, the NT promoted the preservation of labile organic structures. Such effect was more pronounced in BO in comparison to RO. The BO showed a greater C retention in silt (52 g kg-1 under NT and 41 g kg-1 under CT) and clay fractions (61 g kg-1 under NT and 54 g kg-1 under CT) than RO (Csilt = 32 g kg-1 under NT and 31 g kg-1 under CT and Cclay = 25 g kg-1 under NT and CT), regardless the soil management. Furthermore, in BO, the NT system promoted a greater C retention in the two fractions compared to CT, while in RO, the C retention capacity of the silt and clay fraction was not affected by the management system. In both Oxisols, C sequestration can be explained by two main sorption processes: organo-mineral interaction and self-assemblage of organic matter in micelle-like structures. In the RO, the latter process seems to be predominant, whereas in BO both mechanisms contribute equally to the C sequestration.

Studies on electronic patient medication record (ePMR) systems that are used in community pharmacy in England have focused primarily on the ability of these systems to highlight potentially hazardous co-prescriptions and prevent clinical hazards and harm to patients. As such, there is a scarcity of literature on the use of ePMR systems, other safety functionality of the systems and user responses to alerts. This thesis aims to fill this gap by examining the functionality of ePMR systems used in community pharmacy in England, focusing on safety features and alerts. This research was conducted in England between July 2010 and July 2013. Evidence for the effectiveness of safety features and alerts in ePMR systems during the dispensing process was evaluated through a systematic review of the literature. Stakeholder perspectives of ePMR systems’ functionality were then obtained through qualitative interviews. The performance of ePMR systems licensed for the electronic prescription service (release 2) in the community pharmacy setting were then assessed using a simulated observational testing approach. Ethnographically informed observations in community pharmacies were subsequently used to study how community pharmacy professionals use ePMR systems and manage alerts in practice. The systematic review included five studies - three randomised controlled trials and two before-after studies, with drug-drug interaction (1), drug-laboratory (2), drug-pregnancy (1) and drug-age (1) alerts. The review revealed that ePMR systems in conjunction with embedded safety features are effective in picking up clinical hazards at the point of dispensing. However, there are problems of false alerts and inconsistencies in alert management. Empirical findings indicate that there are significant issues with the way ePMR systems and alerts are designed and used. Thirty participants took part in the qualitative interviews - community pharmacy professionals (13), health care policy makers (5), legal practitioners specialising in pharmacy (3), ePMR systems’ software vendors (4) and ePMR systems’ software knowledgebase creators (5). Participants attributed alert ineffectiveness in community pharmacy practice to factors such as lack of harmonisation of alert severity levels in systems, poor alert design, over-presentation of alerts and absence of management advice in alerts. Five unique ePMR systems were evaluated in eight participating pharmacies with a sixth ePMR system assessed in a demonstration setting. The systems’ performance was variable and sub-optimal. The ethnographically informed observations took place in the eight pharmacies where system assessment was conducted. The observations revealed that the current design of ePMR systems and presentation of alerts are limiting the quality of support provided to pharmacists and their support staff. This research is part of a growing body of work on the functionality of ePMR systems, their safety features and alerts indicating that ePMR systems require improvements if they are to effectively support patient safety and consistently deliver better patient outcomes. The findings highlight the need to incorporate patient context into alerting to increase alert relevance. In addition, system vendors need to make use of the evidence in the literature to design effective ePMR systems, alerts and user interfaces. An authoritative body should set the minimum specifications for ePMR systems and alerts, and identify the critical alerts that pharmacy professionals should evaluate at the point of dispensing. Additionally, training of pharmacy professionals in health information and communication technology is required to improve patient safety. This should cover areas such as informatics, human factors, safety culture, clinical decision-making, alert management, risk management and communication. Many of the findings are likely to be relevant to similar medication record systems in ambulatory pharmacies around the world; however, further work is required to understand fully the extent of the issues identified in this research.

Ink-jet printing is a precise and versatile technique that accurately deposits small volumes of solutions (pico litres) in specific locations. Recently inkjet printing has attracted increasing attention in the pharmaceutical industry because of its ability to deliver low adjustable doses, variable drug release profiles and drug combinations suitable for the paradigm of personalised medicines. The significant growth in the aging population and the rise in the number of patients suffering from multiple chronic diseases are the key drivers. The current traditional tablet compression methods are largely limited in terms of flexibility and complexity of dosage form. There is a need for new innovative technologies that can produce bespoke medicines in a relatively cheap and efficient manner at the point of care. 3D inkjet printing (3DIJP) provides a platform with the potential to address the above need. This thesis investigates the capability of 3DIJP as a tool for manufacturing solid dosage forms. In chapter 3, a piezoelectric drop on demand printer was used. The chapter focuses on two solvent based inkjet printing methods. In the first solvent based method, excipients including hydroxypropyl methylcellulose (HPMC), poly (vinyl pyrrolidone) (PVP) and Eudragit RL were investigated for printability. PVP (K10) which showed the best printability behaviour was loaded with digoxin or carbamazepine (CBZ) and printed to obtain films. In the second solvent based method, a solution containing CBZ dissolved in a mixture of of polyethylene glycol diacrylate (PEGDA) and with poly(caprolactone dimethyl acrylate) (PCLDMA) was printed and polymerised in situ using ultraviolet light to form films. The printed drug loaded films were investigated using time of flight secondary ion mass spectroscopy (ToF SIMS), atomic force microscopy (AFM), scanning electron microscopy (SEM) and differential scanning microscopy (DSC). PVP formulations were homogeneous, with no evidence of crystallisation PEGDA/PCLDA/CBZAFM images showed a clear phase separation at the micron scale and no drug was detected at the surface. In this chapter, the production of adjustable doses was also evaluatedusing UV-VIS spectrophotometry. In chapters 4 and 5, a solvent-free hot-melt 3D inkjet printing method suitable for manufacturing solid dosage forms was developed. Excipients including beeswax, carnuba wax, gelucire 44/14 and trimyristin were examined for printability. Beeswax a naturally derived and FDA approved material showed the best printability behaviour and was selected as the drug carrier. Traditional circular shaped tablets and cylindrical implants loaded with 5% w/w fenofibrate were successfully fabricated. The printed tablets and implants were well-defined, smooth surfaced and with no apparent defects. The architecture of the tablets was investigated using 3D micro X-ray computed tomography (μCT), revealing well defined and ordered honeycomb channels in the interior of the tablets. The distribution of the drug was evaluated at the macro scale level using DSC and at the micro scale level using ToF - SIMS and Raman spectroscopy. The drug was homogenously distributed within the drug carrier (beeswax matrix ) at the microscale level. At the micron scale level, the drug was heterogeneously distributed. ToF - SIMS studies also revealed that the drug was depleted from the upper most top surfaces. Production of solid dosage forms with intricate and adaptable geometries was demonstrated by printing honeycomb architecture tablets with predetermined variable cell diameters. The diamater of the honeycomb cells was varied, in order to achieve controlled variable drug release profiles. The ablity to control drug release was only applicable above an established critical cell diameter of 0.5 mm. An analytical model describing Fickian diffusion from a slab geometry was developed to allow for the prediction of drug release from the honeycomb tablets. The predicted drug release profiles varied slightly from the experimental data, but the trends for the two data set were identical. For both data sets the rate of drug release increased with increase in the surface area to volume ratio. The findings and the developments demonstrated in this thesis provide an insight into the potential application of 3DIJP as a tool for manufacturing solid dosage forms with bespoke properties for controlled drug release but also highlights some limitations.

Transition metal coordination complexes show great promise as novel therapeutic agents with new mechanisms of action, but their characterisation, and identification of their target sites present significant challenges. In this thesis a variety of new analytical methods is explored for the study of platinum, ruthenium, osmium and iridium anticancer complexes. High performance liquid chromatography (HPLC) was used to determine the relative hydrophobicity of a series of photoactivatable Pt(IV) diazido complexes of the general type trans,trans,trans-[Pt(N3)2(OH)2(R)(F11]. Interestingly the hydrophobicities did not follow trends based on literature Log P values of individual ligands and did not correlate with the cellular uptake or antiproliferative activity of the drugs. Other factors such as the quantum yield of the complex, and the type of DNA adducts appear to be more important for their efficacy. Chromatography and high-resolution mass spectrometry were used to study the formation of platinum adducts on DNA when the most active complex trans,trans,trans-[Pt(N3)2(OH)2(PYridine)2], 8 was irradiated in the presence of short single strand oligonucleotides 14 bases in length. Complex 8 was found to bind to the oligonucleotides as a {Pt(pyridine)2}2+ adduct. Modifying the wavelength of activation from UVA to 420 nm had no effect on the type of adduct formed, but the higher energy irradiation achieved maximum levels of DNA platination more quickly. Changing the sequence of the oligonucleotide suggested that the photoactivated form of 8 does not favour the formation of the 1,2-(GpG) bisadduct formed by cisplatin and other clinically approved platinum based drugs, but may form 1,3-(GpNpG) or 1,3-(ApNpG) adducts, as is the case with other trans-platinum complexes. Chiral chromatography using cellulose- and amylose-based stationary phases successfully separated the enantiomers of a series of organometallic 'piano stool' anticancer complexes. This appears to be the first successful separation of facially chiral Ru(II) arene complexes, the enantiomers of which were stable in solution for over 3 h. In contrast, separated cyclopentadienyl WI) complexes with chiral metal centres epimerized within 2 h in solution at ambient temperature. Under similar conditions the enantiomers of the Os(II) arene complex [Os(n6-p-cym)(4-(2-pyridylazo)-N,N-dimethylaniline)Ir remained stable, as did those of the ruthenium-based complex [Ru(9,10- diydrophenanthrene)(en)C1r. It was shown that it is possible to separate the diasteriomers of [Ru(t)6-para-cymene)(iminopyridine)I], that can also be resolved by crystallisationtechniques, and hence, decrease the time required to separate the enantiomers. This work will therefore allow exploration of the biological properties of some of these enantiomers A novel technique for the rapid irradiation and detection of light¬senstive species was developed. Photonic crystal fibers (PCFs) were coupled to a mass spectrometer using HPLC tubing and fittings. This continuous flow method of analysis was validated using the photaquation of cyanocobalamin. The PCF system was compared to the conventional cuvette-based approach. No significant difference in the species detected by MS could be found, but the PCF system had the advantage of requiring 20 times less sample (25 pL), and only 15 min of irradiation compared to 10 h by conventional methods. The new PCF-MS system was then used to study the interaction of the photoactivateable ruthenium-based drug [{(e-indan)RuC1}201-2,3-dPa2+ with a range of small molecules that acted as models for intracellular components, e.g. 5'GMP for DNA. The nucleobase binding properties were consistent with those previously reported with plasmid DNA by Magennis et al: a small amount of binding took place in the dark in view of the aquation of the mondentate leaving groups but this dramatically increased upon photoactivation and loss of the arene ligands. The complex was also found to bind to glutathione (GSH), which is known to detoxify metal-based drugs, an observation possibly explaining its poor anticancer activity.

The presence of organic salts as drug counter-ions and buffers in hydroxypropylmethylcellulose (HPMC) matrices is often overlooked. This study investigates their potential to influence polymer solution properties and matrix drug release kinetics. A homologous series of aliphatic organic salts influenced solution and matrix properties in rank order of hydrocarbon chain length. Monovalent salts containing 1to4 C-atoms had little effect on polymer surface activity, but lowered sol:gel transition temperatures (SGTT), and accelerated matrix drug release in comparison with a dextrose control. Divalent salts were more potent. These observations are consistent with Hofmeister effects in which anions restructure water in the polymer hydration sheath, induce 'salting-out' and suppressing particle swelling and matrix gel layer formation. Organic salts with StoB C-atoms increasingly influenced polymer surface activity, elevated SGTT, and retarded matrix drug release. This suggests these salts enhance HPMC hydration, possibly through interaction with hydrophobic regions. The effects of these salts on matrix drug release show that these ions impact on water:polymer interactions important to gel layer formation and diffusion barrier properties. HPMC matrices containing SOS and its homologues were also investigated. Turbidimetric, tensiometric and rheological studies supported a mechanism in which these surfactants solubilise HPMC at post-micellar concentrations. Incorporating 10% SOS into HPMC matrices was shown to increase the resistance of HPMC matrices to sucrose medium up to 2.0M, suggesting a role for surfactants in avoiding food solute effects. This study shows that organic salts incorporated in HPMC matrices have the potential to influence drug release in a rank order that reflects their modulation of the HPMC polymer hydration sheath in solution. SOS and its homologous series could retard drug release from HPMC matrices only when their critical aggregation concentration (CAC) was reached. However, it suggests this excipient may have uses as an excipient for improving HPMC matrix release performance.

Lo stretch film è una diffusa applicazione per imballaggio dei film in polietilene (PE), utilizzato per proteggere diversi prodotti di vari dimensioni e pesi. Una caratteristica fondamentale del film è la sua proprietà adesiva in virtù della quale il film può essere facilmente chiuso su se stesso. Tipicamente vengono scelti gradi lineari a bassa densità (LLDPE) con valori relativamente bassi di densità a causa delle loro buone prestazioni. Il mercato basa la scelta del materiale adesivo per tentativi piuttosto che in base alla conoscenza delle caratteristiche strutturali ottimali per l’applicazione. Come per i pressure sensitive adhesives, le proprietà adesive di film stretch in PE possono essere misurati mediante "peel testing". Esistono molti metodi standard internazionali ma i risultati di tali prove sono fortemente dipendenti dalla geometria di prova, sulla possibile deformazione plastica che si verificano nel peel arm(s), e la velocità e temperatura. Lo scopo del presente lavoro è quello di misurare l'energia di adesione Gc di film stretch di PE, su se stessi e su substrati diversi, sfruttando l'interpretazione della meccanica della frattura per tener conto dell'elevata flessibilità e deformabilità di tali film. Quindi, la dipendenza velocità/temperatura di Gc sarà studiata con riferimento diretto al comportamento viscoelastico lineare dei materiali utilizzati negli strati adesivi, per esplorare le relazioni struttura-proprietà che possono mettere in luce i meccanismi molecolari coinvolti nei processi di adesione e distacco. Nella presente caso, l’adesivo non è direttamente disponibile come materiale separato che può essere messo tra due superfici di prova e misurato per la determinazione delle sue proprietà. Il presupposto principale è che una parte, o fase, della complessa struttura semi-cristallina del PE possa funzionare come adesivo, e un importante risultato di questo studio può essere una migliore identificazione e caratterizzazione di questo "fase adesiva". / Stretch wrap is a widespread packaging application of Polyethylene (PE) films, used to held together and protect many possible products of varying number, sizes and weights. A key feature of stretch wrap films is their adhesive property, by virtue of which the wrap can be easily closed onto itself. Typically, Linear Low Density grades (LLDPEs) with comparatively low density values are chosen, because of their known good adhesive (“cling”) properties. The market relies on trial and error for the choice of the adhesive material rather than choose upon known optimal structure’s properties tailored for the application. As for pressure sensitive adhesives, the adhesive properties of PE stretch films can be measured by “peel testing”. Many international standard methods exist, and the results of such tests are strongly dependent on test geometry, on the possible plastic deformation occurring in the peel arm(s), and on peeling rate and temperature. The aim of the present work is to measure the adhesive energy Gc of PE stretch films onto themselves and on different substrates, by taking advantage of the fracture mechanics approach to account for the high flexibility and deformability of these films. The measured rate/temperature dependence of Gc will be studied with reference to the linear viscoelastic behaviour of the materials used in the adhesive layers, in order to explore the structure-property relationships which could enlighten the molecular mechanisms involved in the adhesion and detachment processes. In the present case, the “adhesive” is not available as a separate material which could be tested and sampled for determination of its properties. The main assumption is that some part, or phase, of the complex semi-crystalline polyethylene material works as an adhesive, and an important outcome of this study can be a better identification and characterization of this “adhesive phase”.