Polymer-based objects are commonly encountered in our daily life. The great versatility and controllable properties that characterize these materials allowed the spreading of polymeric industry to many different areas. In the last years, this huge adaptability was exacerbated by the introduction of smart materials, i.e. materials able to change their physico-chemical properties in response to an external stimulus. In particular, the possibility of applying thermal stimuli in a controlled and simple way, coupled with the natural occurrence of thermal gradients, made thermo-responsive materials one of the most studied categories. Chapter 1 provides an insight of the great potentialities and superior performances that thermo-responsive polymers can impar to a target substrate. The discussion will cover some significant areas of interest in which this class of materials has been employed, including cell culture, chromatography, colloidal stabilization and enhance oil recovery. Many examples from literature are reported in order to highlight the state of the art, criticisms and main advantages of this technology over conventional strategies. Moreover, some successful examples underling the innovative functionalities achievable by these active surfaces are presented. Afterwards, this research was aimed to study and develop thermo-responsive polymers able to impar a dynamic behaviour to target surfaces belonging to two of the above-mentioned categories, namely cell culture and colloidal stabilization. In particular, the first part of this research was addressed to the development of thermo-responsive polymers able to confer a dynamic behaviour to tissue culture polystyrene (TCPS) surfaces. In fact, functionalized TCPSs find particular interest in the area of tissue engineer mainly due to the possibilities that this technology offers in terms of three-dimensional constructs or harvesting of continuous cell sheets. However, the complex procedures commonly implemented to functionalize TCPS often require high surface activation energy thus limiting the implementation and diffusion of this culture approach. With the aim of addressing these limitations, we propose an easy and quick coating strategy to functionalize TCPS surfaces. This strategy was then employed in two case studies to obtain TCPSs that either prevent cell adhesion or allow the harvest of continuous cell sheets. Specifically, Chapter 2 reports a fast and easy-to-use coating method to prevent the nonspecific adhesion of cells on TCPS surfaces. Poly(styrene-co-3-sulfopropyl methacrylate(SPAMK)) copolymers comprising non-fouling hydrophilic moieties as well as functionalities that enhance the polymer adhesion to the substrate were synthesized. The polymer adsorption was obtained from an aqueous mixture with a procedure that can be conveniently performed in short time. The kinetic of polymer adsorption as well as the effect of the polymer concentration were studied in order to reduce the time and cost of the entire procedure. Additionally, the polymer composition and the polymer density were optimized to completely avoid the adhesion of three different adherent cell lines, i.e. CHO, A375-P and HFF-1 cells. This coating strategy was used in Chapter 3 to obtain TCPS with a non-fouling functionality provided by polyampholytes-based polymers. To achieve this scope, we studied the reversible addition-fragmentation chain transfer (RAFT) copolymerization of two oppositely charged monomers investigating the influence of both the monomer and the chain transfer agent (CTA) concentrations over the polymerization rate and copolymer composition. Then, we calculated the reactivity ratios for the two monomers by analysing the residual monomer mixture composition via in situ nuclear magnetic resonance (1H-NMR). The values extrapolated (i.e. rSPMAK = 0.510.03 and rMADQUAT = 0.310.03) were used to optimize the polymer composition in order to obtain polyampholyte coating able to prevent A375-P cell adhesion. Furthermore, these polymers showed interesting aqueous properties, including an upper critical solution temperature (UCST), which was studied as a function of the salt concentration and polymer molecular weight. Towards the same aim of obtaining TCPS with a dynamic behaviour, Chapter 4 reports a class of polymer able to guarantee the harvest of continuous cell sheets in both serum and serum-free cell cultures. First, the thermo-responsive copolymers were synthesized via RAFT polymerization. In this way a high control over the polymer microstructure, a key parameter for tuning its cloud point and architecture, was provided. Taking advantage of this, both block and statistical copolymers were synthesized and compared in terms of temperature-mediated cell-harvesting, resulting in a more efficient performance of the former than the later. Finally, the polymer modification with the tripeptide Arginine-Glycine-Aspartic acid (RGD) was successfully implemented to guarantee the collection of intact cell sheets also in serum-free cell cultures. After this investigation on TCPS functionalization, the second part of this research was addressed to the development of thermo-responsive polymers for colloidal stabilization. In particular, thermo-responsive nanoparticles are coming to the forefront due to their dynamic behavior, useful in applications ranging from biomedicine to advanced separations and smart optics. What is guiding the macroscopic behavior of these systems above their critical temperature is mainly the microstructure of the polymer chains these NPs are made up of. Therefore, a comprehensive understanding of the influence of the polymer properties over the thermal response is mandatory to reproducibly target a specific behavior. To better elucidate this correlation, in Chapter 5 we report a study on the role that size, polymeric microstructure and hydrophilic-lipophilic balance (HLB) have over the phase separation of thermo-responsive NPs. Firstly, four different thermo-responsive oligomers were synthesized via RAFT polymerization. Then, exploiting the RAFT living character, these oligomers were chain-extended with butyl methacrylate obtaining a library of functional NPs. Finally, the NP thermo-responsive behavior, their physical state above the cloud point (Tcp) as well as their reversibility once the stimulus is removed were deeply investigated. The results showed that the solid content plays a minor role compared to the relative length of the two blocks forming the polymer chains. At the same time, the reversibility was mainly achieved at high HLB, independently from the absolute lengths of the block copolymers. The knowledges acquired with this study were used for the development of two different colloidal stabilizers with a dynamic thermo-responsive behaviour. These materials were designed with the aim of addressing some of the limitations characterizing the polymer production via free radical emulsion polymerization (FRPe) and the fragrance delivery. In particular, FRPe is commonly adopted in industry for the production of many polymer-based objects that we encounter in our daily life mainly due to the great advantages that this technique offers in terms of high polymerization rate, good heat management and conduction in a non-toxic solvent like water. On the other hand, these emulsions require surfactants to be stabilized and at the same time, the recovery of a bulk material from a NP suspension needs the addition of salts or alkali for their coagulation. These can contaminate the final polymer and affect its properties. In Chapter 6, we propose a new class of thermo-responsive surfactants able to promote the NP formation during the FRPe, induce their aggregation and guarantee the recovery of both surfactants and bulk material by simply changing the temperature of the system. To address this issue, thermo-responsive surfactants were synthesized via RAFT polymerization obtaining polymers with tunable HLB, controlled molecular weight distribution and well-defined thermo-responsive behaviour. Then, the RAFT agent was removed to avoid the further extension of the block copolymers. This was the key step to avoid the chemical bond between the surfactant and the bulk polymer thus allowing an efficiently recovery of both the materials. Surfactants are commonly employed also in the formulation of home and personal care products. However, the elevate irritancy that characterized these compounds favoured the development of alternative carriers. In this scenario, polymeric NPs are attracting growing attention as valuable fragrance carriers. Moreover, the more and more stringent regulations on the products for home and personal care are pushing the market towards the use of biodegradable materials in order to reduce their environmental impact. In this framework, an appealing opportunity is offered by the use of biodegradable polymeric NPs for the stabilization of fragrance oils in water. In Chapter 7 modular biodegradable NPs were synthesized through a combination of ring opening polymerization (ROP) and RAFT emulsion polymerization and used to produce limonene-in-water Pickering emulsions. This strategy allowed to control independently the NP size, polymer molecular weight, and hydrophobicity acting on the microstructure of the constituting copolymers. Stable limonene-in-water Pickering emulsions could be obtained, with the size of the oil phase that can be strictly controlled by tuning the NP physico-chemical properties. Finally, the adoption of thermo-responsive polymer chains within the shell of the Pickering emulsifiers enabled the on-demand destabilization of the emulsions and hence to selectively dispense limonene by simply increasing the temperature.
Gli oggetti a base di polimeri si incontrano comunemente nella nostra vita quotidiana. La grande versatilità e le proprietà controllabili che caratterizzano questi materiali hanno permesso la diffusione dell'industria polimerica in molti settori diversi. Negli ultimi anni, questa enorme adattabilità è stata accentuata dall'introduzione dei materiali intelligenti, cioè materiali in grado di cambiare le loro proprietà fisico-chimiche in risposta ad uno stimolo esterno. In particolare, la possibilità di applicare stimoli termici in modo controllato e semplice, unita alla naturale presenza di gradienti termici, ha reso i materiali termo-reattivi una delle categorie più studiate. Il capitolo 1 fornisce una panoramica delle grandi potenzialità e delle prestazioni superiori che i polimeri termo-reattivi possono impartire a un substrato di destinazione. La discussione riguarderà alcune significative aree di interesse in cui questa classe di materiali è stata impiegata, tra cui la coltura cellulare, la cromatografia, la stabilizzazione colloidale e il miglioramento del recupero del petrolio. Molti esempi dalla letteratura sono riportati al fine di evidenziare lo stato dell'arte, le critiche e i principali vantaggi di questa tecnologia rispetto alle strategie convenzionali. Inoltre, vengono presentati alcuni esempi di successo che sottolineano le funzionalità innovative ottenibili da queste superfici attive. In seguito, questa ricerca ha avuto come obiettivo lo studio e lo sviluppo di polimeri termo-reattivi in grado di imprimere un comportamento dinamico a superfici bersaglio appartenenti a due delle categorie sopra menzionate, ovvero la coltura cellulare e la stabilizzazione colloidale. In particolare, la prima parte di questa ricerca è stata indirizzata allo sviluppo di polimeri termo-reattivi in grado di conferire un comportamento dinamico a superfici in polistirene per colture cellulari (TCPS). Infatti, i TCPS funzionalizzati trovano particolare interesse nell'ambito dell'ingegneria tissutale soprattutto per le possibilità che questa tecnologia offre in termini di costrutti tridimensionali o di raccolta di fogli cellulari continui. Tuttavia, le complesse procedure comunemente implementate per funzionalizzare TCPS spesso richiedono alta energia di attivazione superficiale limitando così l'implementazione e la diffusione di questo approccio culturale. Con l'obiettivo di affrontare queste limitazioni, proponiamo una strategia di rivestimento facile e veloce per funzionalizzare le superfici TCPS. Questa strategia è stata poi impiegata in due casi di studio per ottenere TCPSs che impediscono l'adesione delle cellule o consentire la raccolta di fogli di cellule continue. In particolare, il Capitolo 2 riporta un metodo di rivestimento veloce e facile da usare per prevenire l'adesione aspecifica delle cellule sulle superfici TCPS. Sono stati sintetizzati copolimeri di poli (stirene-co-3-sulfopropil metacrilato (SPAMK)) che comprendono moieties idrofile non fouling e funzionalità che migliorano l'adesione del polimero al substrato. L'adsorbimento del polimero è stato ottenuto da una miscela acquosa con una procedura che può essere convenientemente eseguita in breve tempo. La cinetica dell'adsorbimento del polimero così come l'effetto della concentrazione del polimero sono stati studiati al fine di ridurre il tempo e il costo dell'intera procedura. Inoltre, la composizione del polimero e la densità del polimero sono state ottimizzate per evitare completamente l'adesione di tre diverse linee cellulari aderenti, cioè CHO, A375-P e cellule HFF-1. Questa strategia di rivestimento è stata utilizzata nel Capitolo 3 per ottenere TCPS con una funzionalità non-fouling fornita da polimeri a base di poliammoliti. Per raggiungere questo scopo, abbiamo studiato la copolimerizzazione reversibile di trasferimento della catena di addizione-frammentazione (RAFT) di due monomeri di carica opposta, studiando l'influenza delle concentrazioni sia del monomero che dell'agente di trasferimento della catena (CTA) sulla velocità di polimerizzazione e sulla composizione del copolimero. Poi, abbiamo calcolato i rapporti di reattività per i due monomeri analizzando la composizione della miscela monomerica residua tramite risonanza magnetica nucleare in situ (1H-NMR). I valori estrapolati (cioè rSPMAK = 0,510,03 e rMADQUAT = 0,310,03) sono stati utilizzati per ottimizzare la composizione del polimero al fine di ottenere un rivestimento poliamplificato in grado di impedire l'adesione delle cellule A375-P. Inoltre, questi polimeri hanno mostrato interessanti proprietà acquose, compresa una temperatura critica superiore della soluzione (UCST), che è stata studiata in funzione della concentrazione di sale e del peso molecolare del polimero. Verso lo stesso obiettivo di ottenere TCPS con un comportamento dinamico, il capitolo 4 riporta una classe di polimeri in grado di garantire la raccolta di fogli cellulari continui in colture cellulari sia in siero che senza siero. In primo luogo, i copolimeri termo-reattivi sono stati sintetizzati tramite polimerizzazione RAFT. In questo modo è stato fornito un elevato controllo sulla microstruttura del polimero, un parametro chiave per sintonizzare il suo punto di nuvola e la sua architettura. Approfittando di questo, sia i copolimeri a blocchi che quelli statistici sono stati sintetizzati e confrontati in termini di raccolta cellulare mediata dalla temperatura, risultando in una performance più efficiente dei primi rispetto ai secondi. Infine, la modifica del polimero con il tripeptide arginina-glicina-acido aspartico (RGD) è stata implementata con successo per garantire la raccolta di fogli cellulari intatti anche in colture cellulari senza siero. Dopo questa indagine sulla funzionalizzazione del TCPS, la seconda parte di questa ricerca è stata indirizzata allo sviluppo di polimeri termo-reattivi per la stabilizzazione colloidale. In particolare, le nanoparticelle termo-reattive stanno venendo alla ribalta per il loro comportamento dinamico, utile in applicazioni che vanno dalla biomedicina alle separazioni avanzate e all'ottica intelligente. Ciò che guida il comportamento macroscopico di questi sistemi al di sopra della loro temperatura critica è principalmente la microstruttura delle catene polimeriche di cui queste NP sono composte. Pertanto, una comprensione completa dell'influenza delle proprietà dei polimeri sulla risposta termica è obbligatoria per riprodurre un comportamento specifico. Per chiarire meglio questa correlazione, nel capitolo 5 riportiamo uno studio sul ruolo che la dimensione, la microstruttura polimerica e l'equilibrio idrofilo-lipofilo (HLB) hanno sulla separazione di fase delle NP termoresponsive. In primo luogo, quattro diversi oligomeri termo-reattivi sono stati sintetizzati tramite polimerizzazione RAFT. Poi, sfruttando il carattere vivente RAFT, questi oligomeri sono stati estesi a catena con metacrilato di butile ottenendo una libreria di NP funzionali. Infine, il comportamento termo-reattivo delle NP, il loro stato fisico al di sopra del punto di nuvola (Tcp) così come la loro reversibilità una volta che lo stimolo è stato rimosso sono stati profondamente studiati. I risultati hanno mostrato che il contenuto solido gioca un ruolo minore rispetto alla lunghezza relativa dei due blocchi che formano le catene polimeriche. Allo stesso tempo, la reversibilità è stata raggiunta principalmente ad alti HLB, indipendentemente dalle lunghezze assolute dei copolimeri a blocchi. Le conoscenze acquisite con questo studio sono state utilizzate per lo sviluppo di due diversi stabilizzatori colloidali con un comportamento dinamico termo-reattivo. Questi materiali sono stati progettati con l'obiettivo di affrontare alcune delle limitazioni che caratterizzano la produzione di polimeri tramite polimerizzazione in emulsione a radicali liberi (FRPe) e la consegna di fragranze. In particolare, la FRPe è comunemente adottata nell'industria per la produzione di molti oggetti a base di polimeri che incontriamo nella nostra vita quotidiana principalmente a causa dei grandi vantaggi che questa tecnica offre in termini di alto tasso di polimerizzazione, buona gestione del calore e conduzione in un solvente non tossico come l'acqua. D'altra parte, queste emulsioni richiedono tensioattivi per essere stabilizzate e allo stesso tempo, il recupero di un materiale sfuso da una sospensione NP ha bisogno dell'aggiunta di sali o alcali per la loro coagulazione. Questi possono contaminare il polimero finale e influenzare le sue proprietà. Nel capitolo 6, proponiamo una nuova classe di tensioattivi termo-reattivi in grado di promuovere la formazione di NP durante la FRPe, indurre la loro aggregazione e garantire il recupero sia dei tensioattivi che del materiale bulk semplicemente cambiando la temperatura del sistema. Per affrontare questo problema, i tensioattivi termo-reattivi sono stati sintetizzati tramite polimerizzazione RAFT ottenendo polimeri con HLB sintonizzabile, distribuzione di peso molecolare controllata e un comportamento termo-reattivo ben definito. Poi, l'agente RAFT è stato rimosso per evitare l'ulteriore estensione dei copolimeri a blocchi. Questo è stato il passo chiave per evitare il legame chimico tra il tensioattivo e il polimero bulk permettendo così un recupero efficiente di entrambi i materiali. I tensioattivi sono comunemente impiegati anche nella formulazione di prodotti per la cura della casa e della persona. Tuttavia, l'elevata irritabilità che caratterizza questi composti ha favorito lo sviluppo di vettori alternativi. In questo scenario, le NP polimeriche stanno attirando una crescente attenzione come validi vettori di fragranze. Inoltre, le normative sempre più stringenti sui prodotti per la cura della casa e della persona stanno spingendo il mercato verso l'uso di materiali biodegradabili al fine di ridurre il loro impatto ambientale. In questo quadro, un'opportunità interessante è offerta dall'uso di NPs polimeriche biodegradabili per la stabilizzazione di oli profumati in acqua. Nel capitolo 7 le NP modulari biodegradabili sono state sintetizzate attraverso una combinazione di polimerizzazione ad apertura di anello (ROP) e polimerizzazione in emulsione RAFT e utilizzate per produrre emulsioni Pickering limonene-in-acqua. Questa strategia ha permesso di controllare indipendentemente la dimensione della NP, il peso molecolare del polimero e l'idrofobicità che agisce sulla microstruttura dei copolimeri costituenti. Si sono potute ottenere emulsioni stabili limonene-in-acqua Pickering, con la dimensione della fase oleosa che può essere strettamente controllata regolando le proprietà fisico-chimiche delle NP. Infine, l'adozione di catene polimeriche termo-reattive all'interno del guscio degli emulsionanti Pickering ha permesso la destabilizzazione su richiesta delle emulsioni e quindi di dispensare selettivamente il limonene semplicemente aumentando la temperatura.
Thermo-responsive polymers as surface active compounds
NICOLÒ, MANFREDINI
2021
Abstract
Polymer-based objects are commonly encountered in our daily life. The great versatility and controllable properties that characterize these materials allowed the spreading of polymeric industry to many different areas. In the last years, this huge adaptability was exacerbated by the introduction of smart materials, i.e. materials able to change their physico-chemical properties in response to an external stimulus. In particular, the possibility of applying thermal stimuli in a controlled and simple way, coupled with the natural occurrence of thermal gradients, made thermo-responsive materials one of the most studied categories. Chapter 1 provides an insight of the great potentialities and superior performances that thermo-responsive polymers can impar to a target substrate. The discussion will cover some significant areas of interest in which this class of materials has been employed, including cell culture, chromatography, colloidal stabilization and enhance oil recovery. Many examples from literature are reported in order to highlight the state of the art, criticisms and main advantages of this technology over conventional strategies. Moreover, some successful examples underling the innovative functionalities achievable by these active surfaces are presented. Afterwards, this research was aimed to study and develop thermo-responsive polymers able to impar a dynamic behaviour to target surfaces belonging to two of the above-mentioned categories, namely cell culture and colloidal stabilization. In particular, the first part of this research was addressed to the development of thermo-responsive polymers able to confer a dynamic behaviour to tissue culture polystyrene (TCPS) surfaces. In fact, functionalized TCPSs find particular interest in the area of tissue engineer mainly due to the possibilities that this technology offers in terms of three-dimensional constructs or harvesting of continuous cell sheets. However, the complex procedures commonly implemented to functionalize TCPS often require high surface activation energy thus limiting the implementation and diffusion of this culture approach. With the aim of addressing these limitations, we propose an easy and quick coating strategy to functionalize TCPS surfaces. This strategy was then employed in two case studies to obtain TCPSs that either prevent cell adhesion or allow the harvest of continuous cell sheets. Specifically, Chapter 2 reports a fast and easy-to-use coating method to prevent the nonspecific adhesion of cells on TCPS surfaces. Poly(styrene-co-3-sulfopropyl methacrylate(SPAMK)) copolymers comprising non-fouling hydrophilic moieties as well as functionalities that enhance the polymer adhesion to the substrate were synthesized. The polymer adsorption was obtained from an aqueous mixture with a procedure that can be conveniently performed in short time. The kinetic of polymer adsorption as well as the effect of the polymer concentration were studied in order to reduce the time and cost of the entire procedure. Additionally, the polymer composition and the polymer density were optimized to completely avoid the adhesion of three different adherent cell lines, i.e. CHO, A375-P and HFF-1 cells. This coating strategy was used in Chapter 3 to obtain TCPS with a non-fouling functionality provided by polyampholytes-based polymers. To achieve this scope, we studied the reversible addition-fragmentation chain transfer (RAFT) copolymerization of two oppositely charged monomers investigating the influence of both the monomer and the chain transfer agent (CTA) concentrations over the polymerization rate and copolymer composition. Then, we calculated the reactivity ratios for the two monomers by analysing the residual monomer mixture composition via in situ nuclear magnetic resonance (1H-NMR). The values extrapolated (i.e. rSPMAK = 0.510.03 and rMADQUAT = 0.310.03) were used to optimize the polymer composition in order to obtain polyampholyte coating able to prevent A375-P cell adhesion. Furthermore, these polymers showed interesting aqueous properties, including an upper critical solution temperature (UCST), which was studied as a function of the salt concentration and polymer molecular weight. Towards the same aim of obtaining TCPS with a dynamic behaviour, Chapter 4 reports a class of polymer able to guarantee the harvest of continuous cell sheets in both serum and serum-free cell cultures. First, the thermo-responsive copolymers were synthesized via RAFT polymerization. In this way a high control over the polymer microstructure, a key parameter for tuning its cloud point and architecture, was provided. Taking advantage of this, both block and statistical copolymers were synthesized and compared in terms of temperature-mediated cell-harvesting, resulting in a more efficient performance of the former than the later. Finally, the polymer modification with the tripeptide Arginine-Glycine-Aspartic acid (RGD) was successfully implemented to guarantee the collection of intact cell sheets also in serum-free cell cultures. After this investigation on TCPS functionalization, the second part of this research was addressed to the development of thermo-responsive polymers for colloidal stabilization. In particular, thermo-responsive nanoparticles are coming to the forefront due to their dynamic behavior, useful in applications ranging from biomedicine to advanced separations and smart optics. What is guiding the macroscopic behavior of these systems above their critical temperature is mainly the microstructure of the polymer chains these NPs are made up of. Therefore, a comprehensive understanding of the influence of the polymer properties over the thermal response is mandatory to reproducibly target a specific behavior. To better elucidate this correlation, in Chapter 5 we report a study on the role that size, polymeric microstructure and hydrophilic-lipophilic balance (HLB) have over the phase separation of thermo-responsive NPs. Firstly, four different thermo-responsive oligomers were synthesized via RAFT polymerization. Then, exploiting the RAFT living character, these oligomers were chain-extended with butyl methacrylate obtaining a library of functional NPs. Finally, the NP thermo-responsive behavior, their physical state above the cloud point (Tcp) as well as their reversibility once the stimulus is removed were deeply investigated. The results showed that the solid content plays a minor role compared to the relative length of the two blocks forming the polymer chains. At the same time, the reversibility was mainly achieved at high HLB, independently from the absolute lengths of the block copolymers. The knowledges acquired with this study were used for the development of two different colloidal stabilizers with a dynamic thermo-responsive behaviour. These materials were designed with the aim of addressing some of the limitations characterizing the polymer production via free radical emulsion polymerization (FRPe) and the fragrance delivery. In particular, FRPe is commonly adopted in industry for the production of many polymer-based objects that we encounter in our daily life mainly due to the great advantages that this technique offers in terms of high polymerization rate, good heat management and conduction in a non-toxic solvent like water. On the other hand, these emulsions require surfactants to be stabilized and at the same time, the recovery of a bulk material from a NP suspension needs the addition of salts or alkali for their coagulation. These can contaminate the final polymer and affect its properties. In Chapter 6, we propose a new class of thermo-responsive surfactants able to promote the NP formation during the FRPe, induce their aggregation and guarantee the recovery of both surfactants and bulk material by simply changing the temperature of the system. To address this issue, thermo-responsive surfactants were synthesized via RAFT polymerization obtaining polymers with tunable HLB, controlled molecular weight distribution and well-defined thermo-responsive behaviour. Then, the RAFT agent was removed to avoid the further extension of the block copolymers. This was the key step to avoid the chemical bond between the surfactant and the bulk polymer thus allowing an efficiently recovery of both the materials. Surfactants are commonly employed also in the formulation of home and personal care products. However, the elevate irritancy that characterized these compounds favoured the development of alternative carriers. In this scenario, polymeric NPs are attracting growing attention as valuable fragrance carriers. Moreover, the more and more stringent regulations on the products for home and personal care are pushing the market towards the use of biodegradable materials in order to reduce their environmental impact. In this framework, an appealing opportunity is offered by the use of biodegradable polymeric NPs for the stabilization of fragrance oils in water. In Chapter 7 modular biodegradable NPs were synthesized through a combination of ring opening polymerization (ROP) and RAFT emulsion polymerization and used to produce limonene-in-water Pickering emulsions. This strategy allowed to control independently the NP size, polymer molecular weight, and hydrophobicity acting on the microstructure of the constituting copolymers. Stable limonene-in-water Pickering emulsions could be obtained, with the size of the oil phase that can be strictly controlled by tuning the NP physico-chemical properties. Finally, the adoption of thermo-responsive polymer chains within the shell of the Pickering emulsifiers enabled the on-demand destabilization of the emulsions and hence to selectively dispense limonene by simply increasing the temperature.File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.14242/204482
URN:NBN:IT:POLIMI-204482