This thesis reports the preparation of novel multi-responsive and multiply stimulable triblock copolymers. The resultant polymers were used to coat cotton fabrics and glass to render them amphiphobic. Further, a method was developed for the preparation of poly(ethylene glycol)-block-poly(hydroxyethyl methacrylate) (PEG-b-PHEMA) via anionic polymerization. The multi-responsive copolymer refers to poly(ethylene glycol)-orthonitrobenzyl-poly[2-(perfluorooctyl)ethyl methacrylate)-block-poly(2-cinnamoloxyethyl methacrylate) (PEG-ONB-PFOEMA-b-PCEMA, or P1). P1 was synthesized via atom transfer radical polymerization (ATRP) of FOEMA and a precursory monomer of CEMA using a PEG macroinitiator. The copolymer was multi-responsive or dual light-responsive because the ONB junction cleaves and PCEMA block becomes crosslinked upon UV photolysis. The multiply stimulable copolymers are a series of poly(ethylene glycol)-disulfide-poly[2-(perfluorooctyl)ethyl methacrylate)-block-poly(2-cinnamoloxyethyl methacrylate) (PEG-S2-PFOEMA-b-PCEMA) copolymers. These polymers were synthesized by the end-coupling Py-S2-PFOEMA-b-PHEMA and PEG-SH, and subsequent cinnamation of the PHEMA block. These polymers are multiply stimulable because the S2 junction and PCEMA block respond to different stimulations, such as reducing agents and light, respectively. These synthetic strategies will advance the field of stimuli-responsive polymers by providing novel functional polymers for the generation of durable self-cleaning surfaces. The above polymers form micelles in water or water/organic solvent mixtures because of the water-soluble PEG blocks. Polymer-coated cotton was obtained by immersing cotton in micellar copolymer solutions before subsequent drying and annealing treatment. Upon photolysis, the PEG block was cleaved and the PCEMA anchoring layer became crosslinked. Such a crosslinked and stable layer was rendered amphiphobic because of the exposed PFOEMA block. A similar coating can be obtained from P2. Two types of stimulations including photolysis and reduction treatment need to be applied to yield amphiphobic textiles. This coating strategy is unique and environmentally friendly because the water- and oil-repellent coatings were prepared from an aqueous solution for the first time. In a further study, a novel and long-sought method was developed for the anionic polymerization of PEG-b-PHEMA. A PEG-DPE macroinitiator was synthesized and subsequently converted into an active initiator by reaction with sec-butyl lithium. Consequently, the active initiator underwent polymerization with HEMA-TMS to yield PEG-b-P(HEMA-TMS). Upon post-polymerization modification, PEG-b-PHEMA was obtained with a low polydispersity of 1.08. / Thesis (Ph.D, Chemistry) -- Queen's University, 2013-04-29 12:25:54.593

Neste trabalho foram preparados nanocompósitos de polímeros estirênicos com argilas organofílicas. Os polímeros estudados foram o poliestireno (PS), um copolímero tribloco de poliestireno-b-polibutadieno-b-estireno (SBS) e quatro copolímeros tribloco de poliestirenob- poli(etileno-co-butileno)-b-estireno (SEBS), sendo um deles modificado com anidrido maléico. Os nanocompósitos foram preparados por três técnicas de obtenção: mistura no fundido, solução e uma técnica híbrida que combina as duas primeiras. Os materiais obtidos foram caracterizados por difração de raios X (XRD), microscopia óptica (OM), microscopia eletrônica de transmissão (TEM), espalhamento de raios X a baixo ângulo (SAXS) e também foram realizados estudos reológicos através do ensaio de cisalhamento oscilatório de pequenas amplitudes (SAOS). O grau de dispersão de argila em algumas amostras foi avaliado por uma técnica baseada na análise de imagens obtidas por TEM. Os resultados mostraram que na maioria dos casos foram obtidos nanocompósitos intercalados, graças à presença da fase de PS em cada polímero. Amostras preparadas por solução tiveram o melhor grau de dispersão de argila, e o polímero que resultou na estrutura mais exfoliada foi o SEBS maleatado. Estudos reológicos mostraram-se muito sensíveis à formação de reticulados de partículas de argila nos nanocompósitos, que passaram a ter comportamento semelhante ao de sólidos. A combinação de técnicas de SAXS com reologia foi bastante útil para estudar a morfologia de fases ordenadas em copolímeros em bloco, permitindo identificar e distinguir estruturas lamelares, cilíndricas e esféricas em cada copolímero. Foi possível verificar que a presença de argila perturba a ordem das fases dos copolímeros e causa diferentes efeitos nas propriedades reológicas destes materiais. / In this work nanocomposites of styrenic polymers and organoclays were prepared. The polymers studied were polystyrene (PS), a polystyrene-b-polybutadiene-b-polystyrene triblock copolymer (SBS) and four polystyrene-b-poly(ethylene-co-butylene)-polystyrene triblock copolymers (SEBS), with one containing maleic anhydride. The nanocomposites were prepared using three different techniques: melt mixing, solution casting and a hybrid technique combining the former two. The materials obtained were characterized by x-ray diffraction (XRD), optical microscopy (OM), transmission electron microscopy (TEM), small angle x-ray scattering (SAXS) and by rheological studies, through small amplitude oscillatory shear tests (SAOS). The degree of clay dispersion was evaluated in some samples using a TEM image analysis technique. The results have shown that in most cases intercalated nanocomposites were obtained, due to the PS phase present in each polymer. Samples prepared by solution had the highest degree of clay dispersion, and the maleated SEBS was the polymer which originated the most exfoliated nanocomposite. The results have also shown that rheological studies are very sensitive to the formation of clay networks within the nanocomposites, which behave more solidlike. The combination of SAXS techniques and rheology was very useful to study the morphology of ordered phases in block copolymers, allowing to identify and distinguish the different structures of each copolymer, such as the lamellar, cylindrical and spherical phases. It was possible to verify that the presence of clay disturbs the phase order in the copolymers and has different effects on the rheological properties of these materials.

Ce travail décrit la séparation de microphase à l'état solide d'un copolymère dibloc comprenant un bloc hautement biocompatible poly [2 - (méthacryloyloxy) éthyl phosphorylcholine] et un bloc pH-sensible poly [2 - (diisopropylamino) méthacrylate d'éthyle] (PMPC-b-PDPA). L'auto-assemblage d'un copolymère dibloc amphiphiles à base de polystyrène (PS) et le poly (acide acrylique) (PAA), a été étudié en suspension aqueuse, et leur décoration par du chitosane, afin de vérifier leur capacité à encapsuler et à libérer par voie transdermique la finastéride, une molécule stéroïdiens inhibiteur de la enzyme 5-alpha-réductase, qui a été recommandée pour le traitement de l'alopécie androgénétique. La morphologie des films PMPC30-b-PDPA60 a été analysée par SAXS et (S) TEM. Films du PMPC30-b-PDPA60 préparés dans une solution de l'éthanol à température ambiante présentent une morphologie cylindrique, qui subit une transition ordre-ordre sur un recuit thermique à 170 ° C: la structure lamellaire résultant coexiste avec une proportion de cylindres organisée dans une phase hexagonale compacte. En revanche, les films du copolymère préparé à partir de méthanol ne subissent pas la même transition morphologique, résultant dans des structures mal organisées, indépendante de traitement thermique. Enfin, les structures lamellaires sont obtenues directement à partir d'une solution aqueuse à pH 4, sans traitement thermique. Ces systèmes offrent une nouvelle alternative pour la fabrication de structures lamellaires constituées d'un matériau biomimétique et anti-fouling, élargissant l'éventail des possibilités dans le domaine de l'ingénierie macromoléculaire.Une autre stratégie adoptée dans ce travail a été basé sur le développement de nanoparticules bien organisé avec des propriétés de surface nature bioinspirés, formé entre polymersomes chargés négativement à base des copolymères à blocs de polystyrène (PS) et le poly (acide acrylique) (PAA) décorés avec du chitosane, un polysaccharide de charge opposée. Le rôle de l'adsorption du chitosane avec deux poids moléculaires distincts (chitosane oligosaccharides et du chitosane avec un faible poids moléculaire) sur la surface des nanoparticules PS139-b-PAA17 et des nanoparticules PS404-b-PAA63 ont été démontrés par diffusion dynamique de la lumière, potentiel zêta et caractérisation morphologiques. En présence du chitosane, le potentiel zêta de polymersomes devient positif. Ce résultat a été interprété en termes d'interactions électrostatiques, qui induisent une adsorption du chitosane sur la surface des polymersomes. Ce résultat a été confirmé par une observation comparative par microscopie entre des polymersomes et des polymersomes décorées. Polymersomes avec un diamètre <200 nm et une distribution granulométrique relativement étroite ont été obtenus pour les deux systèmes. L'effet de la décoration des nanoparticules par du chitosane sur la perméation cutanée in vitro du finastéride, incorporé dans la paroi hydrophobe de polymersomes, a également été évaluée. La pénétration cutanée du finastéride a été estimée par les paramètres de perméabilité tels que le flux, temps de latence et du coefficient de perméabilité de la finastéride. Une amélioration de la perméation du finastéride à partir des nanoparticules a été observée, en particulier à partir de nanoparticules décorées avec du chitosane. Le polymersome PS404-b-PAA63 décorées avec du chitosane semble être le système le plus approprié car il favorisé une meilleure rétention du médicament dans la peau et les faibles valeurs de flux de perméation, suggérant que le système fournit un véhicule de remplacement pour l'administration transdermique de finastéride. / This work describes the microphase separation in bulk of an diblock copolymer comprising a highly biocompatible poly[2-(methacryloyloxy)ethyl phosphorylcholine] block and a pH-sensitive poly[2-(diisopropylamino) ethyl methacrylate] block (PMPC-b-PDPA). The self-assembly of an amphiphilic diblock copolymer based on polystyrene (PS) and poly(acrylic acid) (PAA) was studied in terms of their decoration with the chitosan, verifying their ability to incorporate and transdermally release the drug finasteride, a steroidal molecule 5-alpha-reductase inhibitor that has been recommended for the treatment of androgenetic alopecia. The morphology of PMPC30-b-PDPA60 films was analyzed using SAXS and (S)TEM. PMPC30-b-PDPA60 films cast from ethanol solution at room temperature exhibit a thermodynamically quasi-stable cylindrical morphology, which undergoes an order-order transition upon thermal annealing at 170 oC: the resulting lamellar structure coexists with a minor proportion of cylinders organized into a hexagonal compact phase. In contrast, copolymer films cast from methanol do not undergo the same morphological transition. Instead, short-range liquid-like structures are obtained regardless of the annealing processes. Finally, direct self-assembly to form a lamellar morphology at room temperature can be achieved by solvent-casting from aqueous solution at pH 4. These systems offer a new alternative for the fabrication of lamellar structures in which one layer is biomimetic and non-fouling, expanding the range of possibilities in the macromolecular engineering field. Another strategy adopted in this work was based on the development of well-organized nanoparticles with nature-bioinspired surface properties, formed between negatively charged polymersomes based on polystyrene (PS) and poly(acrylic acid) (PAA) block copolymers decorated with chitosan, an oppositely charged polysaccharide. The role of chitosan with two distinct molecular weights (chitosan oligosaccharide and low molecular weight chitosan) adsorption on the surface of oppositely charged PS139-b-PAA17 and PS404-b-PAA63 nanoparticles were demonstrated by dynamic light scattering measurements, zeta potential and morphological characterization. In the presence of chitosan, the zeta potential of polymersomes becomes positive. This result was interpreted in terms of electrostatic interactions, which induce a flat adsorption of the chitosan on the surface of the polymersomes. This result was further confirmed by a comparative observation by microscopy of bare and chitosan-decorated polymersomes. Polymersomes with a diameter < 200 nm and a relatively narrow size distribution were obtained for both systems. The effect of chitosan decoration of self-assembled nanoparticles on skin penetration in vitro of finasteride was also evaluated, once incorporated in the wall hydrophobic of polymersomes. The skin permeation through pig ear skin of finasteride was estimated by the permeability parameters such as flux, lag time and permeability coefficient of finasteride. An improved permeation of finasteride from the nanoparticle system was observed, especially from nanoparticles decorated with chitosan. The PS404-b-PAA63 polymersome decorated with chitosan seems to be the most appropriate system since it provided higher drug retention in skin and low permeation flux values, suggesting that the PS-b-PAA/chitosan system provides an alternative for transdermal drug delivery system of finasteride.

A novel methodology has been developed for the formation of block copolymers that combines ring-opening metathesis polymerization (ROMP) with functional chain-transfer agents (CTAs), functional chain-terminators (CTs) and self-assembly. Telechelic homopolymers of cyclooctene derivatives that are end-functionalized with hydrogen-bonding or metal-coordination sites are formed via the combination of ROMP with a corresponding functional CTA. These telechelic homopolymers are fashioned with a high control over molecular weight and without the need for post-polymerization procedures. The homopolymers undergo fast and efficient self-assembly with their complement homopolymer or small molecule analogues to form block copolymer architectures. The block copolymers have similar association constants to small molecule analogues described in the literature, regardless of size or the nature of the complementary unit or the polymer side-chain. The ROMP of side-chain functionalized norbornene polymers is coupled with functional CTs to produce block copolymer with main- and side-chain self-assembly sites. Combinations of these norbornene polymers with their complement polymer via self-assembly produce non-covalent AB type block copolymers fast and efficiently. ABA type block copolymers are realized by combining the difunctional homopolymer formed via the CTA pathway with the CT synthesized mono-functional polymer. These polymers show similar association constants regardless of the sequence of polymer formation.

This research focuses on the modeling of surfaces decorated by grafted polymers in order to understand their structure, energetics, and phase behavior. The systems studied include flat and curved surfaces, grafted homopolymers and random copolymers, and in the presence of solvent conditions, homopolymer melt conditions, and diblock copolymer melt conditions. We use self-consistent field theory to study these systems, thereby furthering the development of new tools especially applicable in describing curved particle systems and systems with chemical polydispersity. We study a polymer-grafted spherical particle interacting with a bare particle in a good solvent as a model system for a polymer-grafted drug interacting with a blood protein in vivo. We calculate the energy of interaction between the two particles as a function of grafting density, particle sizes, and particle curvature by solving the self-consistent field equations in bispherical coordinates. Also, we compare our results to those predicted by the Derjaguin approximation. We extend the previous study to describe the case of two grafted particles interacting in a polymer melt composed of chains that are chemically the same as the grafts, especially in the regime where the particle curvature is significant. This is expected to have ramifications for the dispersion of particles in a polymer nanocomposite. We quantify the interfacial width between the grafted and free polymers and explore its correlation to the interactions between the particles, and use simple scaling theories to justify our results. In collaboration with experimentalists, we study the behavior of the glass transition of polystyrene (PS) films on grafted PS substrates. Using the self consistent field theory methods described above as well as a percolation model, we rationalize the behavior of the glass transition as a function of film thickness, chain lengths, and grafting density. Grafting chemically heterogeneous polymers to surfaces in melt and thin film conditions is also relevant for both particle dispersion and semiconductor applications. To study such systems, we model a random copolymer brush in a melt of homopolymer that is chemically identical to one of the blocks. We modify the self-consistent field theory to take into account the chemical polydispersity of random copolymer systems and use it to calculate interfacial widths and energies as well as to make predictions about the window in which perpendicular morphologies of diblock copolymer are likely to form. We also explore the effect of the rearrangement of the chain ends on the surface energy and use this concept to create a simple modified strong stretching theory that qualitatively agrees with our numerical self-consistent field theory results. We explicitly study the system that is most relevant to semiconductor applications - that of a diblock copolymer melt on top of a substrate modified by a random copolymer brush. We explore the morphologies formed as a function of film thickness, grafting density, chain length, and chain blockiness, and make predictions about the effect of these on the neutral window, that is, the range of brush volume fractions over which perpendicular lamellae are expected to occur. / text

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Polyferrocenylsilane (PFS) diblock copolymers self-assemble in selective solvents to form one-dimensional micelles for a broad range of polymer compositions and experimental conditions, driven by the crystallization of the PFS block that forms the micelle core. The most striking feature of these micelles is that they remain active for further growth. They can be extended in length when additional polymer, dissolved in a good solvent, is added to a solution of the pre-existing micelles. This thesis describes several studies investigating the factors that affect the growth and fragmentation of PFS diblock copolymer micelles in solution, with a particular emphasis on polyisoprene-PFS (PI-PFS) diblock copolymers. The goal of my research was trying to provide deeper understanding of this crystallization-driven self-assembly (CDSA) process. In an attempt to understand the growth kinetics of the PI-PFS cylindrical micelles, I added tiny amount of short micelle seeds into supersaturated solution of the same polymer, and followed the micelle growth by light scattering. The data analysis showed that the increase of micelle length could be described by an expression with two exponential decay terms. In another attempt to examine the factors that may affect the growth behavior of the PI-PFS micelles, I found that PI-PFS long micelles underwent fragmentation when they were subjected to external stimuli, e.g. addition of polar solvent, or heating. During the course of studying the effect of heating on the micelles, I developed a new approach to generate cylindrical micelles with controllable and uniform length, a one-dimensional analogue of self-seeding of crystalline polymers. I carried out a systematic study to investigate the self-seeding behavior of PFS block copolymers.

Polyferrocenylsilane (PFS) diblock copolymers self-assemble in selective solvents to form one-dimensional micelles for a broad range of polymer compositions and experimental conditions, driven by the crystallization of the PFS block that forms the micelle core. The most striking feature of these micelles is that they remain active for further growth. They can be extended in length when additional polymer, dissolved in a good solvent, is added to a solution of the pre-existing micelles. This thesis describes several studies investigating the factors that affect the growth and fragmentation of PFS diblock copolymer micelles in solution, with a particular emphasis on polyisoprene-PFS (PI-PFS) diblock copolymers. The goal of my research was trying to provide deeper understanding of this crystallization-driven self-assembly (CDSA) process. In an attempt to understand the growth kinetics of the PI-PFS cylindrical micelles, I added tiny amount of short micelle seeds into supersaturated solution of the same polymer, and followed the micelle growth by light scattering. The data analysis showed that the increase of micelle length could be described by an expression with two exponential decay terms. In another attempt to examine the factors that may affect the growth behavior of the PI-PFS micelles, I found that PI-PFS long micelles underwent fragmentation when they were subjected to external stimuli, e.g. addition of polar solvent, or heating. During the course of studying the effect of heating on the micelles, I developed a new approach to generate cylindrical micelles with controllable and uniform length, a one-dimensional analogue of self-seeding of crystalline polymers. I carried out a systematic study to investigate the self-seeding behavior of PFS block copolymers.