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A novel polymeric nano-capsule bearing quaternary ammonium iodide (QAI) groups on both the outer and inner surfaces of the shell was synthesized via self-catalyzed polymerization-induced self-assembly (PISA). Because QAI works as a catalyst of reversible complexation mediated living radical polymerization (RCMP), the obtained nano-capsule was exploited as a dual RCMP catalyst based on the outer and inner QAI groups. Benefitting from the outer QAI groups, the nano-capsule served as a supported heterogeneous RCMP catalyst with good recyclability to generate polymers outside the nano-capsule. Benefitting from the inner QAI groups, the nano-capsule served as a nano-reactor to generate polymers inside the nano-capsule. The nano-capsule served as a substrate-sorting nano-reactor based on the selective diffusivity of small molecules and polymers through the shell by their sizes. Namely, large molecules (polymers) once generated in the nano-reactor are not permeable through the shell, enabling the entrapment of the generated polymers in the nano-capsule. A homopolymer, an amphiphilic block copolymer, and a multi-polarity and multielemental block copolymer were synthesized and entrapped in the nano-capsule. National Research Foundation (NRF) Published version This work was supported by the National Research Foundation (NRF) Investigatorship in Singapore (NRF-NRFI05-2019-0001).

Herein, nontoxic and metabolizable choline iodide analogues, including choline iodide, acetylcholine iodide, and butyrylcholine iodide, were successfully utilized as novel catalysts for “green” living radical polymerization (LRP). Through the combination of several green solvents (ethyl lactate, ethanol, and water), this green LRP process yielded low-polydispersity hydrophobic, hydrophilic, zwitterionic, and water-soluble biocompatible polymethacrylates and polyacrylates with high monomer conversions. Well-defined hydrophobic–hydrophilic and hydrophilic–hydrophilic block copolymers were also synthesized. The accessibility to a range of polymer designs is an attractive feature of this polymerization. The use of nontoxic choline iodide catalysts as well as green polymerization conditions can contribute to sustainable polymer chemistry. ASTAR (Agency for Sci., Tech. and Research, S’pore) MOE (Min. of Education, S’pore) Accepted version

This work reports the first use of organic chloride salts as catalysts for reversible complexation mediated living radical polymerization. Owing to the strong halogen-bond forming ability of Cl−, the studied four tetraalkylammonium chloride catalysts (R4N+Cl−) successfully control the polymerizations of methyl methacrylate, yielding polymers with low dispersities up to high monomer conversion (>90%). Benzyldodecyldimethylammonium chloride is further exploited to other methacrylates and yields low-dispersity block copolymers. The advantages of the chloride salt catalysts are wide monomer scope, good livingness, accessibility to block copolymers, and good solubility in organic media. Because of the good solubility, the use of the chloride salt catalysts can prevent agglomeration of catalysts on reactor walls in organic media, which is an industrially attractive feature. Among halide anions, chloride anion is the most abundant and least expensive halide anion, and therefore, the use of the chloride salt catalysts may lower the cost of the polymerization. National Research Foundation (NRF) Submitted/Accepted version This work was partly supported by National Research Foundation (NRF) Investigatorship in Singapore (NRF-NRFI05-2019-0001).

In this paper, the straightforward preparation of a range of functionalized trithiocarbonates as RAFT chain transfer agents (CTAs) is presented. The crucial step in the one-pot, three-step reaction sequence is the aminolysis of a thiolactone precursor as it introduces the desired functional handle (double bond, hydroxyl, furan, protected amine, ... ) and generates the corresponding thiol in situ, facilitating further elaboration of the CTA. Furthermore, the newly synthesized trithiocarbonates were positively evaluated as mediators in the RAFT polymerization of styrene, isobornyl acrylate, and N-isopropylacrylamide, while the presence of the end groups in the heterotelechic polymers was confirmed by NMR and UV-vis analysis.

La polimerització radicalària controlada catalitzada per Cu(0) es una de les metodologies més importants en l’àmbit de les polimeritzacions radicalàries degut a seva simplicitat i la possibilitat de sintetitzar polímers amb estructures ben definides i arquitectures complexes. En aquesta mateixa línia el desenvolupament de sistemes polimèrics capaços d’encapsular i alliberar fàrmacs es una de les línies de investigació més explotades e investigades en els darrers anys, ja que millorar la solubilitat de fàrmacs hidrofòbics i alliberar-los sota la presencia de certs estímuls biològics segueix sent una tasca bastant laboriosa. El objectiu principal d’aquesta tesis es investigar la polimerització radicalària catalitzada per Cu(0) en presencia de sistemes bifàsics i tanmateix explorar el potencial i les limitacions d’aquesta metodologia per obtindré polímers amb una estructura perfectament definida. En ultima instancia l’aplicació d’aquest tipus de polimerització radicalària catalitzada i altres mètodes de polimerització seran emprats per la síntesi de polímers sensibles a certs estímuls i amb la finalitat d’encapsular fàrmacs per actuar com vehicles en l’alliberació controlada dels mateixos. La polimerización radicalaria catalizada por Cu(0) es una de las principales metodologías en el campo de las polimerizaciones radicalarias debido a su alto grado de simplicidad i la posibilidad de sintetizar polímeros con estructuras perfectamente definidas. En esta misma línea el desarrollo de sistemas poliméricos capaces de encapsular fármacos es una línea de investigación en constante desarrollo y de gran interés ya que la necesidad de mejorar la solubilidad de fármacos hidrofóbicos y liberarlos bajo la presencia de determinados estímulos de biológica relevancia sigue siendo una tarea complicada. El objetivo principal de esta tesis es investigar la polimerización radicalaria catalizada por Cu(0) en sistemas bifásicos con el objetivo de obtener polímeros con un alto grado de estructura definida. En última instancia la aplicación de este tipo de polimerización radicalaria junto con otros métodos de polimerización será empleado para el desarrollo de polímeros sensibles a ciertos estímulos de biológica relevancia con la finalidad encapsular fármacos y liberarlos de manera controlada. Cu(0)wire-catalyzed SET-LRP has been postulated as one of the most versatile LRP techniques due to its operational simplicity which enables the construction of well-defined polymers and more complex architectures. In particular, the development of polymeric materials with suitable applications for medicine (e.g. polymeric nanoparticles able to encapsulate and release drugs) is a field of growing interest since they improve the poor solubility of hydrophobic drugs in aqueous media. However, their selective delivery under the application of different biological relevant stimuli still remains challenging. The main objective of this thesis is to investigate the Cu(0)wire-catalyzed SET-LRP in “programmed” biphasic systems and to explore the potential and limitations of this methodology with the ultimate goal of obtaining well-defined polymers with complex architectures and maximum end-group fidelity. Eventually, the application of biphasic SET-LRP and other polymerization techniques has been used for the synthesis of stimuli cleavage polymers and their potential application as drug delivery systems has been studied.

Preparation of stimuli-responsive hyperbranched glycopolymers that are able to simultaneously enhance and control the lectin–polymer interaction has been challenging. Hyperbranched glycopolymers have been prepared in which thermo-responsive Poly(N-isopropylacrylamide) [poly(NIPAM)], connected by redox-responsive disulfide bonds, forms the skeleton and for which mannose units are present at each branching point. Degradation of the hyperbranched structure via chemical reduction of the disulfide bond was demonstrated. Moreover, the thermoresponsive behaviour of the glycopolymer was studied. Finally, the lectin–polymer interaction was investigated in order to understand the influence of both the polymer concentration and different chain conformations below and above the cloud point, respectively.

Well-defined diblock and triblock copolymers, star polymers, and concentrated polymer brushes on solid surfaces were prepared using living radical polymerization with organic catalysts. Polymerizations of methyl methacrylate, butyl acrylate, and selected functional methacrylates were performed with a monofunctional initiator, a difunctional initiator, a trifunctional initiator, and a surface-immobilized initiator.

The effects of photoirradiation in controlled and living radical polymerization (LRP), namely nitroxide-mediated polymerization (NMP), atom-transfer radical polymerization (ATRP), cobalt-mediated radical polymerization (CMRP), reversible addition-fragmentation chain transfer polymerization (RAFT), organoiodine-mediated radical polymerization (IRP), and organotellurium-mediated radical polymerization (TERP), are summarized. As in the conventional radical polymerization, photoirradiation has been used for generating radicals under mild conditions in LRP methods. In addition to this use, photoirradiation is also used to overcome the difficulties characteristic to each method, such as activation of catalysis, generation of controlling agents, and increasing the polymer-end structure. The most-recent developments in the use of photochemistry in LRP are summarized in this review.

Controlled and very rapid ambient temperature polymerization of tert-butyl acrylate (tBA) via atom transfer radical polymerization (ATRP) and single electron transfer living radical polymerization (SET-LRP) conditions is reported. Two initiators, one that would generate a secondary radical and another that would generate a primary radical, upon activation, are used. A very active catalyst CuBr/Me6TREN was found to initiate rapid polymerization whether it was the primary or the secondary initiator. The polymerization was well controlled and very rapid. The initiator that produces secondary initiating site is found to result in more rapid polymerization than the one that produces primary initiating site. To explore the possibility of rapid ambient temperature polymerization through the SET-LRP mechanism, the polymerization was also carried out in the presence of DMSO. It was found that the polymerization was much faster compared to the bulk ATRP, without loss of control. Styrene was block copolymerized from PtBA macroinitiators and vice versa. In both the cases, block copolymers with controlled molecular weights were obtained. The tBA block of the polymer was selectively hydrolyzed to get amphiphilic block copolymers. This amphiphilic block copolymer was found to be useful in preparing stable cadmium sulfide (CdS) nanoparticulate dispersion. VC 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 996–1007, 2012

Catalytic aqueous living radical polymerization was achieved through a ligand design for a ruthenium-based catalyst. A phenolic phosphine ligand [PPh2(pPhOH)] was combined with a pentamethylcyclopentadienyl (Cp*)-based tetrameric ruthenium precursor, and the resulting complex showed a high catalytic activity for aqueous living radical polymerizations of hydrophilic methacrylates (for example, poly(ethylene glycol) methacrylate and 2-hydroxyethyl methacrylate) in conjunction with a chlorine initiator [H–(MMA)2–Cl]. The catalytic system allowed very fast living polymerizations, block copolymerizations and syntheses of high-molecular-weight polymers (DPn~1000) with narrow-molecular-weight distributions. Importantly, the activity was high enough to control the polymerization using a catalytic amount of the complex, even though the polymerizations were performed at low temperature (40 °C). Such advanced catalysis was achieved by not only simple hydrophilicity of the ligand but also by a water-assisted dynamic transformation from the original coordinatively saturated form [Cp*RuCl(PR3)2; 18e; PR3=phosphine] into an unsaturated and active form [Cp*RuCl(PR3); 16e]. Water molecule(s) may also coordinate for further stabilization as demonstrated by 31P NMR analyses.

Since its introduction, click chemistry has received a considerable amount of interest. In this contribution, the term click chemistry and the reactions that fall under this term are briefly explained. The main focus of this review is on the application of click chemistry in conjunction with living radical polymerization for the synthesis of advanced macromolecular architectures. Therefore the most powerful living radical polymerization (LRP) techniques are discussed and an overview of click chemistry in the different synthetic schemes is given. A large number of examples are shown that include the synthesis of block copolymers, star-shaped polymers, surface modified particles, and polymer-protein conjugates. The enormous potential of LRP/click chemistry is probably best exemplified by the synthesis of different miktoarm star copolymers, to which a separate section is dedicated.

Hyperbranched polycaprolactone with controlled structure was synthesized by reversible addition-fragmentation chain transfer radical ring-opening polymerization along with self-condensed vinyl polymerization (SCVP) of 2-methylene-1,3-dioxepane (MDO). Vinyl 2-[(ethoxycarbonothioyl) sulfanyl] propanoate (ECTVP) was used as polymerizable chain transfer agent. Living polymerization behavior was proved via pseudo linear kinetics, the molecular weight of polymers increasing with conversion and successful chain extension. The structure of polymers was characterized by 1H NMR spectroscopy, tripe detection gel permeation chromatography, and differential scanning calorimetry. The polymer composition was shown to be able to tune to vary the amount of ester repeat units in the polymer backbone, and hence determine the degree of branching. As expected, the degree of crystallinity was lower and the rate of degradation was faster in cases of increasing the number of branches.

Macrocyclic polymers present an important class of macromolecules, displaying the reduced radius of gyration or impossibility to entangle. A rare approach for their synthesis is the ring expansion-controlled radical “vinyl” polymerization, starting from a cyclic alkoxyamine. We here describe ring-expansion radical crossover reactions of cyclic alkoxyamines which run in parallel to chain-propagation reactions in the polymerization system. The radical crossover reactions extensively occurred at 105–125 °C, eventually producing high molecular weight polymers with multiple inherent dynamic covalent bonds (NOC bonds). A subsequent ring-contraction radical crossover reaction and the second ring-expansion radical crossover reaction are also described. The major products for the respective three stages were shown to possess cyclic morphologies by the molecular weight profiles and the residual ratios for the NOC bonds (φ in %). In particular, the high φ values ranging from ca. 80% to 98% were achieved for this cyclic alkoxyamine system. This result verifies the high availability of this system as a tool demonstrating the ring-expansion “vinyl” polymerization that allows them to produce macrocyclic polymers via a one-step vinyl polymerization.

This article introduces the new family of living radical polymerizations with germanium (Ge), tin (Sn), phosphorus (P), and nitrogen (N) catalysts which we recently developed. The polymerizations are based on a new reversible activation mechanism, Reversible chain Transfer (RT) catalysis. Low-polydispersity polymers are obtained in the homopolymerizations and random and block copolymerizations of styrene, methyl methacrylate, and functional methacrylates. The background, performance, and kinetic features of the polymerizations are described. Attractive features of the catalysts include their high reactivity, low toxicity (Ge, P, and N), low cost (P and N), and ease of handling (robustness).

The systematic search and design of phosphine ligands (PR(3)) and amine cocatalysts resulted in obtaining pentamethyl-cyclopentadienyl (Cp*) ruthenium(II) phosphine complexes [RuCp*Cl(PR(3))(2)], which are highly active and removable catalysts, for transition-metal-catalyzed living radical polymerization of methyl methacrylate (MMA). The catalysts are conveniently prepared in situ from a tetrameric precursor [RuCp*(mu(3)-Cl)](4) and a selected phosphine (PR(3)). The combination of the meta-tolyl phosphine [P(m-Tol)(3)] ligand and a primary diamine cocatalyst [NH(2)(CH(2))(6)NH(2)] provides a highly active catalytic system with precision control of the molecular weight of the polymer. The high activity enables a low catalyst dose and a high turn-over frequency without deteriorating the controllability. A hydrophilic amine cocatalyst (amino alcohol) in place of the diamine, further forms an active and removable catalyst; simple treatment with acidic water gave colorless polymers visually free from metal residues (>97 % removal

The polymerization of styrene with a polystyrene-dimethylstibanyl (PS-SbMe2) adduct as a mediator and azobis(isobutyronitrile) (AIBN) as a conventional radical initiator was kinetically studied. PS-SbMe2 had no detectable effect on the polymerization rate R p, which was virtually the same as that of the conventional (stibanyl-free) system. The pseudo-first-order activation rate constant k act was proportional to R p, meaning that degenerative (exchange) chain transfer is the only important activation mechanism, in the examined range of temperature (40–100 °C). The exchange rate constant k ex was sufficiently large at these temperatures, explaining why this polymerization can afford low-polydispersity polymers. The k ex was about twice as large as that for polystyrene-methyltellanyl (PS-TeMe). This rationalizes the better polydispersity controllability in the PS-SbMe2 system than in the PS-TeMe system. The activation energy of k ex was 22.6 kJ mol−1, which is smaller than that (27.8 kJ mol−1) for polystyrene-iodide (PS-I) and slightly larger than that (21.0 kJ mol−1) for polystyrene-dithioacetate (PS-SCSMe).

The structure and dynamics for the two types of polystyrene gels prepared by conventional and living radical polymerizations have been investigated by time-resolved dynamic light scattering (TRDLS). The reaction was initiated with the monomer solutions with and without a reversible addition–fragmentation chain transfer (RAFT) agent and was monitored through the gelation process. In the absence of a cross-linker, the reaction process was characterized by the appearance of a maximum when the excess scattering intensity divided by concentration was plotted as a function of reaction time. The intensity maximum was ascribed to an increase in the molecular weight and subsequent suppression of the concentration fluctuations, which was qualitatively reproduced by the Flory–Huggins free energy formula. As the concentration became higher, the time–intensity correlation functions (ICFs) exhibited two modes, suggesting the formation of larger aggregates in addition to the cooperative mode. The intensities were successfully decomposed into the two components by taking account of the relative amplitude of the fast and slow modes. The difference of the time-course between the two types of polymerizations was clearly detected by combining TRDLS and gel permeation chromatography, GPC, data. For the cross-linking system, the kinetics was characterized by the universal gelation mechanism, namely: (1) divergence of the slow mode and (2) appearance of the power law in ICF around the gelation threshold regardless of the polymerization method. On the other hand, the real time intensity decomposition analysis revealed striking differences in the gelation mechanism between the two types of polymerization. For example, the slow mode appeared at an early stage of reaction for the conventional system and sustained its amplitude through the gelation process. For the living (RAFT) system, the appearance of the slow mode was limited in a narrower range of the reaction time with a much smaller amplitude.

This review covers fundamental kinetic features of living radical polymerization (LRP). Theories on polymerization rate R p and polydispersity index (PDI) and experimental investigations into individual LRP systems are summarized. The presence of bimolecular termination, which is unavoidable in LRP as well as in conventional radical polymerization, provides LRP with the characteristic time dependence of radical concentrations and hence R p and PDI, depending on experimental conditions, such as the presence or absence of conventional initiation. Despite the presence of termination (and initiation, in some cases), the product from LRP can have a low polydispersity, provided that the number of terminated chains is small compared to the number of potentially active, i.e. living, chains. On the premise that an activation–deactivation quasi-equilibrium holds, a large rate constant of activation, k act , is another fundamental requisite for low polydispersities. The kinetic parameters related to reversible activation reactions are tabulated. Treated in this review are nitroxide-mediated polymerization, atom transfer radical polymerization, iodide-mediated polymerization, reversible addition–fragmentation chain transfer polymerization, and organotellurium-mediated radical polymerization.

Star poly(methyl methacrylate)s (P*) of various arm lengths and core sizes were synthesized in high yields by the polymer linking reaction in Ru(II)-catalyzed living radical polymerization. The yields of the star polymers were strongly dependent on the reaction conditions and increased under the following conditions: (1) at a higher overall concentration of arm chains ([P*]), (2) with a larger degree of polymerization (DP) of the arm chains (arm length), and (3) with a larger ratio (r) of linking agents to P* (core size). In particular, the yields sharply increased in a short time at a higher temperature, in a polar solution, and at a higher complex concentration after the addition of linking agents. These star polymers were then analyzed by multi-angle laser light scattering to determine the weight-average molecular weight (3.8 × 103 to 1.5 × 106), the number of arm chains per molecule (f = 4–63), and the radius of gyration (Rz = 2–22 nm), which also depended on the reaction conditions (e.g., f and Rz increased as [P*], DP, and r increased). Small-angle X-ray scattering analyses of the star polymers showed that they consisted of spheres for which the radius of the microgel core was 2.7 nm. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2245–2255, 2002

A theoretical analysis of the basic mechanism of living radical polymerization provides criteria for the rate constants required for optimized processes. It is extended to cover borderline cases and important side reactions as cross-disproportionation, the role of an initial excess of persistent species and of additional initiation.

Cellulose nanocrystals (CNCs) from ramie fibers are studied as stabilizers of oil-in-water emulsions. The phase behavior of heptane and water systems is studied, and emulsions stabilized by CNCs are analyzed by using drop sizing (light scattering) and optical, scanning, and freeze-fracture electron microscopies. Water-continuous Pickering emulsions are produced with cellulose nanocrystals (0.05–0.5 wt%) grafted with thermo-responsive poly(NIPAM) brushes (poly(NIPAM)-g-CNCs). They are observed to be stable during the time of observation of 4 months. In contrast, unmodified CNCs are unable to stabilize heptane-in-water emulsions. After emulsification, poly(NIPAM)-g-CNCs are observed to form aligned, layered structures at the oil–water interface. The emulsions stabilized by poly(NIPAM)-g-CNCs break after heating at a temperature above the LCST of poly(NIPAM), which is taken as indication of the temperature responsiveness of the brushes installed on the particles and thus the responsiveness of the Pickering emulsions. This phenomenon is further elucidated via rheological measurements, in which viscosities of the Pickering emulsions increase on approach of the low critical solution temperature of poly(NIPAM). The effect of temperature can be counterbalanced with the addition of salt which is explained by the reduction of electrostatic and steric interactions of poly(NIPAM)-g-CNCs at the oil–water interface.

Thermoresponsive polymers that undergo a solubility transition by variation of the temperature are important materials for the development of ‘smart’ materials. In this contribution we exploit the solubility phase transition of poly(methoxy diethylene glycol methacrylate), which is accompanied by a transition from hydrophilic to hydrophobic, for the development of a fluorescent thermometer. To translate the polymer phase transition into a fluorescent response, the polymer was functionalized with pyrene resulting in a change of the emission based on the microenvironment. This approach led to a soluble polymeric fluorescent thermometer with a temperature range from 11 °C to 21 °C. The polymer phase transition that occurs during sensing is studied in detail by dynamic light scattering.

International audience; A new and versatile synthetic strategy that provides access to precisely defined and totally soluble multicarbanionic initiators has been implemented to obtain by divergent growth dendrimer-like samples of polystyrene (PS) (up to the seventh generation) or polybutadiene (PB) (up to the third generation) and also asymmetric and miktoarm stars. This strategy rests on lithium-halide exchange reactions to generate multicarbanionic species and on the design of an original reagent that can concomitantly react with living carbanionic chains/arms to deactivate them and produce multicarbanionic sites after exchange of its bromides against lithium. This reagent, 4,4'-dibromodiphenylethylene (1), functions as a TERminating agent and a Multifunctional INItiator (TERMINI), according to a concept first proposed by Percec in another context. Upon using this anionic TERMINI in living carbanionic polymerization and repeating the two steps of chain end derivatization by 1 and divergent arm growth from the multifunctional sites generated, perfectly defined dendrimer-like polystyrene and polybutadiene could be obtained up to the seventh generation for the former and up to the third generation for the latter. Each step, i.e., chain end modification and arm growth, was carefully monitored, and the dendrimer-like samples of PS and PB were all characterized by size exclusion chromatography equipped with a multiangle laser light scattering detector (SEC/LS) and high-temperature size exclusion chromatography equipped with a viscometric detector (HT-SEC). The viscosity behavior of these dendrimer-like polystyrenes-bell-shaped variation versus the number of generation-was found to be similar to that reported for regular dendrimers. This chemistry, namely this anionic TERMINI, was also exploited to derive three-arm asymmetric and miktoarm stars.

International audience; Poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA), two polymers known to form pH-sensitive aggregates through noncovalent interactions, were assembled in purposely designed architecture sa dendrimer-like PEO scaffold carrying short inner PAA chains-to produce unimolecular systems that exhibit pH responsiveness. Because of the particular placement of the PAA chains within the dendrimer-like structure, intermolecular complexation between acrylic acid (AA) and ethylene oxide (EO) units-and thus macroscopic aggregation or even mesoscopic micellization-could be avoided in favor of the sole intramolecular complexation. The sensitivity of such interactions to pH was exploited to generate dendrimer-like PEOs that reversibly shrink and expand with the pH. Such PAA-carrying dendrimer-like PEOs were synthesized in two main steps. First, a fifth-generation dendrimer-like PEO was obtained by combining anionic ring-opening polymerization (AROP) of ethylene oxide from a tris-hydroxylated core and selective branching reactions of PEO chain ends. To this end, an AB(2)C-type branching agent was designed: the latter includes a chloromethyl (A) group for its covalent attachment to the arm ends, two geminal hydroxyls (B-2) protected in the form of a ketal ring for the growth of subsequent PEO generations by AROP, and a vinylic (C) double bonds for further functionalization of the interior of dendrimer-like PEOs. Reiteration of AROP and derivatization of PEO branches allowed us to prepare a dendrimer-like PEO of fourth generation with a total molar mass of 52,000 g center dot mol(-1), containing 24 external hydroxyl functions and 21 inner vinylic groups in the interior. A fifth generation of PEO chains was generated from this parent dendrimer-like PEO of fourth generation using a "conventional" AB(2)-type branching agent, and 48 PEO branches could be grown by AROP. The 48 outer hydroxy-end groups of the fifth-generation dendrimer-like PEO obtained were subsequently quantitatively converted into inert benzylic groups using benzyl bromide. The 21 internal vinylic groups carried by the PEO scaffold were then chemically modified in a two-step sequence into bromoester groups. The latter which are atom transfer radical polymerization (ATRP) initiating sites thus served to grow poly(tert-butylacrylate) chains. After a final step of hydrolysis of the tert-butyl ester groups, double, hydrophilic, dendrimer-like PEOs comprising 21 internal junction-attached poly(acrylic acid) (PAA) blocks could be obtained. Dynamic light scattering was used to determine the size of these dendrimer-like species in water and to investigate their response to pH variation: in particular, how the pH-sensitive complexation of EO and AA units affects their overall behavior.

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2006, Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2006, Atom transfer radikal polimerizayonu (ATRP) ve nitroksit ortamlı polimerizasyon (NMP) kontrollü polimerizasyon yöntemleri içinde en başarılı olanlarıdır. NMP ve ATRP gibi kontrollü polimerizasyon tekniklerinin avantajlarından biri de elde edilen polimerlerin molekül ağırlıklarının ve zincir uç grubu fonksiyonalitesinin kontrol edilebilir olmasıdır. Ayrıca iki fonksiyonlu asimetrik başlatıcılar kullanılarak polimer zincir uç gruplarına çok çeşitli fonksiyonellikler kazandırılabilmesidir. Bu çalışmada, iki fonksiyonlu asimetrik başlatıcı, 2-fenil-2-[(2,2,6,6-tetrametilpiperidinil)oksi]etil 2-bromo propanoat sentezlenmiş ve ATRP ve NMP yöntemleri kullanılarak SAN kopolimerler, polystyrene-block-polyacrylonitrile (PS-b-PAN), polystyrene-b-poly(n-butyl acrylate)-polyacrylonitrile (PS-b-PBA-b-PAN) and ayrıca styrene ve düzensiz SAN segmentlerini içeren blok kopolimerleri sentezlenmiştir. 1H-NMR(Nükleer Manyetik Rezonans Spektroskopisi), GPC(Jel Geçirgenlik Kromatografisi), IR(Infrared Spektroskopisi) ve DSC(Diferansiyel Taramalı Kalorimetri) cihazlarından alınan sonuçlar doğrultusunda elde edilen blok kopolimerlerin gerçekten de ATRP ve NMP tekniklerinin kombinasyonu ile oluştukları belirlenmiştir., Atom transfer radical polymerization (ATRP) and Nitroxide Mediated Polymerization (NMP) are the most successful systems in controlled radical polymerization. One of the advantageous of controlled radical polymerizations such as NMP and ATRP is that the molecular weight and the chain end functionality can be controlled.Moreover,the wide range of functionality can be introduced into a polymer chain end using asymmetric difunctional initiator. In this study, novel asymmetric double functional initiator, 2-phenyl-2- [(2,2,6,6-tetramethylpiperidino) oxy] ethyl 2-bromopropanoate was synthesized and we extend the use of difunctional initiator for the synthesis of well-defined SAN copolymers, polystyrene-block-polyacrylonitrile (PS-b-PAN), polystyrene-b-poly(n-butyl acrylate)-polyacrylonitrile (PS-b-PBA-b-PAN) and also block copolymers containing random SAN sequences and styrene by the combination of ATRP and NMP processes in a novel approach. 1H-NMR(Nuclear Magnetic Resonance), GPC (Gel Permeation Chromatography), IR(Infrared Spectrum) and DSC(Differantial Scanning Calorimetry) studies of the obtained polymers show that block copolymers are readily formed as a result of combination of ATRP and NMP mechanisms., Yüksek Lisans, M.Sc.

Dextran-b-polystyrene diblock copolymers forming miscellaneous spherical self-assemblies in water were obtained by chemical modification of the anomeric extremity of a commercial dextran followed by atom transfer radical polymerisation of styrene.

Nanocrystalline cellulose (NCC) was grafted with the thermo-responsive polymer poly(N-isopropylacrylamide) (Nipaam) via living radical polymerization. Various techniques were used to characterize the physical, chemical, morphological and thermal properties of the resulting material. The viscoelastic properties and the stability of the functionalized NCC were compared to the unmodified NCC using rheometry. The shear viscosity of the NCC suspension decreased slightly with an increase in temperature from 20°C to 45°C, indicating a stable system. The storage modulus and shear viscosity values both exhibited a burst increase at about 32.5°C, which is assigned to be the lower critical solution temperature (LCST) of poly(Nipaam). This indicates the successful functionalization of Nipaam polymer chains on NCC. In addition, the thermodynamic property of poly(Nipaam) also prevailed on the grafted NCC., Nanotech Conference and Expo 2012, June 18-21, 2012, Santa Clara, CA, USA