Marinos Pitsikalis | National & Kapodistrian University of Athens (original) (raw)

Papers by Marinos Pitsikalis

Research paper thumbnail of Association behavior of linear ω‐functionalized polybutadienes in cyclohexane

Journal of Polymer Science Part B, Jan 30, 1996

The dilute solution properties of linear polybutadienes with dimethylamine and zwitterionic end g... more The dilute solution properties of linear polybutadienes with dimethylamine and zwitterionic end groups were studied by membrane osmometry (MO), low-angle laser light scattering (LALLS), viscometry, and dynamic light scattering (DLS) in cyclohexane. The polymers were prepared by anionic polymerization, under high vacuum conditions using [3-(dimethylamino)propyl]lithium as initiator. The dimethylamine groups were converted to zwitterions by reaction with cyclopropane sultone. No evidence of association was found for the amine-capped polymers, whereas the zwitterionic samples exhibited strong association in cyclohexane. The degrees of association increase by decreasing molecular weight of the base polymer due to the excluded volume repulsions. These aggregation numbers are of the same order as those found for w-functionalized polyisoprenes, with the same polar groups in the same solvent. The hydrodynamic properties, measured by viscometry and dynamic light scattering, supported the conclusions drawn by LALLS and provide strong evidence that the aggregates behave hydrodynamically as star polymers. Comparison with theoretical models shows that the association behavior is best described by the linear head packing model.

Research paper thumbnail of Well-Defined Complex Macromolecular Architectures by Anionic Polymerization High Vacuum Techniques: Synthesis, Properties and Applications

Anionic polymerization high vacuum techniques have proven to be a very powerful tool for the synt... more Anionic polymerization high vacuum techniques have proven to be a very powerful tool for the synthesis of well-defined macromolecules with complex architectures. Until now, however only a relatively limited number of such structures with two or thee different components (star block, miktoarm star, graft, branched, cyclic, hyperbranched) have been created, the potential of anionic polymerization is unlimited. Imagination, nature, and other scientific disciplines (i.e., polymer physics, materials science, and molecular biology) will lead polymer scientists to novel structures, with the ultimate goal of designing and synthesizing polymeric materials with predetermined properties. A short review of the structure/property relationships and applications of selected polymers will be presented.

Research paper thumbnail of Recent Advances in the Synthesis of Complex Macromolecular Architectures Based on Poly(N-vinyl pyrrolidone) and the RAFT Polymerization Technique

Polymers, Feb 11, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Statistical copolymers of N-vinylpyrrolidone and benzyl methacrylate via RAFT: Monomer reactivity ratios, thermal properties and kinetics of thermal decomposition

Journal Of Macromolecular Science, Part A, Dec 28, 2017

Statistical copolymers of N-vinylpyrrolidone (NVP) with 2-(dimethylamino)ethyl methacrylate (DMAE... more Statistical copolymers of N-vinylpyrrolidone (NVP) with 2-(dimethylamino)ethyl methacrylate (DMAEMA) were prepared by Reversible Addition-Fragmentation chain Transfer Polymerization (RAFT), employing three different RAFT agents: [(O-ethylxanthyl)methyl]benzene, [1-(O-ethylxanthyl)ethyl]benzene, and O-ethyl S-(phthalimidylmethyl) xanthate. The reactivity ratios were estimated using the Fineman-Ross, inverted Fineman-Ross, Kelen-T€ udos, and extended Kelen-T€ udos graphical methods, along with the computer program COPOINT. Structural parameters of the copolymers were obtained by calculating the dyad sequence fractions and the mean sequence length. All the methods indicate that the DMAEMA reactivity ratio is much greater than the one of NVP, thus, the statistical copolymers are in fact pseudo-diblocks. The glass-transition temperature (T g) values of the copolymers were measured by Differential Scanning Calorimetry. Furthermore, a systematic and detailed investigation has been done, on the thermal degradation of the copolymers compared with the respective homopolymers, by Thermogravimetric Analysis, within the framework of the Ozawa-Flynn-Wall and Kissinger methodologies. Apparently, the thermal stability of the copolymers is influenced by both monomers and by the structure of the thiocarbonylthio end groups due to the RAFT agents. V

Research paper thumbnail of Model Mono-, Di-, and Tri-ω-Functionalized Three-Arm Star Polybutadienes. Association Behavior in Dilute Solution by Dynamic Light Scattering and Viscometry

Macromolecules, 1996

The dilute solution properties of three-arm star polybutadienes with one, two, and three dimethyl... more The dilute solution properties of three-arm star polybutadienes with one, two, and three dimethylamino or sulfobetaine end groups were studied in tetrahydrofuran (THF) and cyclohexane by dynamic light scattering and viscometry. The polymers were prepared by anionic polymerization ...

Research paper thumbnail of Hyperbranched Architectures

Springer eBooks, Oct 12, 2007

ABSTRACT

Research paper thumbnail of CHAPTER 1. Miktoarm Star (µ-Star) Polymers: A Successful Story

RSC polymer chemistry series, Apr 13, 2017

The term miktoarm stars (coming from the Greek word µικτός meaning mixed) was adopted in 1992 by ... more The term miktoarm stars (coming from the Greek word µικτός meaning mixed) was adopted in 1992 by our group for star polymers with either chemical (e.g., A2B), molecular weight (e.g., A2A′), topological (e.g., (AB)2-junction-(BA)2), or functional group (e.g., AFA2) asymmetry. The first µ-stars synthesized by anionic polymerization, on the one hand, guided polymer chemists working with other types of polymerization techniques towards this direction and, on the other hand, helped polymer physicists to carry out experiments and develop theories on the influence of the architecture on the morphology of block copolymers. Synthetic strategies based on anionic polymerization, as well as a few examples showing the influence of the miktoarm structure on the morphology of block copolymers, are reviewed in this chapter.

Research paper thumbnail of Synthesis and characterization of chiral poly(l-lactide-b-hexyl isocyanate) macromonomers with norbornenyl end groups and their homopolymerization through ring opening metathesis polymerization to afford polymer brushes

Journal of Polymer Science Part A, Jan 26, 2017

ABSTRACTWe report the synthesis of the novel half‐titanocene alkoxide complex bischloro‐η5‐cyclop... more ABSTRACTWe report the synthesis of the novel half‐titanocene alkoxide complex bischloro‐η5‐cyclopentadienyl(bicyclo[2.2.1]‐hept‐5‐en‐2‐oxy) titanium (IV), [CpTiCl2(O‐NBE)]. This complex was employed for the synthesis of chiral poly(l‐lactide‐b‐hexyl isocyanate) diblock copolymer bearing a norbornene end group with sequential addition of monomers. The poly(hexyl isocyanate) block is chiral due to the last l‐lactide unit of the poly(l‐lactide) block. This macromonomer was polymerized towards a chiral polymer brush structure with polynorbornene backbone and chiral poly(l‐lactide‐b‐hexyl isocyanate) side chains using Grubbs first‐generation catalyst. The polymers were characterized using size exclusion chromatography (SEC), nuclear magnetic resonance (NMR), and circular dichroism (CD) spectroscopy and their thermal properties were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1102–1112

Research paper thumbnail of Synthesis, Characterization and Thermal Properties of Poly(ethylene oxide), PEO, Polymacromonomers via Anionic and Ring Opening Metathesis Polymerization

Polymers, Apr 21, 2017

Branched polymers are a valuable class of polymeric materials. In the present study, anionic poly... more Branched polymers are a valuable class of polymeric materials. In the present study, anionic polymerization techniques were employed for the synthesis of low molecular weight poly(ethylene oxide) (PEO) macromonomers bearing norbornenyl end groups. The macromonomers were characterized by SEC, MALDI-TOF and NMR spectroscopy. Subsequent ring opening metathesis polymerization (ROMP) of the macromonomers using ruthenium catalysts (Grubbs catalysts of the 1st, 2nd and 3rd generations) afforded the corresponding polymacromonomers. The effects of the macromonomer molecular weight, the type of the catalyst, the nature of the solvent, the monomer concentration and the polymerization temperature on the molecular characteristics of the branched polymers were examined in detail. The crystallization behavior of the macromonomers and the corresponding polymacromonomers were studied by Differential Scanning Calorimetry (DSC). The thermal stability and the kinetics of the thermal decomposition of the samples were also studied by Thermogravimetric Analysis (TGA). The activation energies of the thermal decomposition were analyzed using the Ozawa-Flynn-Wall and Kissinger methodologies.

Research paper thumbnail of A3 polycondensation: A multicomponent step-growth polymerization reaction for the synthesis of polymeric propargylamines

Research paper thumbnail of Graft Copolymers

Encyclopedia of Polymer Science and Technology, Jul 15, 2002

Research paper thumbnail of Ring-opening polymerization of lactones using zirconocene catalytic systems: Block copolymerization with methyl methacrylate

Journal of Polymer Science Part A, 2007

The ring-opening polymerization of e-caprolactone (e-CL) and d-valerolactone (d-VL) using nine ca... more The ring-opening polymerization of e-caprolactone (e-CL) and d-valerolactone (d-VL) using nine catalytic systems consisting of a combination of three C 2v zirconocene complexes and three borate cocatalysts is discussed. The polymerizations proceed in a well-controlled manner, producing polymers with relatively high molecular weights and narrow molecular weight distributions. Kinetic experiments of the polymerization of e-CL with the catalytic system Cp 2 ZrMe 2 /B(C 6 F 5) 3 (1) showed a linear dependence between polymerization yield and molecular weight with time, as well as between the molecular weight with the molar ratio of the monomer over the catalyst [e-CL]/[Zr], indicating sufficient control of the polymerization reaction. The catalytic system (1) was utilized for the synthesis of well-defined block copolymers of MMA with e-CL and d-VL. All samples were characterized by size exclusion chromatography, nuclear magnetic resonance, and differential scanning calorimetry. V

Research paper thumbnail of Synthesis and morphological characterization of miktoarm star copolymers (PCL)2(PS)2 of poly(ɛ-caprolactone) and polystyrene

Journal of Polymer Science Part A, 2007

ABSTRACT An heterofunctional initiator combining two reactive sites for ring opening polymerizati... more ABSTRACT An heterofunctional initiator combining two reactive sites for ring opening polymerization and two for atom transfer radical polymerization was used to prepare three A2B2 miktoarm star copolymers of poly(ε-caprolactone) (PCL) and polystyrene (PS). The morphology and thermal properties were studied by transmission electron microscopy, polarized light optical microscopy, and differential scanning calorimetry. The (PCL)2(PS)2 72/28 (72 wt % PCL) sample was crystallized from a disordered melt. In this case, crystallization drove the structure formation and a lamellar morphology was obtained at the microdomain level, while spherulites were observed at a superstructural level. The other two samples, 39/61 and 27/73, with lower PCL content and higher total molecular weight, were not able to form spherulites. Surprisingly, these miktoarm star copolymers exhibited hexagonally packed cylinders and spheres morphologies, respectively, instead of lamellar and cylindrical morphology. Such unexpected and novel behavior was explained in terms of the higher resistance of the arms to be stretched in a miktoarm star copolymer when compared with the corresponding linear diblocks. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5387–5397, 2007

Research paper thumbnail of Synthesis and Micellization Behavior of Amphiphilic Block Copolymers of Poly(N-vinyl Pyrrolidone) and Poly(Benzyl Methacrylate): Block versus Statistical Copolymers

Polymers, May 8, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Statistical Copolymers of N-Vinylpyrrolidone and Isobornyl Methacrylate via Free Radical and RAFT Polymerization: Monomer Reactivity Ratios, Thermal Properties, and Kinetics of Thermal Decomposition

Polymers, Mar 3, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Polymerization of higher α-olefins using a C<sub>s</sub>-symmetry hafnium metallocene catalyst. Kinetics of the polymerization and microstructural analysis

Journal of Polymer Science Part A, Sep 1, 2009

ABSTRACT The Cs-symmetry hafnium metallocene [(p-Et3Si)C6H4]2C(2,7-di-tert-BuFlu)(C5H4)Hf(CH3)2 a... more ABSTRACT The Cs-symmetry hafnium metallocene [(p-Et3Si)C6H4]2C(2,7-di-tert-BuFlu)(C5H4)Hf(CH3)2 and tetrakis(pentafluorophenyl) borate dimethylanilinium salt ([B(C6F5)4]−[Me2NHPh]+) were used as the catalytic system for the polymerization of higher α-olefins (from hexene-1 to hexadecene-1) in toluene at 0 °C. The evolution of the polymerization was studied regarding the variation of the molecular weight, molecular weight distribution and yield with time. The effect of the monomer structure on the polymerization kinetics was established. The role of trioctylaluminum in accelerating the polymerization was investigated. 13C NMR spectroscopy was used to study the microstructure of the poly(α-olefins) by the determination of the pentad monomer sequences. The thermal properties of the polymers were obtained by differential scanning calorimetry, DSC. The results were discussed in connection with the polymer microstructure. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4314–4325, 2009

Research paper thumbnail of Statistical Copolymers Of Benzyl Methacrylate And Diethylaminoethyl Methacrylate: Monomer Reactivity Ratios And Thermal Properties

Journal of organic & inorganic chemistry, 2015

Statistical copolymers of benzyl methacrylate (BzMA) and diethylaminoethyl methacrylate (DEAEMA) ... more Statistical copolymers of benzyl methacrylate (BzMA) and diethylaminoethyl methacrylate (DEAEMA) were prepared by free radical polymerization. The reactivity ratios were estimated using the Finemann-Ross, inverted Finemann-Ross, and Kelen-Tüdos graphical methods, along with the computer program COPOINT. Structural parameters of the copolymers were obtained by calculating the dyad monomer sequence fractions and the mean sequence length. The glass-transition temperature (T g) values of the copolymers were measured and examined by means of several theoretical equations, allowing the prediction of these T g values. The kinetics of thermal degradation behavior of the copolymers was also studied by thermogravimetric analysis and compared with the respective homopolymers.

Research paper thumbnail of High frequency acoustic excitations in ordered diblock copolymer studied by inelastic x-ray scattering

Journal of Chemical Physics, Jul 14, 2004

The phonon propagation in lamellar nanostructures formed via self-assembling of short styrene-b-i... more The phonon propagation in lamellar nanostructures formed via self-assembling of short styrene-b-isoprene ͑SI͒ as well as of its more incompatible styrene-b-͑ethylene-alt-propylene͒ ͑SEP͒ counterpart was studied by inelastic x-ray scattering. Irrespective of the physical state of the block copolymers, a single acoustic phonon was observed in SI ͑ordered and disordered͒ and SEP ͑ordered͒. At GHz frequencies, inelastic light scattering from the same samples revealed very small dispersion in the sound phase velocity but a short phonon lifetime.

Research paper thumbnail of Complex Brush-Like Macromolecular Architectures via Anionic and Ring Opening Metathesis Polymerization: Synthesis, Characterization, and Thermal Properties

Macromolecular Chemistry and Physics, Sep 27, 2017

Since the seminal work of Szwarc in 1955, the livingness of macroanions was proved, and the term ... more Since the seminal work of Szwarc in 1955, the livingness of macroanions was proved, and the term "living" was coined. [4] The ground breaking discovery of Szwarc was followed by subsequent developments by Morton, [5] Bywater, Worsfold, [6] Roovers, Fetters, Quirk, and many other researchers leading to the synthesis of well-defined polymeric materials with high molecular weight, structural and compositional homogeneity, predetermined properties, and a rich variety of applications. [7] Furthermore, complex macromolecular architectures were obtained either purely by anionic polymerization techniques or by combination with other controlled/living polymerization methods, such as controlled radical (nitroxide-mediated, atom transfer radical polymerization (ATRP), reversible addition fragmentation chain transfer radical polymerization (RAFT)), cationic, ring opening, ring opening metathesis (ROMP), group transfer, and coordination polymerization. [8] Adopting these approaches, stars, cyclic, comb, dendritic, hyperbranched, and other more complex structures have been prepared. [9] Among all of these structures, special interest has been dedicated to branched polymers, which are composed of macromolecular chains regularly spaced along a polymeric backbone. [10] Probably the most important subclass of branched polymers are the bottlebrushes, in which the side chains are densely distributed along the polymeric backbone. [11] They can be synthesized either through the grafting to, the grafting from, or the grafting through methodology. The last method is the most efficient, affording the highest grafting density and is based on the polymerization of macromonomers. Macromonomers are oligomeric or polymeric chains bearing polymerizable end groups. They have been widely and successfully used as building blocks for the synthesis of an enormous number of branched macromolecular architectures. [11a,12] This is a consequence of the huge variety of macromonomers that have been prepared as well as the different methods that have been employed for their homo-and/or copolymerization with either low molecular weight monomers or other macromonomers. These branched structures are well-defined since: (a) the length of the branches is predetermined by the molecular weight of the macromonomer, (b) the size of the main Polymer Brushes Combination of anionic and ring opening metathesis (ROMP) polymerizations is conducted for the synthesis of different series of brush polymers adopting the macromonomer methodology. Specifically, poly(tert-butoxystyrene) (PtBOS), polystyrene (PS), and poly(ethylene oxide) (PEO) macromonomers, having end norbornene groups, are prepared by anionic polymerization techniques and suitable termination reactions or functional anionic initiators. These macromonomers are either homopolymerized or copolymerized by ROMP employing Ruthenium Grubbs catalysts of the 1st or 3rd generation leading to the formation of polymer brushes. Using this synthetic approach, PtBOS polymacromonomers, PtBOS-PEO block and random copolymacromonomers, and PtBOS-PS random copolymacromonomers are prepared. Acidic hydrolysis of the tert-butoxy groups of the PtBOS brushes affords the corresponding polyhydroxystyrene (PSOH) brushes. Subsequent activation of the hydroxyl groups upon reaction with triphenylmethyl potassium and addition of ethylene oxide lead to the formation of PEO brushes on the PSOH brushes (brush on brush structures). These materials are thoroughly characterized by size exclusion chromatography, and 1 H-NMR spectroscopy. The thermal properties are studied by differential scanning calorimetry, thermogravimetric analysis , and differential thermogravimetry.

Research paper thumbnail of Effect of the Soluble Block Size on Spherical Diblock Polymer Micelles

Bulletin of the American Physical Society, Mar 23, 2005

Carolina at Chapel Hill-In order to understand the effect that the soluble block has on the equil... more Carolina at Chapel Hill-In order to understand the effect that the soluble block has on the equilibrium size and shape of polymer micelles, we have characterized spherical micelles formed from two series of polystyrene-bpolyisoprene in dilute solutions of the selective solvent, heptane. We show that varying the soluble (PI) block from 10-100K when the insoluble (PS) block is kept constant (20K and 40K) changes the CMC by over an order of magnitude for both series and the aggregation number by an order of magnitude for the 20K series and a factor of 3 for the 40K series. We have also studied the effect that temperature has on the CMC of the two series. The results are found to be in good agreement with recently developed theory.

Research paper thumbnail of Association behavior of linear ω‐functionalized polybutadienes in cyclohexane

Journal of Polymer Science Part B, Jan 30, 1996

The dilute solution properties of linear polybutadienes with dimethylamine and zwitterionic end g... more The dilute solution properties of linear polybutadienes with dimethylamine and zwitterionic end groups were studied by membrane osmometry (MO), low-angle laser light scattering (LALLS), viscometry, and dynamic light scattering (DLS) in cyclohexane. The polymers were prepared by anionic polymerization, under high vacuum conditions using [3-(dimethylamino)propyl]lithium as initiator. The dimethylamine groups were converted to zwitterions by reaction with cyclopropane sultone. No evidence of association was found for the amine-capped polymers, whereas the zwitterionic samples exhibited strong association in cyclohexane. The degrees of association increase by decreasing molecular weight of the base polymer due to the excluded volume repulsions. These aggregation numbers are of the same order as those found for w-functionalized polyisoprenes, with the same polar groups in the same solvent. The hydrodynamic properties, measured by viscometry and dynamic light scattering, supported the conclusions drawn by LALLS and provide strong evidence that the aggregates behave hydrodynamically as star polymers. Comparison with theoretical models shows that the association behavior is best described by the linear head packing model.

Research paper thumbnail of Well-Defined Complex Macromolecular Architectures by Anionic Polymerization High Vacuum Techniques: Synthesis, Properties and Applications

Anionic polymerization high vacuum techniques have proven to be a very powerful tool for the synt... more Anionic polymerization high vacuum techniques have proven to be a very powerful tool for the synthesis of well-defined macromolecules with complex architectures. Until now, however only a relatively limited number of such structures with two or thee different components (star block, miktoarm star, graft, branched, cyclic, hyperbranched) have been created, the potential of anionic polymerization is unlimited. Imagination, nature, and other scientific disciplines (i.e., polymer physics, materials science, and molecular biology) will lead polymer scientists to novel structures, with the ultimate goal of designing and synthesizing polymeric materials with predetermined properties. A short review of the structure/property relationships and applications of selected polymers will be presented.

Research paper thumbnail of Recent Advances in the Synthesis of Complex Macromolecular Architectures Based on Poly(N-vinyl pyrrolidone) and the RAFT Polymerization Technique

Polymers, Feb 11, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Statistical copolymers of N-vinylpyrrolidone and benzyl methacrylate via RAFT: Monomer reactivity ratios, thermal properties and kinetics of thermal decomposition

Journal Of Macromolecular Science, Part A, Dec 28, 2017

Statistical copolymers of N-vinylpyrrolidone (NVP) with 2-(dimethylamino)ethyl methacrylate (DMAE... more Statistical copolymers of N-vinylpyrrolidone (NVP) with 2-(dimethylamino)ethyl methacrylate (DMAEMA) were prepared by Reversible Addition-Fragmentation chain Transfer Polymerization (RAFT), employing three different RAFT agents: [(O-ethylxanthyl)methyl]benzene, [1-(O-ethylxanthyl)ethyl]benzene, and O-ethyl S-(phthalimidylmethyl) xanthate. The reactivity ratios were estimated using the Fineman-Ross, inverted Fineman-Ross, Kelen-T€ udos, and extended Kelen-T€ udos graphical methods, along with the computer program COPOINT. Structural parameters of the copolymers were obtained by calculating the dyad sequence fractions and the mean sequence length. All the methods indicate that the DMAEMA reactivity ratio is much greater than the one of NVP, thus, the statistical copolymers are in fact pseudo-diblocks. The glass-transition temperature (T g) values of the copolymers were measured by Differential Scanning Calorimetry. Furthermore, a systematic and detailed investigation has been done, on the thermal degradation of the copolymers compared with the respective homopolymers, by Thermogravimetric Analysis, within the framework of the Ozawa-Flynn-Wall and Kissinger methodologies. Apparently, the thermal stability of the copolymers is influenced by both monomers and by the structure of the thiocarbonylthio end groups due to the RAFT agents. V

Research paper thumbnail of Model Mono-, Di-, and Tri-ω-Functionalized Three-Arm Star Polybutadienes. Association Behavior in Dilute Solution by Dynamic Light Scattering and Viscometry

Macromolecules, 1996

The dilute solution properties of three-arm star polybutadienes with one, two, and three dimethyl... more The dilute solution properties of three-arm star polybutadienes with one, two, and three dimethylamino or sulfobetaine end groups were studied in tetrahydrofuran (THF) and cyclohexane by dynamic light scattering and viscometry. The polymers were prepared by anionic polymerization ...

Research paper thumbnail of Hyperbranched Architectures

Springer eBooks, Oct 12, 2007

ABSTRACT

Research paper thumbnail of CHAPTER 1. Miktoarm Star (µ-Star) Polymers: A Successful Story

RSC polymer chemistry series, Apr 13, 2017

The term miktoarm stars (coming from the Greek word µικτός meaning mixed) was adopted in 1992 by ... more The term miktoarm stars (coming from the Greek word µικτός meaning mixed) was adopted in 1992 by our group for star polymers with either chemical (e.g., A2B), molecular weight (e.g., A2A′), topological (e.g., (AB)2-junction-(BA)2), or functional group (e.g., AFA2) asymmetry. The first µ-stars synthesized by anionic polymerization, on the one hand, guided polymer chemists working with other types of polymerization techniques towards this direction and, on the other hand, helped polymer physicists to carry out experiments and develop theories on the influence of the architecture on the morphology of block copolymers. Synthetic strategies based on anionic polymerization, as well as a few examples showing the influence of the miktoarm structure on the morphology of block copolymers, are reviewed in this chapter.

Research paper thumbnail of Synthesis and characterization of chiral poly(l-lactide-b-hexyl isocyanate) macromonomers with norbornenyl end groups and their homopolymerization through ring opening metathesis polymerization to afford polymer brushes

Journal of Polymer Science Part A, Jan 26, 2017

ABSTRACTWe report the synthesis of the novel half‐titanocene alkoxide complex bischloro‐η5‐cyclop... more ABSTRACTWe report the synthesis of the novel half‐titanocene alkoxide complex bischloro‐η5‐cyclopentadienyl(bicyclo[2.2.1]‐hept‐5‐en‐2‐oxy) titanium (IV), [CpTiCl2(O‐NBE)]. This complex was employed for the synthesis of chiral poly(l‐lactide‐b‐hexyl isocyanate) diblock copolymer bearing a norbornene end group with sequential addition of monomers. The poly(hexyl isocyanate) block is chiral due to the last l‐lactide unit of the poly(l‐lactide) block. This macromonomer was polymerized towards a chiral polymer brush structure with polynorbornene backbone and chiral poly(l‐lactide‐b‐hexyl isocyanate) side chains using Grubbs first‐generation catalyst. The polymers were characterized using size exclusion chromatography (SEC), nuclear magnetic resonance (NMR), and circular dichroism (CD) spectroscopy and their thermal properties were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1102–1112

Research paper thumbnail of Synthesis, Characterization and Thermal Properties of Poly(ethylene oxide), PEO, Polymacromonomers via Anionic and Ring Opening Metathesis Polymerization

Polymers, Apr 21, 2017

Branched polymers are a valuable class of polymeric materials. In the present study, anionic poly... more Branched polymers are a valuable class of polymeric materials. In the present study, anionic polymerization techniques were employed for the synthesis of low molecular weight poly(ethylene oxide) (PEO) macromonomers bearing norbornenyl end groups. The macromonomers were characterized by SEC, MALDI-TOF and NMR spectroscopy. Subsequent ring opening metathesis polymerization (ROMP) of the macromonomers using ruthenium catalysts (Grubbs catalysts of the 1st, 2nd and 3rd generations) afforded the corresponding polymacromonomers. The effects of the macromonomer molecular weight, the type of the catalyst, the nature of the solvent, the monomer concentration and the polymerization temperature on the molecular characteristics of the branched polymers were examined in detail. The crystallization behavior of the macromonomers and the corresponding polymacromonomers were studied by Differential Scanning Calorimetry (DSC). The thermal stability and the kinetics of the thermal decomposition of the samples were also studied by Thermogravimetric Analysis (TGA). The activation energies of the thermal decomposition were analyzed using the Ozawa-Flynn-Wall and Kissinger methodologies.

Research paper thumbnail of A3 polycondensation: A multicomponent step-growth polymerization reaction for the synthesis of polymeric propargylamines

Research paper thumbnail of Graft Copolymers

Encyclopedia of Polymer Science and Technology, Jul 15, 2002

Research paper thumbnail of Ring-opening polymerization of lactones using zirconocene catalytic systems: Block copolymerization with methyl methacrylate

Journal of Polymer Science Part A, 2007

The ring-opening polymerization of e-caprolactone (e-CL) and d-valerolactone (d-VL) using nine ca... more The ring-opening polymerization of e-caprolactone (e-CL) and d-valerolactone (d-VL) using nine catalytic systems consisting of a combination of three C 2v zirconocene complexes and three borate cocatalysts is discussed. The polymerizations proceed in a well-controlled manner, producing polymers with relatively high molecular weights and narrow molecular weight distributions. Kinetic experiments of the polymerization of e-CL with the catalytic system Cp 2 ZrMe 2 /B(C 6 F 5) 3 (1) showed a linear dependence between polymerization yield and molecular weight with time, as well as between the molecular weight with the molar ratio of the monomer over the catalyst [e-CL]/[Zr], indicating sufficient control of the polymerization reaction. The catalytic system (1) was utilized for the synthesis of well-defined block copolymers of MMA with e-CL and d-VL. All samples were characterized by size exclusion chromatography, nuclear magnetic resonance, and differential scanning calorimetry. V

Research paper thumbnail of Synthesis and morphological characterization of miktoarm star copolymers (PCL)2(PS)2 of poly(ɛ-caprolactone) and polystyrene

Journal of Polymer Science Part A, 2007

ABSTRACT An heterofunctional initiator combining two reactive sites for ring opening polymerizati... more ABSTRACT An heterofunctional initiator combining two reactive sites for ring opening polymerization and two for atom transfer radical polymerization was used to prepare three A2B2 miktoarm star copolymers of poly(ε-caprolactone) (PCL) and polystyrene (PS). The morphology and thermal properties were studied by transmission electron microscopy, polarized light optical microscopy, and differential scanning calorimetry. The (PCL)2(PS)2 72/28 (72 wt % PCL) sample was crystallized from a disordered melt. In this case, crystallization drove the structure formation and a lamellar morphology was obtained at the microdomain level, while spherulites were observed at a superstructural level. The other two samples, 39/61 and 27/73, with lower PCL content and higher total molecular weight, were not able to form spherulites. Surprisingly, these miktoarm star copolymers exhibited hexagonally packed cylinders and spheres morphologies, respectively, instead of lamellar and cylindrical morphology. Such unexpected and novel behavior was explained in terms of the higher resistance of the arms to be stretched in a miktoarm star copolymer when compared with the corresponding linear diblocks. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5387–5397, 2007

Research paper thumbnail of Synthesis and Micellization Behavior of Amphiphilic Block Copolymers of Poly(N-vinyl Pyrrolidone) and Poly(Benzyl Methacrylate): Block versus Statistical Copolymers

Polymers, May 8, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Statistical Copolymers of N-Vinylpyrrolidone and Isobornyl Methacrylate via Free Radical and RAFT Polymerization: Monomer Reactivity Ratios, Thermal Properties, and Kinetics of Thermal Decomposition

Polymers, Mar 3, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Polymerization of higher α-olefins using a C<sub>s</sub>-symmetry hafnium metallocene catalyst. Kinetics of the polymerization and microstructural analysis

Journal of Polymer Science Part A, Sep 1, 2009

ABSTRACT The Cs-symmetry hafnium metallocene [(p-Et3Si)C6H4]2C(2,7-di-tert-BuFlu)(C5H4)Hf(CH3)2 a... more ABSTRACT The Cs-symmetry hafnium metallocene [(p-Et3Si)C6H4]2C(2,7-di-tert-BuFlu)(C5H4)Hf(CH3)2 and tetrakis(pentafluorophenyl) borate dimethylanilinium salt ([B(C6F5)4]−[Me2NHPh]+) were used as the catalytic system for the polymerization of higher α-olefins (from hexene-1 to hexadecene-1) in toluene at 0 °C. The evolution of the polymerization was studied regarding the variation of the molecular weight, molecular weight distribution and yield with time. The effect of the monomer structure on the polymerization kinetics was established. The role of trioctylaluminum in accelerating the polymerization was investigated. 13C NMR spectroscopy was used to study the microstructure of the poly(α-olefins) by the determination of the pentad monomer sequences. The thermal properties of the polymers were obtained by differential scanning calorimetry, DSC. The results were discussed in connection with the polymer microstructure. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4314–4325, 2009

Research paper thumbnail of Statistical Copolymers Of Benzyl Methacrylate And Diethylaminoethyl Methacrylate: Monomer Reactivity Ratios And Thermal Properties

Journal of organic & inorganic chemistry, 2015

Statistical copolymers of benzyl methacrylate (BzMA) and diethylaminoethyl methacrylate (DEAEMA) ... more Statistical copolymers of benzyl methacrylate (BzMA) and diethylaminoethyl methacrylate (DEAEMA) were prepared by free radical polymerization. The reactivity ratios were estimated using the Finemann-Ross, inverted Finemann-Ross, and Kelen-Tüdos graphical methods, along with the computer program COPOINT. Structural parameters of the copolymers were obtained by calculating the dyad monomer sequence fractions and the mean sequence length. The glass-transition temperature (T g) values of the copolymers were measured and examined by means of several theoretical equations, allowing the prediction of these T g values. The kinetics of thermal degradation behavior of the copolymers was also studied by thermogravimetric analysis and compared with the respective homopolymers.

Research paper thumbnail of High frequency acoustic excitations in ordered diblock copolymer studied by inelastic x-ray scattering

Journal of Chemical Physics, Jul 14, 2004

The phonon propagation in lamellar nanostructures formed via self-assembling of short styrene-b-i... more The phonon propagation in lamellar nanostructures formed via self-assembling of short styrene-b-isoprene ͑SI͒ as well as of its more incompatible styrene-b-͑ethylene-alt-propylene͒ ͑SEP͒ counterpart was studied by inelastic x-ray scattering. Irrespective of the physical state of the block copolymers, a single acoustic phonon was observed in SI ͑ordered and disordered͒ and SEP ͑ordered͒. At GHz frequencies, inelastic light scattering from the same samples revealed very small dispersion in the sound phase velocity but a short phonon lifetime.

Research paper thumbnail of Complex Brush-Like Macromolecular Architectures via Anionic and Ring Opening Metathesis Polymerization: Synthesis, Characterization, and Thermal Properties

Macromolecular Chemistry and Physics, Sep 27, 2017

Since the seminal work of Szwarc in 1955, the livingness of macroanions was proved, and the term ... more Since the seminal work of Szwarc in 1955, the livingness of macroanions was proved, and the term "living" was coined. [4] The ground breaking discovery of Szwarc was followed by subsequent developments by Morton, [5] Bywater, Worsfold, [6] Roovers, Fetters, Quirk, and many other researchers leading to the synthesis of well-defined polymeric materials with high molecular weight, structural and compositional homogeneity, predetermined properties, and a rich variety of applications. [7] Furthermore, complex macromolecular architectures were obtained either purely by anionic polymerization techniques or by combination with other controlled/living polymerization methods, such as controlled radical (nitroxide-mediated, atom transfer radical polymerization (ATRP), reversible addition fragmentation chain transfer radical polymerization (RAFT)), cationic, ring opening, ring opening metathesis (ROMP), group transfer, and coordination polymerization. [8] Adopting these approaches, stars, cyclic, comb, dendritic, hyperbranched, and other more complex structures have been prepared. [9] Among all of these structures, special interest has been dedicated to branched polymers, which are composed of macromolecular chains regularly spaced along a polymeric backbone. [10] Probably the most important subclass of branched polymers are the bottlebrushes, in which the side chains are densely distributed along the polymeric backbone. [11] They can be synthesized either through the grafting to, the grafting from, or the grafting through methodology. The last method is the most efficient, affording the highest grafting density and is based on the polymerization of macromonomers. Macromonomers are oligomeric or polymeric chains bearing polymerizable end groups. They have been widely and successfully used as building blocks for the synthesis of an enormous number of branched macromolecular architectures. [11a,12] This is a consequence of the huge variety of macromonomers that have been prepared as well as the different methods that have been employed for their homo-and/or copolymerization with either low molecular weight monomers or other macromonomers. These branched structures are well-defined since: (a) the length of the branches is predetermined by the molecular weight of the macromonomer, (b) the size of the main Polymer Brushes Combination of anionic and ring opening metathesis (ROMP) polymerizations is conducted for the synthesis of different series of brush polymers adopting the macromonomer methodology. Specifically, poly(tert-butoxystyrene) (PtBOS), polystyrene (PS), and poly(ethylene oxide) (PEO) macromonomers, having end norbornene groups, are prepared by anionic polymerization techniques and suitable termination reactions or functional anionic initiators. These macromonomers are either homopolymerized or copolymerized by ROMP employing Ruthenium Grubbs catalysts of the 1st or 3rd generation leading to the formation of polymer brushes. Using this synthetic approach, PtBOS polymacromonomers, PtBOS-PEO block and random copolymacromonomers, and PtBOS-PS random copolymacromonomers are prepared. Acidic hydrolysis of the tert-butoxy groups of the PtBOS brushes affords the corresponding polyhydroxystyrene (PSOH) brushes. Subsequent activation of the hydroxyl groups upon reaction with triphenylmethyl potassium and addition of ethylene oxide lead to the formation of PEO brushes on the PSOH brushes (brush on brush structures). These materials are thoroughly characterized by size exclusion chromatography, and 1 H-NMR spectroscopy. The thermal properties are studied by differential scanning calorimetry, thermogravimetric analysis , and differential thermogravimetry.

Research paper thumbnail of Effect of the Soluble Block Size on Spherical Diblock Polymer Micelles

Bulletin of the American Physical Society, Mar 23, 2005

Carolina at Chapel Hill-In order to understand the effect that the soluble block has on the equil... more Carolina at Chapel Hill-In order to understand the effect that the soluble block has on the equilibrium size and shape of polymer micelles, we have characterized spherical micelles formed from two series of polystyrene-bpolyisoprene in dilute solutions of the selective solvent, heptane. We show that varying the soluble (PI) block from 10-100K when the insoluble (PS) block is kept constant (20K and 40K) changes the CMC by over an order of magnitude for both series and the aggregation number by an order of magnitude for the 20K series and a factor of 3 for the 40K series. We have also studied the effect that temperature has on the CMC of the two series. The results are found to be in good agreement with recently developed theory.