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International audience; To the best of our knowledge, this is the very first time that a thorough study of the synthetic procedures, molecular and thermal characterization, followed by structure/properties relationship for symmetric and non-symmetric second generation (2-G) dendritic terpolymers is reported. Actually, the synthesis of the non-symmetric materials is reported for the first time in the literature. Anionic polymerization enables the synthesis of well-defined polymers that, despite the architecture complexity, absolute control over the average molecular weight, as well as block composition, is achieved. The dendritic type macromolecular architecture affects the microphase separation, because different morphologies are obtained, which do not exhibit long range order, and various defects or dislocations are evident attributed to the increased number of junction points of the final material despite the satisfactory thermal annealing at temperatures above the highest glass transition temperature of all blocks. For comparison reasons, the initial dendrons (miktoarm star terpolymer precursors) which are connected to each other in order to synthesize the final dendritic terpolymers are characterized in solution and in bulk and their self-assembly is also studied. A major conclusion is that specific structures are adopted which depend on the type of the core connection between the ligand and the active sites of the dendrons.

Aromatic polyimides containing an ortho-allyloxy group with different ratios (in the range of 10–100%) of the ortho-allyloxy to ortho-hydroxy units were synthesized. The allyl ether synthesis was done via a post-polymerization Williamson etherification reaction. Thermally induced Claisen-rearrangement of the allyloxy-phenyl unit was conducted in the solid-state, followed by isothermal treatments at 250 °C leading to a crosslinked ortho-hydroxy containing polyimide. Further thermal annealing at 350 °C was employed to achieve a high imide-to-benzoxazole conversion, commonly described as the thermal rearrangement process (TR). The influence of the degree of modification on the crosslinking reaction as well as the imide-to-benzoxazole conversion temperature and the rate were studied by means of TG-FTIR, DSC and dielectric spectroscopy. A nearly linear change of the material properties, such as film density, d-spacing and gel-fraction, with an increasing number of allylated units was observed. Additionally, an incline of the permeability, due to an increase of the free volume elements, was observed. Moreover, the polymer chain mobility in terms of relaxation times was demonstrated to depend on the degree of allylation, which in turn led to a reduction of the TR temperature of about 80 °C compared to the pristine polyimide. The thermally induced imide-to-benzoxazole rearrangement occurred already to a large extent of 77% at 350 °C. In comparison, the pristine polymer showed only a conversion of 20%. Furthermore, the observed HPI-to-PBO conversions at 350 °C surpassed those of various other reported TR polyimides treated at even higher temperatures of 400 to 450 °C. Side-reactions and degradation that usually accompany treatments at 400 °C and above might be avoided at lower treatment temperatures of 350 °C.

In this paper, the formation of nanostructured triblock terpolymer polystyrene-b-poly(4-vinylpyridine)-b-poly(solketal methacrylate) (PS-b-P4VP-b-PSMA), polystyrene-b-poly(4-vinylpyridine)-b-poly(glyceryl methacrylate) (PS-b-P4VP-b-PGMA) membranes via block copolymer self-assembly followed by non-solvent-induced phase separation (SNIPS) is demonstrated. An increase in the hydrophilicity was observed after treatment of non-charged isoporous membranes from PS-b-P4VP-b-PSMA, through acidic hydrolysis of the hydrophobic poly(solketal methacrylate) PSMA block into a hydrophilic poly(glyceryl methacrylate) PGMA block, which contains two neighbored hydroxyl (&ndash, OH) groups per repeating unit. For the first time, PS-b-P4VP-b-PSMA triblock terpolymers with varying compositions were successfully synthesized by sequential living anionic polymerization. Composite membranes of PS-b-P4VP-b-PSMA and PS-b-P4VP-b-PGMA triblock terpolymers with ordered hexagonally packed cylindrical pores were developed. The morphology of the membranes was studied with scanning electron microscopy (SEM) and atomic force microscopy (AFM). PS-b-P4VP-b-PSMA triblock terpolymer membranes were further treated with acid (1 M HCl) to get polystyrene-b-poly(4-vinylpyridine)-b-poly(glyceryl methacrylate) (PS-b-P4VP-b-PGMA). Notably, the pristine porous membrane structure could be maintained even after acidic hydrolysis. It was found that membranes containing hydroxyl groups (PS-b-P4VP-b-PGMA) show a stable and higher water permeance than membranes without hydroxyl groups (PS-b-P4VP-b-PSMA), what is due to the increase in hydrophilicity. The membrane properties were analyzed further by contact angle, protein retention, and adsorption measurements.

Two well-defined heptablock quaterpolymers of the ABCDCBA type [Α: polystyrene (PS), B: poly(butadiene) with ∼90% 1,4-microstructure (PB1,4), C: poly(isoprene) with ∼55% 3,4-microstructure (PI3,4) and D: poly(dimethylsiloxane) (PDMS)] were synthesized by combining anionic polymerization high vacuum techniques and hydrosilylation/chlorosilane chemistry. All intermediates and final products were characterized by size exclusion chromatography, membrane osmometry, and proton nuclear magnetic resonance spectroscopy. Fourier transform infrared spectroscopy was used to further verify the chemical modification reaction of the difunctional PDMS. The self-assembly in bulk of these novel heptablock quarterpolymers, studied by transmission electron microscopy and small angle X-ray scattering, revealed 3-phase 4-layer alternating lamellae morphology of PS, PB1,4, and mixed PI3,4/PDMS domains. Differential scanning calorimetry was used to further confirm the miscibility of PI3,4 and PDMS blocks. It is the first time that PDMS is the central segment in such multiblock polymers (≥3 chemically different blocks). © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1443–1449

In this study, the thermal and rheological properties of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) diblock copolymers are investigated in order to get information about the optimum foaming temperature. Foams of these diblock copolymers were prepared using the technique of batch foaming with carbon dioxide as environmentally-benign blowing agent. The tailored PS-b-P4VP diblock copolymers with different molecular weights and a cylindrical morphology were prepared and analysed regarding their thermal stability. High-pressure differential scanning calorimetry exposes the plasticising effect of the blowing agent which yields a decrease of the glass transition temperature of the polystyrene and the poly(4-vinylpyridine) blocks. Sorption measurements were performed in order to measure the uptake of carbon dioxide in the diblock copolymer. Additionally, rheological experiments in the oscillatory mode were conducted which confirmed a microphase-separated structure of the PS-b-P4VP diblock copolymers by a plateau of the storage and loss moduli in the temperature range of processing. In shear and melt elongation, the transient shear viscosity and the transient elongational viscosity were much smaller than the linear viscoelastic prediction at later times. The analysis of the foam morphology revealed that the foam density of the diblock copolymers as measured via Archimedes' principle exhibits the lowest foam density at a molecular weight in the order of 160 kg mol−1.

Synthesis, molecular, and morphological characterization of two linear diblock copolymers consisting of two polydienes with specific geometric isomerisms and two triblock terpolymers with a combination of the same polydienes with polystyrene are investigated for both lower and very high molecular weights. This work is inspired from a previous research study which demonstrated that linear ABC terpolymers consisting of polystyrene, poly(butadiene), and poly(isoprene), with specific geometric isomerisms for the polydienes, lead to 3-phase microphase separated systems. We report also the coexistence of the core-shell double gyroid and the 3-phase 4-layer alternating lamellae morphologies with the majority fraction being the lamellar structure. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1238–1246

In this paper; we compare double hydrophobic polystyrene-b-poly(solketal methacrylate) (PS-b-PSMA) and amphiphilic polystyrene-b-poly(glyceryl methacrylate) (PS-b-PGMA) diblock copolymer membranes which are prepared by combining the block copolymer self-assembly in solution with a non-solvent induced phase separation (SNIPS). Diblock copolymers (i.e., PS-b-PSMA) were synthesized by sequential living anionic polymerization, whereas polystyrene-b-poly(glyceryl methacrylate) (PS-b-PGMA) were obtained by acid hydrolysis of the acetonide groups of the polysolketal methacrylate (PSMA) blocks into dihydroxyl groups (PGMA). Membrane structures and bulk morphologies were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM); respectively. The resulting PS-b-PGMA diblock copolymers produce an ordered hexagonal cylindrical pore structure during the SNIPS process, while membranes fabricated from the double hydrophobic (PS-b-PSMA) do not under similar experimental conditions. Membrane performance was evaluated by water flux and contact angle measurements.

The objective of this study is to analyze the glass transition temperature and relaxation processes of low molecular weight polystyrene-block-polyisoprene diblock copolymers with different compositions, synthesized via anionic polymerization. Thermal properties were investigated by differential scanning calorimetry and dynamic-mechanical thermal analysis, while the morphologies at room temperature were investigated by transmission electron microscopy and small-angle X-ray scattering. The χN values indicate that the diblock copolymers lie near the weak segregation regime. Three different experimental techniques were applied to determine the dynamic properties, i.e., linear viscoelastic shear oscillations, creep recovery experiments, and dielectric spectroscopy. The rheological experiments were performed above the order–disorder transition temperature where the diblock copolymers behave like a Maxwell fluid. Our results indicate that the presence of the polyisoprene segments strongly influences the monomeric friction coefficient and the tendency to form entanglements above the order–disorder temperature. Consequently, the zero-shear rate viscosity of a diblock copolymer is much lower than the zero-shear rate viscosity of the neat polystyrene block (the polystyrene precursor of the polymerization procedure). Dielectric spectroscopy enables the analysis of relaxation processes below the glass transition of the polystyrene microphase. Frequency sweeps indicate the dynamic glass transition of the polyisoprene blocks, which are partly mixed with the polystyrene blocks, which are always the majority component in the block copolymers of this study.

Membrane formation via the combination of self-assembly and the non-solvent induced phase separation (NIPS) process of diblock copolymers is investigated. Several polystyrene- block -poly(4-vinylpyridine) (PS- b -P4VP) diblock copolymers with different molecular weights and weight percentages of both blocks are tested under different parameters, leading to membrane surfaces with uniform pores of approximately 20–70 nm diameter. The average pore diameter is proved to be adjustable by changing the total molar mass of the block copolymer. The solution composition is an additional parameter controlling the structure formation. The purpose was to explore the upper and lower limits of the membrane structure formation by varying the molecular weight and the composition of the block copolymer. Scanning electron microscopy (SEM) is used to image the surface morphology and the homogeneity of the pore sizes. Primary results of water flux and retention are presented.

The formation of integral asymmetric membranes from ABC triblock terpolymers by non-solvent-induced phase separation is shown. They are compared with the AB diblock copolymer precursors. Triblock terpolymers of polystyrene-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) (PS-b-P2VP-b-PEO) with two compositions are investigated. The third block supports the formation of a membrane in a case, where the corresponding diblock copolymer does not form a good membrane. In addition, the hydrophilicity is increased by the third block and due to the hydroxyl group the possibility of post-functionalization is given. The morphologies are imaged by scanning electron microscopy. The influence of the PEO on the membrane properties is analyzed by water flux, retention, and dynamic contact angle measurements.

The synthesis via anionic polymerization of six linear triblock terpolymers with various sequences of blocks such as PS (polystyrene), PB [poly(butadiene)], PI [(poly(isoprene)] and PCHD [poly(1,3-cyclohexadiene)] is reported. The synthesis of the terpolymers was carried out by the use of anionic polymerization with high-vacuum techniques and sequential monomer addition. Molecular characterization of the samples was performed via size exclusion chromatography (SEC) and membrane osmometry (MO) to measure the polydispersity indices and the number-average molecular weights, respectively. Proton nuclear magnetic resonance spectroscopy ( 1 H NMR) was employed to verify the microstructure type for the polydienes, as well as, to calculate the molar composition. Structural characterization of the terpolymers was performed via transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS), and several morphologies were observed including one which has not been reported previously. Real-space self-consistent field theory (SCFT) without a priori knowledge about the symmetry of the periodic structures was used to elucidate the thermodynamics of the synthesized triblock copolymers.

Polystyrene-b-polyisoprene-b-polystyrene (PS-b-PI-b-PS), a widely used linear triblock copolymer of the glassy-rubbery-glassy type, was prepared in this study by anionic polymerization and was further used for the development of novel polymer nanocomposite materials. Hybrid nanoadditives were prepared by the catalytic chemical vapor deposition (CCVD) method through which carbon nanotubes were grown on the surface of smectite clay nanolayers. Side-wall chemical organo-functionalization of the nanotubes was performed in order to enhance the chemical compatibilization of the clay-CNT hybrid nanoadditives with the hydrophobic triblock copolymer. The hybrid clay-CNT nanoadditives were incorporated in the copolymer matrix by a simple solution-precipitation method at two nanoadditive to polymer loadings (one low, i.e., 1 wt %, and one high, i.e., 5 wt %). The resulting nanocomposites were characterized by a combination of techniques and compared with more classical nanocomposites prepared using organo-modified clays as nanoadditives. FT-IR and Raman spectroscopies verified the presence of the hybrid nanoadditives in the final nanocomposites, while X-ray diffraction and transmission electron microscopy proved the formation of fully exfoliated structures. Viscometry measurements were further used to show the successful incorporation and homogeneous dispersion of the hybrid nanoadditives in the polymer mass. The so prepared nanocomposites exhibited enhanced mechanical properties compared to the pristine polymer and the nanocomposites prepared by conventional organo-clays. Both tensile stress and strain at break were improved probably due to better interfacial adhesion of the clay-CNT hybrid of the flexible rubbery PI middle blocks of the triblock copolymer matrix.

This work studies the origin of the so called "strain hardening" observed when comparing the transient stress response of entangled melts to uniaxial extension with that to simple shear. Strain hardening occurs when the transient extensional viscosity measured from a startup uniaxial extension of finite rate deviates upward from the zero-rate transient viscosity. Our theoretical analysis shows that polymer melts would always exhibit strain hardening at sufficient high Hencky rates because the entanglement network can be effectively strengthened during extension and can only be weakened during shear for linear chains. The kinematic difference between simple shear and uniaxial extension has two effects: (a) The force resulting from the startup deformation is measured from an increasingly shrinking area in uniaxial extension instead of a constant area as in simple shear; and (b) the tendency of the entanglement network to yield, i.e., to undergo chain disentanglement is partially suppressed during startup extension at high Hencky rates. In short, the phenomenon of strain hardening reflects the reality that entangled melts are not fluids but temporary solids and that the conventional description of their uniaxial extension in terms of the Cauchy stress contains a geometric condensation factor.

Second generation of thermally rearranged polymers presents low temperatures for a complete rearrangement., Thermally rearranged (TR) polymers, which are considered the next-generation of membrane materials because of their excellent transport properties and high thermal and chemical stability, are proven to have significant drawbacks because of the high temperature required for the rearrangement and low degree of conversion during this process. We demonstrate that using a [3,3]-sigmatropic rearrangement, the temperature required for the rearrangement of a solid glassy polymer was reduced by 200°C. Conversions of functionalized polyimide to polybenzoxazole of more than 97% were achieved. These highly mechanically stable polymers were almost five times more permeable and had more than two times higher degrees of conversion than the reference polymer treated under the same conditions. Properties of these second-generation TR polymers provide the possibility of preparing efficient polymer membranes in a form of, for example, thin-film composite membranes for various gas and liquid membrane separation applications.

Highly porous polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) diblock copolymer membranes are prepared using carbohydrates as additives. Therefore α-cyclodextrine, α-(D)-glucose, and saccharose (cane sugar) are tested for the membrane formation of three different PS-b-P4VP polymers. The addition of the carbohydrates leads to an increasing viscosity of the membrane solutions due to hydrogen bonding between hydroxyl groups of the carbohydrates and pyridine units of the block copolymer. In all cases, the membranes made from solution with carbohydrates have higher porosity, an improved narrow pore distribution on the surface and a higher water flux as membranes made without carbohydrates with the same polymer, solvent ratio, and polymer concentration.

In this study, pristine as well as polystyrene (PS) and poly(2-vinylpyridine) (P2VP) functionalized multi-wall carbon nanotubes (MWCNTs) were selectively incorporated in homopolymer binary blends of PS/P2VP and diblock copolymer (BCP) of the PS-b-P4VP type [P4VP: poly(4-vinylpyridine)]. Studies on the blends verified the chemical affinity of PS and P2VP grafted MWCNTs to the corresponding phase. Based on the results obtained from the blend systems, MWCNTs were incorporated in a PS-b-P4VP copolymer matrix with lamellar morphology and large amplitude oscillatory shear (LAOS) experiments were performed to achieve orientation of the BCP lamellae. The PS grafted MWCNTs (MWCNT-g-PS) were selectively sequestered in the PS phase and the P2VP grafted MWCNTs (MWCNT-g-P2VP) in the P4VP phase of the diblock copolymer. Unfunctionalized pristine MWCNTs were localized on the PS phase of the blend system and no special preference was observed towards the diblock copolymer PS domains. Small angle X-ray scattering (SAXS) analysis revealed the orientation of the alternating lamellae formed by the diblock copolymer when studied by LAOS. The localization of PS and P2VP grafted MWCNTs on the corresponding blend and BCP phase was also verified by transmission electron microscopy (TEM) studies. (C) 2012 Elsevier Ltd. All rights reserved. Polymer

The formation of an integral asymmetric membrane composed of a cylinder-forming polystyrene-block-poly(2-vinylpyridine) on a nonwoven by using solvent casting followed by solvent/nonsolvent exchange (phase inversion) is reported for the first time. The influence of parameters such as solvent composition, evaporation time of the solution-cast block copolymer film before phase inversion, and immersion bath temperature is demonstrated. The optimized membranes are characterized in terms of stimuli-responsive water flux properties. The morphologies of the membranes as well as of the bulk of the block copolymer are imaged by scanning force microscopy, scanning electron microscopy, and transmission electron microscopy.

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Double stimuli-responsive membranes are prepared by modification of pH-sensitive integral asymmetric polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) diblock copolymer membranes with temperature-responsive poly(N-isopropylacrylamide) (pNIPAM) by a surface linking reaction. PS-b-P4VP membranes are first functionalized with a mild mussel-inspired polydopamine coating and then reacted via Michael addition with an amine-terminated pNIPAM-NH2 under slightly basic conditions. The membranes are thoroughly characterized by nuclear magnetic resonance (1H-NMR), Fourier transform infrared spectroscopy and X-ray-induced photoelectron spectroscopy. Additionally dynamic contact angle measurements are performed comparing the sinking rate of water droplets at different temperatures. The pH- and thermo-double sensitivities of the modified membranes are proven by determining the water flux under different temperature and pH conditions.

Using the example of an integral-asymmetric isoporous membrane prepared from polystyrene-block-poly(2-hydroxyethyl methacrylate) (PS-b-PHEMA), physical and chemical ways of post-treatment are introduced with the aim to tailor the pore size. These post-treatments are i) thermal annealing and ii) urethane chemistry of ethyl isocyanate (EI) in the presence of perfluoro(methyl cyclohexane). Via these approaches, the pore size of PS-b-PHEMA membranes is successfully tailored in the range of 10-20 nm with narrow pore size distribution by controlling the duration of thermal annealing and chemical reaction, respectively. The excellent hydrophilicity of the PS-b-PHEMA membrane is not changed by thermal annealing. The chemical postmodification using EI is associated with a loss of hydrophilicity with increasing conversion.

The present article offers a new approach to create a multifunctional material based on magnetic nanoparticles, which can be dispersed in aqueous and organic media. The preparation of this material was performed by binding covalently polymer chains based on a reactive diblock-copolymer of the polystyrene-SiCl 2 -poly(2-vinylpyridine) type, with average molecular weight per number (M n ) equal to 14,700 g/mol and a polydispersity index (PDI) less than 1.1, onto the surface of γ-Fe 2 O 3 magnetic nanoparticles. The dichlorosilane moiety of the diblock-copolymer reacted with the -OH groups of the magnetic nanoparticles immobilizing the polymer chain onto its surface. This reaction was monitored by FTIR and the polymer grafting density was determined by TGA and BET. Dynamic light scattering revealed that the hydrodynamic diameter of the nanoparticles increased after immobilizing the polymer. Contact angle measurements demonstrated the ability of the hybrid material to interact with organic and aqueous media allowing its dispersion in solvents with different polarities. This property was used to prepare a magnetically active emulsion.

The effect of block copolymer chain connectivity on the structure formation in binary blends comprising block copolymer hosts and enthalpically neutralized particle filters is investigated for linear diblock (AB) and triblock (ABA and BAB) as well as four-arm star copolymer architectures (AB(3) and A(3)B). For particles with approximately constant effective size (defined here as the ratio of filler particle diameter to host polymer radius of gyration), miscibility was observed only within diblock copolymers and within the domains formed by the end blocks of triblock copolymers. The limitation of particle miscibility within the triblock mid-domain is interpreted as a consequence of the entropy loss associated with particle deposition due to the stretched configuration of bridged midblock chains. Particle aggregation was observed in both star copolymer samples irrespective of the architecture of the particle-loaded polymer domain. In the case of particle loading of the branched copolymer domain, this is rationalized as a consequence of the increased effective particle size, whereas the incompatibility of particle fillers in the linear block. domain of miktoarm copolymer hosts is interpreted as a result of the coupling of dimensional changes within the microstructure along with the reduced axial compressibility of the particle-free branched domain. The sensitive dependence of the particle compatibility oil the chain architecture of the polymer host illustrates a yet unexplored parameter space that will need to be taken into account if particle blends are to be designed with branched or multiblock host copolymer architectures. Macromolecules

Synthesis of 2 nd generation dendritic polymeric materials via anionic polymerization procedures in combination with chlorosilane chemistry, consisting either from one polydienic segment (homopolymers) or from two chemically different polydienic components (copolymers), is described. The polydienes used were poly(butadiene) (PB) with ∼90% 1,4-isomerism and poly(isoprene) (PI) with increased 3,4-isomerism (∼60%). Molecular characterization of intermediate products and the final dendritic materials was made with Gel Permeation Chromatography (GPC), Membrane and Vapour Pressure Osmometry (MO and VPO respectively), Gas Chromatography -Mass Spectroscopy (GC-MS) and 1 H-Nuclear Magnetic Resonance ( 1 H-NMR) Spectroscopy, leading to the conclusion that they can be considered model polymers. Morphological studies solely with Transmission Electron Microscopy (TEM) have been conducted on two of the four synthesized copolymer samples exhibiting microphase separation between the two polydiene segments.

We report the Synthesis of first generation dendritic homopolymers consisting of either poly(butadiene) (PB) of 1,4-microstructure or poly(isoprene) enriched in 3,4-microstructure (at least 55% PI3,4). The main aspect was the synthesis of polymers exhibiting high molecular and compositional homogeneity. The preparation of these materials was achieved via anionic polymerization techniques in combination with chlorosilane chemistry. The molecular characterization of the final dendritic materials was made via size exclusion chromatography (SEC), membrane osmometry (MO), dilute solution viscometry and H-1 nuclear magnetic resonance (NMR) spectroscopy, leading to the conclusion that they can be considered as model polymers. The conformational properties of the synthesized dendritic polymers were studied by means of analytical theory and Monte Carlo simulations using coarse graining models with the same number of segments. The radii of gyration and the length of the branches of zeroth and first generations were calculated via lattice, off-lattice algorithms, and renormalization group techniques. The theoretical findings were compared with the respective results of star polymers with the same functionality and equivalent branch lengths. (c) 2006 Elsevier Ltd. All rights reserved. Polymer

In this study, the rheological properties of polystyrene-block-polyisoprene (PS-b-PI) diblock copolymer melts with different types of morphology are analysed. Using the technique of anionic polymerization three different PS-b-PI diblock copolymers with a spherical, cylindrical and lamellar morphology, respectively, were synthesised. The objective of our study was to determine the viscous and elastic properties of these PS-b-PI diblock copolymers and to investigate the influence of morphology on the viscoelastic properties at short and long times. The analysis of our experiments reveals that morphological changes take place in the melt which lead to changes of the dynamic moduli. Furthermore, all three diblock copolymers of this study reveal a non-terminal behaviour in oscillatory shear flow in the microphase-separated state. Our creep recovery experiments indicate that microphase-separated diblock copolymers are characterised by a pronounced recoverable deformation.

The influence of morphology on the viscoelastic properties of melts of microphase-separated polystyrene-block-polyisoprene (PS-b-PI) diblock copolymers was investigated in oscillatory shear and creep recovery experiments. By means of anionic polymerization, three PS-b-PI diblock copolymers with a narrow molecular weight distribution and different types of morphology (spherical, cylindrical and lamellar microstructure) were prepared. Linear viscoelastic shear oscillations and creep recovery experiments in shear were performed in order to determine the elastic and viscous properties of the diblock copolymers in the melt at small and large time scales. Our analysis reveals that melts of diblock copolymers are characterized by a pronounced elastic behavior leading to a relatively large recoverable deformation in creep recovery experiments. The elasticity of the diblock copolymers is also revealed by the appearance of the creep-ringing effect. Morphological investigations were carried out to establish relations between microstructure and melt elasticity. Since ordering phenomena take place in melts of diblock copolymers until an equilibrium morphology is achieved, the storage modulus G′ of diblock copolymer melts increases with time up to a steady-state value.

Deposition of block copolymer thin films is most often accomplished in a serial process where material is spin coated onto a substrate and subsequently annealed, either thermally or by solvent vapor, to produce a well-ordered morphology. Here we show that under appropriate conditions, well-ordered block copolymer films may be continuously grown under substrate equilibrated conditions by slow deposition of discrete subattoliter quantities of material using electrospray. We conduct time-resolved observations and investigate the effects of process parameters that underpin film morphology including solvent selectivity, substrate temperature, block-substrate selectivity, and flow rate of the feed solution. For a PEO cylinder-forming poly(styrene-b-ethylene oxide) block copolymer, we uncover a wide temperature window from 90 to 150 °C and an ideal flow rate of 2 μL/min for ordered film deposition from dilute acetone solutions. PEO cylinders aligned with their long axes perpendicular to the film-air interface at optimal spray conditions. Using poly(styrene-b-methyl methacrylate) deposited onto neutrally selective surfaces, we show that the substrate-equilibrated process results in vertically oriented microdomains throughout the film, indicating a preservation of the initial substrate-dictated morphology during the film deposition. Electrospray offers a new and potentially exciting route for controlled, continuous growth of block copolymer thin films and manipulation of their microstructure.

In this work, the localization of functionalized multi-walled carbon nanotubes (MWCNT) with random copolymers of methyl methacrylate and styrene (P(MMA-co-S)) in poly(styrene-co-acrylonitrile)/poly(2, 6-dimethyl-1,4-phenylene ether) blends (SAN/PPE) and its influence on morphological, rheological and dielectric properties of the composites were investigated. P(MMA-co-S) copolymers were grafted onto MWCNT via atom transfer radical polymerization (ATRP). The molecular weight of the copolymers was adjusted by controlling the time of reaction. In SAN/PPE blends, MWCNT grafted with low molecular weight copolymers were predominantly located at the interface of the blend and a few individual tubes were dispersed in the PPE phase. Aggregation of MWCNT was observed nearby the interfacial region because of micellization of grafted copolymers. Aggregation was more pronounced with increasing molecular weight of the grafted P(MMA-co-S) copolymer. In the melt, the composite containing MWCNT with low molecular weight copolymers had higher dynamic moduli than the one with pristine MWCNT. An increasing molecular weight of grafted copolymer led to a softening effect which resulted in a reduction of the moduli of the composite. Although a pronounced enhancement was observed for the composites with pristine MWCNT, only a small increase in electrical conductivity was achieved by adding functionalized MWCNT owing to the poor network formed by functionalized MWCNT in the blends.

We have synthesized linear ABC triblock terpolymers containing poly(1,3-cyclohexadiene), PCHD, as an end block and characterized their morphologies in the melt. Specifically, we have studied terpolymers containing polystyrene (PS), polybutadiene (PB), and polyisoprene (PI) as the other blocks. Systematically varying the ratio of 1,2- /1,4-microstructures of poly(1,3-cyclohexadiene), we have studied the effects of conformational asymmetry among the three blocks on the morphologies using transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and self-consistent field theory (SCFT) performed with PolySwift++. Our work reveals that the triblock terpolymer melts containing a high percentage of 1,2-microstructures in the PCHD block are disordered at 110 °C for all the samples, independent of sequence and volume fraction of the blocks. In contrast, the triblock terpolymer melts containing a high percentage of 1,4-microstructure form regular morphologies known from the literature. The accuracy of the SCFT calculations depends on calculating the χ parameters that quantify the repulsive interactions between different monomers. Simulations using χ values obtained from solubility parameters and group contribution methods are unable to reproduce the morphologies as seen in the experiments. However, SCFT calculations accounting for the enhancement of the χ parameter with an increase in the conformational asymmetry lead to an excellent agreement between theory and experiments. These results highlight the importance of conformational asymmetry in tuning the χ parameter and, in turn, morphologies in block copolymers.

For the first time the combination of solution casting and solvent–nonsolvent exchange (phase inversion) has been applied to generate asymmetric membranes with highly ordered hexagonally packed cylinders with perpendicular orientation composed of polystyrene-block-poly(ethylene oxide). The influence of parameters like solvent composition and evaporation time on the membrane formation is presented. The development is based on a study of the solution behavior by dynamic light scattering and the precipitation behavior of the cylinder forming diblock copolymer by turbidity measurements from different solvent and nonsolvent systems. The water flux properties, as an important membrane characteristic, show a time dependent behavior, due to swelling of the polyethylene oxide blocks. The morphologies of the membranes are imaged by scanning electron microscopy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013

The development of well defined nanostructured thermosets from epoxy/PS-b-P2VP blends are presented in this study. For this purpose an epoxy system constituted by an epoxy resin (Araldite LY556), an anhydride hardener (Aradur 917), and an imidazole accelerator (DY 070) was employed and a block copolymer of PS-b-P2VP, where the block length of poly (2-vinylpyridine) (P2VP) was selected to allow the formation of microphase separated PS block nanodomains. Different ratios of PS-b-P2VP and epoxy system were used to analyze the nanostructuration of the system. Samples were characterized by transmission electron microscopy (TEM), fourier transform infrared, thermogravimetric analysis, and differential scanning calorimetry (DSC). DSC indicated that depletion of T-g occurred when concentration of block copolymer increased in the blend. TEM images showed vesicles and well defined cylindrical and lamellar nanostructured thermoset materials which were obtained when the PS-b-P2VP content was higher than 20 wt%. Journal of Materials Science

Poly(vinyl trimethylsilane) (PVTMS) and block copolymers of vinyl trimethylsilane with isoprene were synthesized by anionic polymerization and characterized. The synthesized pure PVTMS has properties similar to a reference material produced about two decades ago and can be used for thin film composite membrane formation. Even at low isoprene content the block copolymers have improved film forming properties compared to the pure PVTMS. However, the presence of the isoprene units in the block copolymers leads to a decrease of the gas permeability but does not affect the selectivity of the membranes (α(O2/N2) = 3.9).

A new technique for the modification of lamellar domain sizes in polymeric ionic liquid block copolymers has been proposed. Anion exchange in polymeric ionic liquids opens new ways to modify the sizes of lamella domains without modifying the ratio between the two different blocks of the neat copolymer. This study focuses on the influence of quaternization of poly(2-vinylpyridine) in poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) and the effect of anion exchange in the nanostructured phases for thin films. The resulting materials obtained from the quaternization modification technique of the block copolymers and the anion exchange of the polymeric ionic liquid were characterized with Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and nuclear magnetic resonance (NMR). Furthermore, morphological characterization of the initial block polymer and several polymeric ionic liquid block copolymers has been carried out by atomic force microscopy (AFM) in order to analyze the influence of the anion in the nanostructures of these block copolymers. Macromolecules

We report the synthesis of two 2nd generation dendritic terpolymers consisting of poly(butadiene) (PB) of 1,4 geometric isomerism, poly(isoprene) (PI) enriched in 314 geometric isomerism (at least 55% PI(3,4)) and polystyrene (PS). The main focus of this work was the synthesis of well-defined dendritic terpolymers exhibiting high levels of molecular and compositional homogeneity. The preparation of these materials was achieved via anionic polymerization techniques in combination with chlorosilane linking chemistry. The molecular characterization of the intermediate products and the final dendritic materials was accomplished via gel permeation chromatography, membrane osmometry, differential scanning calorimetry, and (1)H-nuclear magnetic resonance spectroscopy, leading to the conclusion that they can be considered model polymers. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1567-1574, 2009 Journal of Polymer Science Part a-Polymer Chemistry

We report the synthesis of a silylated monomer, specifically p-trimethylsilyl styrene, its homopolymerization, and its block copolymerization with 1,3-cyclohexadiene. Controlled Grignard reactions were adopted for the preparation of the monomer. Anionic polymerization high-vacuum techniques were employed for all polymerization procedures. The kinetics of poly(P-trimethylsilyl styrene) homopolymers were also studied. Molecular characterization for all intermediate and final products was accomplished via size exclusion chromatography, membrane osmometry, and proton nuclear magnetic resonance spectroscopy. Finally, the self-assembly of the block copolymers was studied with transmission electron microscopy, where well-ordered microstructures were observed (alternating lamellae and hexagonally closed packed cylinders). International Journal of Polymer Analysis and Characterization

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Isoporous integral-asymmetric membranes of tailor-made poly(tert-butylstyrene)- and poly(4-trimethylsilylstyrene)-block-poly(4-vinylpyridine) diblock copolymers are reported here for the first time. The membrane development involved the optimization of the production process—which is a combination of block copolymer self-assembly and the non-solvent induced phase inversion process. The membranes showed an improved thermal and chemical stability compared to previously reported polystyrene-block-poly(4-vinylpyridine) membranes, thus the number of potential application areas for such type of isoporous membranes is increased.

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