Synthesis of poly(trioctylammonium p-styrenesulfonate) homopolymers and block copolymers by RAFT polymerization

A method to prepare sulfonated polystyrene-containing block copolymers has been investigated by neutralizing styrene sulfonic acid with trioctylamine to produce the hydrophobic monomer trioctylammonium p-styrenesulfonate (SS-TOA). This monomer was polymerized by reversible addition fragmentation chain transfer (RAFT) polymerization to produce PSS-TOA homopolymers. A PSS-TOA homopolymer was then used as a macro-RAFT agent for the polymerization of styrene to prepare poly(trioctylammonium p-styrenesulfonate)-block-poly(styrene) (PSS-TOA-b-PS). These block copolymers could be ion-exchanged to produce either the hydrophilic sodium salt form of PSS or a hydrophobic quaternary ammonium salt. This approach will be useful for preparing PSS-containing block copolymers with a range of hydrophobic blocks for applications such as ion-exchange membranes.     

Synthesis of amine‐functionalized block copolymers for nanopollutant removal from water

Polyamines are rare in literature owing to increased reactivity, sensitivity to air and moisture, low stability, and processing difficulties. Here, we report the synthesis and characterization of highly processable polyamines and use them for the removal of dissolved metallic nanoparticles from water. Three amphiphilic block polyamines such as poly(N‐aminoethyl acrylamide‐b‐styrene), poly(N‐aminopropyl acrylamide‐b‐styrene), and poly(N‐aminoxylyl acrylamide‐b‐styrene) have been synthesized using atom transfer radical polymerization of ethyl acrylate and styrene followed by aminolysis of the acrylic block. The polymerization and properties of the polymers are studied using different physicochemical techniques. Surface morphology of films prepared from these block copolymers by dissolving in different solvents such as chloroform, tetrahydrofuran and N,N‐dimethylformamide, and drop‐casting polymers on a glass substrate show interesting porous films and spherical nanostructures. In addition, the amine‐functionalized block copolymers have been used for the removal of nanoparticles from water and show high extraction efficiency toward silver (Ag) and gold (Au) nanoparticles. All three amine‐functionalized block copolymers show higher extraction capacities (Q_e) toward Au NPs (50–109 mg g^?1) and Ag NPs (99–117 mg g^?1). Our approach allows us to make amine‐functionalized block copolymers which are stable in air and can be easily processed in nonpolar solvents. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40943.     

Block copolymerization by a cation to anion transformation process: 1. Reaction of butyl lithium with polyTHF possessing terminal styryl groups

A route for preparing novel block copolymers by a cation to anion transformation process is examined. The process involves reacting living polyTHF with the lithium salt of cinnamyl alcohol to prepare a polymer possessing a styryl terminal group and this has been shown to be virtually quantitative. The second stage involves reacting this product with n-butyl lithium in benzene to form an adduct to which monomer such as styrene or isoprene is added to prepare a block copolymer anionically. This last stage has been shown to operate with only about 20% efficiency and, although the reason for this low efficiency has not been elucidated, it is suspected that it is due to side reactions of the butyl lithium.     

Compatibilizing efficiency of copolymer precursors for immiscible polymer blends

An anhydride‐terminated polystyrene (PS‐b‐Anh) as a block copolymer precursor and a copolymer (PS‐co‐TMI) of styrene (St) and 3‐isopropenyl‐α,α‐dimethylbenzene isocyanate (TMI) as a graft copolymer precursor are chosen to investigate the effect of the type of the copolymer precursor on its compatibilizing and stabilizing efficiency for polymer blends. Results show that during the melt blending of the PS and PA6, the addition of PS‐b‐Anh dramatically decreases the size of the dispersed phase domains, irrespective of its molecular weight. This indicates that a diblock copolymer PS‐block‐PA6 (PS‐b‐PA6) is formed by a reaction between the terminal anhydride moiety of the PS‐b‐Anh and the terminal amine group of the PA6. When PS/PA6 (30/70) blends are annealed at 230°C for 15 min, their morphologies are much more stable in the presence of the PS‐b‐Anh block copolymer precursor than in the presence of the PS‐co‐TMI graft copolymer precursor. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

A Thiolactone Strategy for Straightforward Synthesis of Disulfide‐Linked Side‐Chain‐to‐Tail Cyclic Peptides Featuring an N‐Terminal Modification Handle

The development of straightforward and versatile peptide cyclisation methods is highly desired to meet the demand for more stable peptide‐based drugs. Herein, a new method for the synthesis of side‐chain‐to‐tail cyclic peptides with the simultaneous introduction of an N‐terminal handle, based on the introduction of an N‐terminal thiolactone building block, is described. A primary amine liberates a homocysteine analogue from the thiolactone building block, which further enables cyclisation of the peptide through disulfide‐bond formation with a C‐terminal cysteamine. Postcyclisation modification can be achieved by using small bifunctional amines. Alternatively, the synthesis of lipopeptides is demonstrated through direct thiolactone opening with long‐chain alkyl amines.     

Reactions of Living Polytetrahydrofuran with Amines V - Tertiary Amine Terminated Polybutadienes; The Synthesis of Novel Ionically Linked Block Copolymers

The reactions of mono- and difunctional tertiary amine ended polybutadienes with mono- and difunctional living cationic poly THF have been studied. It is shown that the reaction to form quaternary ammonium linking groups takes place rapidly in all cases, and AB. ABA, BAB and (AB) block copolymers have been prepared. The efficiency of the process is extremely high and the degree of conversion is essentially controlled by the efficiency with which the terminal tertiary amine groups can be introduced on to the polybutadiene. The block copolymers show anomalous behaviour on gel permeation chromatography columns and this has been related to a specific interaction of the created ionic groups with polar species on the column packing. This effect is greatest with (AB) block copolymers where substantial proportions are retained indefinitely on the columns.     

Application of styrene‐acrylonitrile random copolymer–polyarylate block copolymer as reactive compatibilizer for polyamide and acrylonitrile‐butadiene‐styrene blends

Styrene‐acrylonitrile random copolymer (SAN) and polyarylate (PAr) block copolymer were applied as a reactive compatibilizer for polyamide‐6 (PA‐6)/acrylonitrile‐butadiene‐styrene (ABS) copolymer blends. The SAN–PAr block copolymer was found to be effective for compatibilization of PA‐6/ABS blends. With the addition of 3.0–5.0 wt % SAN–PAr block copolymer, the ABS‐rich phase could be reduced to a smaller size than 1.0 μm in the 70/30 and 50/50 PA‐6/ABS blends, although it was several microns in the uncompatibilized blends. As a result, for the blends compatibilized with 3–5 wt % block copolymer the impact energy absorption reached the super toughness region in the 70/30 and 50/50 PA‐6/ABS compositions. The compatibilization mechanism of PA‐6/ABS by the SAN–PAr block copolymer was investigated by tetrahydrofuran extraction of the SAN–PAr block copolymer/PA‐6 blends and the model reactions between the block copolymer and low molecular weight compounds. The results of these experiments indicated that the SAN–PAr block copolymer reacted with the PA‐6 during the melt mixing process via an in situ transreaction between the ester units in the PAr chain and the terminal amine in the PA‐6. As a result, SAN–PAr/PA‐6 block copolymers were generated during the melt mixing process. The SAN–PAr block copolymer was supposed to compatibilize the PA‐6 and ABS blend by anchoring the PAr/PA‐6 and SAN chains to the PA‐6 and ABS phases, respectively. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2300–2313, 2002     

Limitation of the Coalescence of Evolutive Droplets by the Use of Copolymers in a Thermoplastic/Thermoset Blend

Summary: Polystyrene (PS)/epoxy‐amine (DGEBA‐MDEA) is a thermoplastic/thermoset precursor blend which is miscible at high temperature (177 °C), and which phase separates under the polymerization of the epoxy‐amine system. Previous studies have shown that the morphology of this blend polymerized under shear is coarse and irregular because the dispersed epoxy‐amine domains coalesce before they gel. Several styrene‐methyl methacrylate and a styrene‐butadiene‐styrene block copolymers have been added to the PS/DGEBA‐MDEA 60/40 blend in order to limit the coalescence and thus obtain a finer morphology. Two of the copolymers used were reactive either with the epoxy or with the amine. It was shown that the addition of 15 wt.‐% of non reactive copolymer had a positive but limited effect on the size of the final epoxy‐amine particles. The copolymer remained at the interface at the early stages of the polymerization. However, it was pulled out by the shear forces around the gel point of the epoxy domains. Most of the non reactive copolymer was present in the shape of micelles at the end of the process. On the other hand, the reactive copolymers were able to establish covalent bonds with the epoxy‐amine drops and hence were not extracted at all. Consequently they allowed the decrease the size of the particles by a factor of 15. Despite this, the observation of the morphology at different stages of the polymerization has revealed that the copolymer moved at the interface of the epoxy domains during the collision of two droplets. The movements of fluids into the epoxy domains pushed the copolymer out of the inter‐droplet zone so that it could not prevent the drainage of the liquid film between the droplets and consequently their coalescence.

TEM showing that the layer of copolymer (in dark grey) has moved along the interface of epoxy‐amine drops during their successful collision in a polystyrene‐rich matrix.     

Softening phenomenon by remilling of styrene–butadiene copolymer rubber–general-purpose polystyrene resin blend

The softening phenomenon by remilling of uncured blends of various commercia styrene—butadiene copolymer rubber (styrene content, 23.5 to 48 wt-%, styrene block 0 to 18 wt-%) with general-purpose polystyrene resin was mainly studied by examining the blend ratio dependence of hardness and compression modulus (in logarithmic form), with special attention to the state of dispersion of the polymers. It was found that the blend of styrene—butadiene copolymer rubber with general-purpose polystyrene resin forms a microheterogeneous polymer blend system and that the hardness and the compression modulus change in S-shaped curves versus blend ratio. However, the degree of softening phenomenon by remilling (roll surface temperature, 70°–90°C) was found to be different for the two blend systems, i.e., random styrene—butadiene copolymer rubber and block styrene—butadiene copolymer rubber. The softening phenomenon is more pronounced in random-type rubbers; and in some block-type rubbers, no softening phenomenon was observed. The influence of the styrene content of the polymer is small. Further discussions have shown us that the strong interaction between the polystyrene block of the copolymer and the styrene homopolymer of the general-purpose polystyrene resin controls the state of dispersion of polymers thereby causing this difference in the softening phenomena among the different kinds of styrene—butadiene copolymer rubbers.     

Changes in mixing states of styrene–butadiene copolymer rubber and general-purpose polystyrene resin mill blend by heat treatment

The effect of heat treatment in the so-called phase inversion region was studied using uncured mill blends of various commercial styrene—butadiene copolymer rubbers (styrene content, 23.5 to 48 wt-%; styrene block, 0 to 18 wt-%) with general-purpose polystyrene resin (blend ratio, 80–40: 20–60, in wt-%). It was found that the effect of heat treatment on the hardening or softening phenomenon of blends is different in the random type from that in the block-type styrene—butadiene copolymer rubber. A thorough discussion led us to conclude that this difference is caused by the strong interaction between the polystyrene block of the copolymer and the styrene homopolymer of general-purpose polystyrene resin.     

Degradation of styrene by a new isolatePseudomonas putida SN1

Twelve styrene-utilizing bacteria were isolated from a biofilter used for treating gaseous styrene. A gramnegative strain had a high styrene-degrading activity and was identified as Pseudomonas putida SN1 by 16S rDNA analysis. The styrene degradation in SN1 was regarded to start with a monooxygenase enzyme which converted styrene to styrene oxide, a potentially important chiral building block in organic synthesis. SN1 could grow on styrene and styrene oxide, but not on benzene and toluene. The styrene degradation activity in SN1 was induced when incubated with styrene, and the induction was not inhibited by the presence of readily usable carbon sources such as glucose and citrate. The optimal activity was shown at pH 7.0 and 30 °C and estimated as 170 unit/g cell.     

挤出过程中交联聚氯乙烯的研究

应用过氧化二异丙苯 /苯乙烯 /三乙醇胺体系在挤出过程中实现了聚氯乙烯的一步交联 ,研究了三乙醇胺和过氧化二异丙苯用量对交联产物力学性能及交联凝胶率的影响。研究发现 ,三乙醇胺对PVC交联结构的形成具有明显的促进作用。在苯乙烯用量 5 phr,三乙醇胺用量为 0 33phr时 ,过氧化二异丙苯在 0 15phr取得最佳值 ;当苯乙烯用量 5 phr,过氧化二异丙苯用量 0 15 phr时 ,三乙醇胺用量在 0 4hpr取得最佳值。交联可以使聚合物材料的力学强度得到提高     

Premade vs. reactively formed compatibilizers for PMMA/PS melt blends

The efficiency of two compatibilization methods, adding premade copolymers versus in situ formation of copolymers, were compared by evaluating the minor phase size and size distribution. Premade diblock copolymers were formed by coupling amine terminal polystyrene (PS-NH₂) with anhydride terminal poly(methyl methacrylate) (PMMA-An) in solution. Mid-functional PMMA was coupled with the PS-NH₂ to form graft copolymers. The same block and graft copolymers were formed in situ during melt blending. After mixing, the particle size and distribution were analyzed by transmission electron microscope (TEM). While both methods compatibilized blends, in situ formation reduced the minor phase size further. For the reactive case, graft copolymers are slight better than the block ones. This is attributed to a greater capacity for reducing interfacial tension. For the premade case, block copolymers compatibilize better at low copolymer concentration while graft copolymers work better at high concentration. As the amount of block copolymers added into the blends increases, the number of micelles increases significantly. This is believed to be the reason why premade copolymers are less capable of compatibilizing blends than the reactively formed ones.     

Synthesis of diblock and triblock copolymers from butyl acrylate and styrene by reverse iodine transfer polymerization

Well‐defined AB and BA diblock copolymers were obtained by a one‐pot two‐step sequential block copolymerization by reverse iodine transfer polymerization (RITP), A being a poly(styrene) block and B a poly(butyl acrylate) block. High monomer conversions during the formation of the first block avoided the purification steps before growing the second block. In a third sequential step, the diblock copolymers were further extended to synthesize ABA and BAB triblock copolymers. Furthermore, the synthesis of ABA and BAB copolymers in only two steps by RITP was investigated starting with the formation of the central block using 2,5‐di(2‐ethylhexanoylperoxy)‐2,5‐dimethylhexane as a difunctional initiator and then resuming the polymerization to grow the external blocks in a second step. The obtained copolymers were analyzed by size exclusion chromatography, transmission electron microscopy, and differential scanning calorimetry. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A Synthetic Approach to Star‐Like Polymers of Styrene and Butyl Acrylate by Linking Reactions using Functionalized Methacrylates

Summary: Coupling reactions between terminal functionalized polymer chains were chosen for the synthesis of star‐like polymers consisting of polystyrene and polystyrene‐block‐poly[styrene‐co‐(butyl acrylate)] arms. For the preparation of terminal functionalized polymer chains a side reaction of the 2,2,6,6‐tetramethylpiperidine‐N‐oxyl (TEMPO) mediated free radical polymerization of methacrylates could be used successfully to convert TEMPO terminated polymers into end functionalized polymers. The number of functionalized monomer units attached to the polymer chain is directly related to the TEMPO concentration during this reaction. Different polystyrenes and polystyrene‐block‐poly[styrene‐co‐(butyl acrylate)] block copolymers were functionalized with a variable number of epoxide and alcohol groups at the chain end. For the determination of the optimal reaction parameters for the coupling reactions between these polymer chains, epoxy functionalized polystyrenes were converted with hydroxy functionalized polystyrenes under basic and acidic conditions. By activation with sodium hydride or boron trifluoride star‐like polymers were synthesized under mild conditions. The transfer of the reaction conditions to coupling reactions between end functionalized polystyrene‐block‐poly[styrene‐co‐(butyl acrylate)] copolymers showed that star‐like polymers with more than 12 arms were formed using boron trifluoride as activating agent.

     

Polymericaly modified clays to preparation of polystyrene nanocomposite by nitroxide mediated radical polymerization and solution blending methods

Polymericaly modified clays that contain an oligomeric poly(styrene‐co‐chloromethyl styrene) ammonium salt have been prepared and used to preparation of polystyrene (PS) nanocomposites. First, PS and poly(styrene‐co‐chloromethyl styrene) [P(St‐co‐CMSt)] were synthesized by nitroxide mediated living free radical polymerization (NMRP) by TEMPO iniferter .Then the copolymer was coupled with N, N‐dimethyl hexadecyl amine to prepare polymeric modifier by anion exchange of chlorine group of chloromethyl styrene (CMSt) by quaternary amine. The synthesized polymeric modifier was mixed with nanoparticle of silica to change the property of clay surface from hydrophilic to hydrophobic via cation exchange of Na⁺ with alkylammonium ions. For synthesizing of nanocomposites, we used polymericaly modified montmorillonite and PS that was synthesized by NMRP technique. Intercalated nanocomposites and in some cases, exfoliated or mixed intercalated/exfoliated nanocomposites of all of these polymers have been produced by solution blending method. The prepared materials were characterized by X‐ray diffraction, Transmission electron microscopy, Fourier‐transform infrared, ¹H nuclear magnetic resonance, and gel permeation chromatography techniques. Effect of layered silicates on thermal properties and glass transition temperature of PS was investigated using TGA and DSC techniques. POLYM. COMPOS., 38:1127–1134, 2017. © 2015 Society of Plastics Engineers     

The effect of block lengths on micelle structure in blends of styrene-isoprene diblock copolymer and poly(vinyl methyl ether)

The micellar structure of styrene-isoprene diblock copolymer and poly(vinyl methyl ether) blends was investigated by using small-angle X-ray scattering and transmission electron microscopy techniques. In order to determine the effect of styrene block length on the formation of micellar structure, three sets of diblock copolymers, with near-identical isoprene block molecular weights, but with different styrene block lengths were studied. With modeling based on the polydisperse Percus-Yevick hard sphere fluid model, the structural parameters characterizing the micelles were determined as a function of copolymer concentrations, temperature, and copolymer block lengths. The core radius was found to decrease on increasing the length of styrene block. The degree of swelling of the corona by PVME increased steadily with increasing the styrene block length.     

Bisacylphosphine oxides as bifunctional photoinitiators for block copolymer synthesis

Block copolymers of styrene (St) and methyl methacrylate (MMA) were prepared via a two-step procedure by using bisacylphosphine oxide (BAPO) as photoinitiator. Photolysis of BAPO at λ = 420 nm in the presence of St yielded polymers with monoacylphosphine oxide terminal groups. Subsequent irradiation of the polymers in the presence of MMA at λ = 380 nm produced block copolymers. Block copolymer formation was evidenced by spectral measurements and GPC analysis.     

Compatibilization of polystyrene and polyamide 6 mixtures with poly(styrene‐co‐sodium acrylate)

In this work, the compatibilization of polystyrene‐and‐nylon 6 mixtures with the ionomer, poly(styrene‐co‐sodium acrylate), is investigated. The ionomer was synthesized by emulsion polymerization. Scanning electron microscopy reveals that an appreciable size reduction of the dispersed phase is achieved in the whole composition range, when small amounts of the ionomer were added. IR spectroscopy and water absorption tests disclose that a chemical reaction occurs between the carboxylic group of the ionomer and the terminal amine group of the polyamide 6, which allows the compatibilization process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91:1736–1745, 2004     

Block copolymers obtained by free-radical mechanism. I. Methyl methacrylate and styrene

Block copolymers were synthesized using styrene and methyl methacrylate as the monomers and a multifunctional initiator, di-t-butyl 4,4′-azobis(4-cyanoperoxyvalerate). The unique feature of this sequential initiator is the fact that the formation of the free radicals can be achieved thermally and/or by a redox system at different stages. The polymerizations for the formation of the block copolymer were carried out in two stages. First, a polymeric initiator was synthesized, which was then used in the second stage to initiate the polymerization of the second monomer. Styrene and methyl methacrylate were used as the comonomers. Selective solvent fractionation was used for the separation of the block from the homopolymers. The separation technique was found to be efficient, giving pure block copolymers which could subsequently be characterized by GPC, NMR, IR, and EM techniques.